Extended Flange Hard Seal Butterfly Valve | DN50-2000 Triple Offset Factory

An Extended Flange Hard Seal Butterfly Valve is a high-performance triple-offset (triple-eccentric) hard-seal butterfly valve with an extended flange body that integrates the functions of a butterfly valve and a pipe expansion joint - a circular disc rotates 90° for on-off/flow regulation, with a three-eccentric design (disc shaft axis offset from seat center, disc sealing surface offset, seat cone angle offset) that makes the disc cam out of the seat immediately on opening (zero friction/wear during rotation) and wedge tightly into the seat on closing ("tighter when closed" self-energizing seal), with a multi-layer metal hard seal (J-shaped elastic sealing ring + stainless steel ring + cobalt-based Stellite hardfaced disc) combining metal hard sealing (high temp/wear) and elastic sealing (conformability, zero leakage), an extended flange that can adjust the distance between two pipeline flanges (telescopic/expansion joint function) to relieve pipeline thermal stress (expansion/contraction from temperature changes) and protect the valve, a large-size truss-structure disc (high strength, large flow area, low flow resistance), a replaceable sealing ring (no need to scrap entire valve on seal damage), DN50-2000 large-bore, PN0.6-2.5MPa, carbon steel -29~425°C / stainless steel -40~650°C, worm gear/electric/pneumatic/hydraulic drive with multi-position mounting, for water/air/natural gas/oil/weakly corrosive fluids in petrochemical, power, metallurgy, municipal/environmental, paper/sugar/food/pharma - a reliable, wear-free, high-temp, stress-relieving triple-offset hard-seal butterfly valve for harsh industrial large-bore pipelines. The core highlights are: (a) Triple-offset (triple-eccentric) hard seal structure: three offsets - (1) shaft axis offset from seat centerline, (2) disc sealing surface offset (conical), (3) seat cone angle offset - on opening, disc cams out of seat immediately (no rubbing/scraping = zero friction/wear); on closing, disc wedges into seat with mechanical force = "tighter when closed" (self-energizing, higher pressure = tighter seal); unlike concentric butterfly (disc rubs seat every cycle → wear) or double-offset (still some contact), triple-offset = true zero friction → very long seal life, suitable for high-cycle/high-temp/abrasive; (b) Multi-layer metal hard seal: J-shaped elastic sealing ring (stainless steel, elastic - provides conformability/initial seal) + stainless steel seat ring + cobalt-based Stellite hardfaced disc (Stellite 6/21 - cobalt-chromium-tungsten alloy, HRC 40-45, wear/corrosion/erosion resistant) - combines metal hard seal (high temp, wear, fire-safe) with elastic seal (J-ring flexes = conforms, zero leakage even at low pressure); leakage per GB/T 13927/API 598 (Class IV or better); (c) Extended flange (expansion joint function): body has extended/telescopic flange section - integrates butterfly valve + pipe expansion joint in one unit; can adjust distance between two pipeline flanges (absorb pipeline thermal expansion/contraction - steel pipe expands ~1.2mm per 10m per 100°C), relieve pipeline stress (thermal stress, misalignment, vibration), protect valve body (no force on valve from pipe movement), facilitate installation/removal (adjust telescopic part to create maintenance space); replaces separate expansion joint + valve = saves cost/space; (d) Large-size truss disc: for large DN (≥DN500), disc adopts truss (framework) structure - lightweight but high strength (resists pressure deflection), large flow area (openings in truss = low flow resistance), stable under high pressure; solid disc for small DN; (e) Replaceable sealing ring: seal ring is bolted/replaceable - if worn/damaged, replace ring only (not entire valve) → reduces maintenance cost/downtime; (f) Wide size/pressure/temp: DN50-2000 (medium to very large), PN0.6-2.5MPa (low to medium pressure), carbon steel body -29~425°C, stainless steel body -40~650°C (high-temp steam/hot oil/gas); (g) Multiple drives + multi-position mounting: worm gear (standard, self-locking, labor-saving), electric (remote/DCS, fast), pneumatic (fast, hazardous), hydraulic (high torque, large DN); drive device can be installed in multiple positions (rotated 90°/180°) - adapts to space/access/piping layout; (h) Low maintenance: no special maintenance, only regular inspection of expansion part (leakage/detachment) + seal; replaceable ring; (i) Multiple media: water, air, natural gas, oil products, weakly corrosive fluids, high-temp gas, dusty gas (with hard seal); (j) Standards: JB/T 8527-97 (metal-sealed butterfly valve), GB/T 12238, API 609, BS EN 593; flange GB/T 9113, ANSI B16.1, BS 4504, DIN; (k) Applications: petrochemical (catalytic cracking, hydrogenation, heavy oil, long-distance pipeline stations - high-temp/impurity media), power & new energy (boiler feedwater, main steam bypass, FGD desulfurization, denitrification, pulverized coal - supercritical high-temp/high-pressure), metallurgy & steel (blast furnace gas, hot blast furnace flue gas, dry dust removal - high-temp dusty gas erosion), municipal & environmental (urban water supply/drainage main networks, sewage treatment, waste incineration - large-diameter), other (paper high-viscosity fiber, sugar crystalline, food/pharma, textile, PV); (l) Leakage: GB/T 13927-92 / API 598; (m) Test: seal 1.1×PN, strength 1.5×PN. This is the reliable triple-offset hard-seal extended-flange high-temp butterfly valve solution for harsh industrial large-bore pipelines.

