Overview
ASTM A105 identifies a forged carbon-steel material specification for pressure-piping components such as flanges, forged fittings, and valve parts. Class 150 identifies a pressure-temperature rating class used by a flange standard such as ASME B16.5. These terms describe different things. “A105 Class 150” therefore means a flange made from the ordered A105 material and manufactured to the applicable Class 150 dimensional and rating rules.
The shorthand “105/150” or “105 150” is common in enquiries, but it is incomplete. A supplier still needs flange type, nominal size, facing, bore or pipe schedule, dimensional standard, quantity, certificate level, and service conditions.
Why It Matters for Pipe Components
Confusing material grade with pressure class can produce a technically wrong quotation. ASTM A105 controls material-related requirements for forged carbon-steel piping components. The selected flange standard controls dimensions, tolerances, marking, testing, and pressure-temperature ratings within its scope.
Class 150 does not mean that every flange is limited to exactly 150 psi. Allowable pressure changes with material group and temperature and must be taken from the applicable standard and design basis. A sales quotation should not convert the class designation into one universal pressure value.
A105 should also not be treated as automatic proof of low-temperature toughness. When a project has low design temperatures or impact requirements, the engineer must confirm material suitability and any supplementary testing.
Methods, Parameters, or Process
Convert an incomplete A105 150 request into a purchase-ready description by confirming each field below.
| RFQ field | Why it matters | Example |
|---|---|---|
| Material | Defines the forging grade and certificate basis | ASTM A105/A105M; edition to be agreed |
| Dimensional standard | Controls dimensions and ratings | ASME B16.5 or project-specified standard |
| Flange type | Changes hub, bore, welding, and inspection | Weld neck, slip-on, blind, threaded, socket weld, lap joint |
| Size and class | Selects the dimensional table | NPS 4, Class 150 |
| Facing | Must match gasket and mating flange | RF, FF, RTJ, or specified facing |
| Bore or schedule | Important for weld-neck and socket designs | Bore to match connected pipe |
| Documents | Defines acceptance evidence | EN 10204 3.1, dimensional report, PMI or NDE if ordered |
Supplier and Inspection Checklist
- Verify that the certificate identifies the ordered material specification and heat number.
- Confirm markings remain traceable after machining and coating.
- Check size, class, flange type, facing, OD, thickness, drilling, and bore.
- State whether the bore must match a pipe schedule and whether a bevel is required.
- Inspect the gasket seating surface for finish, dents, corrosion, and machining damage.
- Review chemistry, mechanical properties, and delivered heat-treatment condition.
- Confirm project-specific impact, hardness, PMI, or NDE requirements.
- Do not approve A105 for low-temperature service without engineering review.
- Keep coating off gasket faces, threads, weld ends, and identification where required.
Application to Pipe Fittings, Valves, and Flanges
A105 is frequently requested for forged weld-neck, slip-on, blind, threaded, socket-weld, and lap-joint backing flanges where the selected product standard permits them. Each type has a different connection method and inspection focus.
Forged threaded and socket-weld fittings use rating designations that are different from ASME flange classes. A Class 3000 forged fitting is not the same rating system as a Class 300 flange.
A105 may also be used for forged valve bodies or pressure-containing parts when allowed by the valve specification. Valve class, trim, seat, test standard, and end connection remain separate ordering requirements.
FAQ
What does A105 150 mean?
It normally means ASTM A105 forged carbon-steel material combined with a Class 150 flange rating. It does not identify type, size, facing, bore, or standard.
Is ASTM A105 a flange standard?
No. It is a material specification. Flange dimensions and ratings come from the applicable flange standard.
Is Class 150 equal to 150 psi?
Not as a universal rule. Allowable pressure depends on material group, temperature, standard, and design basis.
Can A105 be used at low temperature?
Suitability depends on design temperature, toughness requirements, code, and ordered testing. It requires engineering review.
What should appear on the quotation?
Standard, size, class, type, facing, bore or schedule, material, quantity, coating, tests, documents, and delivery terms.
Next Steps
Replace “A105 150” with a full flange description before pricing. Attach the project datasheet or drawing when bore, facing, drilling, coating, or inspection differs from a standard catalog item.
Request a Quote
