Series-OP

Supported Applications

The Dwyer Series OP Stainless Steel Orifice Plate Flowmeter is a complete flow metering package designed for use wherever there is an application for a conventional flow orifice plate. It serves as a primary differential producer suitable for compatible liquids and gases, including fluid flow in building water lines, boiler feedwater, cooling water, combustion air, compressed air, and steam flow.

The unit can be used in place of other primary differential producers to improve efficiency and cost effectiveness. Installation is accomplished by slipping the unit between standard flanges; orifice flanges are not required.

Operating Conditions & Performance

The Series OP operates within a process temperature range of -50 to 200°F (-45 to 93°C). The pressure rating is limited only by pipe and flange rating restrictions. Accuracy for the differential signal produced equals or exceeds that of a properly manufactured and installed flange or radius tap orifice meter.

Accuracy specifications are defined by the Beta ratio (d/D):

• Beta = 0.2 to 0.6: ±0.6% of full scale flow
• Beta greater than 0.6: ±0.7%

The series supports line sizes from 1/2" to 24". Capacity ranges include water flow from 0.62 GPM to 8,007.74 GPM and air capacity from 2.35 SCFM to 66,737.64 SCFM (based on base conditions of 70°F, 14.7 psia). Differential pressure values should be less than 50% of the inlet absolute pressure.

Configuration Options

The Series OP incorporates a stainless steel orifice plate with a unique holder or carrier ring containing metering taps and integral gaskets. The overall laying length is 1.25" including pre-attached ring type 1/8" thick Buna 'N' Gaskets.

Construction & Materials

• Orifice Plate: 304 SS (orifice plate thickness is 0.125")
• Gaskets: Pre-attached Buna-N gaskets
• Taps: Corner tap proportions as defined in ISO 5167

Installation & Connections

• Process Connection: Standard flange, any rating (orifice flanges not required)
• Differential Taps: 1/4" female NPT electrical connection for pressure sensing
• Mounting: Self-centering within the bolt circle of standard ANSI 125/150# flanges; no alignment necessary unless used with 300# or non-standard ratings.

Pipe Requirements

General requirements specify 10 pipe diameters upstream and 5 pipe diameters downstream of the orifice plate. For non-critical applications, 5 pipe diameters upstream and 2 pipe diameters downstream are acceptable. The use of straightening vanes is not necessary for most applications.

Key Product Differences

The Series OP model number follows the format OP-<Line Size Letter><Number>-<Beta Value Number>. Examples include models such as OP-A-1, OP-B-1, and OP-C-1. The series is available in line sizes from 1/2" to 24", with specific Beta values determined by the model suffix.

While this page details the stainless steel Series OP, Dwyer also offers PVC (Series PE) and PTFE (Series TE) orifice plate flowmeters for specialized media compatibility. The Series PE is constructed of gray PVC with Buna-N gaskets, while the Series TE utilizes PTFE construction.

For pressure drop measurement across these plates, Dwyer Magnehelic® gages are compatible for gases, and Capsuhelic® gages (brass case) may be used for liquids. Flange bolts should be 1.25" longer than standard flange bolts to accommodate the unit's overall thickness.