Brass Flange Check Valve DN15-200 PN16 Swing/Lift Type Water Oil Gas Factory

A Brass Flange Check Valve (also called Brass Flanged Non-return Valve, Brass Swing Check Valve, Brass Lift Check Valve, or Brass One-way Valve) is an automatic, self-actuated one-way valve that allows medium to flow in only one direction and automatically prevents reverse flow (backflow) - it requires no external actuator, no electricity, no compressed air, and no operator; the valve disc (swing-type hinged clapper or lift-type piston disc) is pushed open by the forward pressure of the flowing medium and closes automatically by gravity, spring force, or reverse pressure when flow stops or reverses, forming a standalone mechanical backflow prevention device that protects pumps, equipment, and pipeline systems from damage caused by reverse flow, water hammer, or medium contamination. The valve body is precision-forged from high-quality brass (C37700 lead-free brass / C36000 free-cutting brass / H62 Chinese standard brass), which offers excellent corrosion resistance (to water, mild acids, alkalis, oils, gases), good dezincification resistance (for long-term water service), excellent machinability, high thermal conductivity, antimicrobial properties (inhibits bacterial growth in water), and low cost compared to stainless steel or cast steel - making it the most cost-effective choice for general-purpose water, oil, gas, and low-pressure steam service in DN15–DN200 (1/2"–8"), PN16 (Class 125/150), temperature -20°C to +180°C (per seal material: NBR ≤80°C, EPDM ≤120°C, PTFE ≤180°C) applications. It features flanged ends (raised face RF or flat face FF, per GB/T 9113, HG/T 20592, ANSI B16.5, EN 1092-1, JIS B2220) for easy installation, removal, and maintenance in standard flanged piping systems, with face-to-face dimensions per GB/T 12221, EN 558, API 594 ensuring interchangeability with other standard check valves. Two main structural types are available: (a) Swing Check Valve (DN50 and above) - a hinged clapper disc swings open/closed around a pin, offering low flow resistance, large flow capacity, and suitability for horizontal pipelines with low pressure drop; (b) Lift Check Valve (DN15–DN50) - a piston-style disc lifts vertically off the seat under forward flow and drops back by gravity/spring, offering tight sealing, compact size, and installation in any orientation (horizontal or vertical with upward flow). The sealing surface uses NBR (nitrile rubber, for water/oil ≤80°C), EPDM (for hot water/steam ≤120°C), or PTFE (for chemicals/corrosive ≤180°C) soft seal for bubble-tight shutoff (zero leakage), with optional stainless steel (304/316) or bronze hard-faced disc/seat for abrasive or high-cycle service. The valve is fully automatic - opens when forward pressure exceeds cracking pressure (typically 0.02-0.05MPa), closes instantly when flow reverses, and requires no maintenance under normal operation (only periodic inspection of seal wear and hinge pin lubrication for swing type). It is widely used in water supply & drainage, HVAC heating/cooling, fire protection systems, oil & gas pipelines, water treatment, municipal engineering, irrigation, and general industrial fluid systems - a reliable, cost-effective, corrosion-resistant, low-maintenance backflow prevention solution for neutral media at low-to-medium pressure. The core highlights are: (a) automatic one-way operation (no external energy, opens by forward pressure, closes by gravity/spring/reverse pressure); (b) forged brass body (C37700/C36000/H62, corrosion/dezincification resistant, low cost, antimicrobial); (c) two types: swing (DN50+, low ΔP, horizontal) / lift (DN15-50, tight seal, any orientation); (d) soft seal NBR/EPDM/PTFE (bubble-tight, per medium/temp); (e) flanged ends (GB/ANSI/EN/JIS, RF/FF, easy install); (f) DN15-200, PN16, -20~180°C; (g) standards: GB/T 12221 face-to-face, API 594, API 598 test; (h) lead-free option for potable water (NSF/WRAS optional); (i) vs cast iron/stainless check valve: brass = better corrosion in water, lighter, lower cost, antimicrobial, but lower pressure/temp (PN16 max, ≤180°C) - for general water/oil/gas; (j) vs brass threaded check valve: this = flanged (DN50+, higher pressure, easier maintenance) vs threaded (small DN, lower cost, compact); (k) key difference: this valve = brass body + flanged ends + automatic one-way check + swing/lift type + soft seal + PN16 general-purpose. This is the reliable cost-effective brass flanged backflow prevention valve.

The automatic self-actuated one-way operation (forward pressure opens disc, gravity/spring/reverse pressure closes - no external energy, no operator, instant response), forged brass construction (C37700/C36000/H62, corrosion/dezincification resistant, antimicrobial, low cost, excellent machinability), two structural types (swing for DN50+ with low pressure drop and large flow capacity in horizontal pipelines, lift for DN15-50 with tight sealing and any-orientation installation), soft seal options (NBR/EPDM/PTFE matched to medium and temperature for bubble-tight shutoff), and standard flanged ends (GB/ANSI/EN/JIS, RF/FF, interchangeable face-to-face) make this valve a specialized general-purpose brass flanged check valve - distinct from cast iron check valves (which are heavier, more prone to corrosion in water, but available in larger DN and higher PN), cast steel/stainless steel check valves (which handle higher pressure/temperature/corrosive media but cost 2-5× more), brass threaded check valves (which are for small DN≤50 with threaded NPT/BSP connections, compact and low-cost but harder to remove from large pipelines), and brass wafer check valves (which are wafer-type (clamp between flanges), ultra-short face-to-face, lightweight, but require flange bolts and have lower pressure rating) - designed for automatic backflow prevention of water, oil, gas, and low-pressure steam in DN15-200, PN16, -20~180°C general-purpose industrial and municipal pipelines where corrosion resistance, cost-effectiveness, easy installation, and reliable zero-leakage shutoff are priorities. Compared to other check valve types: (a) Cast iron swing check valve: (i) DN50-1200, PN10-16, cheaper than brass for large DN; (ii) heavier, corrodes in water (rust), needs painting; (iii) brass better for water (no rust, antimicrobial, lighter); (b) Cast steel WCB check valve: (i) DN15-600, PN16-100, -29~425°C; (ii) for high pressure/temp, oil/gas; (iii) brass = lower cost, better water corrosion, but lower PN/temp; (c) Stainless steel (CF8/CF8M) check valve: (i) DN15-600, PN16-40, -40~450°C; (ii) for corrosive chemicals, seawater, food; (iii) brass = much lower cost, good for neutral water/oil/gas, antimicrobial; (d) Brass threaded check valve: (i) DN8-50, NPT/BSP, PN16; (ii) small, compact, low cost; (iii) this flanged = easier install/remove for DN50+, higher structural strength; (e) Brass wafer check valve: (i) DN50-300, wafer clamp, ultra-short; (ii) lightweight, space-saving; (iii) this flanged = standalone body, more robust, easier maintenance, higher PN; (f) Dual-plate wafer check valve: (i) spring-loaded dual plates, fast close, any orientation; (ii) for high cycle, water hammer reduction; (iii) this swing/lift = simpler, lower cost, easier repair; (g) This valve: brass + flanged + swing/lift + soft seal + PN16 + general water/oil/gas; (h) key difference: this = brass body, flanged ends, automatic one-way, swing/lift, soft seal, PN16, cost-effective general-purpose. Working principle (detailed): (a) forward flow: medium pressure acts on disc → overcomes gravity/spring → disc opens (swing: clapper swings up; lift: disc lifts vertically); (b) full open: disc held open by flow pressure, minimum flow resistance; (c) flow stops/reverses: forward pressure drops → gravity/spring/reverse pressure → disc closes onto seat; (d) closed: disc pressed on seat by reverse pressure → tight seal, no backflow; (e) cracking pressure: 0.02-0.05MPa (minimum forward pressure to open); (f) no external energy - fully automatic. Swing type (detailed): (a) structure: clapper disc hinged on pin at top of body, swings open/closed; (b) flow: low resistance (disc swings fully out of flow path at high flow); (c) install: horizontal (preferred) or vertical with upward flow (not recommended for vertical downward - disc may not close properly); (d) size: DN50-200 (common), can be larger; (e) maintenance: hinge pin lubrication, disc/seat inspect; (f) water hammer: swing type can cause water hammer on fast reverse flow (slow close) - use dual-plate or silent check for critical. Lift type (detailed): (a) structure: piston-style disc in guide, lifts vertically off seat; (b) flow: slightly higher resistance than swing (disc partially in flow path); (c) install: any orientation (horizontal, vertical upward - gravity helps close; vertical downward - spring needed); (d) size: DN15-50 (small, compact); (e) seal: tighter than swing (positive seat contact); (f) maintenance: disc guide clean, spring inspect (if spring-loaded). Seal materials (detailed): (a) NBR (nitrile): (i) water, oil, gasoline, ≤80°C; (ii) most common, low cost; (b) EPDM: (i) hot water, steam (low pressure), ozone, ≤120°C; (ii) HVAC, hot water; (c) PTFE: (i) chemicals, corrosive, high temp ≤180°C; (ii) low friction, long life; (d) metal-to-metal (bronze/SS): (i) high temp, abrasive, ≤200°C; (ii) higher leakage (Class III/IV); (e) select per medium + temp. Brass materials (detailed): (a) C37700 (forging brass, lead-free): (i) excellent forging, corrosion resistant, lead-free (potable water); (ii) NSF/ANSI 61, WRAS compatible; (b) C36000 (free-cutting brass): (i) excellent machinability, good corrosion; (ii) contains lead (~3%) - not for potable water; (c) H62 (Chinese standard, 62% Cu): (i) good strength, corrosion, low cost; (ii) general industrial; (d) DZR brass (dezincification resistant): (i) for aggressive water (soft, acidic), long life; (e) select per application (potable water = C37700 lead-free; industrial = C36000/H62; aggressive water = DZR). Temp/pressure ratings: (a) PN16 (16 bar / 232 psi) - body rating; (b) working pressure: ≤16 bar at ≤80°C (NBR), derate at higher temp; (c) temp: -20~180°C (per seal: NBR≤80, EPDM≤120, PTFE≤180); (d) steam: low-pressure saturated steam ≤180°C (PTFE/EPDM); (e) not for high-pressure steam (>16 bar), high-temp (>180°C), corrosive chemicals (use SS). Connections: (a) flange RF (raised face, standard for PN16); (b) flange FF (flat face, for cast iron piping / low pressure); (c) standards: GB/T 9113, HG/T 20592, ANSI B16.5 Class 125/150, EN 1092-1 PN16, JIS B2220 10K/16K; (d) gasket: rubber sheet, spiral-wound, PTFE (per medium). Testing: (1) hydro shell 1.5×PN (24 bar); (2) seat leakage 1.1×PN (zero leakage soft seal, Class III/IV metal); (3) visual/dimensional; (4) material cert; (5) optional: NSF/WRAS (potable water), fire-safe. Installation: (a) flow direction: arrow on body = permitted flow direction (install with arrow pointing to downstream); (b) swing type: horizontal preferred, actuator (hinge) at top; (c) lift type: any orientation (vertical upward best for gravity close); (d) near pump outlet: install ≥5D after pump (reduce turbulence/water hammer); (e) strainer upstream (protect seat from debris); (f) isolation valves both sides (for maintenance); (g) avoid installing directly before elbow/tee (turbulence); (h) vertical pipe: lift type or spring-loaded swing (gravity may not close standard swing). Maintenance: (a) annual: visual leak, seat leakage test, disc/seat inspect, hinge pin lubricate (swing), spring inspect (lift); (b) 3-5yr: replace seal (NBR/EPDM aging), replace hinge pin/bushing (swing), clean body; (c) spares: seal ring, disc, hinge pin, spring, gasket. Troubleshooting: (a) leakage (backflow): seat worn/debris → clean/lap/replace; disc damaged → replace; wrong flow direction → reverse; (b) noisy/vibration: water hammer (fast reverse flow) → install silent check/dual-plate, add air chamber; disc fluttering (low flow, near cracking pressure) → size correctly; (c) won't open: forward pressure too low (<cracking), disc stuck (debris/corrosion) → clean; (d) won't close: hinge pin seized (swing) → lubricate/replace; disc guide blocked (lift) → clean; spring broken (lift) → replace; (e) external leak: gasket → replace; body crack → replace valve; (f) high pressure drop: oversized (disc not fully open? no - check if valve is correct size, strainer clogged). Important: (a) automatic one-way (no external energy); (b) brass body (corrosion resistant, low cost, antimicrobial); (c) swing (DN50+, horizontal, low ΔP) / lift (DN15-50, any orientation, tight seal); (d) soft seal NBR/EPDM/PTFE (bubble-tight); (e) flanged GB/ANSI/EN/JIS; (f) DN15-200, PN16, -20~180°C; (g) lead-free option for potable water; (h) not for high pressure (>PN16), high temp (>180°C), corrosive chemicals (use SS/cast steel); (i) warranty: 18 months. With proper type (swing/lift), seal material, orientation, installation, and maintenance, this brass flange check valve provides reliable cost-effective backflow prevention.

