F321 Slip-On Flange

QS Flange: Zhangzhou F321 So Flange

Slip-on flange in F321 stabilized stainless steel, positioned over the pipe end and fillet welded, with size and facing agreed per inquiry.

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One-Minute Overview

Slip-on flange in F321 stainless steel, slid over the pipe end before welding.
Fillet welds at the hub and at the bore fix it to the pipe.
The slip fit lets the flange be squared and rotated before the arc starts.
Bore, size, facing and pressure class are confirmed per inquiry.

A slip-on flange is bored slightly larger than the pipe, so it slides along the pipe to the required position and is then fixed with a fillet weld at the hub and a second one at the bore. This one is made in F321, the titanium-stabilized stainless grade, which suits warm lines and welded assemblies that cannot be re-annealed afterwards.

The advantage of the pattern is positioning: the flange can be slid back and forth, squared to the pipe axis and rotated to line up its bolt holes before anything is welded, which matters on site where a mating flange is already fixed. The price is two fillet welds instead of one butt weld, and a joint that is less resistant to bending, so the pattern belongs on moderate duty rather than on a line that shakes. Because the flange is welded on both sides, the heat input is spread and the F321 stabilizer keeps the boundaries beside both welds protected without a post-weld anneal.

Typical use covers utility lines, low pressure process piping, water and chemical services and spool pieces that have to be fitted on site. Check that the pipe end is cut square, leave the flange face protected while welding, and tighten the bolted joint in a star pattern once the welds have cooled. Facing, size, pressure class and bore are settled per inquiry, and detail drawings for a specific joint are available on request.

FAQ

Q1. How does a slip-on flange hold onto the pipe?

By fillet welds, not by a butt weld. The bore is a little larger than the pipe, the flange slides to position and one fillet weld runs around the hub while a second runs inside at the bore. The pair of welds resists pull-out and torsion, though the arrangement is less stiff in bending than a weld neck, which is why the type suits moderate duty.

Q2. Why choose slip-on over weld neck?

Positioning and cost. A slip-on can be slid, squared and rotated to match bolt holes before welding, which saves time on site where the mating flange is already in place. It also needs less precise pipe cutting. The trade is bending stiffness, so keep it on moderate pressure and calm lines rather than on services with heavy vibration or thermal movement.

Q3. What should I watch during installation?

Cut the pipe square and clean the end, slide the flange on and square it to the axis before tacking, and protect the machined face while the arcs are running. Let the welds cool before the joint is bolted up, then bring the bolts to torque in a star pattern. A flange welded out of square will pull the gasket unevenly however carefully it is tightened later.

Q4. What payment terms do you accept?

T/T, L/C at sight and other internationally accepted terms. The exact terms are agreed with you before production starts, because the payment schedule has to match the order value, the shipping method and the delivery schedule you need — which is also why we confirm them up front rather than after shipment.

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