The triple-offset zero-friction hard seal, extended flange with expansion-joint stress relief, large-bore truss disc, replaceable seal ring, wide high-temperature range, and multi-drive/multi-position mounting make this valve a high-performance hard-seal butterfly valve for harsh, high-temperature, large-bore industrial service - distinct from soft-seal/general butterfly valves - designed for petrochemical, power, metallurgy, and municipal large-bore pipelines where high temperature, wear, pipeline thermal stress, and long service life are critical. Compared to other butterfly valves: (a) vs Electric Flange Butterfly Valve (first product): that one is general industrial electric - electric actuator, on-off/regulating, soft/hard seal, DN50-2000, -29~550°C, general industrial (water treatment/petrochemical/power/metallurgy); this one is triple-offset hard seal + extended flange expansion joint - zero-friction wear, high temp to 650°C (stainless), stress relief, large-bore truss disc, replaceable ring, specialized for harsh/high-temp/stress - not general electric; (b) vs Fire Signal Butterfly Valve (second product): that one is fire-protection signal - supervisory switch, manual, soft seal, DN50-400, -10~80°C fire water, fire code; this one is industrial hard-seal high-temp - triple-offset, metal hard seal, DN50-2000, 650°C, no signal, industrial harsh - completely different market; (c) vs concentric soft-seal butterfly: concentric = disc rubs seat (wear), soft seal (temp limited ≤180°C), low cost; this one = triple-offset (zero friction), metal hard seal (650°C), long life, higher cost - for harsh/high-temp; (d) vs double-offset butterfly: double-offset = disc cams out but still some seat contact at end of travel; triple-offset = true zero friction throughout rotation (better wear, longer life, higher temp); (e) vs gate valve (high-temp): gate = multi-turn slow, bulky/heavy at large DN, high cost; this = quarter-turn fast, compact/light, cheaper at large DN, low resistance - but pressure limited ≤PN2.5; (f) vs ball valve (high-temp): ball = better zero leakage, higher pressure, but heavy/costly at large DN; this = compact/light/large-bore, hard seal Class IV (not zero like ball), lower pressure - for large-bore medium-pressure. Triple-offset principle detailed: (a) Offset 1 - shaft axis offset: stem centerline is offset from seat/pipe centerline by distance "e" - when disc rotates, it moves away from seat (not straight in/out); (b) Offset 2 - disc sealing surface offset: disc sealing cone axis is offset from stem axis - disc is "eccentric" relative to rotation; (c) Offset 3 - seat cone angle: seat sealing surface is a cone (not cylinder) with angle "α" - disc wedge matches cone; (d) combined effect: on opening (0°→90°), disc immediately cams out of seat (within first 1-5° rotation, disc separates from seat - no rubbing for rest of travel); on closing (90°→0°), disc only contacts seat in last few degrees - wedges into conical seat with mechanical interference = tight seal; (e) zero friction = no wear on sealing surfaces = very long cycle life (100,000+ cycles vs concentric ~10,000); (f) self-energizing: higher medium pressure = disc pushed harder into conical seat = tighter seal; (g) bidirectional: seals both directions (symmetric cone). Multi-layer metal hard seal detailed: (a) J-shaped elastic ring: stainless steel ring bent into "J" cross-section - elastic (spring-like), provides conformability (compensates for minor surface irregularities, thermal expansion mismatch), initial seal at low pressure; (b) stainless steel seat ring: supports J-ring, corrosion-resistant; (c) Stellite hardfaced disc: disc sealing surface overlay-welded with Stellite (cobalt-chromium-tungsten, HRC 40-45) - wear/corrosion/erosion resistant, hard smooth surface; (d) metal-to-metal contact: Stellite disc contacts J-ring - metal hard seal (high temp, fire-safe, no rubber to burn); (e) elastic + metal dual: J-ring elasticity = zero leakage (even at low pressure, unlike pure metal seal which leaks at low pressure); metal = high temp/wear; (f) leakage: Class IV (GB/T 13927/API 598) - very low for metal seal; (g) for high temp: J-ring + Stellite maintain seal at 650°C (no rubber/PTFE). Extended flange (expansion joint) detailed: (a) structure: valve body has two flange sections - one fixed, one telescopic/sliding (with seal) - can extend/retract axially; (b) function 1 - adjust flange distance: during installation, if pipeline flanges are too close/far, adjust telescopic section to match (no need to cut pipe); (c) function 2 - absorb thermal expansion: pipeline expands/contracts with temperature (steel: ~12μm/m/°C - a 100m pipe at 400°C expands ~480mm!) - telescopic flange absorbs this = no thermal stress on valve/piping; (d) function 3 - relieve misalignment/vibration: absorbs minor angular/lateral misalignment, vibration; (e) function 4 - protect valve: pipeline force (thermal, water hammer) is absorbed by expansion section, not transmitted to valve body/disc; (f) function 5 - maintenance space: extend telescopic part to create gap → remove valve without cutting pipe; (g) replaces separate expansion joint + valve = one unit, saves cost/space/weight; (h) seal: telescopic section has packing/gasket seal (graphite/PTFE) - zero leakage while sliding; (i) travel: typically ±25-100mm depending on DN. Truss disc detailed (large DN): (a) for DN ≥500, solid disc is heavy + may deflect under pressure; (b) truss structure = disc made of framework/ribs (like bridge truss) - lightweight (less material) but high strength (triangular framework resists bending); (c) large flow area = openings between ribs = low flow resistance (K low); (d) stable under high pressure (no deflection = seal maintains); (e) for small DN (<500), solid disc (simpler, sufficient). Replaceable seal ring: (a) seal ring (J-ring + seat) is bolted to body - not welded/integral; (b) if worn/damaged after years, unbolt + replace ring (not entire valve); (c) reduces maintenance cost (ring ~5-10% valve cost) and downtime; (d) can upgrade seal material (e.g., from stainless to Inconel for more corrosive). Multi-position drive mounting: (a) drive (worm gear/electric/pneumatic) mounts on top via flange; (b) can be rotated 90° or 180° (mounting flange has multiple bolt hole positions) - handwheel/actuator can face any direction; (c) adapts to space constraints (e.g., handwheel faces aisle for access, actuator faces cable tray); (d) improves installation flexibility. High-temperature materials: (a) carbon steel (WCB/WC6/WC9): -29~425°C - general high-temp (steam ≤425°C, hot oil); (b) stainless steel (CF8/CF8M/310S/2520): -40~650°C - higher temp (superheated steam, hot gas up to 650°C), corrosion; (c) Stellite hardfacing on disc regardless of body; (d) graphite packing for high temp (no PTFE); (e) for >650°C, special alloy (Inconel) optional. Pressure limitation: (a) PN0.6-2.5 - low to medium pressure; (b) triple-offset butterfly is not for high pressure >PN2.5 (disc deflection, seat leakage) - use gate/ball for higher; (c) for large-bore low/medium pressure (common in water/gas), ideal. Drive options: (a) worm gear (standard): handwheel + worm gear, self-locking, labor-saving, for manual operation; (b) electric: motor+gearbox, remote/DCS, fast, for automated; (c) pneumatic: compressed air, fast, hazardous (ATEX); (d) hydraulic: high torque, for very large DN (≥DN1000), fast; (e) all quarter-turn 90°. Testing: (1) body hydrostatic 1.5×PN; (2) seat leak 1.1×PN (Class IV); (3) torque test (open/close); (4) expansion section test (leakage under telescopic movement, pressure); (5) high-temp test (if specified, thermal cycle); (6) NDT for large DN. Important notes: (a) on-off + regulation - triple-offset can regulate (disc at intermediate angle), but primarily on-off; (b) not for high pressure >PN2.5; (c) not for abrasive slurry (Stellite helps but slurry wears); (d) expansion section - inspect seal regularly, lubricate; (e) high temp >425°C - use stainless body + graphite packing; (f) large DN - support pipeline, truss disc; (g) bidirectional - install either direction; (h) maintenance - replace seal ring if leakage increases, inspect expansion section. The valve is manufactured under strict quality control with 100% body hydrostatic, 100% seat leak, 100% torque, expansion section test, NDT for large DN. With an 18-month warranty and OEM/ODM customization (material, size, pressure, temp, expansion travel, drive, seal material, flange standard), this valve is a reliable triple-offset hard-seal extended-flange high-temp butterfly valve for harsh industrial large-bore pipelines.

1.Triple-Offset Zero-Friction Hard Seal

Three-eccentric (triple-offset) design - shaft axis, disc sealing surface, and seat cone angle all offset. On opening, disc cams out of seat immediately (zero rubbing/friction throughout rotation); on closing, disc wedges into conical seat with mechanical force = "tighter when closed" self-energizing seal. No seat/disc wear = very long cycle life (100,000+ cycles), ideal for high-cycle/high-temp/abrasive service.

2.Extended Flange + Expansion Joint Stress Relief

Extended flange integrates butterfly valve + pipe expansion joint in one unit. Telescopic flange section adjusts distance between pipeline flanges, absorbs thermal expansion/contraction (steel pipe expands ~1.2mm/10m/100°C), relieves pipeline thermal stress/misalignment/vibration, protects valve body, facilitates installation/removal (creates maintenance space). Replaces separate expansion joint + valve - saves cost/space. Expansion section seal (graphite/PTFE) zero leakage.

