Installation of Submersible Flow Meter

The main advantage of immersion flow meters is the ease of installation. Installing these devices does not require cutting a section of the pipeline or using a bypass connection. All you need to do is weld a ball valve, drill a hole in the pipeline, and immerse the flow meter rod into the flow. In this article, we will examine these installation steps in detail.

Step 1. Choose the installation location

Since increased turbulence of the medium can cause deviations in measurement results, it is necessary to ensure that the gas supplied to the sensor is in a calm, low-turbulence state. Calm flow can only be achieved if there is a sufficiently long straight distance before the sensor (L1) and behind the sensor (L2) in the pipeline, and there are no hydraulic obstacles in the pipe (such as edges, seams, bends). The condition of the pipe behind the sensor is also important, as turbulence can occur in the direction opposite to the flow.

Obstacles in the flow located upstream in the pipeline	Minimum length L1	Minimum length L2
Small bend (< 90°)	10 x D	5 x D
Contraction / expansion / 90° turn or T-joint	15 x D	5 x D
Two 90° turns in one plane	20 x D	5 x D
Two 90° turns in different planes	35 x D	5 x D
Shut-off valve	45 x D	5 x D

 This table lists the minimum required values. If these values are not met, measurement accuracy may suffer

Step 2. Weld a threaded half-coupling

A half-coupling with external threads (e.g., G1/2) is welded onto the pipe from above.

Step 3. Install a full-bore valve

A full-bore valve is mounted on the welded half-coupling.

If for any reason welding the half-coupling and installing the full-bore valve (Steps 2 and 3) cannot be performed, installation is possible by using a sealable clamp already equipped with a full-bore valve:

Step 4. Drill a hole for the flow meter

You need to drill a hole in the pipeline into which the flow meter probe will later be lowered. Since drilling a pressurized pipeline is undesirable, installation is usually carried out in a system that is currently not under pressure. However, if stopping production is extremely undesirable, a special tool can be used to drill a working pipeline under pressure:

Step 5. Immerse the flow meter into the pipeline

You need to open the valve and place the flow meter probe into the pipeline cavity. After that, you need to screw the compression fitting of the flow meter into the full-bore valve.

If installation is carried out in a system under high pressure, manually immersing the flow meter into the pipeline may be difficult. In this case, a special device for installing the flow meter in pressurized systems can be used (right image):

Step 6. Align the flow meter

To achieve measurement accuracy, the sensitive element must be located exactly in the center of the pipe. Based on this, you need to calculate the immersion depth of the flow meter. The immersion length will be equal to the sum of half the outer diameter of the pipeline and the height of the half-coupling with the valve. To simplify this task, some flow meters (for example, VA400) are equipped with a measuring scale applied to the probe. After immersing the flow meter to the required depth, it must be aligned by orienting it according to the flow (the direction in which the measurement is made is usually indicated on the device body). This is necessary because most flow meters will only measure accurately if the flow direction corresponds to the orientation of the sensitive element and allow only small deviations. However, some devices, such as SS 20.500, can measure in any position relative to the flow.

Step 7. Secure the flowmeter position

After aligning the flowmeter, it is necessary to secure it in this position by tightening the compression fitting nut.

The flowmeter is installed. You can apply pressure or, if the installation was done in an operating system, immediately connect the flowmeter and start taking measurements.