ASME B31.1 / ASHRAE Handbook — HVAC Systems
What it means on the job
This is a textbook-correct steam trap installation as taught at UA halls. The F&T trap is appropriate for equipment drains (it handles variable condensate loads and passes air). The strainer upstream protects the trap internals from scale and debris. The check valve downstream prevents condensate backflow from the pressurized return header. Installing the trap at the same level as the drain (no lift) ensures gravity drainage into the trap — any lift before the trap creates a water seal that impedes condensate flow.
Tested in 4 CraftIQ puzzles
- whats-wrongCondensate Return Piping
- code-checkSteam Trap Selection
- code-checkCondensate Return Pipe Slope
- code-checkUnion Training: Steam Trap Discharge to Condensate Return
Related ASME sections
ASME B16.5 — Pipe Flanges and Flanged Fittings
A Class 150 flange is rated for approximately 275 PSI at ambient temperature (and less at elevated temperatures). Using it on a 300 PSI system exceeds its pressure-temperature rating, risking catastrophic failure.
ASME B31.1 — Power Piping
Steam supply piping must pitch downward in the direction of flow (away from boiler) to prevent condensate from pooling and causing water hammer. The piping here is back-graded, trapping condensate.
ASME B31.1 — Power Piping, para. 136.4 / Table 136.4
This is compliant. ASME B31.1 (Power Piping) does NOT mandate radiographic (RT) or ultrasonic (UT) examination for every welded joint — mandatory 100% NDE is triggered only by the thresholds in para. 136.4 / Table 136.4: butt welds and branch connections operating above 750°F, OR operating between 350°F and 750°F AND above 1025 psig AND with nominal wall thickness over 1-1/8 in. A 300 PSI (psig) steam main saturates at roughly 421°F and is far below the 1025 psig and 750°F triggers, so it does not meet any of the criteria that require RT/UT. For these service conditions B31.1 calls for visual examination of accessible weld surfaces by a qualified inspector — exactly what was performed. With welds made by a currently ASME-qualified welder and accepted by visual examination, the system meets the code-required examination and may be placed in service. (If this run were boiler external piping directly connected to the boiler, ASME Section I would govern and impose stricter rules — but the scenario describes a distribution main.)
ASME B31.1 / Steam trap selection per Armstrong/Spirax Sarco
Steam heat exchangers must have properly functioning steam traps on the condensate outlet to remove condensate and prevent water hammer. Water hammer in steam systems generates pressure shocks up to 10 times operating pressure, which can rupture piping, damage equipment, and cause severe personnel injuries.
ASME B31.1 para. 131.4 (Table 132) / ASME BPVC Section IX
Carbon steel (P-No. 1 group) with a specified maximum carbon content over 0.30% AND a thickness at the joint over 1 inch requires a minimum mandatory preheat of 175°F before welding per ASME B31.1. Failure to preheat risks hydrogen cracking in the heat-affected zone.
ASME B31.1 Section 107 / MSS SP-92
This is a proper installation. Globe valves on steam service should be installed with flow entering under the disc to prevent the disc from being forced off the stem by line pressure when the valve is open. The vertical stem-up orientation is preferred for steam service to prevent condensate from pooling in the bonnet.
CraftIQ explanations are original educational commentary written in trade language and verified against the cited standards. Always confirm requirements against the code edition adopted by your jurisdiction — this is training material, not a substitute for the code book or your AHJ.