Overview
- Flow Stability: Choose areas with stable liquid flow and avoid elbows, valves, or other turbulence-inducing locations.
- Installation Position: The "At least 10D in the front and 5D behind" rule helps identify the optimal paddle wheel flowmeter installation site.
- Filters: Install filters to extend equipment life and reduce interference.
- In horizontal pipelines, install at the lowest point of a concave section; in vertical pipelines, install where the liquid flows upward to ensure stable flow rates.
Many industries use paddlewheel flowmeters to monitor fluid flow, but they often overlook the importance of choosing the correct installation location, leading to inaccurate measurements. Factors such as impurities in the liquid, pressure, water volume, and air bubbles can interfere with the flowmeter’s readings. To avoid these issues and ensure accurate measurements, LORRIC recommends users decide on an appropriate installation location before cutting the pipe. This approach helps prevent inaccuracies, reduces the hassle of relocating the flowmeter, lowers costs, and improves on-site operational efficiency.
Based on years of experience from our technicians working with clients and conducting on-site installations, we have summarized the following methods to help users identify suitable installation positions on both horizontal and vertical pipes. We also share key techniques to enhance the measurement accuracy of the flowmeter.
1. Stable flow field makes the best accuracy of flow measurement
Firstly, the flowmeter should be installed in a region where the liquid flows smoothly. Avoid placing the flowmeter near elbows, valves, or other components that might cause turbulence.
When liquid initially enters the pipe, the flow speed is erratic due to differing travel directions, resulting in significant measurement errors as the values fluctuate. However, as the water continues to flow and friction occurs, a fully developed flow is achieved. This stabilizes the flow speed, resulting in a steady-state flow field, which allows for the most accurate flow rate measurements.
2. Tips for installing a paddlewheel flowmeter correctly
1 ) At least 10D in the front and 5D behind
After identifying a section of the pipe where the liquid flows smoothly, the next step is to select the precise installation location for the flowmeter. The key is to follow the "10D in the front and 5D behind" rule:
- 10D Upstream: Ensure there is a straight pipe segment at least 10 times the diameter (D) of the pipe upstream (in the direction the fluid is coming from).
- 5D Downstream: Ensure there is a straight pipe segment at least 5 times the diameter (D) of the pipe downstream (in the direction the fluid is flowing towards).
Assuming the pipe's inner diameter (ID) is 4 cm, let's apply the "At least 10D in the front and 5D behind" rule to determine the required lengths of the straight pipe segments:
• Upstream (Flow-in) Straight Pipe Segment Length:
10 × ID = 10 × 4 cm = 40 cm
• Downstream (Flow-out) Straight Pipe Segment Length:
5 × ID = 5 × 4 cm = 20 cm
For a pipe with an inner diameter of 4 cm, the ideal installation position for the flowmeter would require an upstream straight pipe segment of 40 cm and a downstream straight pipe segment of 20 cm.
If the inner diameter (ID) is unknown, the outer diameter (OD) can be used along with the wall thickness to calculate the ID:
Formula: ID = OD − 2 × Wall Thickness
2 ) Install the paddlewheel flowmeter before the valve
The flow meter should be installed upstream of valve, so the fluid will be fully developed. This recommendation is also applicable to other piping components that may affect the flow field.
3 ) Filters Installed Before and After the Flow Meter
For longer service life and better measurement accuracy for the paddlewheel flow meter, we suggest setting filters or related technology before or after the flowmeter. The filter installed before the flow meter can filter impurities or foreign objects from sticking on the blades that make it unable to rotate. The filter installed after the flowmeter can prevent downstream equipment (ex: pump) from being damaged by any falling parts. Lorric’s paddlewheel flow meter equipped with patented AxleSense technology, can detect paddle disappearance by displaying a warning signal (flashing bright red light) on the operational screen.
4 ) Install paddle wheel flowmeter at the pipe which is inclined with horizontal pipe for 45°or 135°
If the paddlewheel flowmeter is installed on top of the high place of the pipeline where air bubbles might form. The air bubbles could get stuck between the paddles which makes it difficult to measure. Also, if the flowmeter is installed right below the pipeline impurities and precipitation could get stuck between the paddles. This could make it difficult to rotate the paddles. In addition, installing at the right side of the pipeline is not recommended. It may cause wear-and-tear caused by high speeds to the ceramic part of the paddle. We highly recommend installing the paddle wheel flowmeter inclined at 45°or 135°on a horizontal pipe. It is the ideal location for accurate measurement.
5 ) Install paddle wheel flowmeter at the location where the pipe is filled with liquid. The most recommended location is the lower place of concave pipeline
a. Horizontal pipe
As you can see the image below, air bubbles stay on the top of higher place of pipeline. However, if with not enough pressure, water stage become lower, and the pipe is not easy to be filled with liquid. However, at this time, if the installation location is at the lower place of concave pipeline which is filled with liquid for sure, the measurement will works as expected definitely.
b. Vertical pipe
LORRIC recommend to install paddle wheel flowmeter on the vertical pipe with liquid flowing to upstream. If the fluid flows from top to bottom in a pipe, the fluid will flow in a free falling pattern, leads to a noncontinuous vertical flow. In this position the flow is not stable and flow volume measured is not accurate. On the contrary, if the fluid flows from bottom to top in a pipe. With the help of gravity, the flow rate will remain relatively stable. Therefore, the measurement is more accurate.
