The complete standards framework — API, ASME, ASTM, BS, ISO, MSS, NACE. What each governs, how they stack in real specifications, and the gotchas that trip up procurement.
Valves are governed by multiple overlapping standards — each addressing a different engineering concern: design integrity, pressure-temperature limits, materials and metallurgy, dimensions and interchangeability, testing and inspection, fire safety, and sour service.
No single standard fully governs a valve. EPC specifications stack them: API for valve type and industry intent, ASME for pressure-temperature ratings and dimensions, ASTM for material chemistry and mechanical properties, MSS for testing details, and NACE for sour service. Understanding which standard governs which aspect is fundamental to correct valve specification.
Pressure class is not the maximum pressure a valve can always withstand. Pressure class defines allowable pressure at a specific temperature — and that allowable pressure drops sharply as temperature rises.
| Class | Typical Use |
|---|---|
| 150 | Low pressure utilities |
| 300 | General process service |
| 600 | Moderate high pressure |
| 900 | High pressure |
| 1500 | Very high pressure |
| 2500 | Extreme pressure |
API standards define valve type-specific construction, inspection, testing, fire safety, fugitive emissions, and performance. API is purchase-driven and service-specific — it tells you how the valve must behave, not just how it is shaped.
Scope:
Bolted bonnet steel gate valves (heavy wall, traditional OS&Y design).
Key features:
Used in: Refineries, pipelines, critical isolation service.
Scope:
Compact forged steel gate, globe, and check valves (typically ≤4").
Key features:
Used in: High-pressure service, limited space.
Scope:
Corrosion-resistant gate valves (thin-wall, lighter than API 600).
Key difference from API 600:
Used in: Chemical plants, corrosive service.
Scope:
Check valves — wafer, lug, flanged, and butt-weld designs.
Covers:
Scope:
Mandatory testing standard for most API valves — shell pressure test, seat leakage test, test pressures, durations, acceptable leakage.
Applies to: Gate, globe, check, ball, plug, butterfly.
Why it matters: Referenced by almost every other API valve standard as the testing baseline.
Scope:
Metal plug valves — lubricated and non-lubricated.
Defines:
Used in: Severe service, dirty or viscous fluids.
Scope:
Metal ball valves (industrial floating and some trunnion designs). Pressure classes vary by size and end connection — includes 150 / 300 / 600 and higher in smaller sizes.
Not a "metal-seated only" standard — covers metal-bodied ball valves broadly.
Scope:
Butterfly valves — double-flanged, lug, wafer.
Covers:
Scope:
Pipeline transportation valves (ball, gate, plug, check). Equivalent to ISO 14313.
Key requirements:
Bore depends on project requirements and purchaser specification.
Scope:
Wellhead and Christmas tree equipment (upstream oil & gas).
Includes:
Focus: Extremely high pressure, harsh service, rigorous testing. API 6A valves are not interchangeable with refinery valves.
Scope:
Fire test for soft-seated quarter-turn valves only — ball, butterfly, plug.
Test conditions:
Outcome: Verifies valve maintains pressure boundary during fire.
Scope:
Alternative fire test — broader applicability than API 607.
Difference from API 607:
Governs how pressure relief valves (PRVs) are sized and selected. Covers gas, vapor, steam, two-phase, and incompressible flow.
Relief scenarios: fire exposure, blocked outlet, thermal expansion, control valve failure, gas blow-by.
Overpressure limits: Normal relief 10%, fire case 21%.
Governs how PRVs must be installed, not how they're sized.
Key requirements:
One of the most commonly violated standards during plant audits.
Standardizes physical dimensions of flanged steel PRVs — orifice letters (D through T), inlet/outlet flange sizes, face-to-face, pressure classes.
Key value: Allows interchangeability between manufacturers. Drop-in replacement during outages.
Does not cover performance or sizing — only geometry.
Defines allowable leakage rates for PRVs (metal-seated, soft-seated, bellows-sealed, pilot-operated).
Leakage measured at 90% of set pressure. Required for environmental compliance.
Inspection practices for piping system components — valves (not control valves), piping, tubing, fittings.
Used by: plant inspectors, reliability engineers, asset integrity teams.
Inspection, testing, and maintenance of PRVs — bench testing, field inspection, repair-vs-replacement, set pressure drift, seat damage assessment.