3.Multi-Layer Metal Hard Seal + Stellite Disc

J-shaped elastic stainless sealing ring (conformability, low-pressure zero seal) + stainless steel seat ring + cobalt-based Stellite hardfaced disc (Stellite 6/21, HRC 40-45, wear/corrosion/erosion resistant). Combines metal hard seal (high temp to 650°C, fire-safe, no rubber) with elastic seal (J-ring flexes = zero leakage even at low pressure). Leakage per GB/T 13927/API 598 (Class IV). Replaceable seal ring - no full valve scrap on damage.

4.Large-Bore Truss Disc + Low Flow Resistance

Large-size discs (DN≥500) adopt truss (framework) structure - lightweight but high strength (resists pressure deflection), large flow area (openings between ribs), low flow resistance (K factor low), stable under high pressure. Solid disc for small DN. Straight-through flow, fully open disc parallel to flow - minimal pressure loss, energy-saving for large-bore pipelines. DN50-2000 wide range.

5.Wide High-Temp Range + Durable Materials

Carbon steel body: -29°C ~ 425°C (steam, hot oil); stainless steel body: -40°C ~ 650°C (superheated steam, hot gas, high-temp process). PN0.6-2.5MPa. Body: carbon steel (WCB/WC6/WC9), stainless (CF8/CF8M/310S/2520); disc Stellite hardfaced; stem stainless/alloy; graphite packing (high temp). For water, air, natural gas, oil, weakly corrosive, high-temp dusty gas.

6.Multi-Drive + Multi-Position Mounting + Low Maintenance

Drives: worm gear (standard, self-locking), electric (remote/DCS), pneumatic (fast, ATEX), hydraulic (high torque large DN). Drive device can be installed in multiple positions (rotated 90°/180°) - adapts to space/access/piping. No special maintenance - only regular inspection of expansion part (leakage/detachment) + seal. Replaceable seal ring reduces cost/downtime. JB/T 8527/GB/T 12238/API 609/BS EN 593; flange GB/T 9113/ANSI B16.1/BS 4504/DIN. 18-month warranty, OEM/ODM.

An Extended Flange Hard Seal Butterfly Valve operates on the principle of a triple-offset (triple-eccentric) quarter-turn rotating disc with a multi-layer metal hard seal and an extended telescopic flange that provides expansion-joint stress relief - the disc is mounted on an offset rotating stem; when the disc is parallel to flow (0°), the valve is fully open (low resistance); when rotated 90°, the disc wedges into the conical metal seat (triple-offset cam action) to form a tight metal hard seal (J-shaped elastic ring + Stellite disc); the three offsets ensure the disc cams out of the seat immediately on opening (zero friction/wear) and wedges tighter on closing (self-energizing); the extended telescopic flange absorbs pipeline thermal expansion/contraction and relieves stress - with large-bore truss disc, replaceable seal ring, DN50-2000, PN0.6-2.5MPa, carbon steel -29~425°C / stainless -40~650°C, worm gear/electric/pneumatic/hydraulic drive - a high-performance, wear-free, high-temp, stress-relieving hard-seal butterfly valve for harsh industrial large-bore pipelines. The valve consists of an extended flange body (fixed + telescopic section, carbon steel/stainless), a circular disc (solid or truss, Stellite hardfaced, on offset stem), a stem (offset axis, stainless/alloy), a multi-layer metal seat (J-shaped elastic ring + stainless ring, in body), packing (graphite, high temp), an expansion section seal (graphite/PTFE, telescopic), and a drive operator (worm gear/electric/pneumatic/hydraulic, multi-position mount). Triple-offset (triple-eccentric) principle - core: (a) Offset 1 - shaft axis offset (e): stem centerline is offset from pipe/seat centerline by distance "e" (typically 5-15mm depending on DN); (b) Offset 2 - disc sealing surface offset: disc's conical sealing surface axis is offset from stem axis - disc is eccentric relative to rotation; (c) Offset 3 - seat cone angle (α): seat sealing surface is a cone (not cylinder) with half-angle "α" (typically 5-15°); (d) opening cam-out: when stem rotates from closed (0°) to open (90°), due to offsets, disc immediately moves away from seat (within first 1-5° rotation, disc separates) - for the remaining 85-89° rotation, disc does not touch seat = zero friction, zero wear; (e) closing wedge-in: when rotating from open to closed, disc only contacts seat in last few degrees - then wedges into conical seat with mechanical interference (cone angle creates wedge action) = tight seal; (f) self-energizing: medium pressure pushes disc further into cone = tighter seal at higher pressure; (g) zero friction benefit: sealing surfaces (Stellite disc + J-ring) do not rub during normal operation → no wear → 100,000+ cycles (vs concentric ~10,000 cycles with rubber wear); (h) bidirectional: symmetric cone seals both directions. Multi-layer metal hard seal principle: (a) J-shaped elastic ring: stainless steel (e.g., 304/316/Inconel) formed into "J" cross-section - acts as a spring (elastic, can compress/deflect); (b) seat ring: stainless ring supports J-ring, bolted to body (replaceable); (c) Stellite disc: disc sealing surface overlay-welded with Stellite 6/21 (Co-Cr-W alloy, HRC 40-45) - ground smooth, hard, wear/corrosion/erosion resistant; (d) sealing contact: when closed, Stellite disc surface contacts J-ring lip - J-ring compresses elastically = conforms to disc surface = zero leakage even at low pressure (pure metal-to-metal leaks at low pressure due to surface roughness); (e) metal hard seal: all metal (no rubber/PTFE) → high temp (650°C), fire-safe (doesn't burn), wear-resistant; (f) elastic + metal = dual benefit: J-ring elasticity = low-pressure zero seal; metal = high temp/wear; (g) leakage: Class IV (GB/T 13927/API 598) - very low for metal seal; (h) replaceable: J-ring + seat ring bolted → replace if worn. Extended flange (expansion joint) principle: (a) body = two sections: (1) main valve body (with seat/disc), (2) telescopic extension (slides axially, with seal); (b) telescopic seal: packing/gasket (graphite/PTFE) between sliding surfaces - zero leakage while allowing axial movement; (c) axial travel: typically ±25mm to ±100mm (depending on DN - larger DN = more travel); (d) absorb thermal expansion: pipeline expands with temperature (ΔL = α·L·ΔT, α_steel ≈ 12×10⁻⁶ /°C) - e.g., 100m pipe at ΔT=400°C → ΔL=480mm - telescopic flange absorbs this = no stress on valve; (e) installation adjustment: if pipe flanges misaligned (too close/far), adjust telescopic section to fit (no pipe cutting); (f) stress relief: absorbs pipeline vibration, water hammer force, minor misalignment - protects valve body/disc from force; (g) maintenance space: extend telescopic section → creates gap between valve and pipe flange → remove valve without cutting pipe; (h) replaces expansion joint: normally pipeline needs separate expansion joint + valve - this valve integrates both = saves one component, cost, space, weight, leak points. Truss disc principle (large DN): (a) for DN ≥500, solid disc is heavy (material cost) and may deflect under pressure (causing seal leakage); (b) truss structure: disc = framework of ribs/struts arranged in triangles (like a bridge truss) - (c) lightweight: less material (openings between ribs); (d) high strength: triangular framework is rigid, resists bending/deflection under pressure; (e) large flow area: openings between ribs = flow passes through = low flow resistance (not blocked by solid disc); (f) stable: no deflection = disc stays flat = seal maintains; (g) for DN <500, solid disc (simpler, sufficient strength). Quarter-turn operation: (1) open (0°): disc parallel to flow - medium flows through (truss openings or around solid disc); low resistance; (2) closed (90°): disc perpendicular, wedged into seat - blocks flow, metal seal; (3) regulate (intermediate): disc at angle = throttles flow (triple-offset can regulate, but primarily on-off); (4) 90° = fast (worm gear ~10-30s, electric 5-15s, pneumatic 1-5s). Drive operation: (a) worm gear: handwheel → worm → worm gear → stem (90°), self-locking (worm cannot be back-driven), labor-saving (gear ratio reduces effort); (b) electric: motor → gearbox → stem, remote/DCS, torque protection, manual override; (c) pneumatic: rack-pinion/scotch-yoke, compressed air, fast, ATEX; (d) hydraulic: hydraulic cylinder → lever → stem, high torque (for DN≥1000), fast; (e) multi-position mounting: drive flange has bolt holes at 90° intervals → rotate drive to desired orientation (handwheel faces aisle, actuator faces cable). High-temperature principle: (a) carbon steel (WCB/WC6/WC9): WCB ≤425°C, WC6 (1.25Cr-0.5Mo) ≤475°C, WC9 (2.25Cr-1Mo) ≤550°C - for steam/hot oil; (b) stainless (CF8/CF8M/310S/2520): 304/316 ≤425°C, 310S ≤1000°C, 2520 ≤1200°C - for high-temp gas; this valve stainless rated to 650°C (with appropriate seal/packing); (c) graphite packing: flexible graphite ≤650°C (no PTFE/rubber); (d) metal seal: J-ring + Stellite ≤650°C (no rubber); (e) body bolt material: high-temp bolts (e.g., 25Cr2MoV) for >425°C; (f) thermal expansion: all components expand - J-ring elasticity compensates. Pressure limitation: (a) PN0.6-2.5 - butterfly valve (even triple-offset) is for low/medium pressure; (b) at high pressure (>PN2.5), disc deflects, seat leaks, body stress high - use gate/ball valve; (c) for large-bore water/gas/ 烟气 (typically PN0.6-1.6), ideal; (d) truss disc helps at larger DN but still limited. Testing: (1) body hydrostatic 1.5×PN - zero external leak (body, expansion section, flange); (2) seat leak 1.1×PN - Class IV (metal seal, bidirectional); (3) torque test - open/close torque within spec; (4) expansion section test - pressurize while telescoping (verify no leakage at full extension/retraction); (5) high-temp test (if specified) - thermal cycle, seal at temp; (6) NDT - body welds (large DN), Stellite overlay (penetrant); (7) face-to-face/flange dimension. Flow regulation (optional): (a) triple-offset butterfly can regulate (disc at intermediate angle controls flow); (b) flow characteristic ~equal percentage/linear (depending on disc shape); (c) but primarily on-off (metal seal at partial opening = high velocity/erosion); (d) for regulation, use at 15-85% opening (avoid <15% - cavitation/erosion); (e) specify if regulation needed. Maintenance: (1) periodic exercise (full open/close) - prevents seat seizure; (2) inspect expansion section - check for leakage at telescopic seal, tightness, travel (if stuck, lubricate); (3) inspect seal - if leakage increases, seat/J-ring worn (replace); (4) lubricate stem (anti-seize, especially high temp); (5) check flange/expansion bolts (re-torque after thermal cycling); (6) replace seal ring (bolted, easy) - not entire valve; (7) large DN - inspect truss disc (cracks, loose ribs). Important: (a) not for high pressure >PN2.5 - use gate/ball; (b) not for abrasive slurry (Stellite helps but slurry erodes); (c) expansion travel - do not exceed rated travel (can damage seal); (d) high temp >425°C - stainless body + graphite packing + high-temp bolts; (e) bidirectional - install either direction; (f) support pipeline for large DN (valve not load-bearing); (g) thermal cycling - re-torque bolts periodically; (h) on-off primary - avoid continuous throttling. Operation: (1) open: rotate drive → disc to 0° (parallel) → flow; (2) close: rotate → disc to 90° → wedge into seat → seal; (3) indication: local position indicator (open/close) on drive; (4) expansion: telescopic section moves with pipeline (no manual adjustment needed normally - set during install).

