Butt-welding pipe cap size introduction

Butt weld cap

　　I. Overview of Butt-Welded Pipe Caps

　　Butt-welded pipe caps are one type of butt-welded pipe fitting. Because they are primarily used for sealing the ends of pipes, their application frequency is generally lower than that of butt-welded elbows, tees, reducers, and other butt-welded pipe fittings.

　　Butt-welded pipe caps also connect to the end of a pipe through welding, serving as a pipe seal to prevent media flow or protect the pipe end face. Butt-welded pipe caps are typically designed to be circular, with one end being a closed hemispherical, elliptical, or flat-bottomed shape, and the other end being a beveled end for easy butt-welding to the pipe.

　　Butt-welded pipe caps are used in pressure piping systems in the petroleum, chemical, natural gas, power, shipbuilding, and pharmaceutical industries. Their main functions include:

　　Sealing pipes: Used at the ends of pipes to prevent media leakage or the entry of foreign objects.

　　System testing: Used as a temporary or long-term seal during pipeline pressure testing or system maintenance.

　　Protective function: Protects the pipe ends from corrosion or mechanical damage.

　　Equipment encapsulation: Used for sealing openings in equipment such as storage tanks and reactors.

　　II. Relevant Standards for Butt-Welded Pipe Fittings

       The production and inspection of butt-welded pipe fittings follow multiple international and industry standards, hence they are also known as standard pipe fittings. The most widely used domestic and international standards include:

　　ASME B16.9: American Society of Mechanical Engineers standard, which specifies the dimensions, tolerances, and testing requirements for factory-manufactured butt-welded pipe fittings and is one of the most widely used standards.

　　ASME B16.25: Specifies the details of the end beveling for butt-welded pipe fittings to ensure the compatibility of the welded joints.

　　MSS SP-43: American Association of Valves and Fittings Manufacturers Standards standard, applicable to lightweight stainless steel butt-welded pipe fittings.

　　GB/T 12459: Chinese national standard, specifying the types, parameters, and dimensions of steel butt-welded pipe fittings.

　　ISO 3419: International Organization for Standardization (ISO) standard for non-alloy and alloy steel butt-welded pipe fittings.

　　These standards cover materials, dimensions, tolerances, pressure ratings, and testing methods, ensuring that the fittings are suitable for harsh operating conditions such as high temperature and high pressure.

　　III. ASME B16.9 Butt-Weld Cap Dimensions and Weight Parameters

　　ASME B16.9 provides detailed specifications for the dimensions and weight of butt-welded pipe caps to ensure design consistency and ease of installation. The following are key parameters:

　　Dimensions:

　　Nominal Diameter (NPS): Ranges from NPS 1/2" to NPS 48", covering common pipe sizes. The cap's port diameter and wall thickness must match those of the mating pipe.

　　Length (E): Refers to the overall height of the cap, varying depending on its shape and outer diameter. Refer to the ASME B16.9 dimensional parameter table for specific values.

　　Wall Thickness (t): Typically matches the wall thickness of the connected pipe. Standard cap wall thickness series include Sch 5S, Sch 10S, Sch 40S, Sch 80S, etc., corresponding to different pressure ratings.

　　ASME B16.9 Butt-Weld Cap Dimensions

　　Theoretical Weight Parameters for Pipe Caps

　　The weight of a pipe cap depends on its material, wall thickness, and dimensions. The following is a reference weight table for butt-welded pipe caps according to ASME B16.9:

　　Weight calculations take into account geometric volume and material density; actual weight may vary slightly depending on the manufacturer's processes. Weight parameters are of significant reference value for logistics and pipeline design.

　　Tolerance Range for Butt-Welded Pipe Fittings

　　ASME B16.9 specifies the critical tolerances for butt-welded pipe caps, ensuring product interchangeability and installation accuracy. Strict tolerance control guarantees weld quality and reduces installation stress.