Often referenced during incident investigations.
ASME standards define pressure-temperature ratings, wall thickness, dimensional consistency, flange compatibility, and face-to-face dimensions. ASME does not tell you how to buy a valve — it tells you what geometry and limits are acceptable.
The core valve "pressure body" standard. Pressure-temperature ratings, design requirements, wall thickness, end connection rules, marking, materials.
Key content:
Gotcha: Many API valve standards (600, 602, 609, 6D) sit "on top of" B16.34. EPCs require both.
P-T ratings, dimensions, tolerances, materials grouping, marking, testing for common flanges.
Used for: weld neck, slip-on, socket weld, threaded, lap joint, blind flanges. Matching bolt circle, hole size/count, facing type.
Gotcha: Large diameter pipeline flanges may fall under ASME B16.47 — common EPC miss. RTJ ring number errors cause field rework.
Standardized lay lengths for valves (face-to-face flanged, end-to-end butt weld).
Used for: Preventing valve-doesn't-fit-the-spool issues. Ensuring interchangeability in turnarounds.
Gotcha: Not every valve is built to B16.10 by default — pipeline (API 6D) and some HP butterfly valves can deviate.
Dimensions, tolerances, marking for forged 90°/45° elbows, tees, couplings, unions, caps, plugs, bushings.
Pressure classes: typically 2000 / 3000 / 6000.
Gotcha: "Class 3000" on fittings is not the same as "Class 300" flanges.
Dimensions for spiral wound, RTJ (oval/octagonal), and metal jacketed gaskets.
Gotcha: Spiral-wound thickness and compression behavior must match flange facing and bolt load. Wrong selection = chronic leaks.
Dimensions and tolerances for soft gaskets on FF / RF flanges. Full-face vs ring styles.
Used in: water, utility, low-temp services.
Not all nonmetallics are acceptable for hydrocarbons or high temperature — project specs restrict by service.
The power-piping code. Used for steam systems, boilers, power generation piping.
The refinery/chemical plant piping code. Design, materials, fabrication, welding, examination, pressure testing, leak testing.
Category fluid service: Normal / Cat. D / Cat. M / High Pressure.
Gotcha: B31.3 governs the system, not the valve design — yet it controls how valves are installed, tested, and accepted.
Liquid hydrocarbon and other liquid pipeline transportation. Pump stations, terminals, cross-country lines.
Gotcha: Valve design usually comes from API 6D + B16.34, but acceptance/testing rules come from B31.4.
Gas pipelines and compressor stations. High consequence area requirements, MAOP rules, testing, integrity management.
Gotcha: Often triggers additional documentation and operational constraints beyond what valve standards require.
ASTM defines chemical composition, mechanical properties, heat treatment, and testing requirements. Valves don't invent materials — they reference ASTM material standards. See the Valve Materials & Trims reference for body and trim selection.
Forged carbon steel for pressure systems (ambient and higher temp). Flanges, forged fittings, forged valve bodies/bonnets in CS service.
Gotcha: A105 is not for low-temperature impact-critical service — use A350 LF2 instead. Common procurement miss.
Forged stainless and alloy materials: F304 / F316, F11 / F22, duplex forging grades.
Gotcha: "F" grades are forging grades. Cast equivalents are different (A351).
Cast CS pressure parts (WCB, WCC). Cast valve bodies/bonnets for general process service.
Gotcha: WCB is not for low-temp impact services. Choose A352 grades.
Cast stainless (CF8 / CF8M, etc.). Stainless valve bodies in corrosive/chemical service.
Gotcha: Cast stainless requires attention to ferrite content and corrosion mechanism (chlorides, SCC).
Cast steels for low-temp service (LCC, LCB). Cryogenic-ish and cold service requiring impact toughness.
Mandatory Charpy impact testing at specified temperature.
Gotcha: LCC gets used loosely — impact test temp/energy requirements must match project spec.
Higher strength cast steels (various grades) for pressure service beyond A216.
Often project-specific — ensure grade is explicitly correct for service and weldability.
Cast Fe-Cr / Fe-Cr-Ni alloys (stainless-type families) for cast valve bodies requiring specific corrosion resistance beyond generic CF8M.
Gotcha: Confusion with A351 is common — A743 is widely referenced for corrosion-resistant casting families.
