An orifice meter is a common device used to measure the flow rate of gas in the oil and gas industry. Gas dehydration units, well site separation skids, inlet separator packages, and line heaters typically use this piece of equipment. It comprises an orifice plate, a housing for the plate, and a meter tube.
The orifice plate is a thin, machined plate with precise dimensions and a hole known as the orifice plate bore. It is placed between two orifice flanges or, more commonly, an orifice plate housing.
Inspection of the Orifice Plate
The condition of the orifice plate is critical to the flow calculation, which is why you should inspect it regularly. After removing the orifice plate safely from its housing, be sure to check the following:
- Record the Size of the Orifice Plate Bore Correctly
Ensure that the size stamped on the plate matches the measurements in the production accounting calculations or flow computer. This is because the plate size is often changed physically but not recorded in the system.
- Verify the Bore Size
Check whether the inside diameter of the orifice plate bore matches the size stamped on the plate using a calibrated micrometre.
- Examine the Condition of Bore Edges
Ensure the bore edges are free of any gouges or nicks. Also, ensure the edge of the plate is sharp by running your fingernail across it. This is because such deformities will affect the flow pattern and differential pressure.
- Check the Overall Condition of the Plate
Make sure the orifice plate is smooth and free of any gouging or pitting. In addition to this, the plate must be perfectly straight without warpage or bulging.
- Review the Seals
Inspect the seals that hold the orifice plate in the housing and look for any signs of splits, cracks, or other damage. This can help ensure no fluids leak around the plate.
If any of the above inspections prove to be unsatisfactory, replace the orifice plate and seal. Also, remember to discard the old plate, so no one uses it again in the future.
Frequency of Inspecting of the Orifice Meter
Directive 017 of the Alberta Energy Regulator (AER)
The inspection cycle of the device, including its plate, depends on the application, customer contract, and government regulations. The AER lists the inspection guidelines under Directive 017: Measurement Requirements for Oil and Gas Operations.
- When it comes to gas plant accounting meters and sales or delivery point (royalty trigger point) meters, you should inspect the devices semi-annually. For all other gas meters, you may examine them annually.
- It is recommended to inspect the equipment at the same time as the calibration of the meter elements and end device, whenever possible. However, to accommodate operational constraints, you may inspect at any time, considering the frequency requirement.
- Ensure that the inspections are according to the procedures specified by the American Gas Association (AGA), API, or other relevant systems accepted by an appropriate industry technical standards association.
- Be sure to attach a label or tag to the orifice meter or end device that identifies the meter serial number, the date of the internal inspection, and any other relevant details.
- Maintain a detailed record of the inspection. Document the condition of the internal components, including any repairs or changes made to them. The reports should be kept for at least one year and provided to the AER on request.
It helps to know that the measurement specifications for oil and gas facilities and operations under the Saskatchewan Energy & Resources Ministry also have similar stipulations.
Examining the Meter Tube
When you depressurize and open the orifice plate housing, it is the right time to inspect it’s upstream and downstream flow. Use an inspection mirror to look inside the meter tube, and check for any foreign objects that may affect the flow.
Reliable Inspection & Refurbishing Services for Orifice Meters
Aspire Energy Resources Inc. has over 20 years of experience refurbishing metering equipment for the oil and gas industry. We have replaced several damaged or non-conforming meter runs. We have the knowledge and expertise to ensure the metering system meets the required standards set out by the Alberta Energy Regulator (AER), Saskatchewan Energy & Resources Ministry, and the BC Oil and Gas Commission.
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