Enhanced Efficiency and Safety with the 4-inch Stainless Steel Orifice Threaded Flange

A 4-inch A182 F316L ASME B16.36 stainless steel orifice threaded flange is the metering flange for lines that must not be welded. The forged 316L pair takes an orifice plate between its faces and has jack screws for plate changes, so flow is measured without cutting the line. On the sealing face it pairs with flange gaskets.

What the Orifice Threaded Flange Is

ASME B16.36 covers orifice flange pairs made to hold a flow-measuring orifice plate. Each pair has two flanges machined from A182 F316L, a low-carbon 316 stainless that resists corrosion and stays weldable; the threaded (NPT) bore screws onto a matching pipe end where welding is unsafe. Pressure taps in the flange body read the drop across the plate.

Pair, Plate, and Jack Screws

• Two flanges per metering run — the plate is clamped between the faces.
• Jack screws — back the flanges apart for plate changes without disturbing the line.
• A182 F316L forged body — low-carbon 316 for corrosion resistance and toughness.
• Threaded (NPT) bore — no welding needed at the joint.

Why F316L and Threaded

F316L resists chloride pitting and creep better than plain 304, and the low carbon keeps it stable if the joint is ever welded later. The threaded form suits skids, hazardous areas, and small-bore branches where a weld would need hot-work permits. For measurement that must stay accurate, the pair also gives the plate a firm, repeatable seat.

Key Benefits

• Accurate flow data from a simple, standard metering principle.
• Corrosion-resistant 316L for water, steam, and mild chemicals.
• Plate changes with jack screws — faster maintenance, less downtime.
• Threaded joint avoids hot work on live or hazardous lines.

Where They Are Used

Orifice threaded flanges meter water, steam, oil, and mild chemicals in utilities, treatment plants, refineries, and process skids. The 4-inch size is common on branch lines and test headers where flow data feeds process control.

In the Metering Run

The orifice plate sits between the two faces and the pipe flanges on each side carry the bolt load and the pressure taps; the gasket between the faces seals the joint. Keep the gasket inside the bolt circle so it never intrudes on the flow path.

Installation and Care

Set the plate with its sharp edge upstream, choose a gasket for the fluid and temperature, and torque the bolts in stages in a cross pattern. Read the taps at the specified spacing; a worn or eccentric plate skews the reading. At turnaround, inspect the plate edge, the faces, and the jack screws, and replace the gasket whenever the joint is opened.

Frequently Asked Questions

Why not use a regular flange pair for metering?

A regular pair has no jack screws or pressure taps. The orifice flange is machined for the plate and the taps, so the reading is reliable and plate service is quick.

Which way does the plate face?

The sharp upstream edge faces the flow, away from the tap side the standard marks. Reversed plates read low; check the marking before assembly.

Does the threaded joint need a sealant?

Yes — thread sealant or tape rated for the fluid keeps the joint tight; the flange-face gasket seals the plate interface, not the thread.