Duplex / super-duplex castings (CD3MN, CE3MN). Chloride service, seawater, sour + chloride environments.
Gotcha: Duplex performance depends heavily on heat treatment and ferrite/austenite balance. Vendor capability matters.
Standard mounting dimensions between actuators / gear operators and quarter-turn valves — flange pattern, drive size, drive shaft squares/stars.
Used for: Automation packages to avoid custom bracket fabrication. Interchangeability of actuator mounting.
Gotcha: A valve can meet API/ASME and still not be ISO 5211 compliant unless designed for it.
See the ISO 5211 reference →
Fire testing methodology for valves. Often treated as comparable to API 607 / 6FA depending on valve type.
Used in: Fire-safe requirements in projects specifying ISO rather than API.
Gotcha: Always confirm which fire test is acceptable (API vs ISO) in the client specification.
The ISO equivalent of API 6D. Same scope — pipeline transmission valves for oil & gas service.
The ISO equivalent of API 608. Used interchangeably in many international specifications.
Fugitive emissions classification for industrial valves. Common alternative to API 641 in emissions-controlled regions.
Materials for H₂S service in oil & gas production. Equivalent to NACE MR0175 — most projects reference both designations.
Manufacturers Standardization Society standards exist where no ASME or API document exists. Often manufacturer-driven, but widely accepted and referenced in EPC specifications.
Standard marking requirements for valves, fittings, flanges, unions — material grade, size, class, melt/heat code.
Gotcha: Marking must match CMTR / heat number logic. Inspectors check this on receipt.
Visual acceptance criteria for casting surface imperfections.
Used for foundry quality control and receiving inspection standards.
Valve pressure test methods (shell test and seat test logic).
Often paired with API 598 or referenced by clients for the testing basis.
Waterworks and utility cast iron gate valves.
Utility check valves (water, low pressure).
Socket-welding reducer inserts. Small-bore branch reductions in socket weld systems.
Bronze gate, globe, angle, and check valves. Utility, low-pressure, non-hydrocarbon services.
Steel pipe unions (SW / threaded) for threaded and socket-weld piping systems.
Integrally reinforced forged branch outlet fittings (weldolet, sockolet, thredolet).
Bellows seal valves for fugitive emissions control applications where bellows seal design is required.
Steel globe and globe stop/check valves (legacy). Used in legacy refinery/utility installations with BS preference.
Check valve requirements (legacy). BS-based projects; often overlaps with API 594 approach.
Cryogenic valve testing and requirements. Referenced for LNG and cryogenic service.
Materials for H₂S service in oil & gas production. Prevents SSC, HIC / SOHIC, stress corrosion issues.
Defines acceptable:
Used in: Upstream, gas gathering, production facilities.
Sulfide stress cracking in refining environments — refinery wet H₂S conditions.
Used in: Refinery piping/valves where sour service exists but the environment differs from upstream production rules.
Gotcha: MR0103 ≠ MR0175. Refinery vs upstream environments differ — don't conflate them.
No single standard fully governs a valve. EPC specifications stack them. Here's how the layers actually work in procurement:
| Valve Type | Primary API | Mandatory ASME Overlay | Mandatory MSS Overlay |
|---|---|---|---|
| Gate (OS&Y, BB) | API 600 | B16.34, B16.10 | SP-61, SP-25 |
| Gate (Forged, ≤4") | API 602 | B16.34 | SP-61 |
| Gate (Corrosion-Resistant) | API 603 | B16.34 | SP-61 |
| Globe Valve | API 602 | B16.34 | SP-61 |
| Check Valve | API 594 | B16.34 | SP-61 |
| Plug Valve | API 599 | B16.34 | SP-61 |
| Ball Valve (Metal) | API 608 | B16.34 | SP-61 |
| Butterfly Valve | API 609 | B16.34 | SP-61 |
| Valve Type | API | ASME Overlay | Additional |
|---|---|---|---|
| Ball Valve | API 6D | B16.34 | API 6FA fire test, SP-61 |
| Gate Valve | API 6D | B16.34 | Often slab or expanding |
| Plug Valve | API 6D | B16.34 | Less common |
| Check Valve | API 6D | B16.34 | Special closure requirements |
| Function | API | ASME Overlay | Purpose |
|---|---|---|---|
| Sizing | API 520-1 | ASME Section VIII | Engineering calculations |
| Installation | API 520-2 | ASME B31.3 | Inlet / outlet piping |
| Geometry | API 526 | ASME B16.5 | Interchangeability |
| Seat Leakage | API 527 | — | Emissions control |
| Testing | API 576 | — | Inspection & repair |
Quick reference for which API standard primarily governs each valve type. ✓ = primary governing standard, — = not applicable.
