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Gaskets for petrochemical and chemical plants
Petrochemical, fertilizer and chemical plants combine high temperatures, thermal cycling and aggressive chemicals. The right combination of gasket type, metal and filler keeps flanges tight through start-ups, shutdowns and years of continuous service.
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| Representative image | Gasket / seal | Petrochemical / chemical use | Typical construction | Petrochemical / chemical applications | Typical standards / specifications |
|---|---|---|---|---|---|
 | Spiral Wound Gasket - QSW4 | High-pressure raised-face sealing where an inner ring is needed to prevent winding extrusion or buckling and to improve service reliability. | Profiled metallic winding with graphite, PTFE or mica filler, plus metallic inner and outer rings. | Ethylene/olefins units; hydrogen-rich synthesis loops; high-pressure reactor systems; ammonia/methanol auxiliaries; high-class process flanges and pressure-vessel piping. | ASME B16.20; mating flanges ASME B16.5 / B16.47; ASME B31.3 at process-piping level. ASME PCC-1 or project bolted-joint procedure may govern assembly. |
| Spiral Wound Gasket - QSW3 | General process-piping flange sealing with centering and compression control. | Profiled metal winding with graphite or other filler and a metallic outer centering/compression ring. | Polymer plants; aromatics; solvents; utilities; steam; cooling water; hydrocarbon and intermediate chemical service on common raised-face flanges. | ASME B16.20; ASME B16.5 / B16.47 for mating flanges; ASME B31.3 for process piping. |
 | Camprofile / Kammprofile Gasket | Severe-service sealing with high recovery under temperature, pressure, thermal cycling or relatively low bolt load. | Grooved metallic core with graphite or PTFE covering layers; fixed or floating guide ring depending on flange arrangement. | Reactor and vessel flanges; heat exchangers; polymerization units; high-temperature chemical processing; cyclic batch plants; large equipment nozzles. | ASME B16.20 for grooved metal gaskets with covering layers; ASME B16.5 / B16.47 flange interfaces; API 660 / TEMA where used on shell-and-tube exchangers. |
 | Metal-Jacketed / Heat-Exchanger Gasket | Large or complex exchanger sealing where a metallic shell protects a softer resilient filler. | Thin metallic jacket enclosing graphite or another resilient filler; single/double-jacketed and ribbed configurations. | Shell-and-tube heat exchangers; condensers; reboilers; coolers; evaporators; acid/solvent exchangers; process equipment with internal pass-partition ribs. | ASME B16.20 for standard metal-jacketed gaskets; API 660 / TEMA where applicable; ASME BPVC Section VIII for pressure-vessel heat exchangers; equipment drawing controls geometry. |
 | Ring Type Joint (RTJ) - R / RX / BX | Metal-to-metal sealing for very high-pressure and high-temperature connections where ring-joint flanges are specified. | Precision-machined metallic ring in R, RX or BX profile, using carbon, alloy or stainless steel selected for process conditions. | High-pressure synthesis gas and hydrogen service; compressor systems; high-pressure reactors; specialty process valves; severe process connections. | ASME B16.20; mating flange specification such as ASME B16.5/B16.47 or API 6A where applicable; ASME B31.3 at system level. |
 | Solid Metal / Metal-Core Gasket | Extreme pressure/temperature sealing where conventional soft gasket materials are unsuitable. | Solid metallic gasket or rigid metal core, optionally faced with expanded graphite or ePTFE. | High-temperature reactors; compressor/turbine casings; autoclaves; vessel covers; polymerization equipment; special OEM joints and custom equipment. | QGER cites ASME B16.20, BS or DIN where applicable; special designs are controlled by purchaser/OEM drawings. ASME BPVC Section VIII may apply at pressure-equipment level. |
 | Flexible Graphite Gasket | High-temperature chemical and steam sealing with excellent recovery and resistance to many process fluids. | Flexible/expanded graphite, with or without reinforcement or metallic insertion; ring or custom-cut shape. | Steam and hot-oil systems; hot organic chemicals; reactor auxiliaries; valve bonnets; vessel manways; heat exchangers and high-temperature process flanges. | ASME B16.21 for nonmetallic flat gaskets where applicable; EN 1514-1 for PN flanges; ASME B31.3 process piping; purchaser purity/oxidation requirements may also apply. |