1.Automatic One-Way Backflow Prevention

Fully automatic self-actuated operation - no external actuator, electricity, compressed air, or operator required. The disc opens by forward medium pressure (cracking pressure 0.02-0.05MPa) and closes instantly by gravity, spring force, or reverse pressure when flow stops/reverses. Reliable zero backflow protection for pumps, equipment, and pipelines. Instant response, simple and dependable.

2.Forged Brass Body - Corrosion Resistant & Cost-Effective

Precision-forged brass body (C37700 lead-free / C36000 free-cutting / H62) - excellent corrosion resistance to water, mild acids/alkalis, oils, and gases; good dezincification resistance; antimicrobial properties (inhibits bacterial growth in water); high thermal conductivity; excellent machinability; 30-60% lower cost than stainless steel. Lead-free C37700 option for potable water (NSF/WRAS compatible). DZR brass option for aggressive water.

3.Swing or Lift Type - Two Structural Options

Swing Check Valve (DN50+, standard): hinged clapper disc swings fully out of flow path - low flow resistance, large flow capacity, ideal for horizontal pipelines. Lift Check Valve (DN15-50): piston-style disc lifts vertically - tight positive sealing, compact, installs in any orientation (horizontal/vertical). Select per DN, pipeline orientation, and sealing requirement.

4.Soft Seal - Bubble-Tight Zero Leakage

NBR (nitrile, water/oil ≤80°C), EPDM (hot water/steam ≤120°C), or PTFE (chemicals/corrosive ≤180°C) soft seal on disc/seat - ensures bubble-tight shutoff (zero backflow leakage) per API 598. Optional stainless steel (304/316) or bronze hard-faced trim for abrasive/high-cycle service. Seal matched to medium and temperature.

5.Standard Flanged Ends - Easy Install & Interchangeable

Flanged ends (raised face RF or flat face FF) per GB/T 9113, HG/T 20592, ANSI B16.5 (Class 125/150), EN 1092-1 (PN16), JIS B2220 (10K/16K). Face-to-face per GB/T 12221, EN 558, API 594 - fully interchangeable with standard check valves. Easy installation, removal, and maintenance in standard flanged piping. Gasket: rubber/spiral-wound/PTFE.

6.Wide Range + Standards + Quality

DN15–200 (1/2"–8"), PN16 (Class 125/150), temp -20~180°C (per seal). Designed per GB/T 12235, API 594, EN 12334; tested per API 598, GB/T 13927 (shell 1.5×PN, seat 1.1×PN, 100% tested). ISO 9001, CE; NSF/WRAS optional (potable water). Compact, lightweight, low maintenance. 18-month warranty, OEM/ODM.

A Brass Flange Check Valve operates as an automatic, self-actuated one-way (non-return) valve - it requires no external actuator, electricity, compressed air, or operator; the valve disc is driven solely by the pressure and flow direction of the medium itself: when medium flows in the permitted forward direction (matching the arrow cast on the valve body), the forward pressure acts on the disc and overcomes the closing force (gravity for swing type, gravity+spring for lift type), pushing the disc open - the disc swings up (swing type) or lifts vertically (lift type), allowing unobstructed forward flow; when flow stops or reverses, the forward pressure drops, and the gravity, spring, or reverse pressure drives the disc back onto the seat, closing the valve and preventing any reverse flow (backflow) - this mechanical, automatic, direction-sensitive operation provides reliable backflow prevention without any external energy input. The valve consists of a brass valve body (with inlet, outlet, seat, hinge pin for swing type / guide for lift type), a disc (clapper for swing, piston for lift), a seal (NBR/EPDM/PTFE on disc or seat), a hinge pin (swing type) or spring (lift type, optional), and flanged ends for pipeline connection. Swing type operation (detailed - DN50+): (a) structure: clapper disc hinged on a horizontal pin at the top of the body interior; (b) forward flow: medium pressure pushes the bottom of the clapper → clapper swings upward around the hinge pin → fully open (clapper rests against the body top, out of flow path); (c) flow stops/reverses: gravity pulls the clapper down → swings back onto the seat → closes; (d) reverse pressure: presses the clapper firmly onto the seat → tight seal; (e) flow resistance: very low (clapper fully out of flow at high flow, Cv high); (f) installation: horizontal preferred (hinge pin at top, gravity assists closing); vertical with upward flow possible (but closing relies on reverse pressure, less reliable); vertical downward NOT recommended (clapper may stay open); (g) water hammer: swing type closes relatively slowly (clapper must swing down) - on fast reverse flow (e.g., pump trip), the clapper may slam shut causing water hammer; for critical applications, use spring-loaded swing, silent check, or dual-plate check; (h) size: DN50-200 (and larger in cast iron/steel). Lift type operation (detailed - DN15-50): (a) structure: piston-style disc with a stem that slides in a vertical guide above the seat; optional spring assists closing; (b) forward flow: medium pressure pushes the disc upward → disc lifts off the seat → flow passes through the annular area; (c) flow stops/reverses: gravity (and spring, if equipped) pushes the disc down → drops onto the seat → closes; (d) reverse pressure: presses disc onto seat → tight seal; (e) flow resistance: slightly higher than swing (disc and guide partially in flow path, but acceptable for small DN); (f) installation: any orientation (horizontal, vertical upward - gravity helps; vertical downward - spring required for reliable closing); (g) sealing: tighter than swing (positive vertical seat contact, no hinge wear); (h) size: DN15-50 (small, compact). Force balance (detailed): (a) opening force = P_forward × A_disc (medium pressure × disc area); (b) closing force = gravity (disc weight) + spring force (if lift type) + friction; (c) at cracking: P_forward × A = closing force → disc starts to open (cracking pressure 0.02-0.05MPa); (d) full open: P_forward × A >> closing → disc held open; (e) closing: P_forward drops → closing force > opening → disc closes; (f) reverse: P_reverse × A adds to closing → tight seal. Sealing mechanism (detailed): (a) soft seal: NBR/EPDM/PTFE ring on disc or seat - when disc closes, rubber/PTFE compresses against mating surface → elastic deformation fills micro-gaps → zero leakage (bubble-tight, Class VI); (b) metal-to-metal: bronze/SS disc on bronze/SS seat - metal contact, higher leakage (Class III/IV), for high temp/abrasive; (c) seat angle: 45° or 90° (per design) - ensures proper alignment and contact; (d) replaceable seat: some designs have replaceable seat ring (easy maintenance); (e) disc guide: ensures disc aligns with seat every time (no side load). Cracking pressure and flow: (a) cracking pressure: minimum forward pressure to start opening (0.02-0.05MPa, 3-7 psi); (b) full open pressure: typically 0.1-0.2MPa above cracking (disc fully lifted); (c) pressure drop (ΔP): at rated flow, ΔP = 0.02-0.1MPa (swing lower, lift slightly higher); (d) flow coefficient (Cv): per DN (swing higher than lift for same DN); (e) minimum flow: if flow too low, disc may flutter (vibrate) - size correctly so normal flow = 30-80% of rated. Water hammer (detailed): (a) cause: fast reverse flow (pump trip, valve closure upstream) → check valve disc slams shut → pressure spike (water hammer); (b) swing type: more prone (slow close, large disc mass); (c) prevention: (i) install closer to pump outlet (shorter reverse column); (ii) use spring-loaded check (faster close); (iii) use silent/dual-plate check; (iv) add air chamber/surge tank; (v) slow pump shutdown; (d) lift type: less water hammer (smaller disc, spring-assisted fast close). Automatic operation advantages: (a) no external energy - works during power failure; (b) instant response - closes immediately on reverse flow; (c) no operator - fully automatic; (d) simple - few moving parts, low maintenance; (e) reliable - mechanical, no electronics to fail. Installation orientation (detailed): (a) swing type: (i) horizontal (preferred): hinge pin horizontal, disc swings in vertical plane, gravity closes reliably; (ii) vertical upward flow: possible (disc swings open upward, gravity + reverse close); (iii) vertical downward flow: NOT recommended (disc may stay open, no gravity assist); (iv) inclined: acceptable if hinge at top; (b) lift type: (i) horizontal: OK (gravity closes); (ii) vertical upward: best (gravity + reverse close); (iii) vertical downward: need spring-loaded (gravity works against closing); (iv) any orientation with spring; (c) always: flow arrow = permitted direction, install with arrow pointing downstream. Near pump installation: (a) location: install on pump discharge, ≥3-5D after pump outlet (reduce turbulence); (b) purpose: prevent reverse flow when pump stops (protects pump from reverse rotation, water hammer); (c) isolation valve: install gate/ball valve after check (for maintenance); (d) strainer: before pump (protect pump + check seat). Testing (detailed): (a) hydro shell: 1.5×PN (24 bar for PN16), hold, no body/gasket leak; (b) seat leakage: 1.1×PN from reverse side, measure leak (soft seal = zero bubbles, metal = ≤Class IV); (c) cracking pressure: verify 0.02-0.05MPa; (d) full open: verify disc opens fully at rated flow; (e) visual/dimensional: flange, face-to-face, wall thickness; (f) material: brass composition cert (lead content for potable). Maintenance (detailed): (a) annual: (i) external leak check; (ii) seat leakage test (isolate, pressurize reverse); (iii) disc/seat inspect (remove bonnet/cap); (iv) hinge pin lubricate (swing type - food-grade grease for potable); (v) spring inspect (lift type); (vi) clean body interior (debris, scale); (b) 3-5yr: (i) replace seal ring (NBR/EPDM aging, even if looks OK); (ii) replace hinge pin + bushing (swing - wear); (iii) replace spring (lift - fatigue); (iv) replace gaskets; (v) full hydro + seat test; (c) spares: seal ring, disc assembly, hinge pin, spring, gaskets. Troubleshooting (detailed): (a) backflow leakage: (i) seat worn/scored → lap or replace seat; (ii) disc seal damaged → replace seal; (iii) debris on seat → clean; (iv) disc not seating (hinge worn, swing) → replace hinge pin/bushing; (v) wrong flow direction → reverse installation (check arrow); (b) noisy/vibration/chatter: (i) water hammer (fast reverse) → silent check, air chamber, slow pump stop; (ii) disc flutter (low flow, near cracking) → size correctly, minimum flow; (iii) loose hinge pin → tighten/replace; (iv) cavitation (high ΔP liquid) → reduce ΔP, use anti-cavitation trim; (c) won't open: (i) forward pressure < cracking → increase pressure or check supply; (ii) disc stuck (debris/corrosion) → clean, lubricate; (iii) hinge seized (swing) → replace pin/bushing; (d) won't close: (i) hinge pin seized (swing) → lubricate/replace; (ii) disc guide blocked (lift) → clean; (iii) spring broken (lift) → replace; (iv) wrong orientation (swing vertical down) → reorient; (e) external leak: (i) flange gasket → replace, retorque; (ii) body crack → replace valve (brass crack from freeze/overpressure); (iii) bonnet cap gasket → replace; (f) high pressure drop: (i) valve undersized → size up; (ii) strainer clogged → clean; (iii) disc not fully open (low pressure) → check forward pressure; (g) brass corrosion/dezincification: (i) aggressive water (soft, acidic) → use DZR brass or SS; (ii) replace valve if dezincified (porous, weak). Safety notes: (a) not for high pressure (>PN16), high temp (>180°C), corrosive chemicals (use SS/cast steel); (b) potable water: use lead-free C37700 + NSF/WRAS certified; (c) freeze protection: drain valve in freezing ambient (water expands, cracks brass); (d) isolate before maintenance (close isolation valves both sides, depressurize); (e) steam: use PTFE/EPDM seal, low-pressure steam only; (f) gas: ensure leak-tight, test with soapy water. Important: (a) automatic one-way (forward pressure opens, gravity/spring/reverse closes); (b) swing (DN50+, horizontal, low ΔP) / lift (DN15-50, any orientation, tight seal); (c) brass body (corrosion resistant, low cost, antimicrobial); (d) soft seal NBR/EPDM/PTFE (bubble-tight); (e) flanged GB/ANSI/EN/JIS; (f) DN15-200, PN16, -20~180°C; (g) install with flow arrow pointing downstream; (h) swing = horizontal preferred, lift = any orientation; (i) warranty: 18 months. With proper type, seal, orientation, installation, and maintenance, this brass flange check valve provides reliable cost-effective backflow prevention.