• Petrochemical Industry 

Catalytic cracking units, hydrogenation units, heavy oil transportation, long-distance pipeline stations, oil & gas processing - handling high-temperature and impurity-containing media (hot oil, hydrocarbon gas, catalyst particles). Triple-offset zero-friction hard seal resists wear/erosion; stainless body to 650°C; extended flange relieves thermal stress in high-temp piping; large-bore for pipeline mains. Reliable for harsh petrochemical high-temp service.

• Power & New Energy Industry

Boiler feedwater, main steam bypass, FGD desulfurization, denitrification (SCR) systems, pulverized coal transportation, supercritical/ultra-supercritical units - high-temperature/high-pressure water/steam/gas, abrasive coal/ash. Carbon steel to 425°C / stainless to 650°C; Stellite disc resists erosion; truss disc for large-bore cooling water; extended flange absorbs steam line thermal expansion. Reliable for power plant boiler/steam/FGD/coal pipelines.

• Metallurgy & Steel Industry

Blast furnace gas (BFG), hot blast furnace flue gas (stove gas), dry dust removal systems, coke oven gas, sintering flue gas - high-temperature (200-600°C) dusty/abrasive gases. Metal hard seal + Stellite disc withstand dust erosion; stainless body for high temp; triple-offset long life in high-cycle gas regulation; large-bore for gas mains. Reliable for metallurgy high-temp dusty gas pipelines.

• Municipal & Environmental Protection

Urban water supply/drainage main networks, sewage treatment plants, waste incineration (flue gas), district heating/cooling mains - large-diameter (DN500-2000) water/wastewater/flue gas. Extended flange relieves thermal stress in long heating mains; truss disc low flow resistance saves pumping energy; worm gear manual for municipal; cost-effective large-bore. Reliable for municipal large-diameter water/wastewater/heating.

• Paper + Sugar + Food + Pharma + Textile + PV

Paper making (high-viscosity fiber media, black liquor), sugar (crystalline media, syrup), food & pharmaceutical (process fluids, CIP), textile (dyeing/heating), photovoltaic (thermal oil, cooling) - varied media with temperature/corrosion. Triple-offset hard seal handles viscous/crystalline without jamming; stainless body for corrosion/food; multi-position drive adapts to process layout. Reliable for process industries with harsh media. 18-month warranty, OEM/ODM.

Our Extended Flange Hard Seal Butterfly 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 triple-offset hard-seal extended-flange butterfly valves are used for petrochemical, power, metallurgy, and municipal large-bore high-temperature pipelines where seal wear, high-temperature failure, expansion-section leakage, disc deflection, or body stress can cause process disruption, safety hazards, environmental incidents, and costly downtime (triple-offset geometry, metal hard seal, Stellite overlay, expansion joint function, and large-bore truss disc require strict dimensional accuracy, material verification, and functional testing).

