What an orifice flange does
An orifice flange assembly holds an orifice plate between two flanges and provides pressure tap connections on either side of the plate. The differential pressure measured across the plate is used to calculate flow rate.
The flanges are supplied as a pair. Each carries a tapped hole drilled through the flange rim to the bore, so pressure can be sensed immediately upstream and downstream of the plate.
Tap location and flange taps
The most common arrangement in the USA is flange taps, where the pressure taps sit a specified distance either side of the plate faces. Other tap schemes exist, and the metering standard for your application defines what is required. Tell us which arrangement your instrument engineer has specified.
Orifice flanges are manufactured with attention to bore finish and concentricity, because the bore adjacent to the plate affects measurement quality. Bore diameter and finish should follow the metering standard and your instrument datasheet.
Details to specify
- Tap size and thread (commonly NPT) and tap orientation
- Jack screw holes for separating the flanges to change the plate
- Flange type: weld neck or slip-on style per your specification
- Bore matched to pipe inside diameter
- Gasket and plate dimensions, if supplied by others
Why copper nickel for metering seawater
Flow measurement points sit in the middle of seawater lines. Using the same alloy as the pipe avoids a galvanic couple at the meter and keeps the corrosion behavior of the line consistent. Orifice flanges are available in Cu-Ni 90/10 (UNS C70600) and Cu-Ni 70/30 (UNS C71500).
Standards and documentation
Orifice flange dimensions are commonly referenced to ASME B16.36 together with ASME B16.5 flange dimensions, and metering practice to your project standard. Material requirements follow the ASTM or ASME specification in your purchase order.
Manufactured to applicable ASME/ASTM requirements based on project specification. Orifice plates and measuring instruments are not part of the flange supply unless stated in the quotation.
- Sizes and classes: available as per applicable standard and customer specification
- Inspection, MTCs and dimensional reports arranged per project requirements
What to send
- Orifice flange datasheet or drawing
- Alloy, NPS, class and facing
- Tap type, size and orientation
- Quantity (pairs) and delivery date
Technical summary
Values below are references, not guarantees. Size range and pressure class depend on flange type, size, alloy and the applicable standard, and are confirmed against your specification at quotation.
| Item | Detail |
|---|---|
| Product type | Orifice flange (pair) |
| Alloy options | Copper-Nickel 90/10 (UNS C70600) and Copper-Nickel 70/30 (UNS C71500) |
| Typical material forms | ASTM B151 rod and bar, ASTM B122 plate; other forms per project specification |
| Dimensional reference | ASME B16.36 with ASME B16.5 typical; project datasheet or drawing |
| Size range (NPS) | Available as per applicable standard and customer specification |
| Pressure class | Per applicable standard and design basis |
| Face / end type | RF typical; per datasheet |
| Typical service | Seawater and cooling-water flow measurement |
| Documentation | Arranged according to project requirements (see Quality and Certifications) |
Copper nickel orifice flange FAQs
Are orifice flanges supplied in pairs?
Yes. A set comprises an upstream and a downstream flange, each with its pressure tap. Specify quantity in pairs.
Do you supply the orifice plate?
Orifice plates and instruments are not included unless stated in the quotation. Flange supply is quoted separately unless agreed otherwise.
Can you drill the taps to my datasheet?
Yes. Provide tap size, thread, orientation and any jack screw holes, and we will confirm against the drawing.
Which standard governs orifice flange dimensions?
ASME B16.36 is commonly referenced for orifice flanges, alongside ASME B16.5 for general flange dimensions. Your metering standard governs the measurement requirements.
