An insertion flow meter primarily includes a flow sensing element, temperature sensing element, and bridge amplifier/signal output board. In addition, they have a microprocessor circuit board, transmitter enclosure, and a probe assembly, which supports the sensing elements. This design requires the probe assembly to be inserted into the process gas flow conduit.
Our insertion flow meter options are available with 1/2″, 3/4″ or 1″ OD probes. Insertion style flow meters can install with proper size bored-through tube fittings to mount them in place. Tube fittings, with or without mounting flange, are also available from the factory as an option. Installing the tube fitting consists of preparing the flow conduit to accept the fitting. First, installers will drill a clearance hole for the transmitter probe assembly and weld it into place. Or, it can thread it into the proper size half coupling, which welds to the flow conduit. Your distributor or the manufacturer will also determine the necessary tube length after considering all installation specifications.
For more tips and tricks, you can consult our article on: Flow Meter Installation.
Optional ball valve assemblies are available for insertion flow meters. Ball valve assemblies allow the removal of the insertion style averaging tubes for service, calibration, cleaning, etc. The valve provides a means to seal off leaks of the process gas at the point of insertion after removal of the probe assembly. Installation requires fitting the flow section to the insertion probe assembly. Then it inserts with a threaded half coupling of the proper size to accommodate the ball valve retractor.
In some instances, this requires direct threading together (or with a reducing bushing) of the retractor assembly. In other cases, it requires welding the half coupling in place and drilling a clearance hole through for the probe assembly. If the flow section is under pressure, a hot tap drill rig (not available through EPI) may be necessary.
The manual for each product states the maximum pressure for an insertion flow meter. To reduce the possibility of personal injury when servicing the flow meter, each size offers a rating such that the maximum force applied to the transmitter is approximately 25 pounds. Installers should also exercise caution if considering applying higher pressures. For example, at higher pressure, a holding device may be necessary to prevent the transmitter from projecting out of the process line when removing or replacing the transmitter assembly.
EPI calibrates insertion flow meters for positioning near the ISO Point-of-Average-Flow (0.243r). See the installation manual for calculation of the probe insertion depth (pipe OD to probe end). It includes the point-of-average-flow, x-factor, and wall thickness of each nominal pipe size. In addition, it will indicate further adjustment recommendations on smaller line sizes to ensure the slot fully inserts through the pipe wall.
Each flow meter undergoes calibration under tightly controlled conditions in an NIST-traceable facility. During the initial factory calibration, EPI accommodates the depth of the pipe for inserting the probe assembly to prevent blockage. Therefore, the factory C-Factor value is now always “1”. The manual also includes product-specific insertion depths for each product. Consult us for any additional C-Factor adjustments required if the flow meter will be used in a pipe size other than that specified for the initial factory calibration.
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