Raw material control: every body/disc/stem/seat material batch comes with material certificate (chemical + mechanical per heat); carbon steel (WCB/WC6/WC9), stainless (CF8/CF8M/310S/2520) verified by PMI (Cr/Ni/Mo/C content); Stellite welding wire verified (Co/Cr/W content, hardness); J-ring stainless verified (hardness, elasticity); graphite packing/expansion gasket verified.

Body manufacturing: (a) casting (carbon steel/stainless body) - sand casting; (b) heat treatment (carbon steel normalizing/tempering, stainless solution annealing, WC6/WC9 QT); (c) 100% visual; (d) NDT - radiographic/ultrasonic of critical sections (body, expansion section, for large DN); (e) wall thickness (per JB/T 8527/API 609); (f) flange machining (both ends - fixed + telescopic, GB/ANSI/BS/DIN); (g) seat cone machining (precision conical seat - angle α, surface finish); (h) expansion section machining (telescopic bore, packing recess); (i) stem bore/bearing; (j) chemical/mechanical/hardness per heat; (k) Stellite overlay on disc (PTA/plasma transfer welding, thickness ≥3mm, hardness HRC 40-45, penetrant inspection for cracks); (l) high-temp bolts (25Cr2MoV, etc.) for >425°C.

Disc manufacturing: (a) cast/forged disc (solid for <DN500, truss for ≥DN500); (b) truss fabrication (rib welding, NDT, stress relief); (c) Stellite overlay on sealing cone (PTA, ≥3mm, HRC 40-45); (d) grinding/lapping of Stellite surface (Ra ≤0.8μm, cone angle accuracy); (e) stem hole/keyway; (f) dynamic balance (for large DN); (g) penetrant inspection of overlay. Seat/J-ring manufacturing: (a) J-ring: stainless sheet formed into J-shape, heat treated (spring temper), dimensional check, elasticity test; (b) seat ring: stainless machined, bolt holes, cone surface; (c) assembly: J-ring + seat ring (bolted or welded), replaceable design verified.

Stem: (a) stainless/alloy machined (offset dimension "e" verified - critical for triple-offset); (b) surface treatment (nitrided/hard chrome for wear); (c) straightness, offset accuracy.

Expansion section: (a) telescopic sleeve machining (clearance fit); (b) packing/gasket (graphite/PTFE); (c) travel test (full extension/retraction, no binding); (d) seal test under pressure (pressurize while telescoping).

Assembly: (1) install seat/J-ring (bolted, torque); (2) install stem + bearings + graphite packing; (3) install disc (align offset, key/pin - verify triple-offset geometry); (4) assemble body (fixed + telescopic section, expansion seal); (5) mount drive (worm gear/electric/pneumatic/hydraulic) - multi-position; (6) full stroke test (0-90°, verify cam-out/wedge-in, smooth, no binding); (7) seat contact test (feel gauge/blue check - verify uniform contact); (8) expansion travel (full extension/retraction); (9) position indicator set.

Pressure testing: (1) 100% body hydrostatic shell 1.5×PN - zero external leak (body, expansion section, flange, stem); (2) 100% seat leak 1.1×PN - Class IV (metal seal, bidirectional, per GB/T 13927/API 598); (3) 100% air tightness (low-pressure); (4) expansion section pressure test - pressurize at full extension, mid, full retraction (zero leak); (5) torque test - open/close torque (within spec, no excessive torque indicating interference); (6) high-temp test (if specified - thermal cycle to rated temp, seal verification); (7) JB/T 8527/API 609. Function testing: open/close 90° travel, triple-offset cam-out verification (disc separates from seat within first 5°), seat contact uniformity, truss disc deflection (under pressure, if large DN), expansion travel, flange dimensions (GB/ANSI/BS/DIN), face-to-face, drive multi-position, Stellite hardness, J-ring elasticity, paint/coating, nameplate.

Coating & marking: exterior - carbon steel epoxy paint (blue standard or customer), high-temp paint for >425°C; stainless pickled/passivated; interior - for high temp bare or high-temp coating; valve permanently marked with DN, PN, material, temp rating, offset, standard, flow direction, manufacturer, year; nameplate (stainless, engraved).

Documentation: shipped with hydrostatic test report, material certificate, seat leak report, torque test report, expansion section test report, Stellite overlay report (hardness/penetrant), NDT report (large DN), high-temp test report (if applicable), and installation/operation/maintenance manual (including triple-offset principle, expansion section adjustment, maintenance, Stellite care).

Warranty: 18 months from shipment or 12 months from installation (valve body); electric/pneumatic actuator 12 months; extended warranty and third-party inspection (BV, SGS, TUV) available.

Q: What is a triple-offset (triple-eccentric) butterfly valve, and how is it different from concentric/double-offset?

A: Triple-offset butterfly valve (also called triple-eccentric or triple-offset) is the most advanced butterfly valve design where three separate offsets are engineered into the disc/stem/seat geometry to achieve zero friction between disc and seat during rotation, and wedge-type metal hard sealing on closing. The three offsets: (1) Offset 1 - Shaft axis offset (e): The stem (shaft) centerline is offset from the pipe/seat centerline by a distance "e" (typically 5-15mm, depending on valve size). This means the disc rotates around an axis that is not through the center of the seat - so the disc moves in an arc that pulls away from the seat on opening. (2) Offset 2 - Disc sealing surface offset: The disc's conical sealing surface axis is offset from the stem axis - the disc itself is "eccentric" relative to its rotation axis. (3) Offset 3 - Seat cone angle (α): The seat sealing surface is a cone (not a cylinder) with a half-angle "α" (typically 5-15°). The disc sealing surface matches this cone. Combined effect - zero friction: (a) On opening (closed 0° → open 90°): Due to the three offsets, the disc immediately cams out of the seat within the first 1-5° of rotation - for the remaining 85-89° of travel, the disc does not touch the seat at all = zero friction, zero rubbing, zero wear. (b) On closing (open → closed): The disc only contacts the seat in the last few degrees - then it wedges into the conical seat with mechanical interference (cone angle creates wedge action) = tight, self-energizing seal. Why zero friction matters: (a) no wear on sealing surfaces (Stellite disc + metal seat don't rub) → very long cycle life (100,000+ operations vs ~10,000 for concentric rubber-seat); (b) no seat damage from scraping (critical for metal hard seal - metal-on-metal rubbing would gall/wear); (c) low torque (no friction to overcome except at closing); (d) suitable for high-cycle (frequent operation) and high-temp/abrasive (no wear = long life). Comparison: (a) Concentric butterfly valve (simplest, cheapest): shaft through center, disc/cylinder seat. Disc rubs against seat throughout entire 90° rotation → seat wears quickly (especially rubber), short life, only soft seal (rubber/PTFE), low temp. Use: water, low-cycle, low-cost. (b) Double-offset (double-eccentric): shaft offset + disc offset (2 offsets). Disc cams out of seat after ~10-15° rotation - still some contact in first 10-15° (some wear). Better than concentric but not zero-friction. Can use metal seal but still some wear. (c) Triple-offset (this valve): 3 offsets = true zero friction throughout rotation (disc separates in first 1-5°). Best for metal hard seal, high temp, high-cycle, long life. Most advanced/expensive. Self-energizing "tighter when closed": (a) The conical seat + wedge disc means that higher medium pressure pushes the disc harder into the cone = tighter seal (unlike concentric where pressure can push disc off seat); (b) this makes triple-offset suitable for both low and high pressure sealing; (c) bidirectional - symmetric cone seals both flow directions. This valve = triple-offset with multi-layer metal hard seal (J-ring + Stellite disc) - the most advanced butterfly valve design for harsh/high-temp/wear service. Note: (a) triple-offset is sometimes called "triple-offset" (TOV) or "triple-eccentric" - same thing; (b) the offset dimensions (e, α) are precision-machined - must be accurate for zero-friction (our valves CNC-machined with verified offset); (c) triple-offset valves are more expensive than concentric but last 5-10× longer in harsh service → lower total cost of ownership.