• Water Supply & Drainage

Backflow prevention in municipal water supply pipelines, building water systems, water distribution networks, and drainage systems. Installed after pumps and at pipeline junctions to prevent reverse flow and water contamination. Lead-free C37700 brass option for potable water (NSF/WRAS compatible). NBR seal for cold water, EPDM for hot water. Reliable, corrosion-resistant, antimicrobial brass for water service.

• HVAC & Heating

Hot water heating systems, chilled water cooling systems, boiler feed lines, and heat exchanger circuits. Prevents reverse circulation when pumps stop, protects boilers and chillers from backflow. EPDM seal for hot water (≤120°C), PTFE for higher temp. Swing type for large DN horizontal mains, lift type for small branch lines. Essential for HVAC system protection and efficiency.

• Fire Protection

Fire sprinkler systems, fire pump discharge lines, standpipe systems, and fire hydrant connections. Prevents reverse flow from fire protection systems into domestic water supply (backflow prevention required by code). Brass body corrosion resistant, reliable automatic operation, tested to fire protection standards. Installed after fire pumps and at cross-connections. Critical for fire safety compliance.

• Oil & Gas / Industrial

Light oil pipelines, compressed air systems, natural gas low-pressure lines, lubrication systems, and general industrial fluid lines. NBR seal for oil/gasoline (≤80°C), brass body resistant to oil and mild hydrocarbons. Prevents reverse flow in pump discharge lines, protects pumps and equipment. Swing type for large DN, low pressure drop. Reliable for industrial fluid control.

• Water Treatment & Irrigation

Water treatment plants (filtration, reverse osmosis, disinfection), sewage treatment, agricultural irrigation systems, and landscape irrigation. Prevents backflow of treated/untreated water, chemicals, and fertilizers into clean water supply. Brass corrosion resistant to water and mild chemicals. PTFE seal for chemical dosing lines. Essential for water treatment integrity and irrigation system protection. 18-month warranty, OEM/ODM.

Our Brass Flange Check Valves are manufactured under an ISO 9001:2015 certified quality management system, with every valve undergoing rigorous inspection and testing at each production stage - because these valves are automatic backflow prevention devices used in water supply, HVAC, fire protection, oil & gas, water treatment, municipal where reliable zero-leakage shutoff, brass material quality (corrosion/dezincification resistance, lead content for potable water), disc/seat sealing, hinge pin/guide function, and flange dimensional interchangeability directly determine backflow prevention effectiveness, pump/equipment protection, water safety, and system reliability.

Raw material control: every brass body/disc/stem/hinge pin material batch comes with material certificate; C37700 verified (lead-free, Cu ≥60%, Pb ≤0.25%, forging quality); C36000 verified (free-cutting, Cu 60-63%, Pb 2.5-3.7%); H62 verified (Cu 60.5-63.5%, Zn balance); DZR brass verified (dezincification resistant, As added); stainless steel trim (304/316) verified; seal NBR/EPDM/PTFE verified (material cert, hardness, temp rating); lead content tested (for potable water valves, ≤0.25% weighted average per NSF/ANSI 61).

Body manufacturing: (a) forging (hot forging from brass billet - grain flow aligned, no porosity, high density); (b) heat treatment (stress relief); (c) 100% visual (surface defects, forging laps, cracks); (d) machining (flange faces, seat bore, hinge pin hole, guide bore - CNC, Ra≤3.2 flange, Ra≤1.6 seat); (e) chemical composition per heat (spectrometer); (f) hardness (HB 80-120 for brass); (g) wall thickness verified (per standard, minimum for PN16); (h) surface treatment - pickled/cleaned (brass natural finish, optional nickel plating for decorative); (i) nameplate/body marking (cast arrow for flow direction, DN, PN, material, standard, year).

Disc/trim manufacturing: (a) brass disc forged/machined, seal groove precision machined; (b) stainless/bronze disc (optional) machined, hard-faced if required; (c) seal ring (NBR/EPDM/PTFE) - molded, 100% inspect (dimensional, visual, no defects); (d) seat - integral (machined in body) or replaceable ring (brass/SS with seal); (e) hinge pin (swing type) - brass/SS, precision ground, lubrication groove; (f) spring (lift type) - 304 SS, calibrated; (g) assembly: disc + seal + pin (swing) / disc + seal + spring + guide (lift), verify smooth movement (no bind), full stroke.

Assembly & functional test: (a) assemble body + disc + seal + pin/spring + bonnet/cap; (b) cracking pressure test: apply forward pressure, verify disc opens at 0.02-0.05MPa; (c) full open test: at 0.2MPa forward, verify disc fully open (no sticking); (d) closing test: release pressure, verify disc closes (gravity/spring); (e) reverse flow test: apply reverse pressure, verify no leak at seat; (f) hinge pin (swing): smooth swing, no excessive play; (g) disc guide (lift): smooth lift, no bind.

Testing - 100% every valve: (1) hydrostatic shell - 1.5×PN (24 bar for PN16), hold 1 min, body/gasket/bonnet no leak; (2) seat leakage - 1.1×PN (17.6 bar) from reverse side, soft seal = zero bubbles (bubble-tight), metal seal ≤Class IV; (3) cracking pressure - 0.02-0.05MPa (record); (4) full open function - disc opens fully, no sticking; (5) closing function - disc closes by gravity/spring; (6) dimensional - flange OD, bolt circle, face-to-face, wall thickness; (7) material cert + lead content (potable water); (8) visual (surface, marking, flow arrow).

Potable water certification (optional): (a) NSF/ANSI 61 (drinking water system components - health effects); (b) WRAS (UK Water Regulations Advisory Scheme); (c) ACS (French); (d) KTW (German); (e) lead-free: C37700 brass, ≤0.25% Pb; (f) test: material extraction, lead leaching.

Material traceability: unique serial/lot; database: material cert (body brass, trim, seal), heat, forging, machining, hydro, seat leakage, cracking pressure, function, dimensional, lead content (if potable), production, inspector, DN, PN, type (swing/lift), seal material, body material, order.

Coating & marking: brass natural finish (pickled/cleaned), optional nickel plating (decorative/corrosion); valve cast/engraved: model, brass flange check valve, DN, PN, flow direction arrow (critical), material (C37700/C36000/H62), seal material, standard, year, manufacturer; flange face marked (RF/FF).