Nominal  Size		All Fittings		45°&90° Elbows & Tees, Crosses	3D Radius Elbows	Returns			Caps	Reducers & Lap Joint Stub Ends	Lap Joint  Stub Ends
DN	NPS	OD 3) 4)	ID 3)	A   B   C   M	A   B	O	K	U	E,  E1	H   F	G	R	t
15-65	1/2 -21/2	+1.6 -0.8	± 0.8	± 2	± 3	± 6	± 6	±  1	± 3	± 2	0     -1	0     -1	+1.6 0
80-90	3-31/2	± 1.6	± 1.6	± 2	± 3	± 6	± 6	±  1	± 3	± 2	0     -1	0     -1	+1.6 0
100	4	± 1.6	± 1.6	± 2	± 3	± 6	± 6	±  1	± 3	± 2	0     -1	0     -2	+1.6 0
125-200	5-8	+2.4 -1.6	± 1.6	± 2	± 3	± 6	± 6	±  1	± 6	± 2	0     -1	0     -2	+1.6 0
250-450	10-18	+4.0 -3.2	± 3.2	± 2	± 3	± 10	± 6	± 2	± 6	± 2	0     -2	0     -2	+3.2 0
500-600	20-24	+6.4 -4.8	± 4.8	± 2	± 3	± 10	± 6	± 2	± 6	± 2	0     -2	0     -2	+3.2 0
650-750	26-30	+6.4 -4.8	± 4.8	± 3	± 6	---	---	---	± 10	± 5	---	---	---
800-1200	32-48	+6.4 -4.8	± 4.8	± 5	± 6	---	---	---	± 10	± 5	---	---	---
1300-1500	52-60	+6.4 -4.8	± 4.8	± 5	---	---	---	---	---	---	---	---	---
1600-1700	64-68	+6.4 -4.8	± 4.8	± 5	---	---	---	---	---	---	---	---	---
1800-2000	72-80	+6.4 -4.8	± 4.8	± 5	---	---	---	---	---	---	---	---	---

　　IV. Applications of Welded Pipe Caps

　　Welded pipe caps are suitable for various industrial applications:

　　Pressure Systems: Used in boilers, pressure vessels, and high-pressure pipelines, withstanding pressures up to 1000 PSI or higher.

　　Corrosive Environments: Available in stainless steel, alloy steel, or nickel-based alloys, for chemical and marine engineering applications.

　　High-Temperature Conditions: In the power or oil refining industries, withstanding temperatures up to 500°C.

　　Food and Pharmaceutical Applications: Polished stainless steel caps meet sanitary requirements.

　　When applying these caps, the appropriate material and wall thickness must be selected based on the characteristics of the medium, temperature, and pressure, and safety standards such as the ASME Boiler and Pressure Vessel Code must be followed.

　　As a key component of piping systems, welded pipe caps, with their reliable sealing, standardized dimensions, and wide range of applications, have become an indispensable part of industrial piping. Choosing products that comply with ASME B16.9 standards ensures safe and efficient system operation.

　　Why Choose Shengtian?

　　Shengtian Group, a professional manufacturer and service provider of oil pipelines and fittings, has been deeply involved in the industrial pipeline field for many years, integrating processing, manufacturing, customized services, and sales. The company undertakes various industrial pipeline system assembly and prefabricated pipeline processing and customization projects. From material cutting, forming, grinding to welding assembly, we provide one-stop processing services, helping customers shorten the supply chain, reduce costs, and improve project execution efficiency.

　　Quality Control: We strictly implement a quality control system, controlling product quality throughout the entire process from raw material procurement and processing technology to product delivery.

　　Customized Services: We always adhere to project-based principles, providing customers with processing and manufacturing services such as bending, cutting, surface grinding, beveling, and professional welding.

　　Professional After-Sales Service: An experienced business team provides customers with professional technical support and problem solutions.

　　Contact Us

　　Shengtian Group is committed to providing customers with one-stop solutions from drawings and processing to finished product delivery. We will provide you with professional technical support and efficient manufacturing services, and look forward to becoming your trusted partner.

　　Email: sale@stpipefitting.cn