Q: What is the extended flange (expansion joint) function, and why is it needed?

A: Extended flange (also called expansion-flange or telescopic flange) on this butterfly valve means the valve body has a telescopic/extendable flange section that integrates the functions of a butterfly valve + a pipe expansion joint in a single unit. How it works: (a) The valve body has two sections: (1) the main valve body (containing seat/disc), and (2) a telescopic extension section that slides axially (in/out) with a packing/gasket seal (graphite/PTFE) between the sliding surfaces - zero leakage while allowing movement. (b) The telescopic section has axial travel (typically ±25mm to ±100mm, depending on DN - larger valves have more travel). Five key functions: (1) Absorb pipeline thermal expansion/contraction: Steel pipes expand/contract with temperature changes (coefficient α ≈ 12×10⁻⁶ per °C). Example: a 100m steam pipe at ΔT=400°C expands ~480mm! Without an expansion joint, this thermal growth creates huge stress on valves, pumps, flanges - causing leakage, bolt failure, pipe buckling. The telescopic flange absorbs this movement = no stress on valve/piping. (2) Adjust flange distance during installation: If pipeline flanges are slightly too close or too far (misalignment from fabrication/installation error), the telescopic section can be adjusted to match - no need to cut or re-weld pipe. Saves installation time. (3) Relieve misalignment/vibration: Absorbs minor angular/lateral misalignment and pipeline vibration (water hammer, pump vibration) - protects valve body/disc from force. (4) Protect the valve: Pipeline forces (thermal stress, water hammer, vibration) are absorbed by the expansion section rather than transmitted to the valve body/disc/stem - extends valve life. (5) Facilitate maintenance/removal: By extending the telescopic section, you create a gap between valve and pipe flange - the valve can be removed without cutting the pipe. Creates maintenance space. Why it's needed (especially for this valve): (a) This valve is for high-temperature service (to 650°C stainless / 425°C carbon steel) - high-temp pipelines have large thermal expansion → expansion joint is essential (not optional); (b) large-bore (DN50-2000) - large pipes have large expansion forces; (c) long pipeline runs (petrochemical, power, district heating) - thermal expansion accumulates over length; (d) normally you would install a separate expansion joint + valve - this valve integrates both = saves one component, cost, space, weight, and leak points (fewer flanges = fewer potential leaks). How to use/install: (a) During installation, set telescopic section to mid-travel (so it can absorb both expansion and contraction); (b) tighten flange bolts; (c) the telescopic section moves automatically with pipeline (no manual adjustment needed during operation); (d) do not weld or lock the telescopic section (it must move freely); (e) inspect periodically for leakage at expansion seal, lubricate if sticking. Expansion seal: (a) Packing/gasket between telescopic surfaces - graphite (high temp, ≤650°C) or PTFE (≤200°C); (b) zero leakage under pressure while sliding; (c) replaceable if worn (like valve packing). Travel specification: (a) typically ±25mm (DN50-300), ±50mm (DN350-800), ±100mm (DN900-2000); (b) specify if more travel needed (custom). Important: (a) do not exceed rated travel (can damage seal, disengage); (b) support pipeline on both sides - expansion joint is not a pipe support; (c) for very high temp (>425°C), use graphite expansion seal (not PTFE); (d) vertical installation - expansion section should be below valve (so debris doesn't enter telescopic bore); (e) this integrated design is patented/common in power/petrochemical for high-temp large-bore lines. This valve's extended flange makes it ideal for high-temp large-bore pipelines where thermal stress would damage a standard flange valve.

Q: What temperature/pressure can this valve handle, and what materials are available?

A: Temperature range: (a) Carbon steel body: -29°C ~ 425°C - standard for most industrial high-temp (steam ≤400°C, hot oil, water). Carbon steel grades: WCB (general, ≤425°C), WC6 (1.25Cr-0.5Mo, ≤475°C), WC9 (2.25Cr-1Mo, ≤550°C) - alloy steels for higher temp/creep resistance. (b) Stainless steel body: -40°C ~ 650°C - for higher temperature and corrosion. Stainless grades: CF8 (304) / CF8M (316) (≤425°C, corrosion), 310S (≤1000°C, high-temp gas), 2520 (310S+Nb) (≤1200°C) - this valve's stainless rating is 650°C (with appropriate seal/packing/bolts). (c) Below -29°C: special low-temp carbon steel (LCB/LCC) or stainless (304L/316L) - not standard, specify. Pressure range: PN0.6, PN1.0, PN1.6, PN2.5 MPa (Class 75/150/300 equivalent). (a) PN0.6 - large-bore water/gas (municipal, low pressure); (b) PN1.0/1.6 - most common (water, steam, gas, oil); (c) PN2.5 - higher pressure (steam, process); (d) not for >PN2.5 - butterfly valves (even triple-offset) are limited to medium pressure (disc deflection at high pressure); use gate/ball for higher. Seal test pressure: 1.1×PN (e.g., PN1.6 → 1.76MPa, PN2.5 → 2.75MPa). Strength test pressure: 1.5×PN (e.g., PN1.6 → 2.4MPa, PN2.5 → 3.75MPa). Body materials: (a) Carbon steel WCB (ASTM A216) - general water/steam/oil, ≤425°C, most economical; (b) Alloy steel WC6/WC9 (ASTM A217) - high-temp steam (425-550°C), creep-resistant; (c) Stainless CF8/CF8M (ASTM A351, 304/316 cast) - corrosion, ≤425°C; (d) Heat-resistant stainless 310S/2520 - high-temp gas (650°C+), specify. Disc material: (a) carbon steel/stainless base + Stellite overlay (Stellite 6 or 21, cobalt-chromium-tungsten, HRC 40-45, thickness ≥3mm) - wear/corrosion/erosion resistant; (b) truss structure for large DN (≥DN500). Seat/J-ring material: (a) J-shaped elastic ring: stainless steel (304/316 standard, Inconel for high-temp/corrosion) - elastic spring action; (b) seat ring: stainless (bolted, replaceable); (c) all-metal hard seal (no rubber/PTFE in sealing contact). Stem material: (a) 410 (13Cr) stainless (general, hardened); (b) 304/316 stainless (corrosion); (c) 25Cr2MoV alloy (high-temp, for >425°C); (d) surface: nitrided or hard chrome (wear). Packing material: (a) flexible graphite (high temp, ≤650°C, fire-safe) - standard for this hard-seal high-temp valve; (b) PTFE (≤200°C, chemical) - optional for low-temp corrosive. Expansion section seal: (a) graphite (high temp) - standard; (b) PTFE (low temp) - optional. Fasteners (bolts): (a) carbon steel (≤425°C); (b) 25Cr2MoV / 35CrMoV alloy (high-temp >425°C, creep-resistant); (c) stainless B8/B8M (corrosion). Gasket (flange): (a) spiral wound graphite (high temp/pressure) - standard; (b) metal jacketed (very high temp); (c) PTFE/rubber (low temp/water). Selection guide: (a) water, ≤200°C, PN1.0/1.6 → WCB body + graphite/PTFE packing; (b) steam 250-400°C → WCB/WC6 + graphite + Stellite + alloy bolts; (c) hot oil 300-425°C → WCB + graphite; (d) high-temp gas 400-650°C → stainless (310S/2520) + graphite + Inconel J-ring + alloy bolts; (e) corrosive (acid/alkali) → CF8/CF8M stainless + PTFE packing (if ≤200°C) or graphite; (f) large-bore water PN0.6 → WCB, truss disc, cost-effective. Important: (a) temp rating depends on all components (body + seal + packing + bolts) - not just body; (b) 650°C requires stainless body + graphite packing + metal seal + high-temp bolts (all upgraded); (c) cyclic thermal service (frequent temp changes) - use alloy steel (WC6/WC9) for creep resistance; (d) specify your actual operating temp/pressure/medium when ordering - we configure all components accordingly; (e) this valve is not for cryogenic (<-40°C) - use cryogenic butterfly with extended bonnet. This valve offers carbon steel to 425°C and stainless to 650°C, PN0.6-2.5 - covers most industrial high-temp large-bore applications.