Documentation: test report (hydro, seat leakage, cracking pressure, function, dimensional), material cert (brass composition, lead content), dimensional drawing, manual (installation, flow direction, orientation, maintenance, troubleshooting, seal replacement, spares), CE/ISO cert, NSF/WRAS cert (if potable water option).

Warranty: 18 months from shipment or 12 months from installation (whichever comes first); wear parts (seal ring, hinge pin, spring, gaskets) not covered under normal wear; freeze damage (water freezing in valve, cracking brass body) not covered; corrosion from improper medium (aggressive water without DZR, strong chemicals) not covered; extended warranty, spare parts kit available.

Safety/performance commitment: (a) no valve ships without 100% hydro + seat leakage + cracking pressure + function test; (b) brass material certified (composition, lead content); (c) flow arrow clearly marked (cast on body); (d) soft seal zero leakage (bubble-tight); (e) potable water option lead-free + NSF/WRAS; (f) face-to-face interchangeable (GB/ANSI/EN/JIS); (g) sizing guidance provided (Cv, ΔP, swing vs lift, orientation); (h) material traceable.

Q: What's the difference between swing type and lift type brass flange check valve, and how do I choose?

A: The two types differ in structure, flow resistance, installation orientation, sealing, and typical size range: Swing Check Valve (DN50 and above, standard for larger sizes) uses a hinged clapper disc that swings open/closed around a horizontal pin - it offers very low flow resistance (clapper swings fully out of the flow path at high flow), large flow capacity (high Cv), and is preferred for horizontal pipelines; Lift Check Valve (DN15–50, small sizes) uses a piston-style disc that lifts vertically off the seat under forward flow and drops back by gravity/spring - it offers tighter positive sealing, compact size, and can be installed in any orientation (horizontal or vertical with upward flow). Choose based on DN, pipeline orientation, flow resistance requirement, and sealing need. Here's the detailed comparison. Swing type (detailed): (a) structure: clapper disc hinged on horizontal pin at top of body; (b) opening: forward pressure pushes clapper bottom → swings up around pin → fully open (clapper rests against body top, completely out of flow path); (c) closing: gravity pulls clapper down → swings onto seat; reverse pressure adds force; (d) flow resistance: very low (Cv high, ΔP low - clapper out of flow at full open); (e) installation: (i) horizontal (preferred, hinge pin horizontal, gravity closes reliably); (ii) vertical upward flow (possible, but closing relies on reverse pressure - less reliable); (iii) vertical downward flow (NOT recommended - clapper may stay open, gravity works against closing); (iv) inclined (acceptable if hinge at top); (f) size: DN50-200 (common in brass; larger in cast iron/steel); (g) sealing: good (soft seal on clapper), but hinge wear can cause slight misalignment over time; (h) water hammer: more prone (large clapper mass, slow close - slams on fast reverse flow); (i) maintenance: hinge pin lubrication, bushing replacement; (j) best for: large DN, horizontal pipelines, low pressure drop requirement, high flow, water/oil/gas mains. Lift type (detailed): (a) structure: piston-style disc with stem sliding in vertical guide; optional spring assists closing; (b) opening: forward pressure pushes disc up → lifts off seat → flow through annular area; (c) closing: gravity (and spring) pushes disc down → onto seat; reverse pressure adds; (d) flow resistance: slightly higher than swing (disc and guide partially in flow path - but acceptable for small DN≤50); (e) installation: (i) horizontal (OK, gravity closes); (ii) vertical upward (best - gravity + reverse pressure close); (iii) vertical downward (need spring-loaded - gravity works against closing); (iv) any orientation with spring; (f) size: DN15-50 (small, compact); (g) sealing: tighter than swing (positive vertical seat contact, no hinge wear, disc self-aligns); (h) water hammer: less prone (smaller disc mass, spring-assisted fast close); (i) maintenance: disc guide cleaning, spring inspection; (j) best for: small DN, any orientation (especially vertical), tight sealing requirement, compact space, branch lines. Comparison summary: | Feature | Swing Type | Lift Type | |---|---|---| | Structure | Hinged clapper disc | Piston-style vertical lift disc | | DN range | DN50–200 (brass) | DN15–50 | | Flow resistance | Very low (clapper out of flow) | Slightly higher (disc in flow path) | | Cv / flow capacity | High | Medium | | Installation | Horizontal preferred (not vertical down) | Any orientation (with spring for vertical down) | | Sealing | Good (soft seal) | Tighter (positive seat contact) | | Water hammer | More prone (large mass, slow close) | Less (small mass, spring fast close) | | Maintenance | Hinge pin + bushing | Disc guide + spring | | Cost | Slightly higher (hinge mechanism) | Lower (simpler) | | Best for | Large DN, horizontal mains, low ΔP, high flow | Small DN, any orientation, tight seal, compact | How to choose: (a) by DN: (i) DN≤50 → lift type (standard, compact, any orientation); (ii) DN≥50 → swing type (standard, low ΔP); (iii) DN50 can be either (choose by orientation/sealing); (b) by pipeline orientation: (i) horizontal → either (swing preferred for DN≥50); (ii) vertical upward → either (lift preferred, swing possible); (iii) vertical downward → lift type with spring (swing NOT recommended); (iv) inclined → swing (if hinge at top) or lift; (c) by flow resistance: (i) low ΔP required (pump discharge, large mains) → swing; (ii) moderate ΔP OK → lift; (d) by sealing: (i) tight zero-leak critical → lift (positive seal); (ii) general → swing; (e) by water hammer risk: (i) fast pump trip, long pipeline → lift or spring-loaded swing/silent check; (ii) general → swing; (f) by space: compact/limited → lift (smaller body); (g) we recommend based on DN, orientation, medium, ΔP, water hammer risk. DN50 overlap zone: (a) both types available at DN50; (b) choose swing if: horizontal, low ΔP, high flow, large main; (c) choose lift if: any orientation (vertical), tight seal, compact, water hammer concern; (d) we can supply either - specify at order. Spring-loaded option: (a) both swing and lift can be spring-loaded (spring assists closing); (b) benefits: (i) faster closing (less water hammer); (ii) reliable closing in any orientation (including vertical downward); (iii) lower cracking pressure consistency; (c) cost: slightly higher; (d) recommended for: vertical pipelines, critical backflow prevention, water hammer-prone systems. Common mistakes: (a) using swing type in vertical downward pipeline (clapper stays open → no backflow prevention - use lift with spring); (b) using lift type for DN>50 (higher ΔP, not standard - use swing); (c) installing against flow arrow (valve always closed - reverse arrow); (d) no strainer upstream (debris damages seat - add strainer); (e) ignoring water hammer (pump trip with swing type → use spring-loaded/silent check). Important: (a) swing: DN50+, horizontal, low ΔP, high flow, more water hammer; (b) lift: DN15-50, any orientation, tight seal, less water hammer; (c) choose by DN first (≤50 lift, ≥50 swing), then orientation/sealing/ΔP; (d) spring-loaded option for vertical/critical; (e) flow arrow = permitted direction (install correctly); (f) we recommend based on your parameters. This valve = the swing type (DN50–200, standard for larger sizes) has a hinged clapper disc that swings fully out of the flow path - it offers very low flow resistance and high flow capacity but is preferred for horizontal pipelines (not recommended for vertical downward flow where gravity works against closing) and can be more prone to water hammer on fast reverse flow due to the large clapper mass and slower closing; the lift type (DN15–50, small sizes) has a piston-style disc that lifts vertically - it offers tighter positive sealing, compact size, and installation in any orientation (horizontal or vertical, with a spring option for vertical downward) but has slightly higher flow resistance due to the disc and guide being partially in the flow path; selection is primarily by DN: DN≤50 → lift type (standard, compact, any-orientation), DN≥50 → swing type (standard, low pressure drop, high flow), with DN50 as an overlap zone where either can be chosen based on orientation (lift for vertical/any orientation, swing for horizontal), sealing requirement (lift for tighter seal), and water hammer risk (lift/spring-loaded for pump-trip-prone systems); both types can be spring-loaded (optional) for faster closing, reliable operation in any orientation including vertical downward, and reduced water hammer; both use the same brass body, flanged ends, soft seal (NBR/EPDM/PTFE), and PN16 rating - the only difference is the disc mechanism; provide your DN, pipeline orientation (horizontal/vertical), medium, and flow rate/pressure drop requirement and we confirm whether swing or lift type is correct (and whether spring-loading is recommended).

Q: What brass material should I choose, and is lead-free available for potable water?

