Top 5 Quality Standards for Pipe Nipples: ASTM A733, MSS SP-95 & More Explained (2025-2026 Guide)

When sourcing pipe nipples for plumbing, oil & gas, or industrial projects, nothing matters more than knowing the product meets recognized quality standards. Poorly manufactured nipples can lead to leaks, pressure failures, and costly downtime. In this guide, we break down the five most important standards every buyer and engineer should understand — including ASTM A733, MSS SP-95, ASME B1.20.1, and others — so you can make informed decisions and choose a reliable pipe nipple manufacturer.

1. ASTM A733 – The Cornerstone Standard for Carbon and Stainless Steel Pipe Nipples

ASTM A733 is the most widely referenced specification for welded and seamless carbon steel and austenitic stainless steel pipe nipples in sizes NPS ⅛ through 12. Key requirements under ASTM A733 include:

• Material grades: ASTM A53, A106, A312, A333, etc.

• Wall thickness: Available in Schedule 40, 80, 160, and XXS

• Threading: Tapered pipe threads per ASME B1.20.1 (NPT)

• Hydrostatic testing optional (but most reputable manufacturers perform it)

• Full traceability and mill test reports (MTR/MTC)

Pro Tip: Always ask for the latest revision (currently A733-16 Reapproved 2022). A trustworthy pipe nipple manufacturer like Pcfspn provides ASTM A733-compliant nipples with complete documentation on every shipment.

2. MSS SP-95 – Swage Nipples and Bull Plugs Standard

While ASTM A733 covers standard threaded nipples, MSS SP-95 governs swage nipples (concentric and eccentric) and bull plugs. These are commonly used when transitioning between different pipe diameters.

Feature	ASTM A733 (Standard Nipples)	MSS SP-95 (Swage Nipples)
Product Type	Close, short, long nipples	Concentric/eccentric swages
End Connections	Threaded both ends	Threaded, beveled, or grooved
Typical Materials	A106 Gr.B, 304/316 SS	Same + higher alloys
Pressure Rating	Schedule-based	Often higher due to wall thickness

Many projects require both standards — which is why leading manufacturers like Pcfspn maintain inventory certified to both ASTM A733 and MSS SP-95.

3. ASME B1.20.1 – The Thread Standard (NPT, NPSC, NPSM)

No pipe nipple is complete without properly cut threads. ASME B1.20.1 defines the dimensions and tolerances for tapered and straight pipe threads:

• NPT (National Pipe Taper) – Most common in North America

• NPSC (straight coupling threads)

• NPSM (free-fitting mechanical joints)

A single imperfect thread can cause leaks under pressure. Reputable manufacturers use CNC threading machines and go/no-go gauges to guarantee 100% compliance with ASME B1.20.1.

4. ASME B16.11 – Forged Fittings and High-Pressure Applications

When projects demand extra-heavy (Schedule 160 or XXS) or 3000/6000 PSI ratings, forged nipples fall under ASME B16.11 instead of A733. These are typically made from A105 carbon steel or F316 stainless steel and are socket-weld or threaded.

If your system operates above 2000 PSI or in critical service, always specify ASME B16.11 compliance.

5. International Equivalents (EN/DIN/BS/JIS) – For Global Projects

Many overseas projects require European or Asian standards:

• EN 10241 – Steel threaded pipe fittings (European equivalent)

• DIN 2440/2441 – German standard for threaded tubes

• BS 1387 – British standard (largely replaced by EN 10255)

• JIS B 2301/2302 – Japanese threaded fittings

Experienced exporters like Pcfspn can supply dual-certified nipples (e.g., ASTM A733 + EN 10241) to satisfy both domestic and international inspectors.

Quick Comparison Table: Which Standard Should You Specify?

Standard	Best For	Thread Type	Typical Material
ASTM A733	General-purpose threaded nipples	NPT	A53, A106, 304/316
MSS SP-95	Swage & bull plugs	NPT/BE	Same + higher alloys
ASME B1.20.1	Thread dimensions & tolerances	NPT/NPSM	All
ASME B16.11	High-pressure forged nipples	Threaded/SW	A105, F91, F304/F316
EN 10241 / DIN	European projects	BSPT/BSPP	S235, P250GH, 1.4301

Why Choosing the Right Pipe Nipple Manufacturer Matters

Not all manufacturers treat standards as seriously as they should. Some cut corners on threading, skip hydrostatic testing, or provide fake certificates. That’s why industry professionals trust Pcfspn — a leading pipe nipple manufacturer that maintains full compliance with ASTM A733, MSS SP-95, ASME B16.11, and international standards. With in-house CNC machining, 100% traceability, and third-party inspection options, Pcfspn delivers ready-to-install nipples that eliminate field failures.

Whether you need standard Schedule 40 close nipples, custom-length stainless steel barrels, or high-pressure forged swages, partnering with a certified manufacturer saves time, reduces risk, and keeps your project on schedule.

Need ASTM A733-compliant pipe nipples with MTRs delivered tomorrow? Contact Pcfspn today for a fast quote and see the difference real quality makes.