Reducing Bushing

What is a Reducing Bushing?

A reducing bushing is a threaded fitting used to reduce the size of a threaded pipe opening or port. It has male threads on the outside and female threads on the inside, allowing it to screw into a larger threaded connection while accepting a smaller pipe. Reducing bushings are widely used in instrumentation, small-bore piping, valve and pump connections where a quick, threaded size reduction is needed.

Standards and Specifications

Reducing bushings are manufactured to ASME B16.11 and ASME B16.14, conforming to MSS SP-79 and BS 3799. They are available in hex-faced or round-body patterns. Size combinations range from NPS 1/8 by NPS 1/4 to NPS 4 by NPS 2, with pressure classes of 3000 LB, 6000 LB, and 9000 LB. NPT threads are standard, with BSPT and metric threads available on request.

Materials and Grades

Carbon steel A105 is standard for high-pressure service. Stainless steel 304/304H and 316/316H provide corrosion resistance for chemical and marine applications. Alloy steel F11, F22, and F91 grades handle high-temperature refinery service. Low-temperature A350 LF2 is available for cryogenic systems. All material is forged and fully traceable by heat number.

Pressure and Temperature Ratings

Reducing bushings are rated for 3000 LB, 6000 LB, and 9000 LB pressure classes per ASME B16.11. The forged construction provides high strength in compact sizes. Temperature ratings depend on material: carbon steel to 425 degrees Celsius, alloy steel to 600 degrees Celsius, stainless steel from cryogenic to 800 degrees Celsius.

Applications

Reducing bushings are used in instrument connections, pressure gauge take-offs, sampling lines, hydraulic systems, valve and pump port reductions, and small-bore process piping. They adapt larger threaded ports on equipment to smaller tubing or instrument lines in oil and gas, chemical, power, and hydraulic systems.

Advantages

Reducing bushings provide a quick, threaded size reduction without welding. The hex-faced pattern allows installation with a standard wrench. They are compact, forged, and rated for high pressure. Threaded connections can be easily disassembled for maintenance and instrument removal.

Installation Guidelines

Apply PTFE tape or thread sealant to the male threads. Screw the bushing into the larger port with a wrench, then screw the smaller pipe into the female threads. Ensure proper alignment and torque. For high-pressure or hazardous service, use seal welds after installation for added security.

Quality Assurance

Each reducing bushing is marked with both sizes, material grade, pressure class, and heat number. Inspection includes dimensional checks, thread verification, visual examination, and NDE when specified. Material test certificates to EN 10204 3.1 are provided. Bushings are protected with thread caps and packaged in small boxes for export.