A: We offer three main brass materials plus a dezincification-resistant option: C37700 lead-free forging brass (Cu≥60%, Pb≤0.25%, best for potable water, NSF/WRAS compatible), C36000 free-cutting brass (Cu60-63%, Pb2.5-3.7%, best machinability, for industrial non-potable), H62 Chinese standard brass (Cu60.5-63.5%, general industrial, low cost), and DZR (dezincification-resistant) brass (for aggressive/soft/acidic water). Lead-free C37700 is required for potable/drinking water and can be certified to NSF/ANSI 61, WRAS, ACS, KTW; C36000/H62 are for industrial water, oil, gas, HVAC where lead content is not regulated. Here's the detailed guide. Brass material options (detailed): (a) C37700 (lead-free forging brass): (i) composition: Cu 60-63%, Pb ≤0.25%, Fe ≤0.3%, Zn balance; (ii) features: excellent forgeability, good corrosion resistance, lead-free (safe for drinking water), good strength; (iii) use: potable water, food/beverage, plumbing, medical gas; (iv) certification: NSF/ANSI 61, WRAS, ACS, KTW compatible; (v) cost: slightly higher than C36000; (b) C36000 (free-cutting brass): (i) composition: Cu 60-63%, Pb 2.5-3.7%, Fe ≤0.35%, Zn balance; (ii) features: excellent machinability (lead acts as lubricant), good corrosion resistance, good strength, lower cost; (iii) use: industrial water, oil, gas, HVAC, compressed air, general fluid (NOT potable water due to lead); (iv) certification: general industrial; (v) cost: lower than C37700; (c) H62 (Chinese standard brass): (i) composition: Cu 60.5-63.5%, Pb ≤0.08% (unwittingly low lead, but not certified lead-free), Zn balance; (ii) features: good strength, corrosion resistance, low cost, common in Chinese market; (iii) use: general industrial, water (non-potable), oil, gas; (iv) certification: GB standard; (v) cost: lowest; (d) DZR brass (dezincification resistant): (i) composition: Cu ~60%, Pb ≤0.25%, As 0.08-0.15% (arsenic inhibits dezincification), Zn balance; (ii) features: resists dezincification (zinc leaching) in aggressive water (soft, acidic, low mineral), long life; (iii) use: aggressive water, seawater (mild), hot water systems, regions with corrosive water; (iv) certification: dezincification test (ISO 6509), WRAS; (v) cost: higher. How to choose brass material: (a) potable/drinking water: (i) C37700 lead-free (required by code in US/EU/China); (ii) add NSF/WRAS certification if needed; (iii) seal: EPDM/PTFE (food-grade); (b) hot water / HVAC: (i) C37700 (if potable hot water) or C36000/H62 (if closed HVAC loop, non-potable); (ii) DZR if aggressive water; (iii) seal: EPDM (≤120°C) or PTFE; (c) industrial water (non-potable): (i) C36000 or H62 (lower cost); (ii) DZR if aggressive/soft water; (d) oil / gasoline / compressed air / natural gas: (i) C36000 or H62 (industrial, lead not an issue); (ii) seal: NBR (oil/gas ≤80°C); (e) aggressive water (soft, acidic, low pH): (i) DZR brass (prevents dezincification); (ii) or consider stainless steel (304/316) if very aggressive; (f) seawater / marine: (i) DZR (mild) or bronze/SS (better - brass can corrode in seawater long-term); (g) chemical / corrosive: (i) brass NOT recommended for strong acids/alkalis/chlorides; (ii) use stainless steel (CF8/CF8M) or plastic-lined. Lead-free requirement (detailed): (a) why lead-free: lead is toxic, leaches into water, regulated for drinking water; (b) standards: (i) US: Safe Drinking Water Act - "lead-free" = ≤0.25% weighted average Pb (wetted surfaces); NSF/ANSI 61 certification; (ii) EU: Drinking Water Directive - lead ≤10μg/L; WRAS (UK), ACS (France), KTW (Germany); (iii) China: GB/T 17219 - drinking water equipment safety; (c) our C37700: Pb ≤0.25%, meets lead-free definition; (d) certification: we can provide NSF/ANSI 61, WRAS (optional, at additional cost/test time); (e) marking: "LF" (lead-free), "NSF/ANSI 61", "WRAS" on body/nameplate if certified. Dezincification (detailed): (a) what: zinc leaches out of brass in aggressive water (soft, acidic, low mineral, high chloride), leaving porous copper (weak, leak); (b) symptoms: valve body porous, white/reddish deposits, leaks, reduced strength; (c) prevention: (i) DZR brass (arsenic added, inhibits dezincification); (ii) avoid brass in very aggressive water (use SS/bronze); (d) test: ISO 6509 dezincification test (max penetration depth); (e) regions: DZR common in UK, Australia, parts of Europe (aggressive water). Brass vs other materials for check valve: (a) brass: (i) pros: corrosion resistant (water), antimicrobial, low cost, lightweight, good machinability, good thermal conductivity; (ii) cons: lower pressure (PN16 max), lower temp (≤180°C), not for strong chemicals, dezincification risk in aggressive water; (b) cast iron: (i) pros: low cost for large DN, high PN; (ii) cons: corrodes/rusts in water, heavy, needs painting; (c) cast steel (WCB): (i) pros: high PN (to PN100), high temp (to 425°C), oil/gas; (ii) cons: corrodes in water, higher cost; (d) stainless steel (CF8/CF8M): (i) pros: corrosion resistant (chemicals/seawater), high temp, hygienic; (ii) cons: 2-5× cost of brass; (e) bronze: (i) pros: marine/corrosion resistant, good for seawater; (ii) cons: higher cost than brass; (f) choose brass for: general water/oil/gas, PN16, ≤180°C, cost-sensitive, antimicrobial benefit. Common mistakes: (a) using C36000 (leaded) for potable water (violates code, health risk - use C37700 lead-free); (b) using standard brass in aggressive water (dezincification - use DZR); (c) using brass for strong chemicals (corrodes - use SS); (d) using brass for >PN16 or >180°C (out of rating - use cast steel/SS); (e) assuming all brass is lead-free (check material cert - C37700 only); (f) no certification for potable water project (require NSF/WRAS at order). Important: (a) C37700 lead-free = potable water (NSF/WRAS optional); (b) C36000/H62 = industrial (non-potable water, oil, gas, HVAC); (c) DZR = aggressive water (dezincification resistant); (d) brass = PN16, ≤180°C, neutral media (not high pressure/temp/corrosive); (e) lead-free required for drinking water (code); (f) we provide material cert + lead content test; (g) tell us medium (potable water? aggressive? chemical?) and region → we recommend brass material + certification. This valve = we offer four brass material options: (1) C37700 lead-free forging brass (Cu≥60%, Pb≤0.25%) - the best choice for potable/drinking water, food/beverage, and medical gas, with optional NSF/ANSI 61, WRAS, ACS, KTW certification (meets US Safe Drinking Water Act "lead-free" definition of ≤0.25% weighted average lead on wetted surfaces); (2) C36000 free-cutting brass (Cu60-63%, Pb2.5-3.7%) - excellent machinability and lower cost, for industrial non-potable water, oil, gasoline, compressed air, natural gas, and HVAC closed loops (NOT for drinking water due to lead content); (3) H62 Chinese standard brass (Cu60.5-63.5%) - general industrial use, lowest cost, for non-potable water/oil/gas; (4) DZR (dezincification-resistant) brass (with ~0.1% arsenic) - for aggressive/soft/acidic/low-mineral water where standard brass would suffer dezincification (zinc leaching leaving porous weak copper), common in UK/Australia/European regions with corrosive water, certified to ISO 6509 dezincification test and WRAS; choose C37700 lead-free for any potable/drinking water application (and specify NSF/WRAS certification if required by your local code), choose C36000 or H62 for industrial non-potable service (lower cost), choose DZR if the water is aggressive/soft/acidic, and note that brass is limited to PN16 and ≤180°C - for higher pressure, higher temperature, or strong corrosive chemicals, use cast steel (WCB) or stainless steel (CF8/CF8M) check valves instead; we provide material certificates and lead-content test reports with every valve, and the lead-free C37700 option is clearly marked "LF" on the body/nameplate - tell us your medium (potable water or industrial), water quality (aggressive/soft or normal), region, and any required certification and we recommend the correct brass material.

Q: What seal material should I choose for my medium and temperature?

A: We offer NBR (nitrile rubber), EPDM, and PTFE soft seals, plus optional metal-to-metal (bronze/stainless steel) for high-temperature/abrasive service: NBR for water, oil, gasoline, and compressed air at ≤80°C (most common, lowest cost); EPDM for hot water, low-pressure steam, ozone, and HVAC at ≤120°C; PTFE for chemicals, corrosive media, and high temperature up to ≤180°C (longest life, lowest friction); metal-to-metal for abrasive media and high temperature up to ≤200°C (higher leakage, Class III/IV). Select based on medium compatibility and maximum working temperature. Here's the detailed guide. Seal material options (detailed): (a) NBR (Nitrile Butadiene Rubber): (i) temp range: -20°C ~ +80°C (continuous), +100°C short-term; (ii) compatible: water, hydraulic oil, gasoline, diesel, lubricating oil, compressed air, natural gas (low pressure), alkalis (dilute); (iii) NOT compatible: gasoline with high aromatic, ozone, strong acids, ketones, chlorinated solvents, brake fluid; (iv) hardness: Shore A 70-80; (v) features: good elasticity, low cost, good abrasion resistance; (vi) use: most common for cold water, oil, gas, general industrial; (b) EPDM (Ethylene Propylene Diene Monomer): (i) temp range: -40°C ~ +120°C (continuous), +150°C short-term; (ii) compatible: hot water, low-pressure steam, ozone, UV, dilute acids/alkalis, polar solvents, ketones, alcohols; (iii) NOT compatible: oil, gasoline, petroleum products, hydrocarbon solvents; (iv) hardness: Shore A 60-75; (v) features: excellent ozone/UV/weather resistance, good for hot water, food-grade option; (vi) use: HVAC hot/chilled water, steam (low pressure), outdoor, food-grade (FDA compatible); (c) PTFE (Polytetrafluoroethylene / Teflon): (i) temp range: -40°C ~ +180°C (continuous), +260°C short-term (but valve body limits to 180°C); (ii) compatible: almost all chemicals (strong acids, alkalis, solvents, chlorine, corrosives), water, oil, gas, steam; (iii) NOT compatible: molten alkali metals, fluorine gas; (iv) hardness: Shore D 50-60 (harder than rubber); (v) features: chemical inert, low friction, no aging, long life, but less elastic (needs higher seating force); (vi) use: chemicals, corrosive media, high temp, long-life no-maintenance; (d) Metal-to-metal (bronze / stainless steel 304/316): (i) temp range: -40°C ~ +200°C (brass body limit); (ii) compatible: abrasive media (sand, slurry), high temp, steam, oil, gas; (iii) leakage: higher (Class III/IV - not bubble-tight); (iv) features: wear resistant, high temp, but leaks; (v) use: abrasive, high cycle, where minor leakage acceptable. Seal selection by medium: (a) cold water (≤40°C): NBR (low cost) or EPDM; (b) hot water (40-120°C): EPDM (best) or PTFE; (c) potable/drinking water: NBR (FDA grade) or EPDM (FDA grade) - specify food-grade; (d) low-pressure steam (≤120°C sat): EPDM (≤120°C) or PTFE (≤180°C); (e) oil / hydraulic oil / lubricant: NBR (≤80°C) or PTFE; (f) gasoline / diesel: NBR (≤80°C, standard grade - not high aromatic); (g) compressed air / natural gas: NBR (≤80°C) or PTFE; (h) ozone / outdoor / UV: EPDM (excellent ozone resistance); (i) chemicals / corrosive (acid/alkali/solvent): PTFE (chemical inert); (j) abrasive (sand/slurry): metal-to-metal (wear resistant) or PTFE (if mild); (k) high temp (120-180°C): PTFE (only option in soft seal); (l) food/beverage: EPDM (FDA) or PTFE (FDA) - specify food-grade. Seal selection by temperature: (a) ≤80°C: NBR (cheapest), EPDM, PTFE; (b) 80-120°C: EPDM, PTFE (NBR NOT recommended); (c) 120-180°C: PTFE only (soft seal); (d) >180°C: metal-to-metal (but brass body limits to ~200°C - consider cast steel/SS valve for higher); (e) note: at higher temp, seal life decreases (even PTFE creeps at 180°C). Seal location/design: (a) seal on disc: NBR/EPDM O-ring or gasket in disc groove (most common, replaceable); (b) seal on seat: PTFE/bronze ring pressed into body seat (replaceable); (c) both: disc seal + seat seal (double seal, tighter); (d) replaceable: all seals designed for replacement (no need to replace whole valve); (e) spares: seal ring available as spare part. Seal life: (a) NBR: 3-5 years (rubber aging, even if unused - ozone/heat); (b) EPDM: 5-8 years (better ozone/heat); (c) PTFE: 10+ years (no aging, but may cold-flow at high temp/pressure); (d) metal: 5-10 years (wear dependent); (e) replace at scheduled maintenance, or if leakage detected. Common mistakes: (a) using NBR for hot water >80°C (NBR hardens/cracks - use EPDM/PTFE); (b) using EPDM for oil/gasoline (EPDM swells/dissolves in hydrocarbons - use NBR/PTFE); (c) using NBR for outdoor/ozone (NBR ozone-cracks - use EPDM); (d) using rubber seal for >180°C (melts/degrades - use PTFE or metal); (e) using soft seal for abrasive media (wears fast - use metal/PTFE); (f) not replacing aged NBR (3-5yr - even if looks OK, rubber hardens); (g) using non-food-grade seal for potable water/food (require FDA/NSF seal). Important: (a) NBR: water/oil/gas, ≤80°C, low cost; (b) EPDM: hot water/steam/ozone, ≤120°C, outdoor; (c) PTFE: chemicals/corrosive/high temp, ≤180°C, long life; (d) metal: abrasive/high temp, ≤200°C, higher leakage; (e) select by medium + temp (temp is often limiting); (f) food-grade option for potable/food; (g) all seals replaceable; (h) tell us medium + max temp → we recommend seal material. This valve = we offer four seal options: (1) NBR (nitrile rubber) - for cold water, oil, gasoline, diesel, compressed air, natural gas at ≤80°C (most common, lowest cost, good elasticity and abrasion resistance, but NOT for hot water >80°C, ozone, or strong chemicals); (2) EPDM - for hot water, low-pressure steam, ozone/UV exposure, HVAC heating/cooling, and outdoor service at ≤120°C (excellent ozone/weather resistance, but NOT for oil/gasoline/petroleum products which cause swelling); (3) PTFE (Teflon) - for chemicals, corrosive media (strong acids/alkalis/solvents), and high temperature up to ≤180°C (chemically inert, no aging, longest life, lowest friction, but harder and less elastic than rubber so it requires proper seating force); (4) Metal-to-metal (bronze or stainless steel 304/316) - for abrasive media and high temperature up to ≤200°C (wear-resistant, but has higher leakage Class III/IV, not bubble-tight); selection is primarily by medium compatibility and maximum working temperature: ≤80°C water/oil/gas → NBR (cheapest), 80-120°C hot water/steam/ozone → EPDM, 120-180°C or chemicals/corrosive → PTFE, abrasive/high-temp with acceptable minor leakage → metal-to-metal; for potable/drinking water or food/beverage, specify FDA/NSF-grade NBR or EPDM; all seals are replaceable (spare seal rings available) and designed into the disc or seat groove so you don't need to replace the whole valve when the seal wears; typical seal life is 3-5 years for NBR (rubber aging), 5-8 years for EPDM, and 10+ years for PTFE (no rubber aging); provide your medium and maximum working temperature and we recommend the correct seal material (and food-grade certification if needed).

