Introduction – Installing an Orifice Plate
At the end of this post you will find the EMERSON document who explains the orifice plate installation guidelines, including:
- orifice plate tap orientation
- orifice plate tapping locations
- orifice tapping
This post is mainly a set of rules for the orifice installation like an orifice flow meter installation guidelines. In order thta a flow instrument may accurately read lofw. it’s necessary that the installation comply with certain rules. Follow the recommendations regarding elimination of flow disturbances, and the general layout and piping data.
The section of the pipe in which the primary element is installed mat be horizontal, inclined or vertical. The direction of the flow is immaterial except when a foreign substance such as sediment or vapor is carried in suspension. In this case it is preferable to install the primary element in vertical section of the line with the flow in such a direction that the foreign substance will readly carry on trough the primary element, i.e. upward in the case of vapor and downward in the case of sediment.
Flow Disturbances and Recomendations
Pipe fittings and valves upstream from the primary element generate swirls and crosscurrents, which if uncorrected by a straightening vane may considerably upset the flow measurement. For accurate measurement the use of straightening vanes is usually imperative; however, if we are mainly concerned in the comparison of relative values or in control, vanes may be unnecessary.
Also, if the only source of disturbance is a single bend, ell, tee, or reducer preceding the orifice run, straightening vanes effect no improvement.
Orifice Straight Run Requirement
A. Straightening Vane IS NOT used
For the various types of upstream disturbances liested bellow, allow the recommended minimum distances of straight pipe between the disturbance and the upstream pressure tap.
- Flanges, collars, wide-open gates, reducers or bends, elbows or tees which are all in the same plane – 10 pipe diameters
- Angle turns in two planes – 50 pipe diameters
- Pressure regulator, control valve or similar apparatus or fitting – 75 pipe diameters
B. Straightening Vane IS used
If a straightening vane is empluyed, 10 pipe diameters of straight pipe preceding the upstream pressure tap and 5 following the downstream tap will be sufficient. The outlet face of the straightening vane should be located 6 or more pipe diameters upstream from the upstream pressure tap regardless of the type of pressure connections employed, but not closer than 4 pipe diameters to the nearest upstream disturbance.
Also I present the rules based on Foxboro Co. on how to install orifice plate in pipeline:
Horizontal Installation Guidelines
A) Horizontal Installation for Clean Fluids
With an horizontal line, the pressure connections should be made at the SIDE of the line to allow trapped vapors to escape from the connectiong lines, and to prevent sediment from enterinf in these lines.
B) Horizontal Installation for dirty or corrosive Fluids using a seal
If liquid being measured must not come in contact with transmitter, 3/8 inch tubing and transmitter body must be filled iwht suitable seal liquid. The 2 filling tees must be at same elevation.
C) Horizontal Installation for clean noncondensable gas
D) Horizontal Installation for vapor or dirty or consensable gases
Can we install orifice plate in vertical line? Yesss
Vertical Installation Guidelines
Depending on the orifice plate installation direction the impulse piping should be set up as shown below :
A) Vertical installation for clean liquids
B) Vertical installation for dirty or corrosive liquids
Mount the transmitter LOWER than the pressure connections.
C) Vertical installation for clean noncondesable gases
Vertical installation for vapor condensable gases or dirty gases
- Orifice Plate Installation Drawings from Foxboro Co.
- BRISTOL BABCOCK (1989) Flowmeter Applications
- SPIRAX SARCO (1997) M410 Orifice Plate Assemblies