WIKA Flow designs and manufactures orifice flange unions according to the latest industry specifications. What’s more, our engineers can tailor the entire package – flow elements, unions, gaskets, and hardware – for the needs of every application.

Model FLC-OP Orifice Plate

Model FLC-OP orifice plate

To the south of Dallas–Ft. Worth is the suburban city of Mansfield, home of WIKA Flow. In an 80,000 sq. ft. state-of-the-art complex is the WIKA USA division that manufactures flow measurement products such as Venturi tubes, Venturi and flow nozzles, HHR (high head recovery) flow tubes, and meter tubes.

Some of WIKA Flow’s most popular products are orifice plates. They are the most economical and, thus, most widely used primary flow elements in the world. In addition, they are easy to install and highly versatile, making them an excellent option for any industry that needs to measure flow. That’s why the ISO 9001 compliant facility in Mansfield contains 4,800 sq. ft. specifically dedicated to produce all types of orifice plates and differential elements, including orifice flange unions (OFUs), to the latest industry specifications.

What Are Orifice Flange Unions?

Orifice flange with orifice plate

Model FLC-FL orifice flange with orifice plate

Orifice flange unions are flange assemblies with pairs of pressure taps machined directly into the orifice flange. These built-in pressure taps eliminate the need for separate orifice carriers or pressure taps into the pipe wall. OFUs replace standard pipe flanges when mounting orifice plates and flow nozzles.

Less expensive than other types of unions, OFUs provide additional flange thickness to properly place flange taps for pressure measurement. In addition, they are installed with jack screws, which makes for easy removal when end users need to inspect the paddle orifice plate.

These unions are ideal for applications in oil and gas exploration and production, midstream gathering, process plants, transportation, and LNG plants. They are also cost-effective solutions for chemical, refining, and petrochemical processes, and a reliable choice for the power industry.

When Not to Use OFUs

Orifice flange unions work best when the flow rate is fairly constant. As an OFU is not a custody transfer element, the orifice plate cannot be “centered centristically” by installing a paddle-type orifice plate between two flanges. A better option alternative would be the single-chamber or dual-chamber orifice fitting. This custody element device (per its design standards) guarantees that the orifice plate is always properly centered.

WIKA Flow’s Standard and Custom Orifice Flange Unions

The Flow Division at WIKA USA has the in-house engineering capabilities to handle all our customers’ needs for standard OFUs and other differential elements. Our warehouse has in stock a comprehensive inventory of flow-measurement products that are manufactured according to international standards ISO 5167/ISO TR 15377, ASME MFC, ASME PTC 6, and ASME PTC 19.5.

Each flow-measurement process is unique, with variations in media, pressure restriction, working temperature, connection types, and so forth. To meet an individual application’s needs, many of our customers consult with a WIKA Flow specialist before placing an order. If an in-stock product does not meet those needs, our in-house experts can specially engineer the required differential elements.

Our OFUs can come in a variety of materials, including: 

  • ASTM A105 and ASTM A350 LF2 carbon steels
  • ASTM A182 F316 and F304 austenitic stainless steel alloys
  • ASTM 182 F11 and F22 steel alloys (for increased corrosion resistance and toughness)
  • A182 Gr. 2205 duplex stainless steel (for better corrosion and stress corrosion resistance, especially against chloride pitting)
  • A182 super duplex stainless steel (for improved resistance to acids, acid chlorides, and caustic solutions)
  • Hastelloy, Monel, Inconel, and other specialty materials by request

Other areas for customization:

  • Pressure taps – Two NPT pressure taps are standard, but OFUs can have as many NPT, SW (socket well), or other types of pressure taps as needed.
  • Size – Standard nominal sizes range from 1″ to 12″ 300#/600# ANSI. Other sizes/or ANSI classes are available by request.
  • Bolting – The standard options are A194, A193 Gr. B7, and 2H. Bolting can also be NACE compliant, painted or coated, made of stainless steel or a higher-grade materials, etc.
  • Extensions – OFUs can come with connection extensions such as nipples (of various lengths) and risers connected to the taps.
  • Pressure tap locations – Customers can specify where they would like to locate the pressure taps on the circumference of the OFU flange.

WIKA Flow is a global leader in flow measurement solutions, including standard and custom-made orifice flange unions. We don’t just sell orifice plates. We manufacture and assemble the entire package – plates, flanges, gaskets, and standard hardware – to the latest industryspecification, and back up every product with exceptional customer service. Contact the team at WIKA Flow for more information on finding just the right flow-measurement product for your applications.

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