Q: What pressure and temperature can this valve handle, and can it be used for steam?

A: The brass flange check valve has a body rating of PN16 (16 bar / 232 psi / Class 125/150) and a temperature range of -20°C to +180°C - but the actual working pressure and temperature are limited by the seal material: NBR seal ≤80°C, EPDM ≤120°C, PTFE ≤180°C, metal-to-metal ≤200°C (brass body limit). It can be used for low-pressure saturated steam (≤16 bar, ≤180°C) with EPDM or PTFE seal, but NOT for high-pressure steam (>16 bar), superheated steam (>180°C), or high-temperature thermal oil - for those use cast steel or stainless steel check valves. Here's the detailed rating guide. Pressure rating (detailed): (a) nominal pressure (PN): PN16 (16 bar = 1.6MPa = 232 psi = ANSI Class 125/150 approximate); (b) body rating: brass body designed and tested for PN16 at ambient temp; (c) working pressure: ≤16 bar at ≤80°C (NBR seal); at higher temp, pressure derates (seal and brass strength decrease); (d) test pressure: shell 1.5×PN = 24 bar (hydro), seat 1.1×PN = 17.6 bar; (e) NOT for: >16 bar (use cast steel PN25/40/64 or SS). Temperature rating (detailed): (a) overall: -20°C ~ +180°C (valve design range); (b) by seal material: (i) NBR: -20 ~ +80°C (continuous), +100°C short-term; (ii) EPDM: -40 ~ +120°C (continuous), +150°C short-term; (iii) PTFE: -40 ~ +180°C (continuous, but brass body limits); (iv) metal-to-metal: -40 ~ +200°C (brass body limit); (c) brass body: brass retains strength to ~200°C (above that, strength decreases, creep); (d) low temp: brass becomes slightly brittle below -20°C (not recommended below -20°C without low-temp brass); (e) derating: at >80°C, max working pressure decreases (e.g., at 120°C EPDM, max ~10 bar; at 180°C PTFE, max ~6-8 bar - consult factory). Steam application (detailed): (a) can be used for: (i) low-pressure saturated steam: ≤16 bar (abs), ≤180°C (saturated at 10 bar = 180°C, at 16 bar = 201°C - so realistically ≤10 bar for ≤180°C); (ii) seal: EPDM (≤120°C, for low-pressure steam ≤2 bar) or PTFE (≤180°C, for steam up to ~10 bar); (iii) body: brass (OK for low-pressure steam); (iv) use: boiler auxiliary steam, heating steam, sterilization (low temp), steam tracing; (b) NOT for: (i) high-pressure steam (>10-16 bar, >180°C) - brass strength + seal limit; (ii) superheated steam (>180°C) - PTFE/body limit; (iii) steam main lines (high pressure, high temp - use cast steel WCB/SS); (iv) steam with high water hammer (brass can crack - use cast steel); (c) recommendation for steam: (i) ≤2 bar, ≤120°C → EPDM seal; (ii) 2-10 bar, ≤180°C → PTFE seal; (iii) >10 bar or >180°C → cast steel (WCB) or SS check valve; (d) install: horizontal (swing type), strainer upstream (steam has condensate/debris), drain valve at low point. Water application (detailed): (a) cold water: ≤40°C, NBR/EPDM, full PN16; (b) hot water: 40-80°C → NBR; 80-120°C → EPDM; 120-180°C → PTFE; (c) potable water: lead-free C37700 + food-grade seal; (d) aggressive water: DZR brass; (e) full PN16 for water at ≤80°C. Oil/gas application (detailed): (a) light oil / hydraulic oil / lubricant: NBR (≤80°C) or PTFE; (b) gasoline / diesel: NBR (≤80°C, standard grade - avoid high aromatic); (c) compressed air: NBR (≤80°C) or PTFE; (d) natural gas / LPG (low pressure): NBR (≤80°C) or PTFE, ensure leak-tight; (e) NOT for: high-pressure gas (>16 bar), corrosive gas (H₂S, chlorine - use SS/monel). Chemical application (detailed): (a) mild chemicals (dilute acid/alkali): PTFE seal, brass body (check compatibility); (b) strong chemicals (concentrated acid/alkali, solvent, chlorine): brass NOT recommended (corrodes) - use SS (CF8/CF8M) or plastic-lined; (c) PTFE seal handles most chemicals, but body may corrode. Pressure-temperature derating (reference): | Temp | NBR seal | EPDM seal | PTFE seal | Metal seal | |---|---|---|---|---| | ≤80°C | 16 bar (full) | 16 bar | 16 bar | 16 bar | | 80-120°C | NOT recommended | 10-12 bar | 12-14 bar | 14 bar | | 120-180°C | NOT | NOT | 6-10 bar | 10-12 bar | | >180°C | NOT | NOT | NOT (body limit) | ≤200°C, 6-8 bar | (exact derating per standard - confirm at order) Common mistakes: (a) using PN16 brass valve for 25 bar system (overpressure - body may fail); (b) using NBR seal for 120°C hot water (NBR fails - use EPDM/PTFE); (c) using brass valve for high-pressure steam (16 bar+ saturated = 201°C >180°C - use cast steel); (d) using EPDM for oil (swells - use NBR/PTFE); (e) ignoring derating at high temp (pressure must reduce); (f) using brass for strong chemicals (corrodes - use SS). Important: (a) PN16 body (16 bar max, Class 125/150); (b) temp -20~180°C (overall), but seal-limited: NBR≤80, EPDM≤120, PTFE≤180, metal≤200; (c) steam: low-pressure saturated ≤10 bar/≤180°C with PTFE (or ≤2 bar with EPDM); NOT high-pressure/superheated; (d) derate pressure at higher temp; (e) NOT for >16 bar, >180°C (PTFE), strong chemicals; (f) for high pressure/temp → cast steel (WCB) or SS check valve; (g) tell us medium + max pressure + max temp → we confirm if brass valve is suitable + recommend seal. This valve = the valve has a body rating of PN16 (16 bar / 232 psi / ANSI Class 125/150) and an overall temperature range of -20°C to +180°C, but the actual working pressure and temperature are limited by the seal material: NBR seal allows ≤80°C at full 16 bar, EPDM allows ≤120°C (pressure derated to ~10-12 bar), PTFE allows ≤180°C (pressure derated to ~6-10 bar at high temp), and metal-to-metal allows ≤200°C (brass body limit, pressure derated); it can be used for low-pressure saturated steam - specifically ≤10 bar and ≤180°C with PTFE seal (or ≤2 bar and ≤120°C with EPDM seal), suitable for boiler auxiliary steam, heating steam, low-temperature sterilization, and steam tracing - but it is NOT suitable for high-pressure steam (>10-16 bar), superheated steam (>180°C), high-pressure gas (>16 bar), or high-temperature thermal oil because the brass body loses strength above ~180-200°C and the PN16 rating is exceeded; for cold water and oil/gas at ≤80°C, the valve operates at full PN16 (16 bar) with NBR seal; for hot water 80-120°C use EPDM, and for 120-180°C use PTFE (with pressure derating); for strong corrosive chemicals, brass is generally not recommended (use stainless steel CF8/CF8M instead), even with PTFE seal, because the brass body itself may corrode; if your application exceeds PN16 or 180°C, or requires high-pressure steam, we recommend cast steel (WCB, PN25-100, -29~425°C) or stainless steel (CF8/CF8M, PN16-40, -40~450°C) flange check valves instead; provide your medium, maximum working pressure, and maximum temperature and we confirm whether this brass valve is suitable (and recommend the correct seal material, or suggest an alternative valve material if your parameters exceed brass limits).