Q: How does the multi-layer metal hard seal (J-ring + Stellite) achieve zero leakage, and how long does it last?

A: Multi-layer metal hard seal on this valve consists of three components working together: (1) J-shaped elastic sealing ring (stainless steel), (2) stainless steel seat ring (support), (3) cobalt-based Stellite hardfaced disc. How it achieves zero (near-zero) leakage: (a) J-shaped elastic ring: A stainless steel ring (304/316/Inconel) bent into a "J" cross-section - this shape acts like a spring (it can compress/deflect elastically when loaded, then return). The J-ring is mounted in the seat with the lip facing the disc. (b) On closing: When the disc wedges into the seat (triple-offset action), the Stellite disc surface presses against the J-ring lip - the J-ring compresses elastically (like a spring) and conforms to the disc surface (compensating for minor surface roughness, flatness errors, thermal expansion mismatch). (c) Conformability = zero leakage: Because the J-ring is elastic, it maintains intimate contact with the disc across the entire sealing circumference - even at low pressure (where pure metal-to-metal seal would leak due to microscopic surface gaps). This is the key advantage over pure metal-to-metal seal (which leaks at low pressure because metal doesn't conform). (d) Metal hard seal benefits: All sealing components are metal (stainless J-ring + Stellite disc) - no rubber/PTFE - so they withstand high temperature (650°C), fire (doesn't burn), wear/erosion (Stellite HRC 40-45), and abrasive media (dust, particles). (e) Self-energizing at high pressure: Medium pressure pushes disc harder into J-ring → J-ring compresses more → tighter seal (higher pressure = lower leakage). (f) Leakage rate: Class IV per GB/T 13927/API 598 - for a metal-seated valve, this is very low (typically ≤0.01% of Cv, or ~bubbles for small DN). It is not "bubble-tight zero" like a soft rubber seal, but it is the practical limit for metal hard seal at high temp. Why not pure rubber/PTFE? (a) rubber/PTFE melts/burns at >180-250°C - cannot handle 650°C; (b) rubber/PTFE wears in abrasive/dusty media; (c) metal seal = high temp + wear + fire-safe. Why not pure metal-to-metal (no J-ring)? (a) pure metal-to-metal (rigid seat + rigid disc) requires extreme precision (lapped surfaces, Ra ≤0.1μm) and still leaks at low pressure (no conformability); (b) J-ring elasticity solves this - it's a compliant metal seal (metal that flexes). Service life of the seal: (a) Triple-offset zero friction = disc does NOT rub J-ring during opening/closing (only contacts in last 1-5° of closing) → no sliding wear on sealing surfaces; (b) Stellite disc (HRC 40-45) = very hard, wear/erosion resistant; (c) J-ring stainless = elastic, fatigue-resistant (can compress/release many cycles); (d) typical life: 100,000+ cycles (operations) before seal needs attention - vs ~10,000 cycles for concentric rubber-seat; (e) in years: 8-15+ years under normal use (depending on cycle frequency, media abrasiveness, temp); (f) abrasive/dusty media (blast furnace gas, coal) may reduce life (Stellite helps but fine dust can still erode) - inspect regularly; (g) high-temp cyclic (frequent heating/cooling) - thermal fatigue may affect J-ring over time (Inconel better than 304 for cyclic). When to replace seal: (a) leakage exceeds Class IV (visible bubbles or measurable); (b) J-ring shows cracks, permanent set (doesn't spring back), corrosion; (c) Stellite disc shows deep scratches/galling; (d) replaceable - J-ring + seat ring are bolted → unbolt and replace (no need to scrap entire valve) → low maintenance cost. Maintenance tips: (a) exercise valve periodically (full open/close) - prevents J-ring/disc seizure (especially if idle long); (b) do not throttle at small opening (<15°) - high velocity can erode J-ring/disc; (c) inspect seal annually (leakage test, visual if accessible); (d) clean sealing surfaces if media has deposits (carbon, scale) - can prevent proper seating; (e) replace J-ring/seat as a set (both surfaces should be matched). This valve's multi-layer metal hard seal combines the best of elastic compliance (zero low-pressure leakage) and metal hardness (high temp/wear/fire) - with triple-offset zero friction = very long life.

Q: What is a truss disc, and when is it used?

A: Truss disc (also called framework disc or truss-type butterfly disc) is a disc design for large-diameter butterfly valves (typically DN ≥500) where the disc is constructed as a truss (framework/rib structure) instead of a solid plate. Why truss disc is needed for large DN: (a) Solid disc problem: For large diameters (e.g., DN1000 = 1m disc), a solid steel disc is: (i) very heavy (hundreds of kg) - high material cost, high inertia (hard to open/close quickly), high bearing load; (ii) prone to deflection - under pressure, a large solid disc can bend/deflect (like a large drum head), causing the sealing edge to lift off the seat → leakage; (iii) high flow resistance - a large solid plate blocks flow even when "open" (though parallel to flow, it still obstructs). (b) Truss disc solution: Replace solid plate with a truss framework - (i) lightweight: framework of ribs/struts uses much less material (e.g., 50-70% lighter than solid) → lower cost, lower inertia, easier/faster operation, less bearing stress; (ii) high strength: triangular truss geometry is inherently rigid (triangles don't deform) - resists bending/deflection under pressure → sealing edge stays flat → maintains seal; (iii) large flow area: open spaces between truss ribs allow flow through → low flow resistance (K factor low, close to empty pipe) → energy saving; (iv) stable: no deflection under high pressure = consistent seal, no disc flutter. Truss structure details: (a) ribs/struts: steel plates/sections welded into triangular framework (like a bridge truss or lattice tower); (b) sealing rim: outer edge of truss is a solid ring (with Stellite overlay) that contacts the seat - only the rim needs to be solid/smooth (the rest is framework); (c) hub: center hub connects to stem; (d) fabrication: ribs welded, then stress relief (to remove welding residual stress), NDT (radiographic/ultrasonic of welds), Stellite overlay on sealing rim, grinding of rim. When is truss disc used? (a) DN ≥500 (20") - standard for this valve at large sizes; (b) DN <500 - solid disc (simpler, cheaper, sufficient strength - small disc doesn't deflect); (c) high pressure (PN2.5) at large DN - truss needed for rigidity; (d) low flow resistance required (large-bore water/gas mains) - truss open area helps; (e) fast operation (electric/pneumatic quick cycling) - lightweight truss = lower inertia = faster. Truss vs solid comparison: | Feature | Solid Disc (<DN500) | Truss Disc (≥DN500) | |---|---|---| | Weight | Heavy (large DN) | Light (50-70% less) | | Strength/Deflection | May deflect at large DN | Rigid, no deflection | | Flow Resistance | Moderate (solid plate obstructs) | Low (open framework) | | Cost | High material (large DN) | Lower material | | Operation Torque | High (heavy inertia) | Low (light) | | Complexity | Simple (cast/machined) | Complex (fabricated/welded) | This valve: (a) DN50-450: solid disc (standard); (b) DN500-2000: truss disc (standard) - high strength, large flow area, low resistance, stable under pressure; (c) truss discs are 100% NDT inspected (welds, stress relief) for large DN; (d) Stellite overlay on truss sealing rim (same as solid disc). Important notes: (a) truss disc is not for abrasive slurry (slurry can pack in truss framework, cause imbalance/wear) - use solid disc or other valve for slurry; (b) for gas/water/steam (clean or slightly dusty) - truss is ideal; (c) inspect truss welds periodically (cracks, corrosion) for large DN; (d) dynamic balance - truss disc is balanced (symmetric) to avoid vibration; (e) if you need solid disc at large DN (special media), specify (custom, but heavier/costlier). This valve's truss disc for large DN makes it ideal for large-bore water/gas/steam mains in municipal, power, petrochemical - where low flow resistance + light weight + high strength are critical.

