Carbon Steel End Cap Manufacturer & Exporter

Solitaire Overseas manufactures carbon steel end caps in both large bore buttweld construction dimensioned to ASME B16.9 and small bore forged threaded or socket weld construction dimensioned to ASME B16.11. A carbon steel end cap closes off the terminal end of a pipe run, branch, header or drain point, and is one of the most frequently specified carbon steel pipe fittings on any bill of materials. Buttweld caps in ASTM A234 Grade WPB or WPC cover NPS 1/2 inch to 48 inch, while forged caps in ASTM A105 cover NPS 1/8 inch to 4 inch in Class 3000 and Class 6000, with full mill test certification on every batch.

Technical Data

Specifications Chemical Composition (ASTM A234, %) Mechanical Properties (ASTM A234) Chemical Composition (ASTM A105, %) Mechanical Properties (ASTM A105) Equivalent Grades Weights Buttweld Cap vs Threaded/Socket Weld Cap

Carbon Steel End Cap Specifications

Parameter	Specification
Standard	ASME B16.9 (buttweld caps, NPS 1/2" - 48"); ASME B16.11 (threaded / socket weld caps, NPS 1/8" - 4")
Material Specification	ASTM A234 Grade WPB / WPC (buttweld); ASTM A105 (forged threaded and socket weld)
Size Range	NPS 1/2" to 48" buttweld; NPS 1/8" to 4" forged threaded/socket weld
Wall Thickness / Class	Any producible wall thickness per ASME B36.10M (buttweld); Class 3000 or 6000 (forged)
End Connection	Butt weld, square or bevel cut (buttweld cap); NPT taper thread or socket weld bore (forged cap)
Manufacturing	Wrought from plate or pipe (buttweld); forged from bar stock (forged)
Fitting Types	Buttweld end cap, threaded pipe cap, socket weld cap
Heat Treatment	Not mandatory for standard hot formed WPB/WPC or as-forged A105; normalized A105N on request
Certification	Mill Test Certificate EN 10204 3.1, 3.2 on request

Chemical Composition (ASTM A234, %) - Buttweld Grades

Element	WPB max	WPC max
Carbon	0.30 (0.35 bar/plate/forging)	0.35
Manganese	0.29 - 1.06	0.29 - 1.06
Phosphorus max	0.050	0.050
Sulfur max	0.058	0.058
Silicon min	0.10	0.10
Chromium max	0.40	0.40
Molybdenum max	0.15	0.15
Nickel max	0.40	0.40
Copper max	0.40	0.40
Vanadium max	0.08	0.08

Sum of Cu, Ni, Cr and Mo shall not exceed 1.00%. Carbon equivalent (C.E. = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) shall not exceed 0.50 for WPB and WPC, reported on the test report.

Mechanical Properties (ASTM A234)

Grade	Tensile Strength min	Yield Strength min	Elongation min
WPB	415 MPa (60 ksi)	240 MPa (35 ksi)	22% (longitudinal, round specimen)
WPC	485 MPa (70 ksi)	275 MPa (40 ksi)	22% (longitudinal, round specimen)

Chemical Composition (ASTM A105, %) - Forged Grade

Element	A105 max/range
Carbon max	0.35
Manganese	0.60 - 1.05
Phosphorus max	0.035
Sulfur max	0.040
Silicon	0.10 - 0.35
Copper max	0.40
Nickel max	0.40
Chromium max	0.30
Molybdenum max	0.12
Vanadium max	0.08

Sum of Cu, Ni, Cr, Mo and V shall not exceed 1.00%; sum of Cr and Mo shall not exceed 0.32%. A105N denotes the normalized condition, offering improved impact toughness for low-temperature or critical service.

Mechanical Properties (ASTM A105)

Property	Requirement
Tensile Strength min	485 MPa (70 ksi)
Yield Strength min	250 MPa (36 ksi)
Elongation min (2 in.)	22%
Reduction of Area min	30%
Brinell Hardness	137 - 197 HBW

Equivalent Grade of Carbon Steel End Cap

ASTM Grade	EN	JIS
A234 WPB	P235GH / P265GH (EN 10253-2)	STPG370
A234 WPC	P280GH (EN 10253-2)	STPG410

ASTM Grade	EN	DIN	JIS
A105	P245GH / P250GH (EN 10222-2)	1.0460	SFVC1 (G3202)