Q: How do I install this check valve correctly, and does orientation matter?

A: Installation requires correct flow direction (the arrow cast on the body must point in the permitted flow direction, i.e., downstream), proper orientation (swing type: horizontal preferred, NOT vertical downward; lift type: any orientation, with spring for vertical downward), straight pipe and strainer upstream, and isolation valves for maintenance. Orientation does matter - swing type relies on gravity to close, so it must be installed horizontally (or vertical with upward flow), while lift type can be installed in any orientation. Here's the detailed installation guide. Flow direction (critical): (a) arrow on body: cast/marked arrow indicates permitted forward flow direction; (b) install: arrow pointing downstream (in the direction of normal flow); (c) if reversed: valve stays closed (disc can't open against seat), no flow, or disc forced open backwards (damages seat/hinge); (d) verify: before installing, check arrow, mark pipeline direction. Swing type orientation (detailed): (a) horizontal (preferred): (i) valve body in horizontal pipeline, hinge pin at top (horizontal axis); (ii) clapper swings in vertical plane; (iii) gravity pulls clapper down to close reliably; (iv) best orientation; (b) vertical with upward flow: (i) flow goes up, clapper swings open upward; (ii) closing: gravity + reverse pressure pull clapper down; (iii) possible, but less reliable (if reverse flow slow, gravity may not close fast); (iv) use spring-loaded swing for vertical; (c) vertical with downward flow: (i) NOT recommended - flow goes down, clapper swings open downward; (ii) closing: gravity works AGAINST closing (clapper wants to stay open downward); (iii) only reverse pressure can close (may not close at zero flow); (iv) use lift type with spring instead; (d) inclined: (i) acceptable if hinge pin axis is horizontal (clapper swings in vertical-ish plane); (ii) avoid steep incline (>45°). Lift type orientation (detailed): (a) horizontal: (i) disc lifts vertically (perpendicular to pipe), gravity pushes down to close; (ii) OK, reliable; (b) vertical with upward flow: (i) best orientation - flow pushes disc up, gravity + reverse push down to close; (ii) reliable; (c) vertical with downward flow: (i) flow pushes disc down? No - disc lifts off seat in direction of flow (upward if flow up, but if flow down, disc would need to lift downward); (ii) standard lift valve designed for flow from bottom to top (under seat); (iii) for vertical downward, need spring-loaded or special design; (iv) consult factory; (d) any orientation (with spring): spring assists closing regardless of orientation. Installation steps (detailed): (a) pre-install: (i) inspect valve (damage, flow arrow, DN/PN, seal material); (ii) verify pipeline (flange rating, gasket, bolt size); (iii) flush pipeline (remove weld slag, dirt, debris - debris damages seat); (b) position valve: (i) flow arrow pointing downstream; (ii) correct orientation (swing horizontal, lift any); (iii) valve body supported (don't hang by flanges); (c) gaskets: (i) place gasket on both flanges (rubber for water, spiral-wound for steam/oil, PTFE for chemical); (ii) align bolt holes; (d) tighten bolts: (i) criss-cross pattern (star pattern); (ii) torque evenly (3-4 passes, final torque per bolt size); (iii) don't over-torque (brass flange can crack); (e) accessories: (i) strainer upstream (Y-strainer, 40-80 mesh - protect seat); (ii) isolation valves (gate/ball) upstream + downstream (for maintenance); (iii) pressure gauge (optional, downstream); (iv) bypass (optional, for large systems); (f) startup: (i) slowly open upstream isolation (fill line, check leaks); (ii) open downstream; (iii) verify flow (valve opens, no noise); (iv) check reverse (stop flow, verify no backflow leak). Straight pipe requirement: (a) upstream: ≥3-5DN straight pipe before valve (reduce turbulence from elbow/tee/pump); (b) downstream: ≥2-3DN straight pipe after; (c) if space limited: accept slightly lower performance, but avoid directly after pump/elbow (causes disc flutter, wear). Strainer upstream (essential): (a) purpose: catch debris (weld slag, rust, dirt) before it reaches check valve seat (debris scratches seat → leakage); (b) type: Y-strainer (most common) or basket strainer; (c) mesh: 40-80 mesh (water/oil/gas); (d) location: immediately upstream of check valve (between isolation and check); (e) maintenance: clean periodically (differential pressure indicator or scheduled); (f) for steam: use steam strainer with blowdown valve. Isolation valves: (a) upstream + downstream: gate valve or ball valve (full port); (b) purpose: isolate check valve for inspection/maintenance without draining whole system; (c) location: one before strainer, one after check valve; (d) bypass: optional manual bypass around check (for startup or emergency). Near pump installation: (a) location: pump discharge line, 3-5DN after pump outlet; (b) purpose: prevent reverse flow when pump stops (protects pump from reverse rotation, water hammer); (c) consider: water hammer (pump trip → fast reverse flow → check slams) - use spring-loaded/silent check or add air chamber; (d) isolation + strainer as above. Vertical pipeline installation: (a) vertical upward flow: (i) lift type (best) or spring-loaded swing; (ii) standard swing possible but less reliable; (b) vertical downward flow: (i) lift type with spring (required); (ii) standard swing NOT recommended; (iii) consult factory for standard lift; (c) support: valve and piping supported (weight on supports, not valve). Steam installation: (a) horizontal (swing type preferred); (b) strainer + drain valve (steam has condensate); (c) warm up slowly (avoid thermal shock, water hammer); (d) insulate (energy saving, prevent burns); (e) PTFE/EPDM seal (per temp). Testing after installation: (a) hydro/pressure test: pressurize line, check flange/gasket/body leaks; (b) function test: open flow → valve opens (listen/observe), stop flow → valve closes; (c) backflow leak test: close downstream, pressurize from downstream? No - verify no reverse flow by observing downstream pressure when upstream closed (should not rise); (d) noise check: no chatter/vibration at normal flow. Common installation mistakes: (a) flow direction reversed (arrow pointing upstream - valve closed, no flow - reverse); (b) swing type vertical downward (clapper stays open - no backflow prevention - use lift with spring); (c) no strainer (debris damages seat - add); (d) no straight pipe (turbulence → disc flutter/wear - add straight pipe); (e) valve not supported (piping weight cracks flange - support); (f) over-torque bolts (brass flange cracks - torque to spec); (g) wrong gasket (wrong material → leak/corrosion - select per medium); (h) no isolation valves (can't maintain without system shutdown - add); (i) pump too close (turbulence/water hammer - 3-5DN distance); (j) startup too fast (water hammer, disc slam - slow fill). Maintenance access: (a) space: leave room above swing type (hinge pin removal) or above lift type (bonnet/cap removal); (b) isolate before maintenance (close both isolation valves, depressurize, drain); (c) spares: keep seal kit, hinge pin, gaskets on hand. Important: (a) flow arrow = downstream (critical - install correctly); (b) swing type: horizontal preferred, NOT vertical downward; (c) lift type: any orientation (spring for vertical down); (d) strainer upstream (essential); (e) isolation valves both sides; (f) 3-5DN straight pipe upstream; (g) support valve (don't hang by flanges); (h) torque bolts evenly (brass cracks); (i) startup slowly (avoid water hammer); (j) warranty: 18 months. With correct flow direction, orientation, accessories, and startup, this brass flange check valve provides reliable backflow prevention. This valve = correct installation requires: (1) flow direction - the arrow cast on the valve body must point downstream (in the permitted forward flow direction); if installed backwards, the valve stays closed and blocks flow (or damages the seat); (2) orientation - swing type must be installed horizontally (hinge pin at the top, clapper swings in a vertical plane so gravity pulls it closed reliably), it can be used in vertical-upward pipelines but is NOT recommended for vertical-downward flow (gravity works against closing and the clapper may stay open); lift type can be installed in any orientation (horizontal, vertical-upward, or vertical-downward with a spring-loaded option); (3) straight pipe - install with ≥3-5DN straight pipe upstream and ≥2-3DN downstream (avoid directly after a pump, elbow, or tee which causes turbulence and disc flutter); (4) strainer upstream - install a Y-strainer (40-80 mesh) immediately before the valve to catch weld slag/rust/debris that would scratch the seat and cause leakage; (5) isolation valves - install a gate/ball valve upstream and downstream so the check valve can be serviced without draining the whole system; (6) support - support the valve body and piping (don't let the valve hang by the flanges, which can crack the brass flange); (7) bolt tightening - tighten flange bolts in a criss-cross (star) pattern with even torque in 3-4 passes (don't over-torque, brass flanges can crack); (8) gasket - use the correct gasket material (rubber for water, spiral-wound for steam/oil, PTFE for chemicals); (9) startup - slowly open the upstream isolation valve to fill the line and check for leaks, then open downstream, verify the valve opens and closes properly; for pump discharge service, install 3-5DN after the pump outlet and consider spring-loaded or silent check if water hammer is a concern (pump trip causes fast reverse flow that can slam a swing-type disc); for steam service, install horizontally, use a strainer with blowdown, warm up slowly to avoid thermal shock/water hammer, and insulate the line; provide your pipeline orientation (horizontal/vertical-up/vertical-down), medium, and nearby equipment (pump/elbow) and we can confirm the correct installation orientation and accessories.

Q: What maintenance and troubleshooting does this valve need?