 | Graphite Pressure-Seal / Cover-Seal Ring | Self-energizing sealing in pressure-seal valve bonnets and other self-sealing covers under severe temperature and pressure cycling. | Preformed high-density flexible graphite ring or cover-seal profile compressed by system pressure and bonnet geometry. | High-pressure process valves; hydrogen/ammonia systems; high-pressure steam and hot process services; self-sealing covers and selected pressure equipment. | ASME B16.34 and valve/OEM specification for pressure-containing valve assemblies; API 600/623 where those valve types are specified; ASME B31.3 at piping-system level. |
 | PTFE / ePTFE Flat Gasket | Chemically resistant sealing for aggressive acids, caustics, oxidizers and solvents where PTFE compatibility is appropriate. | Virgin/filled PTFE, restructured PTFE or 100% expanded PTFE flat gasket. | Chlor-alkali; acid plants; specialty chemicals; solvent systems; chlorine/caustic auxiliaries; corrosive transfer piping; lined and nonmetallic equipment interfaces. | ASME B16.21; EN 1514-1 for PN-designated flanges; ASME B31.3 at piping-system level. Chemical compatibility and permeation requirements govern final material selection. |
| PTFE Envelope / Filter Gasket | Combines broad chemical resistance and low contamination risk with a compressible core. | PTFE envelope around compressed non-asbestos fibre or flexible graphite core; standard or custom geometry. | Strong acids and caustics; glass-lined reactors; filters; centrifuge/filter housings; chemical vessels; piping and equipment requiring a PTFE wetted surface. | ASME B16.21 where standard flat-gasket dimensions apply; EN 1514-1 for compatible PN flanges; glass-lined equipment/filter OEM drawings control proprietary geometry. |
 | CNAF / Compressed Fibre Gasket | General-purpose sealing for utilities, water, steam, oils, mild acids/alkalis and selected chemical services. | Compressed non-asbestos fibre sheet with synthetic/inorganic fibres, fillers and elastomeric binder. | Cooling water; compressed air; low-pressure steam; utility skids; lubrication systems; general plant piping and ancillary equipment. | ASME B16.21; EN 1514-1; ASME B31.3 at piping-system level; material-specific purchaser/OEM requirements. |
 | ePTFE Gasket Tape / Joint Sealant | Form-in-place sealing for large, irregular, damaged or non-standard flanges and equipment covers exposed to aggressive chemicals. | 100% expanded PTFE tape or cord compressed in place around the flange or cover. | Large reactor manways; glass-lined vessel nozzles; tank covers; ductwork; large process-equipment flanges; custom chemical-processing equipment. | Equipment/OEM drawing and pressure-vessel requirements govern geometry; ASME PCC-1 or project bolted-joint procedures may govern assembly; ASME B31.3 applies at process-piping system level where relevant. |
 | Flange Insulation Kit / Insulating Gasket | Electrical isolation of flanged assemblies to control galvanic interaction or support cathodic-protection/isolation requirements. | High-strength insulating gasket plus full-length sleeves, insulating washers and steel washers for each bolt. | Tank farms; transfer pipelines; buried or cathodically protected lines; dissimilar-metal interfaces; plant boundary isolation points. | ASME B16.5 / B16.47 or other applicable flange dimensions; AMPP/NACE SP0286 where electrical isolation of cathodically protected piping is required; project corrosion-control specification governs. |
| Graphite / PTFE Compression Packing | Dynamic/static sealing around valve stems and selected pump or agitator shafts, including fugitive-emissions-sensitive services. | Preformed graphite rings or braided graphite/PTFE packing sets selected for temperature, chemical exposure and stem/shaft conditions. | Control and isolation valves; toxic/VOC chemical service; pumps; mixers; agitators; solvent and corrosive-process equipment. | API 622 for process-valve packing type testing; API 624 for rising-stem valves with graphite packing; API 641 for quarter-turn valves; ISO 15848-1 for valve fugitive-emissions qualification. ISO 12101 may be used for stem-seal type testing where specified. |