Weights of Carbon Steel End Cap

APPROXIMATES WEIGHTS PIPE END CAPS/ PLUGS

Nominal Pipe Size	ANSI 5S	ANSI 10S	ANSI 40S	ANSI 80S	MSS 5S	MSS 10S	MSS 40S	MSS 80S
1/2	0.059	0.077	0.145	0.172	0.047	0.060	0.077	-
3/4	0.068	0.086	0.163	0.231	0.058	0.073	0.099	-
1	0.091	0.141	0.222	0.395	0.104	0.172	0.206	-
11/4	0.132	0.209	0.318	0.562	0.130	0.217	0.276	-
11/2	0.159	0.250	0.400	0.685	0.145	0.242	0.315	-
2	0.245	0.377	0.704	1.406	0.184	0.308	0.424	-
21/2	0.350	0.472	1.071	2.105	0.303	0.430	0.731	-
3	0.468	0.640	1.489	2.885	0.342	0.484	0.870	-
31/2	-	-	-	-	-	-	-	-
4	0.713	0.981	2.533	4.250	0.432	0.641	1.200	-
5	1.049	1.239	3.609	7.575	0.726	0.878	1.680	-
6	1.625	1.952	5.580	10.433	0.887	1.080	2.210	-
8	2.452	3.110	10.002	15.831	1.360	1.940	3.930	-
10	4.045	4.871	13.892	24.313	2.150	2.530	5.800	-
12	6.615	7.123	19.976	29.348	2.890	3.250	7.340	-

Buttweld Cap vs Threaded/Socket Weld Cap

Criteria	Buttweld End Cap	Threaded / Socket Weld Cap
Size Range	NPS 1/2" to 48"	NPS 1/8" to 4"
Connection	Full penetration butt weld	NPT thread or fillet socket weld
Pressure Basis	Rated by wall thickness / schedule	Class 3000 or 6000 rating
Typical Use	Large bore process and pipeline piping	Small bore utility, instrument and drain lines
Removability	Permanent once welded	Threaded caps are removable; socket weld caps are permanent

Types of Carbon Steel End Cap

Buttweld End Cap (ASME B16.9) - hemispherical or flat crown design, NPS 1/2" to 48", welded directly to the pipe end.
Threaded Pipe Cap (ASME B16.11) - NPT internal thread, Class 3000 or 6000, removable for periodic access.
Socket Weld Cap (ASME B16.11) - socket bore for fillet welding onto small bore pipe, Class 3000 or 6000.

Need forged elbows, tees or unions in the same small bore range? See our Carbon Steel Forged Fittings range (ASME B16.11, NPS 1/8" to 4"), or request a combined quote.

Applications of Carbon Steel End Cap

Terminating pipeline runs, headers and branch lines
Vent and drain line closures on process and utility systems
Blanking off spare nozzles or future tie-in points
Pressure and hydrostatic testing of pipe spools before commissioning
Temporary or permanent isolation of decommissioned lines

Frequently Asked Questions

What is a carbon steel end cap used for?

A carbon steel end cap seals the open end of a pipe, header or branch line, commonly at line terminations, drain points, spare nozzles, or during hydrostatic pressure testing.

What is the difference between a buttweld cap and a threaded cap?

A buttweld end cap is welded directly to large bore pipe per ASME B16.9 and is permanent, while a threaded or socket weld cap follows ASME B16.11 for small bore pipe up to NPS 4 inch and, in the threaded version, can be removed for access.

What standard governs carbon steel end cap dimensions?

ASME B16.9 covers buttweld end caps from NPS 1/2 inch to 48 inch, while ASME B16.11 covers forged threaded and socket weld caps from NPS 1/8 inch to 4 inch.

What material grade is used for carbon steel end caps?

Buttweld caps are typically supplied in ASTM A234 Grade WPB, with WPC available for higher strength requirements. Forged threaded and socket weld caps use ASTM A105.

What size range is available for carbon steel end caps?

Buttweld caps are available from NPS 1/2 inch through NPS 48 inch. Forged threaded and socket weld caps are available from NPS 1/8 inch through NPS 4 inch.

Can carbon steel end caps be used for pressure testing?

Yes. Both buttweld and forged carbon steel end caps are routinely used to blank off pipe spools during hydrostatic or pneumatic pressure testing prior to commissioning.

Get a quote for carbon steel end caps from Solitaire Overseas, or visit our Carbon Steel Pipe Fittings hub to compare buttweld, forged and material grade options.