3000# vs 6000# Forged Fitting

Quick Answer

3000# and 6000# are pressure classes for socket weld and threaded forged fittings per ASME B16.11. A 6000# fitting has approximately double the pressure capacity of a 3000# fitting. The class number represents the cold working pressure (CWP) in psi at ambient temperature for standard materials. Most oil and gas piping specifications default to 3000# for standard process piping; 6000# is used for high-pressure services.

Detailed Comparison

Both 3000# and 6000# fittings are manufactured by forging and machining from bar stock or billets. The higher class uses thicker walls and heavier bodies to withstand greater internal pressure. The fitting types (elbows, tees, couplings, crosses, caps) are identical between classes; only the dimensions and wall thickness differ.

Feature	3000#	6000#
Pressure rating (CWP, A105, ambient)	3,000 psi (207 bar)	6,000 psi (414 bar)
Matching pipe schedule (SW)	Sch 80 (Sch 80S for SS)	Sch 160 (XXS)
Matching pipe schedule (THD)	Sch 80	Sch 160
Wall thickness (1” SW elbow)	~4.5 mm	~7.5 mm
Socket depth (typical)	Standard per B16.11	Deeper (thicker body)
Weight (1” SW elbow)	~0.22 kg	~0.40 kg
Size range	NPS 1/8 to NPS 4	NPS 1/8 to NPS 4
Available connections	Socket weld, threaded	Socket weld, threaded
Standard	ASME B16.11	ASME B16.11
Common material	ASTM A105 (CS), A182 F316 (SS)	ASTM A105, A182 F316
Cost	1.0x (baseline)	1.5-2.0x
Availability	Widely stocked	Less commonly stocked (longer lead times)
Applications	Standard process piping, utility	HP instrumentation, HP/HT services, hydraulic systems

How the Class Relates to Pipe Schedule

ASME B16.11 defines the pressure class of forged fittings based on the wall thickness of the matching pipe:

• 3000# socket weld fittings match Schedule 80 pipe
• 6000# socket weld fittings match Schedule 160 pipe
• 3000# threaded fittings match Schedule 80 pipe
• 6000# threaded fittings match Schedule 160 pipe

The fitting bore must match the pipe ID for a proper fit. Using a 6000# fitting with Schedule 80 pipe (or vice versa) creates a bore mismatch, resulting in a step at the connection that causes turbulence, erosion, and potential fatigue cracking.

When to Specify Each Class

3000# is the default class for most oil and gas process piping and utility services. It pairs with Schedule 80 pipe, which is the standard small-bore schedule in most piping specifications. The vast majority of small-bore elbows, tees, and couplings in a typical plant are 3000#.

6000# is specified when:

• Design pressure exceeds the 3000# rating at the design temperature
• The piping specification calls for Schedule 160 or XXS pipe
• The service is high-pressure instrumentation tubing or hydraulic piping
• Additional corrosion allowance is needed (thicker wall provides more margin)

Pro Tip

Always check that the fitting class matches the pipe schedule in the piping material specification (PMS). A 3000# fitting on Schedule 160 pipe, or a 6000# fitting on Schedule 80 pipe, results in a bore step that creates a weak point and a flow restriction. The ASME B16.11 guide provides matching tables.

Read the full guide to pipe fittings