Primary Flow Elements - Orifice Plates
Accurate and reliable flow measurement equipment is essential for all types of industry processes all over the world. Whatever your process requirement for flow measurement, be it water, oil and gas, air, steam, waste water or other fluid, we have the answer, combined with the added flexibility of designing and manufacturing a system to suit your requirements.
Our vast knowledge and experience of providing solutions for organisations worldwide has proven our understated capability to provide the complete range of flow measurement equipment.
Our custom-designed measurement solutions are typically of the differential pressure (DP) type, including orifice plates, Venturi tubes, Pitot tubes and flow nozzles.
Orifice Plates
The most common and widely used differential producers, suitable for a wide range of flow measurement applications in line sizes of 50 mm and above. Choose ‘concentric square edged’ for general application, ‘conical entrance’ or ‘quarter circle’ for low Reynolds number flows, and ‘segmental’ or ‘eccentric’ for flows containing light solids and slurries.
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Tab Handled Orifice Plates
• Design to BS EN ISO 5167
• Range of Orifice Types
- Concentric Square Edge
- Conical Entrance
- Quarter Circle
- Segmental
- Eccentric
• Wide range of materials
• Proven technology
• Suitable for 1” lines and above
• Orifice sizing on request
General Description
The orifice plate is the most common differential pressure flow primary element. It is based on proven technology, has no moving parts and is suitable for high temperature and pressure applications. Orifice plates are recommended for clean liquids, gases and low velocity steam flows.
Dimensions
The outside diameter of the orifice plate is equal to the bolt circle diameter of the connecting flanges minus the diameter of the bolt. This ensures that the plate is centred accurately in the line.
Plate thicknesses depend on line size and differential pressure, and should be sufficient to prevent the plate from bending under operating conditions. Recommended plate thicknesses are shown in the product data sheet
Orifice plates can be made in accordance with customer drawings as required.
Materials
Standard material grades include 316 Stainless Steel, 304 Stainless Steel, 310 Stainless Steel, Hastelloy® C276, Hastelloy® B3, Duplex Stainless Steel, Super Duplex Stainless Steel, Monel® 400, Carbon Steel, Titanium, Incoloy® 800, Incoloy® 825, Inconel® 600, Inconel® 625, Tantalum, PTFE and PVDF.
Please contact the sales office for other grades.
Incoloy, Inconel and Monel and are trademarks of INCO Alloys International Inc. Hastelloy is a trademark of Haynes International Inc.
Orifice Bore Sizing
Orifice calculations are performed to the latest revision of BS EN ISO 5167, when requested.
Orifice Carrier Assemblies
Orifice plates can be supplied complete with one or two piece orifice carriers, or ANSI B16.36 orifice flanges. Orifice meter runs are also available.
Restriction Orifice Plates
• Wide range of materials
• Proven technology
• Suitable for most pipe sizes
• Orifice sizing on request
General Description
Restriction orifice plates can be used as a simple pressure reducing device, or to limit the flow rate in a pipeline.
They are designed to slip between pipe flanges. Versions to suit RTJ type flanges are available
Dimensions
The outside diameter of the orifice plate is equal to the bolt circle diameter of the connecting flanges minus the diameter of the bolt. This ensures that the plate is centred accurately in the line.
Plate thicknesses depend on line size and differential pressure, and should be sufficient to prevent the plate from bending under operating conditions.
Orifice plates can be made in accordance with customer drawings as required.
Materials
Standard material grades include 316 Stainless Steel, 304 Stainless Steel, 310 Stainless Steel, Hastelloy® C276, Hastelloy® B3, Duplex Stainless Steel, Super Duplex Stainless Steel, Monel® 400, Carbon Steel, Titanium, Incoloy® 800, Incoloy® 825, Inconel® 600, Inconel® 625, Tantalum, PTFE and PVDF.
Please contact the sales office for other grades.
Orifice Bore Sizing
Orifice calculations are performed generally in accordance with the formulae detailed in RW Miller’s Flow Measurement Handbook , when requested.
Orifice Carrier Assemblies
• Design to BS EN ISO 5167
• Range of Carrier Types
- Single Ring, Corner Tappings
- Double Ring, Flange Tappings
- Double Ring, Corner Tappings
- Double Ring, Annular Chambers
• Wide range of materials
• Proven technology
• Suitable for 1” lines and above
• Orifice sizing on request
General Description
The orifice plate is the most common differential pressure flow primary element. It is based on proven technology, has no moving parts and is suitable for high temperature and pressure applications. Orifice plates are recommended for clean liquids, gases and low velocity steam flows.