 | Mechanical Seal | Controls leakage around rotating pump and mixer shafts in hazardous, corrosive or volatile process service. | Precision stationary/rotating seal faces with springs, secondary seals and single/dual arrangements selected for the process fluid. | Chemical process pumps; transfer pumps; reactor circulation; solvent and monomer service; corrosive chemical pumps; condensate and utility systems. | API 682 / ISO 21049 where an API-type shaft-sealing system is specified; API 610 / ISO 13709 for applicable heavy-duty pumps; ISO 5199/OEM requirements for other chemical-process pumps. |
 | Expansion Joint / Flexible Coupling | Absorbs thermal movement, vibration, pressure surges and piping/duct misalignment. | Engineered non-metallic/fabric or elastomeric flexible joint with flanged ends; metallic bellows may be used in other designs. | Chemical-process ducts; blower/fan connections; scrubber systems; utility piping; pump discharge; large-diameter chemical and cooling-water systems. | ASME B31.3 at piping-system level; FSA guidance and purchaser specification for non-metallic expansion joints; EJMA standards where metallic bellows are used. |
 | EPDM / NBR / FKM / FFKM Elastomeric Gasket | Low-to-medium pressure sealing where elastomer flexibility and chemical-specific resistance are advantageous. | Cut or molded full-face/ring gasket in EPDM, NBR, Viton/FKM, silicone, neoprene, SBR or FFKM; reinforcement may be added. | Cooling water; caustic/water service; hydrocarbons/oils; selected solvents and chemicals; utility flanges; lined piping; pump and equipment auxiliaries, with compound chosen for compatibility. | ASME B16.21; EN 1514-1; ASME B31.3 at piping-system level. Chemical-resistance, temperature and permeation limits must be verified for the selected compound. |
 | Pump Diaphragm | Flexible pumping barrier for aggressive chemicals, dosing service and contaminated or solids-bearing liquids. | ePTFE wetted face bonded to reinforced elastomer backing, or other OEM-specific PTFE/elastomer diaphragm construction. | AODD chemical transfer; acids/caustics; dosing skids; resins, coatings and specialty chemicals; filter feed; viscous or solids-bearing process streams. | Pump OEM dimensional/material specification governs. API 675 applies to hydraulic-diaphragm controlled-volume metering pumps where specified; it does not universally apply to AODD pumps. |
 | Plate Heat-Exchanger Gasket | Seals individual plates and separates process streams in gasketed plate-and-frame heat exchangers. | Precision-molded EPDM, NBR, FKM or specialty elastomer perimeter gasket clipped or bonded to the heat-exchanger plate. | Cooling and heat-recovery systems; polymer and chemical process heating/cooling; solvents; water/glycol loops; utility and specialty process exchangers. | API 667 where adopted for plate-and-frame heat exchangers in petroleum/petrochemical service; otherwise exchanger-OEM drawing/specification governs geometry and compound. |
 | Precision O-Rings / Molded Elastomer Seals | Compact static and dynamic sealing in instrumentation, valve actuators, dosing equipment, pumps and hydraulic/pneumatic systems. | Precision-molded EPDM, NBR, FKM/Viton, silicone, FFKM or other specialty elastomer; backup rings may be added for high pressure. | Analyzer systems; instrument fittings; valve actuators; metering equipment; dosing pumps; hydraulic/pneumatic skids; pump and compressor auxiliaries. | ISO 3601 series for O-ring dimensions, housings and quality acceptance; ISO 3601-4 for anti-extrusion rings where used. Equipment/OEM chemical-compatibility specification governs. |
These are typical starting points. Final selection depends on your service conditions and is confirmed with QGER engineering before manufacture.
Points to watch
- Flexible graphite oxidises in air above about 450 °C. For hotter oxidising service, ask us about ceramic fillers.
- With a PTFE filler, a spiral wound gasket needs an inner ring to prevent inward buckling.
- Give the exact chemical name and concentration in your enquiry. The same acid at two strengths can need different materials.
Selected QGER clients in this sector
Qatar Petrochemical Co. ↗Qatar Chemical Company ↗Qatar Vinyl Company ↗Ras Laffan Olefins ↗Qatar Fertiliser Co. ↗Qatar Fuel Additives ↗SEEF Limited ↗ORPIC (Oman) ↗
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