| API Standard | Gate | Globe | Check | Ball | Plug | Butterfly |
|---|---|---|---|---|---|---|
| API 600 | ✓ | — | — | — | — | — |
| API 602 | ✓ | ✓ | ✓ | — | — | — |
| API 603 | ✓ | — | — | — | — | — |
| API 594 | — | — | ✓ | — | — | — |
| API 599 | — | — | — | — | ✓ | — |
| API 608 | — | — | — | ✓ | — | — |
| API 609 | — | — | — | — | — | ✓ |
| API 598 | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
API 598 applies as the baseline inspection & pressure test standard to almost every manual isolation valve.
| API Standard | Gate | Globe | Check | Ball | Plug | Butterfly |
|---|---|---|---|---|---|---|
| API 607 | — | — | — | ✓ | ✓ | ✓ |
| API 6FA | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
API 607 → soft-seated quarter-turn valves only. API 6FA → broad fire testing for pipeline and metal-seated valves.
| Valve Type | Primary API Spec(s) |
|---|---|
| OS&Y Gate Valve (Refinery) | API 600 + API 598 |
| Small Forged Gate / Globe | API 602 + API 598 |
| Stainless Gate Valve | API 603 + API 598 |
| Check Valve | API 594 + API 598 |
| Ball Valve (Metal Seat) | API 608 + API 598 |
| Butterfly Valve | API 609 + API 598 |
| Pipeline Ball Valve | API 6D + API 598 + API 6FA |
| Pressure Relief Valve | API 520 / 526 / 527 |
| Fire-Safe Quarter-Turn | API 607 or API 6FA |
This is the part most valve documents do not explain clearly — but automation lives or dies here. Torque, mounting, cycling, and fire safety drive automated valve packages.
| Standard | Why It Matters for Automation |
|---|---|
| ASME B16.34 | Defines maximum pressure → maximum torque |
| API 600 / 602 / 609 | Defines seat load, friction, stem design |
| API 6D | Break-to-open and end-of-travel torque limits |
| Item | Governing Standard | Impact |
|---|---|---|
| Actuator Mount | ISO 5211 | Flange size and bolt pattern |
| Accessory Mount | NAMUR / VDI-VDE 3845 | Solenoid, positioner interface |
| Travel Stops | API 609 / API 6D | Defines hard stops vs actuator stops |
| Stem Design | API 600 / 609 | Anti-blowout stem affects actuator selection |
API valves do not guarantee ISO 5211 mounting. Many cast valves require custom brackets — verify in the procurement specification.
| Fire Spec | Valve Type | Automation Impact |
|---|---|---|
| API 607 | Quarter-turn soft seated | Seat survival, stem sealing |
| API 6FA | All valve types | Actuator must survive fire scenario |
Automation add-ons for fire-safe service: fire-safe actuators, fail-close or fail-open logic, fireproof tubing and solenoids.
"Valve shall comply with API 609, ASME B16.34, API 598, API 607, with actuator mounted per ISO 5211, sized for 130% of maximum torque, complete with fail-safe pneumatic actuator, NAMUR solenoid, and limit switches."
| Automated Valve | Must-Have Specs |
|---|---|
| Automated Gate | API 600 + ASME B16.34 + API 598 |
| Automated Ball | API 608 / 6D + API 607 / 6FA |
| Automated Butterfly | API 609 + API 607 |
| Pipeline MOV | API 6D + API 6FA |
Every line item on a valve datasheet should map to one or more of these standards. If it doesn't, the specification is incomplete — and the vendor will fill in the cheapest interpretation by default.
Send us your EPC valve datasheet or specification. We'll cross-reference every API / ASME / ASTM / MSS / NACE callout, identify gaps, and come back with a compliant valve recommendation including all stacked standards.
For standard API / ASME / ASTM compliant valves, E4 Industrial supports procurement through our e-commerce arm at Watermain Supply.
Shop at Watermain Supply
