Stub Ends

QS Pipe Fitting: Fujian Stub Ends

Stub Ends in carbon, stainless, alloy and duplex steel, the weld-on pipe end that pairs with a backing flange for bolted, easy-to-align joints.

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One-Minute Overview

Stub ends are the short weld-on pipe ends used with loose backing flanges.
Carbon, stainless, alloy and duplex steel to match the service.
The backing flange rotates freely, so bolt holes line up fast.
Common where pipework meets flanges, valves and pumps.

A stub end is the short length of pipe that is butt welded to the line and then gripped by a loose backing flange. Because the flange itself is not welded to the stub, it can be rotated until the bolt holes line up, and the joint can be taken apart for maintenance without cutting the pipe. That makes stub ends a practical answer wherever pipework meets flanges, valves and pumps, especially on spools that have to be aligned in the field or stripped down on a regular basis. They are offered in carbon steel for general strength, stainless steel for corrosive environments, alloy steel for high-temperature and high-pressure duty, and duplex steel where strength and corrosion resistance are both needed in oil, gas and petrochemical service.

Name: Stub Ends
Type: Weld-on pipe end for use with a loose backing flange
Material: Carbon Steel, Stainless Steel, Alloy Steel, Duplex Steel
Function: Joins pipework to flanges, valves and pumps
Sizes, wall schedules and end preparations are confirmed per inquiry, and a detailed specification sheet is available on request.

The material choice follows the same logic as the pipe it is welded to. Carbon steel gives strength and durability where high corrosion resistance is not required, so it is the economical pick for general utility and process lines. Stainless steel stub ends are chosen for corrosive environments and clean service, alloy steel for the enhanced mechanical properties that high temperature and pressure demand, and duplex steel for the combination of strength and corrosion resistance that oil, gas and petrochemical duty often calls for. Keep the stub and the run pipe in the same grade so the butt weld joins compatible metals. The stub end itself carries the fluid and the pressure; the loose flange only provides the bolting, which is why the flange can be a cheaper material while the wetted stub still has to be right.

Installation is straightforward but the sequence matters. Butt weld the stub end to the pipe first, with the same bevel, root gap and qualified procedure as any other welding fitting, and finish the lap face that the gasket will seat against. Slip the backing flange on before welding the remaining joint, because it cannot be added afterwards. Once the stub is in place, rotate the flange to match the mating bolt holes, fit the gasket, and tighten the bolts evenly in a cross pattern. Check that the lap face is clean and free of weld spatter, since the seal is made there. Because the stub and flange are separate, confirm both the stub length and the flange series on the inquiry so the assembly closes up with the right gasket seating and bolt reach.

FAQ

Q1. Why use a stub end with a loose flange instead of a welded neck flange?

Because the backing flange is free to rotate. On a stub end the flange is not welded to the pipe, so the crew can turn it until the bolt holes match the mating flange, which saves a lot of grief on field fit-up and on spools that must be dismantled for cleaning. It also lets the flange be a different, cheaper material from the wetted stub, since only the stub sees the fluid and pressure.

Q2. Do I really need the stainless or duplex version?

Only where the service asks for it. Carbon steel is the sensible default when corrosion is not the problem; stainless earns its keep in corrosive or clean environments; alloy suits high temperature and pressure; and duplex combines strength with corrosion resistance for oil, gas and petrochemical duty. Whatever you pick, keep the stub in the same grade as the run pipe so the butt weld is between compatible metals and the corrosion allowance matches.

Q3. Anything that can go wrong during fitting?

One classic: welding both ends and then discovering the backing flange is still sitting on the bench. Slip the loose flange onto the stub before you close the last joint, because it cannot be added later. After that, bevel and weld the stub like any butt weld fitting, keep the lap face clean for the gasket, rotate the flange to line up the bolt holes, and tighten the bolts evenly in a cross pattern.

Q4. How long will production take?

Standard sizes are typically ready within 30 days, and in-stock items ship immediately. Larger or custom orders get a confirmed date per order, because the schedule depends on quantity, material, the bolt pattern you specify, and how busy production is at the moment you order.

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