A: A brass flange check valve is low maintenance (few moving parts, automatic operation) - it needs annual inspection (leak check, disc/seat inspect, hinge pin lubrication for swing type) and periodic seal replacement every 3-5 years for NBR, 5-8 years for EPDM, 10+ years for PTFE; common issues are backflow leakage (worn seat/seal/debris), noise/vibration/chatter (water hammer or disc flutter), won't open (low pressure or stuck disc), won't close (seized hinge pin or broken spring), external leakage (gasket or body crack), and high pressure drop (undersized valve or clogged strainer). Here's the detailed maintenance and troubleshooting guide. Maintenance philosophy: (a) simple, few moving parts (disc, hinge pin for swing / spring for lift, seal) - very low maintenance; (b) key wear parts: (i) seal ring (NBR/EPDM aging, PTFE cold-flow); (ii) hinge pin + bushing (swing type - wear, corrosion); (iii) spring (lift type - fatigue, corrosion); (iv) seat/disc (wear, scoring, debris); (v) gaskets (aging); (c) frequency: normal duty = annual; heavy duty (high cycle, abrasive, steam) = quarterly; (d) preventive avoids backflow leakage and equipment damage. Daily/weekly inspection (operator): (a) visual: external leak at flanges/body/bonnet (water/oil dripping, gas hiss); (b) noise: (i) normal: quiet (flow through open valve); (ii) abnormal: chatter/vibration (disc flutter), water hammer (bang on pump stop), whistling (cavitation/high ΔP); (c) vibration: piping vibration (loose support, disc flutter); (d) backflow indication: downstream pressure rising when upstream closed (leakage); (e) strainer: differential pressure (if equipped) or scheduled clean. Monthly maintenance: (a) external leak check: soapy water at flanges, gaskets, body (for gas), visual for liquid; (b) strainer clean/blowdown: close isolation, open strainer blowdown, clean screen; (c) valve exercise (if normally static): (i) for check valve, can't manually exercise, but can cycle flow (open/close upstream valve) to move disc; (ii) prevents sticking; (d) check support/tightness: flange bolts (retorque if loose), piping support. Annual maintenance (recommended minimum): (a) isolate: close upstream + downstream isolation, depressurize, drain (for steam/oil, flush); (b) remove valve (or remove bonnet/cap if top-entry design): (i) swing type: remove top cap/cover, inspect clapper disc, seal, hinge pin, bushing, seat; (ii) lift type: remove bonnet, inspect disc, seal, spring, guide, seat; (c) seat leakage test (in-line or removed): (i) pressurize reverse side at 1.1×PN; (ii) soft seal = zero bubbles; if leaking → seat worn/scored (lap or replace), seal damaged (replace), debris (clean); (d) disc/seat inspect: (i) wear, scoring, corrosion, debris; (ii) clean, lap if minor wear, replace if deep score; (e) seal inspect: (i) NBR/EPDM: hardness, cracks, blisters, permanent set → replace if aged (even if looks OK at 3-5yr); (ii) PTFE: cold-flow, scratches → replace if deformed; (f) hinge pin (swing): (i) inspect wear (pin diameter, bushing ID); (ii) lubricate (food-grade grease for potable water); (iii) replace if worn (excessive play); (g) spring (lift): (i) inspect (corrosion, fatigue, broken); (ii) replace if suspect; (h) guide (lift): clean, check for scoring; (i) gaskets: replace (don't reuse); (j) body interior: clean (scale, debris, biological growth for water); (k) reassemble: verify disc moves freely (no bind), full open/close; (l) reinstall + test: hydro leak, seat leakage, function (open/close). 3-5 year major overhaul (NBR seal) / 5-8 year (EPDM) / 10+ year (PTFE): (a) replace seal ring (NBR at 3-5yr, EPDM at 5-8yr, PTFE at 10+yr or if cold-flow); (b) replace hinge pin + bushing (swing type - wear); (c) replace spring (lift type - fatigue); (d) replace disc (if worn/scored beyond lapping); (e) replace seat ring (if replaceable, worn); (f) replace all gaskets; (g) body inspect: wall thickness (corrosion), cracks, dezincification (for aggressive water - if porous, replace valve); (h) hydro test (1.5×PN, no leak); (i) seat leakage test (zero bubbles soft seal); (j) function test (cracking pressure, full open, close); (k) paint/finish (if nickel plated, re-plate if corroded). Seal replacement procedure: (a) isolate/depressurize/drain (LOTO); (b) remove valve from line (or top-entry remove bonnet); (c) swing type: remove hinge pin, take out clapper disc, remove old seal from disc groove, clean groove, install new seal (lubricate with silicone or water), reinstall disc + pin; (d) lift type: remove bonnet, take out disc+spring, remove old seal, clean, install new seal, reinstall disc+spring+bonnet; (e) reassemble, test (seat leakage, function); (f) time: 15-30min (simple). Hinge pin replacement (swing type): (a) remove top cap, drive out old hinge pin (drift punch), remove clapper; (b) inspect bushing (in body/clapper) - replace if worn; (c) install new pin (lubricated), verify clapper swings freely (no bind, no excessive play); (d) reinstall cap, test. Spare parts kit (recommended): (a) seal ring (1, correct material/size); (b) disc assembly (1, with seal); (c) hinge pin + bushing (swing type); (d) spring (lift type); (e) gaskets (flange + bonnet, 2 sets); (f) label with valve tag/DN/PN/type/seal material; (g) store cool/dry, rubber away from ozone/UV/solvents. Troubleshooting - detailed: Problem 1: Backflow leakage (medium flows backward when valve should be closed) (a) causes: (i) seat worn/scored (from debris, high cycle) → lap or replace seat; (ii) disc seal damaged/cracked/aged (NBR/EPDM hardening) → replace seal; (iii) foreign material on seat (weld slag, rust, sand) → clean, check strainer; (iv) disc not seating properly (hinge pin worn/bent, swing type - clapper misaligned) → replace hinge pin/bushing; (v) wrong flow direction (valve installed backwards - arrow upstream) → reverse installation; (vi) valve oversized (disc doesn't fully seat at low reverse pressure? No - check pressure); (vii) spring broken (lift type) → replace spring; (b) fixes: clean/lap/replace seat, replace seal, clean strainer, replace hinge pin, verify flow direction, replace spring. Problem 2: Noise / vibration / chatter / disc flutter (a) causes: (i) water hammer (fast reverse flow from pump trip - swing type slams shut) → install silent/dual-plate check, spring-loaded check, add air chamber/surge tank, slow pump shutdown; (ii) disc flutter (low flow near cracking pressure, disc vibrates) → size valve correctly (normal flow = 30-80% rated), install minimum flow bypass; (iii) loose hinge pin (swing) → tighten/replace; (iv) cavitation (high ΔP liquid, pressure drops below vapor pressure → bubbles collapse → noise/erosion) → reduce ΔP, use anti-cavitation trim, or different valve; (v) pulsating flow (pump/compressor pulsation) → add pulsation damper, install further from pump; (vi) turbulence (no straight pipe, near elbow/pump) → add 3-5DN straight pipe; (b) fixes: address water hammer, size correctly, tighten/replace pin, reduce ΔP, add straight pipe/damper. Problem 3: Won't open (no forward flow through valve) (a) causes: (i) forward pressure below cracking pressure (<0.02-0.05MPa) → increase pressure or check supply (pump, valve); (ii) disc stuck (debris, corrosion, seal bonded to seat) → clean, lubricate, free disc; (iii) hinge pin seized (swing type, corrosion/lack of lubrication) → lubricate/replace pin; (iv) disc guide blocked (lift type, debris) → clean guide; (v) wrong flow direction (installed backwards) → reverse; (vi) line pressure too low (gravity system) → use lighter spring or different valve; (b) fixes: verify pressure, clean/free disc, lubricate/replace hinge pin, clean guide, verify flow direction. Problem 4: Won't close (disc stays open, backflow) (a) causes: (i) hinge pin seized/bent (swing type) → lubricate/replace; (ii) disc guide blocked/stuck (lift type) → clean; (iii) spring broken/weak (lift type) → replace; (iv) wrong orientation (swing type vertical downward - gravity keeps open) → reorient to horizontal or use lift with spring; (v) debris jamming disc open → clean; (vi) seal swollen (wrong seal material, e.g., EPDM in oil → swells) → replace with correct seal; (b) fixes: lubricate/replace pin, clean guide, replace spring, reorient, clean, replace seal. Problem 5: External leakage (at flange, body, bonnet) (a) causes: (i) flange gasket damaged/wrong material/aged → replace gasket, retorque bolts; (ii) flange bolts loose/unequal torque → retorque evenly (criss-cross); (iii) body crack (from freeze, overpressure, water hammer) → replace valve (brass crack not repairable); (iv) bonnet/cap gasket leak → replace gasket; (v) pin hole (casting defect, corrosion) → replace valve; (vi) threaded connection (if any) → re-seal; (b) fixes: replace gaskets, retorque, replace valve if body cracked. Problem 6: High pressure drop (low flow, ΔP too high) (a) causes: (i) valve undersized (Cv too small for flow) → size up; (ii) strainer clogged (restricts flow) → clean strainer; (iii) disc not fully open (low forward pressure, or stuck) → check pressure/free disc; (iv) wrong type (lift type has higher ΔP than swing for same DN) → use swing type for low ΔP; (v) pipeline restriction elsewhere; (b) fixes: size up, clean strainer, verify disc full open, use swing type. Problem 7: Brass corrosion / dezincification (a) causes: (i) aggressive water (soft, acidic, low mineral, high chloride) → dezincification (zinc leaches, porous copper); (ii) strong chemicals (brass not compatible) → corrosion; (iii) stray electrical current (electrolysis) → pitting; (b) symptoms: body porous, white/reddish deposits, leaks, reduced wall thickness; (c) fixes: replace with DZR brass or stainless steel valve, install dielectric union (stray current), water treatment. Problem 8: Freeze damage (cold climate) (a) cause: water trapped in valve freezes, expands → cracks brass body; (b) prevention: drain valve in freezing ambient, install drain valve, heat trace/insulate, use freeze-tolerant design; (c) fix: replace valve (crack not repairable). Maintenance schedule summary: | Frequency | Tasks | |---|---| | Daily/Weekly | Visual leak, noise, vibration, backflow check, strainer ΔP | | Monthly | External leak check, strainer clean, valve exercise, bolt/support check | | Annual | Isolate, seat leakage test, disc/seat inspect, seal inspect, hinge pin lubricate (swing), spring inspect (lift), gaskets inspect, body clean, reassemble/test | | 3-5yr (NBR) / 5-8yr (EPDM) / 10+yr (PTFE) | Replace seal, hinge pin+bushing (swing), spring (lift), disc/seat if worn, gaskets, body inspect (wall thickness/corrosion), hydro+seat+function test | Safety during maintenance: (a) isolate both ports (close isolation, lockout/tagout); (b) depressurize (verify 0 pressure); (c) drain/flush (hot water/steam/oil/chemical - burn/hazard, PPE); (d) for gas: ventilate, no ignition source, test atmosphere; (e) brass body may be hot (steam) - allow cool; (f) spring-loaded (lift type): spring under preload - release slowly when disassembling; (g) re-test (seat leakage + function) before service. Important: (a) annual inspection + seal replacement at interval (NBR 3-5yr, EPDM 5-8yr, PTFE 10+yr); (b) swing type: hinge pin lubricate/replace; lift type: spring inspect/replace; (c) common: backflow leak (seat/seal/debris), noise (water hammer/flutter), won't open/close (stuck pin/spring), external leak (gasket/body crack); (d) strainer clean monthly; (e) isolate/depressurize before maintenance; (f) keep spare parts kit; (g) warranty: 18 months (wear parts not covered). With proper maintenance and timely troubleshooting, this brass flange check valve provides long reliable backflow prevention.

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