Q: How do I install, maintain, and troubleshoot an extended flange hard-seal butterfly valve?

A: Installation: (1) Verify: check DN, PN, body material (carbon/stainless), temp rating, seal type, flange standard, expansion travel - match pipeline; (2) Inspect: remove flange protectors, inspect flange faces (fixed + telescopic), seat/J-ring (no damage, no debris), disc (move manually via override to verify smooth 90° + cam-out), expansion section (move telescopic part by hand - should slide smoothly, no binding); (3) Orientation: can install any orientation (flow bidirectional); recommend stem horizontal or actuator on top (packing life, access); for gas/dust, stem horizontal (prevents debris entering stem bore); for vertical pipe, expansion section below valve (debris doesn't enter telescopic bore); (4) Set expansion travel: Loosen telescopic section bolts, set to mid-travel (e.g., if travel ±50mm, set at 0 = center) so it can absorb both expansion and contraction; then tighten (or leave free-floating - depends on design, follow manual); (5) Gasket: place spiral wound graphite (high temp) or appropriate gasket on both flanges; (6) Bolting: use correct bolts (alloy for high temp), lubricate threads (anti-seize for stainless/alloy), torque in cross-pattern (3-4 passes, final torque per spec); (7) Support pipeline: for large DN, support pipe on both sides near valve - do not let valve body support pipe weight (can distort body/expansion section); (8) Test: pressurize slowly, check external leaks (flange, body, expansion section, stem), operate full open/close, verify no binding, check expansion section moves with pipe (if thermal). Maintenance: (1) Periodic exercise: full open/close every 3-6 months (prevents J-ring/disc seizure, especially if idle); (2) Inspect external leaks: flange, body, expansion telescopic seal, stem packing - fix immediately; (3) Expansion section inspection (key for this valve): (a) check for leakage at telescopic seal (if leak, tighten packing or replace); (b) verify free movement (pipe should expand/contract freely - if stuck, lubricate/repair); (c) check travel limit (not over-extended/retracted); (d) clean debris from telescopic bore (if gas/dust service); (4) Seal inspection: if seat leakage increases (audible/visible bubbles, or measured), J-ring/disc may be worn - replace J-ring/seat (bolted, replaceable); (5) Stem packing: if stem leaks, tighten gland (1/4 turn, don't over-tighten); replace graphite packing if needed; (6) Lubrication: stem/bearing (anti-seize, high-temp grease), expansion section (if sticking); (7) Bolts: re-torque flange/expansion bolts after first thermal cycle (gaskets settle), then periodically; (8) Large DN truss disc: inspect truss welds (cracks/corrosion), disc for vibration/looseness; (9) Coating: touch up paint chips (prevent corrosion, especially carbon steel). Troubleshooting: (a) Won't open/close (jammed): (i) disc seized to seat (idle long + deposits) - exercise gently with worm gear (do not force with cheater bar - may break stem); (ii) stem/packing seized - lubricate, loosen packing; (iii) expansion section seized - lubricate telescopic bore; (iv) foreign object in seat - remove, clean; (b) Seat leakage (through valve): (i) disc not fully closed (calibrate stop); (ii) J-ring worn/damaged/permanent set (replace); (iii) Stellite disc scratched/galled (re-grind or replace); (iv) deposits on sealing surface (carbon/scale - clean); (v) triple-offset misadjusted (stem/disc shifted - re-calibrate offset); (c) External leak - flange: tighten bolts (cross pattern), replace gasket; (d) External leak - expansion section: tighten telescopic packing, replace expansion gasket/packing; (e) External leak - stem: tighten packing gland, replace packing; (f) High torque/hard to operate: (i) J-ring/disc galling (metal contact - triple-offset should be zero friction, if rubbing = offset misadjusted); (ii) stem bearing seized; (iii) disc binding in body (thermal expansion - check clearance); (iv) over-torqued packing; (g) Noise/vibration/chatter: (i) cavitation (high ΔP, small opening - avoid <15% opening); (ii) disc flutter (truss loose, or low pressure instability); (iii) water hammer (close slowly, install bypass); (h) Expansion section not moving: (i) telescopic bore corroded/seized (clean/lubricate); (ii) pipe supports locked (pipe not free to move); (iii) travel exceeded (damaged seal); (i) Signal/actuator fault (if electric/pneumatic): check power, wiring, limit switches, torque switch, air supply (per actuator manual). After maintenance/repair: (1) reopen fully (if was closed for maintenance); (2) re-test pressure (if seal/expansion replaced - 1.1×PN seat, 1.5×PN shell); (3) verify expansion travel reset to mid; (4) update records. Service life: (a) body: 20+ years; (b) J-ring/seat: 8-15 years (replaceable); (c) packing/expansion seal: 5-10 years; (d) actuator: 10-15 years; (e) with proper maintenance, 15-25+ years overall. Spare parts: J-ring + seat ring set, disc (or Stellite re-overlay), stem, graphite packing, expansion gasket/packing, flange gasket, bolts, actuator repair kit - order with valve. Important: (a) always isolate/depressurize/drain/cool before maintenance (high temp - allow to cool <50°C); (b) high-temp bolts - do not reuse if yielded (replace); (c) Stellite surfaces - do not grind excessively (removes hardfacing - re-overlay if worn through); (d) expansion section - critical component, inspect regularly (failure = pipeline stress + valve damage); (e) do not use as pipe support; (f) 18-month warranty from shipment. With proper installation, periodic exercise, and expansion-section inspection, this extended flange hard-seal butterfly valve provides long, reliable, low-maintenance service in harsh high-temp large-bore pipelines.

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