Flow Measurement

“If you know the physical and chemical characteristics of a fluid, you can determine the flow rate through a pipe. We manufacture the products that are used to do that.

An Orifice Flange Union consists of two pipe flanges with pressure taps in each flange. The Orifice Plate placed in between them creates a differential pressure required to measure the flow.

Raised Face Flanges are bolted together with a Paddle Type Orifice Plate and two gaskets between the flanges. RTJ Flanges are bolted together with an RTJ Orifice Plate between the flanges. The RTJ Orifice Plate also acts as the gasket.

Types of Flanges

There are four different types of flanges used for Flow Measurement – The Weld Neck, Slip On, Socket Weld, and Threaded Flange.

Weld Neck Flange

This flange has a tapered hub that matches the pipe O.D./I.D. at the weld bevel. This allows for a full penetration weld that can be UT or X-Ray tested.

Slip On Flange

This flange slips over the pipe O.D. It is welded on the flange I.D. at the raise face and on the pipe O.D. at the rear of the flange hub. After welding, you must drill a pressure tap hole thru the pipe and de-burr.


The pipe slips into the counter bore in the hub of the Socket Weld Flange. The bore of the flange matches the pipe I.d. The flange is welded to the pipe O.D. at the rear of the flange hub. It is not necessary to drill the pressure tap hole into the pipe as required with the Slip On.

Threaded Flange

The Threaded Flange is threaded to screw onto the threaded pipe. The pipe must be threaded so that the pipe comes even with the raise face of the flange when the pipe make-up is complete. After installing the flange, the pressure tap hole must be drilled thru the pipe and then de-burred.

Flange Products

Flange Tap
Orifice Flange

Normally this Flange has a 1/2″ MPT tap, located 1″ from the orifice plates. The tap goes straight through the Flange and comes out in a pre-determined location on the I.D. of the pipe.

Corner Tap
Orifice Flange

The tap here is in the flange. It does not have to be 1″ from the face of the flange. It measures the pressure at the face of the plate instead of 1″ back from the face.

Restriction Plate
Holding Flange

This Flange does not have a tap normally. But does have Jack screws and an orifice plate. It is used to restrict flow, rather than measure it.

Orifice Plate
Holding Blocks

This system consists of separate rings. Each element will have bolt holes that match the O.D. and I.D. of the pipe, and they have a pressure tap in the block. They are used in a pipeline where the orifice flange would be exceedingly expensive – as in nickel or Monel Hastalloy, or as used in a corrosive line service, where you have plastic lined pipe. Since you cannot weld the pipe to the flange, because of the plastic, we use inserts. The arrangement is: a Flange Holding Block – an Orifice Plate – another Holding Block – and a Flange, all bolted together. The flanges hold everything together, and the Holding Block has the pressure tap in it.

Orifice Plate Products

Series 500
Universal Orifice Plate

This Plate Flange goes into an orifice fitting, or into an RTJ or Orifice Plate holder. It is a special O.D. plate. It does not change O.D. with the pressure rating. It always fits into another device that varies with the pressure rating of the plate.

Series 520
Paddle Type Orifice Plate

This Plate fits snugly within the bolt circle of the raised face flanges, so that when the bolt circle gets bigger and smaller the Plate also gets bigger and smaller. The O.D. of the Orifice Plate varies with the pressure of the flange.

Series 560
Integral RTJ Orifice Plate

The 560 Integral RTJ Orifice Plates are of one piece construction – ring and plate together. They are for use with RTJ Orifice or Holding Flanges. They can be used as Measurement or Restriction Plates. They may be made from 316SS, 304SS or Carbon Steel. Our standard is 316SS with other alloys available on application.

Series 590
Holding Screw
Type RTJ Orifice Plate

Similar to the Integral RTJ Orifice Plate, this plate is held in place by pan head screws. The plate can be removed, in order to put in another plate. Commonly used on larger lines.

ASME Short-Form
Weld Type Venturi

ASME Short Form Venturi is a head type measurement device that functions similar to an Orifice Plate, but has less permanent pressure loss. It consists of a conical inlet, straight throat, and conical outlet. It is used for clean and dirty fluid service. The conical inlet prevents damming in dirty fluid service, and the conical outlet reduces permanent pressure loss. They are furnished with flanged ends or ends beveled for welding. Commonly made from Carbon Steel, 304SS and 316SS. Other alloys available on application.

Flow Nozzles

The Flow Nozzle is a head type measurement device commonly used in high velocity steam flow applications. It consists of an elliptical inlet with a straight throat. Available as Flanged, Weld In, or Holding Ring type. Commonly made from CarbonSteel, 304SS, and 316SS. Other alloys available on application.

Flange Type
Straightening Vane

Straightening Vanes are 7 or 19 tube concentric bundle flow straightening devices. They are used to reduce the turbulence upstream of the measurement device. The number of tubes depends on line size. 7 tubes for 2” line size; 9 tubes for larger. Flanged type is installed between flanges.

Line Type
Straightening Vane

Line type is held in place by one or two set screws, depending on the size. The set screw is inserted thru a threaded hole in the pipe wall, then sealed with a coupling or weld outlet, and welded to the pipe.