Orifice Unions (OU)
+/- 0.50 to 0.75% Uncalibrated Uncertainty
Lower Cost, Field Welded Install
- Line Size: ½” to 40”
- Meets ISO, AGA, ASME, API requirements
- Flange Taps / Corner Taps
Orifice Flange Unions for Reliable Differential Pressure Flow Measurement
Orifice unions are ready-to-install assemblies used to measure and control flow, or to reduce pressure in a pipe system. Each assembly includes precision-machined orifice flanges with pressure sensing ports, along with gaskets and hardware, and is typically paired with an orifice plate to create a complete differential pressure (dP) flow measurement point.
Once the orifice union is welded into the line, you can connect your dP transmitter and begin measuring flow. Because the assembly is highly configurable, it can be specified to match a wide range of line conditions and project requirements. Carbon steel flanges with a stainless-steel orifice plate are the most common configuration, but components can be tailored for the application.
Key Benefits & Features:
- Ready-to-Install Orifice Flange Assembly: Includes orifice flanges, gaskets, and hardware, with pressure tap sets for high and low pressure signals.
- Fast Setup for dP Flow Measurement: Weld into the line, connect a dP transmitter, and start measuring flow.
- Precision Pressure Tap Machining: Orifice flange unions are machined with the appropriate tap sets to capture accurate differential pressure across the plate.
- Highly Configurable: Components can be specified to match line conditions, materials, and project standards.
- Common Material Options Available: Often supplied with carbon steel flanges and a stainless-steel orifice plate, with other combinations available.
- Supports Clean Service Applications: Designed for clean liquids and gases where orifice-based measurement is a fit.
- Standard Orifice Plate Integration: Holds the orifice plate between flanges with suitable gaskets, creating a stable, serviceable DP measurement point.
Orifice Union Specifications
Uncalibrated: +/- 0.50% to 0.75%, beta dependent
Orifice Union Model Types
Model Types
- OU — Orifice, Union (No Plate) with and without hardware, gaskets
- OUP — Orifice, Union, with Plate
- OUPFR — Orifice, Union, Plate, Flanged, Run
- OUPWR — Orifice, Union, Plate, Welded, Run
Orifice Unions Materials
Typical material selections for standard applications:
- 304 stainless steel
- 316 stainless steel
Other options for material selection:
- Monel
- Hastelloy
- Titanium
- Brass
Orifice Union Certifications
PFS is a contributor to various international standards committees, fully supporting our staff’s memberships to these commissions.
Individual products follow relevant industry regulations, including requirements specific to the oil and gas, water/wastewater, and power generation industries.
PFS maintains the following certifications, standards & compliances:
- ISO 9001
- AGA
- ASME S & U
- API
- ANSI
- European Pressure Equipment Directive (PED)
Applications
Oil & Gas
Orifice unions are widely used in oil and gas operations for compact, economical differential pressure flow measurement in pressurized lines. They are commonly installed in gas production, gathering systems, fuel gas lines, and process piping where space is limited and standardized measurement is required.
Industrial Process & Utilities
Across industrial facilities, orifice unions are used to measure clean gases and liquids in compressed air systems, plant utilities, chemical dosing lines, and general process piping. They offer a simple, low-cost alternative to full meter runs while maintaining dependable, repeatable performance.
Power Generation & Steam Systems
Orifice unions are applied in steam and clean gas service within power and cogeneration facilities. Their straightforward installation and proven measurement principle support plant efficiency, control, and reporting requirements.
Industry-Leading Orifice Union Supplier Since 1983
Proven Manufacturing Expertise
For more than 40 years, PFS has produced orifice unions and differential pressure components used in pressurized piping systems across industrial and utility environments. Each union is built around precision-machined pressure taps and robust flange construction, giving you a reliable foundation for repeatable DP signals when paired with the correct orifice plate
Real-World Application and Support Services
PFS supports more than the hardware. Our team helps with selection guidance, sizing inputs, and pressure tap and flange configuration so your orifice union is specified correctly the first time. We can also advise on DP transmitter pairing, installation best practices, and documentation needs, helping you reduce field guesswork and get reliable measurement faster.
Certifications and Compliance Documentation
PFS maintains ISO 9001 certification and holds ASME S and U and European PED certifications. CRN documentation can also be provided when required for Canadian installations.
