Each flange of the pair carries pressure taps — typically a pair of holes drilled into the flange at the standard positions relative to the plate — connecting the upstream and downstream pressure to the transmitter. Jack (jacking) bolts in the flange lugs let the pair be sprung apart evenly so the orifice plate and its gaskets can be changed without cutting the line.
The pair is built on a base flange pattern — weld neck is the usual choice — with the stiffness and bolting the measuring assembly needs. The pattern, class and facing for a specific set are confirmed at enquiry.
| Item | Range / Options |
|---|---|
| Standards | Confirmed per product at enquiry |
| Types | Supplied as matched pairs; the pattern for a specific set is confirmed per product at enquiry |
| Size range | Confirmed per product at enquiry |
| Pressure classes | Confirmed per product at enquiry |
| Features | Pressure tap holes (flange taps), jack bolts |
| Materials | Confirmed per product at enquiry |
What the Pair Includes
An orifice flange set is two flanges with taps positioned as a matched pair, plus jack bolts. The orifice plate itself, its gaskets and the transmitter connections are specified with the metering package — state on the enquiry whether a plate is in scope, so the scope for the specific set is settled before order; the plate bore is a measurement value calculated by your instrument engineer, not a machining convenience.
Taps and Orientation
Tap holes are drilled at the standard flange-tap positions. On horizontal lines the tap orientation (top, side or 45 degrees) follows the service — gas, liquid or steam — to keep impulse lines correct. State the orientation requirement on the order; taps drilled in the wrong clock position are not reworkable.
Ordering
Define: pattern (weld neck usual), NPS, class, facing, grade, bore schedule for weld neck pairs, tap size and orientation, and whether the plate is in scope. With those, the pair can be quoted as a set.
Frequently Asked Questions
Why do orifice flanges use the higher classes?
The orifice assembly — plate, gaskets and the flange pair — needs the rigidity and bolt load of the higher classes to seal and to hold the plate flat and repeatable. The class for a specific set is confirmed at enquiry.
Is the orifice plate included?
The plate is not part of the flange pair as supplied. Plates are usually supplied by the metering package, because the plate bore is calculated from your flow data by your instrument engineer. If a plate is in scope for your set, state it on the enquiry and it will be assessed for the specific set before order.
What are jack bolts for?
They screw through lugs on the flange pair to force the flanges apart evenly against the bolting, opening a gap so the orifice plate can be swapped. Without them, changing a plate means cutting or springing the line.
Which orifice flange pattern should I choose?
Weld neck pairs are the usual choice for process metering because the bore is machined to the pipe and the joint is full strength; lighter metering duties are also served by other patterns. If in doubt, weld neck is the default — and the pattern for a specific set is confirmed at enquiry.
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Send Your Specification
Tell us the size, schedule or pressure class, material grade and quantity for the orifice flanges you need. MOQ and lead time are confirmed in the quotation for your exact specification.