Stainless Steel Pipe Fittings

Stainless steel pipe fittings are threaded SS 316 connectors such as nipples, adapters, couplings, reducers and plugs that join instruments, manifolds and process ports without welding. Vikay catalogues over 340 part numbers in NPT, ISO tapered and SAE/UNF thread forms, in sizes from 1/8 to 1 inch.

Threaded pipe fittings are the connective tissue of an instrument installation: the hex nipple that takes a gauge off a manifold, the male-to-female adapter that changes thread form, the reducer that steps a port down, the plug that closes a spare tapping.

The Vikay stainless pipe range covers close nipples, hex nipples, hex long nipples, hex reducing nipples, male and female adapters, SAE adapters in UNF thread, couplings, reducing couplings, caps, plugs, hex head plugs and bushings. Male-by-female adapters are catalogued across NPT, ISO tapered and ISO parallel combinations so a change of thread form does not need a purpose-made part.

Bodies are machined from SS 316 bar to ASTM A276 / A479 rather than cast, giving a denser, more consistent section for high-pressure instrument duty. Threads are cut to ASME B1.20.1 (NPT), ISO 7/1 (BSPT), ISO 228 (BSPP) or SAE J514 UNF. Tapered threads seal on the flanks and need PTFE tape or a compatible thread sealant, applied leaving the first thread bare so nothing enters the line; parallel threads seal on a face or bonded seal. Send your two thread forms and sizes and we will identify the adapter.

Frequently Asked Questions

What is the difference between a close nipple and a hex nipple?

A close nipple is threaded along its entire length with no plain or hex section, giving the shortest possible male-to-male connection. A hex nipple has a wrench flat between the two threads, so it can be tightened properly without marking the threads, and it is preferred wherever there is room for it.

Do NPT threads need PTFE tape?

Yes. NPT is a tapered thread that seals on the flanks, and it needs PTFE tape or a compatible thread sealant to fill the spiral leak path. Wrap two to three turns in the direction of thread engagement and leave the first thread bare so no tape shreds into the process line.

Can I connect an NPT fitting to a BSP port?

Not reliably. NPT and BSPT differ in thread angle, 60 degrees against 55, and in pitch at most sizes, so a mixed joint engages only partly and leaks under pressure. Use a purpose-made NPT-to-BSP adapter, which is catalogued in this range.

Are these fittings machined or cast?

Machined from SS 316 bar to ASTM A276 / A479. Bar stock avoids the porosity that can appear in castings, which matters on high-pressure instrument and hydraulic service and where a helium leak test has to be passed.

What is an SAE adapter and when is it used?

An SAE adapter carries a UNF straight thread with an O-ring boss on one end, used on hydraulic manifolds and gauge ports where a soft seal at the face is preferred to a tapered thread. It removes the sealant from the joint and allows the fitting to be clocked to a chosen orientation.