Series OP Orifice Plate Flowmeter

Stainless Steel for Use with Compatible Liquids and Gases

The Series OP Orifice Plate Flowmeter is a complete orifice plate flow metering package. It incorporates a stainless steel orifice plate with a unique holder or carrier ring containing metering taps and integral gaskets. It was designed for use wherever there is an application for a conventional flow orifice plate. It can also be used in place of other primary differential producers for efficiency and cost effectiveness. Installation is accomplished simply by slipping the unit between standard flanges (orifice flanges are not required). The Series OP is available in line sizes from 1/2" to 24" and can be used with compatible liquids and gases. (18", 20" & 24" sizes are available, please consult factory for pricing).

Product Applications

  • Fluid flow rates in building water lines
  • Boiler feedwater
  • Cooling water
  • Combustion or compressed air
  • Steam flow

Models & Ordering

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Shipping Information

All shipping times are dependent on product availability at time of shipment.

Although we make every effort to ensure a continuous supply of our products, occasional circumstances may force us to temporarily run out of a product, or have shipping delays. Should this occur, customers will be notified soon after placement of any orders for such products and, if applicable, items will be put on backorder. For orders requiring expedited shipment, our customer service team can be contacted to confirm product availability

Model Description Usually Ships* Price Code Order
Ships: 4-5 Weeks
Price: $426.00
Orifice plate flowmeter, 0.5" line size, 0.200" bore, 0.32 Beta, water capacity: 20" d.p. W/C, 0.62 GPM flow; air capacity: 2.35 SCFM @ 14.7 psia, 3.63 SCFM @ 20 psig, 6.61 SCFM @ 100 psig; 1 lb. 4-5 Weeks* $426.00 B Order
Ships: 4-5 Weeks
Price: $426.00
Orifice plate flowmeter, 0.5" line size, 0.310" bore, 0.50 Beta, water capacity: 100" d.p. W/C, 3.44 GPM flow; air capacity: 100" d.p. W/C, 12.21 SCFM @ 14.7 psia, 19.58 SCFM @ 20 psig, 36.37 SCFM @ 100 psig; 1 lb. 4-5 Weeks* $426.00 B Order
Ships: 4-5 Weeks
Price: $426.00
Orifice plate flowmeter, 0.5" line size, 0.430" bore, 0.69 Beta, water capacity: 320" d.p. W/C, 13.00 GPM flow; air capacity: 200" d.p. W/C, 32.77 SCFM @ 14.7 psia, 56.15 SCFM @ 20 psig, 107.47 SCFM @ 100 psig; 1 lb. 4-5 Weeks* $426.00 B Order


Compatible liquids and gases.
Wetted Material:
304 SS, Buna-N gaskets.
±0.6% full scale flow. (Beta= .2-.6) ±0.7% for Beta greater than .6.
Temperature Limits:
-50 to 200°F (-45 to 93°C).
Pressure Limits:
150 psi max.
Head Loss:
1 - Beta ratio², eg: 1 - 07² = 1 - 0.49 = 51% of the d.p.
Line Sizes:
1/2" to 24".
Process Connections:
1/4" female NPT.
Standard flange 125#/150# rating.
Pipe Requirements:
General requirements 10 diameter upstream and 5 diameter downstream.
Varies with line size. See Catalog page.


  • Mounted with standard flanges
  • Standard "corner tap" configuration
  • Corrosion free material
  • Simplified installation
  • Built in metering taps (1/4" female NPT STD)
  • Proven through a wide range of applications for accuracy and energy efficiency
  • Assures long term reliability and accuracy


Product Literature


Catalog Pages



I purchased 4 OP-F-3 orifice plates. I do not find a torque value in the IOM for our flanges. What should these be torqued to? We typically buy 2", 3", and 4" orifice plates and are seeking to standardize on Dwyer. When you provide torque valves include all sizes. Our flanges are 150# RF.
For all orifice plate installations, please follow the recommended flange torque rating based on the specific flanges used.

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