In hydroprocessing applications, the piping is very heavy. Therefore, due to the manufacturing process, the WP22 elbow might be thicker than the connected pipe, owing to the fact that the forming process adds excess iron to the extrados. The heat treatment time is determined based on the thickness of the joint, whereby the fitting determines how long, not the pipe, the entire weld is kept in the furnace or under temperature. On a shutdown schedule that is real time. ASTM A234 WP22 buttweld fittings carry hydrogen and high temperature service in refineries across Oman and the GCC. The wider range is on the alloy steel fittings and flanges hub.
Why Section Thickness Governs the Joint
PWHT tempers the hard martensite that forms in the heat affected zone as chrome-moly cools from welding, and it relieves residual stress. The cycle has two numbers, soak temperature and hold time, and the hold time scales with the thickest section in the joint because the heat has to reach through it.
| What happens | Consequence |
|---|---|
|
A heavy fitting is welded to lighter pipe |
The hold time follows the fitting, so the pipe sits in the cycle longer than its own thickness would need |
|
Hold time runs long or hot |
Over-tempering reduces strength, and on the higher alloy grades it costs creep performance |
|
Hold time runs short |
Hardness in the heat affected zone stays above the limit, which matters for sour service and for toughness |
|
Multiple PWHT cycles accumulate |
Repair welds add cycles, and the total exposure is what counts, not each one separately |
Two things follow for procurement. Ask what wall the fitting will actually be supplied at, not just the schedule, because B16.9 permits the fitting to be heavier than nominal. And where several PWHT cycles are foreseen, the material order and the welding procedure need to agree on a cumulative limit.
Where WP22 Is Used
- Hydrotreating and hydrocracking units in refinery and petrochemical service
- Catalytic reformer and hydrogen plant piping
- High temperature steam headers in power generation plants
- Crude and vacuum heater transfer lines
Below WP22 the usual grade is WP11; above it, WP91. Matching flanges are ASTM A182 F22 and matching pipe is ASTM A335 P22.
ASTM A234 WP22 Buttweld Fittings: Price Factors
Each enquiry is priced on its own, because grade, class and testing scope move the figure more than quantity does. What counts:
- Grade and the alloying elements it carries
- Size, pressure class, facing and bore
- Schedule or wall the item is made to
- Production route, forged or formed from pipe or plate
- Supplementary testing and inspection scope
- Order quantity and availability
- Certificate level and witness requirements
- Delivery terms and port of discharge
Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms.
What to send for a quotation: item type, material grade and standard, size, pressure class, facing, schedule or wall, quantity, testing, certification, inspection, destination port and required date.
Certification, Traceability and PMI
Material comes with EN 10204 3.1 certificates as standard, and EN 10204 3.2 certificates on request. Inspection by the buyer's nominated third-party agency can be arranged; state your requirement in the RFQ. Check that the heat number on the certificate matches the marking on the item itself, and that the heat treatment condition is stated, the class, and the J-factor where temper embrittlement limits are ordered. Positive material identification confirms the grade before anything is welded in. See the MTC and EN 10204 certification guide.
Delivery and Handling
Lead time is confirmed at quotation. Fittings ship bundled or crated with bevel protection; flanges ship with face and ring groove protection, since a scored face leaks whatever the gasket. In coastal Oman, salt deposits build up on anything left in the open, so a rinse and a dry before fitting up is worth the time.
Related Alloy Steel Products
- ASTM A234 WP11 fittings
- ASTM A234 WP91 fittings
- ASTM A182 F22 flanges
- Alloy steel fittings and flanges
- ASTM A335 P22 pipes
ASTM A234 WP22 Fittings: Buyer Questions
Why does a heavy fitting affect the whole joint?
Post-weld heat treatment hold time is set by the thickest section in the joint, so a fitting thicker than the pipe keeps the entire weld in the cycle longer than the pipe alone would need.
What classes does WP22 come in?
Class 1 at 415 MPa minimum tensile with 205 MPa yield, and Class 3 at 515 MPa with 310 MPa yield. The chemistry is the same; the heat treatment differs.
What is temper embrittlement?
Long exposure between roughly 340 and 575 degrees C raises the ductile-to-brittle transition temperature, so the risk appears during shutdown and start-up rather than at operating temperature.
How is temper embrittlement controlled?
Through a chemistry restriction expressed as the J-factor, silicon plus manganese multiplied by phosphorus plus tin and by ten thousand, with a maximum stated on the order. Step-cooling tests can be added.
Is WP22 suitable for hydrogen service?
It is the common choice. API RP 941 Nelson curves set the envelope by grade and hydrogen partial pressure, and 2.25Cr-1Mo has a wider margin than the lower alloy grades.
What should I send for a quotation?
Send the fitting type, class, NPS, schedule or wall, quantity, J-factor and step-cooling requirements, testing, certification, inspection and destination port.
Request a Quote for ASTM A234 WP22 Buttweld Fittings
Send the fitting type, class, size and wall with quantities, and state whether J-factor limits or step-cooling testing apply. Both are supplementary requirements that have to be on the order to be supplied.