Flow measurement using orifice plates requires the accurate location of upstream and downstream pressure tappings. Various types of orifice carrier assemblies are available to suit a wide range of applications.
Orifice flange assemblies in accordance with ANSI B16.36 are also available.
Pressure Connections
The style of the pressure tappings may be as follows:-
(a) Flange Tappings - located 25.4 mm upstream and 25.4 mm downstream from the corresponding face of the orifice plate.
(b) Corner Tappings - single tappings located flush with the upstream and downstream faces of the orifice plates.
(c) Annular Chambers - slots located flush with the upstream and downstream faces of the orifice plate.
Flange tappings are recommended for general applications.
Corner tappings or annular chambers are particularly recommended for use in small lines (less than 50 mm diameter) and when the orifice plate is either of quarter circle, conical entrance or eccentric in design.
Double Ring Orifice Carriers
Double ring orifice carrier are designed to be mounted between standard pipe flanges. Versions are available to suit all common flange standards, including ANSI B16.5.
Double ring orifice carriers may be provided with flange tappings, single corner tappings or annular chambers. Double ring orifice carriers use a standard tab handled plate, which allows for easy replacement of the plate if it is damaged, or changes in process data necessitate a change of orifice bore.
Standard material of construction is 316L Stainless Steel, but a wide range of alternative common and exotic materials are available. Gaskets are provided - 1.5 mm thick non asbestos type, unless requested otherwise.
Annular Chamber Orifice Carriers
Annular chamber type orifice carriers are a special form of corner tappings. The annular slots break through to the pipe over the entire perimeter.
Versions to suit other flange sizes and ratings are available on request.
Single Ring Orifice Carriers
The single ring orifice carrier is a simple, compact orifice carrier, which may be machined in one piece, or be provided with a screwed-on plate. This carrier occupies the minimum of space between the pipeline flanges.
Standard material of construction is 316L Stainless Steel. Due to its small thickness, the single ring orifice carrier is often a cost effective solution, and may be manufactured in a wide range of exotic materials including Hastelloy®, Monel®, Duplex Stainless Steel, Inconel® and Incoloy®
Download Datasheet (PDF)
RTJ Type Orifice Plates
• Design Generally to BS EN ISO 5167
• Range of Orifice Types
- Concentric Square Edge
- Restriction
• Range of Designs
- One Piece Construction
- Screwed On Plate
• Proven technology
• Suitable for 1” lines and above
• Orifice sizing on request
General Description
The RTJ type orifice plate incorporates an integral gasket, either oval or octagonal ring, for mounting between ring type joint flanges. It is based on proven technology, has no moving parts and is suitable for high temperature and pressure applications. Orifice plates are recommended for clean liquids, gases and low velocity steam flows.
Dimensions
Plate thicknesses depend on line size and differential pressure, and should be sufficient to prevent the plate from bending under operating conditions.
Orifice plates can be made in accordance with customer drawings as required.
Materials
RTJ type orifice plates may be machined in one piece, or alternatively from two pieces, with an orifice plate screwed onto a carrier ring/gasket. Standard material grades for orifice plates include 316 Stainless Steel, 304 Stainless Steel, 310 Stainless Steel, Hastelloy® C276, Hastelloy® B3, Duplex Stainless Steel, Super Duplex Stainless Steel, Monel® 400, Carbon Steel, Titanium, Incoloy® 800, Incoloy® 825, Inconel® 600 and Inconel® 625.
Common carrier ring/gasket materials include Stainless Steel and soft iron. To ensure correct sealing when installed between flanges, the hardness of the carrier ring/ gasket material is limited to a maximum value, typically 120HB for soft iron rings and 160HB for Stainless Steel Rings.
Please contact the sales office for other grade
ANSI B16.36 Orifice Flanges
• Wide range of materials, including
- ASTM A105N Carbon Steel
- ASTM A350 LF2 Carbon Steel
- ASTM A182 F316L Stainless Steel
• Ratings from 300 lb to 2500 lb
• Sizes from 1” Nominal Bore
• Corner Tapping Versions Available
General Description
Orifice flanges are intended for use instead of standard pipe flanges when an orifice plate or flow nozzle must be installed. Pairs of pressure tappings are machined into the orifice flange, making separate orifice carriers or tappings in the pipe wall unnecessary.
The range of orifice flanges covers all standard sizes and ranges, and all common flange materials. Flanges are available in socket weld or weld neck form, and are typically supplied with two ½” NPT tappings in each flange. Jacking screws to ensure ease of removal of the primary flow element are provided.
Orifice plates and flow nozzles can also be supplied. See individual Product Data Sheets for more information.
Orifice flanges may also be supplied complete with bolting and gasket kits.
Materials
We can supply orifice flanges in a wide range of standard and special materials, including:
ASTM A105 Carbon Steel
ASTM A350 LF2 Low Temp Carbon Steel
ASTM A182 F316 Stainless Steel
ASTM A182 F304 Stainless Steel
ASTM A182 F11 1¼% Cr ½% Mo
ASTM A182 F22 2¼% Cr 1% Mo
Pressure Tappings
As standard, two ½” NPT tappings are provided in each flange, one with a plug. Other thread sizes are available on request. Socket weld connections may be specified, and butt weld pipe nipples are also available. Tappings are generally ‘flange’ type, but corner tappings are optional.
Gaskets
A range of suitable gaskets for use with orifice flanges is also available.
Typical specifications include:
- 1.5 mm thick IBC ring type, non asbestos
- 3.2 mm thick sprial wound type, carbon steel outer, stainless steel inner, 316L windings with graphite filler
Studbolts and Nuts
Suitable bolting may be supplied on request. Standard materials include:
- ASTM A193 B7 and ASTM A194 Gr 2H
- ASTM A320 L7 and ASTM A194 Gr 4 or 7
- ASTM A320 B8 and ASTM A194 Gr 8
Bolting conforming to NACE is also available.
Weldneck Orifice Flange Assemblies
Weldneck orifice flanges are butt-welded into the pipline. The inside diameter (or the schedule) of the pipe should be specified when ordering.
Weldneck orifice flanges are available in classes 300, 600, 900, 1500 and 2500. Raised face (RF) and ring type joint (RTJ) versions can be supplied.
Slip-On Orifice Flange Assemblies
Slip-on orifice flanges are designed to slip over the pipeline before welding. Slip-on orifice flanges are available in class 300, with a raised face (RF).
Multi-Stage Orifice Assemblies
Applications
• Gas and Liquid Flows
• High Pressure Drops
Prevents
• Cavitation and Flashing in Liquid flows
• Choked flow in gases.
• Excessive Noise / Vibration
Restriction orifice plates have traditionally been
used to reduce pressures in GAS AND LIQUID
FLOWS by forcing the flow through a restricted
bore. The precise pressure drop is produced by
accurately calculating the orifice bore, having taken
into account all the relevant process and flow
conditions.
Where very HIGH PRESSURE DROPS in liquid flows are required MULTISTAGE RESTRICTION ORIFICE ASSEMBLIES may be required to achieve the desired pressure drop whilst preventing problems such as CAVITATION, FLASHING and high NOISE and VIBRATION levels.
CAVITATION is a potentially damaging, erosive condition which occurs when the internal pressure of the liquid passing through the orifice falls below its vapour pressure and vapour bubbles form. Further downstream from the orifice the pressure recovers sufficiently to collapse the bubbles with extreme violence. Cavitation calculations are performed during the design stage of a Multistage RO to calculate cavitaion factors at each stage in the orifice assembly.
FLASHING is a similar phenomenon to cavitation except that the process pressure never recovers sufficiently to collapse the gas bubbles resulting in two phase flow - liquid and gas - downstream of the orifice. Erosion of pipe work and valves and other instrumentation can occur due to the impact of liquid droplets carried at high speed in the vapour flow.
CHOKED FLOW IN GASES – also know as critical flow – occurs when too large a pressure drop is attempted across a single orifice plate. When the downstream pressure is less than 52.8% of the upstream pressure, the flow through the orifice will become sonic, at which point no further increase in flow can be achieved by either increasing the upstream pressure or lowering the downstream pressure. A multistage RO will enable staged reductions in pressure to prevent choked flow occurring.
Rototherm Multistage ROs are manufactured from a wide range of materials and are engineered to meet specific project process conditions and requirements. Plates are usually welded into pipe with a separation of one pipe diameter, the number of plates and orifice bores being determined by calculation. Process connections to existing pipe work can be either standard process flanges or machined ends suitable for butt welding.