Case Study: Clamp-on Flowmeter
- Apr 9
- 3 min read
The Problem:
MHR was recently involved in troubleshooting a RIM machine that was showing erratic flow rates on the ISO line. (It's always the ISO line, isn't it?). The machine is set up with a variable speed frequency drive that controls the motor speed, and hence the pump flowrate, based on the measured flowrate and the desired target flowrate. The actual flowrate was varying significantly due to the inaccurate readings from the flowmeter.
The flowmeter in question was a gear style flowmeter.
It was determined that the flowmeter was defective after multiple attempts to clean and fix it. Unfortunately, a spare was not readily available, and a purchased unit was a week or two out.
Exploring Options:
Recently MHR had been testing an alternate method for flowrate measurement on a machine being refurbished. This new style flowmeter uses ultrasonic waves to determine the flow of liquid through a pipe or tube. The great advantage is that the sensor can be clamped onto existing rigid tubing (steel or stainless steel). This makes installation extremely easy, especially on systems where you don't want to break into the plumbing and expose the chemistry to atmospheric air.
Our initial testing on the refurbished system had been very promising, with measured flow rate accuracies within 1% of actual measured flowrates.
In order to get the machine running as quickly as possible, we "borrowed" the flowmeter and installed it on the machine with the defective flowmeter.
Set-Up and Configuration:
As mentioned, the installation of the flowmeter only took a few minutes. There was a section of straight pipe conveniently located near the control panel that worked well for our purposes.
Next the flowmeter had to be wired into the control panel. We simply had to hook up the flowmeter to 24 VDC, and then connect the analog output signal to the corresponding input. Essentially we replaced the input wiring of the existing gear flowmeter with the wiring from the new clamp on flowmeter.
After that, the flowmeter needed to be configured. Variables such as pipe OD and wall thickness and liquid viscosity are input into the flowmeter.
Calibration:
Since the flowmeter uses ultrasonics to determine flow, and not positive displacement, calibration is critical. The initial readings will not be correct, since every system is different.
Multiple calibrations were performed in order to determine the proper scaling of the flowmeter. Once the scaling was determined and input into the flowmeter, the machine began production.
Other Applications:
On a different machine we were having issues with flow rates dropping as pressure increased. It was thought that we were getting blow-by on the switching valve. However, after installing the clamp-on flowmeter in strategic locations in the fluid circuit, we were able to determine that the pump was actually failing to provide the required flow as pressures increased. After replacing the pump, the system returned to normal operations.
Using the clamp-on flowmeter allowed us to troubleshoot the source of our flow issues and prevented us from wasting time and parts fixing components that were working properly to begin with.
Here is a short list of possible applications for the clamp-on flowmeter that may benefit your system and process:
Quick replacement for a defective flowmeter
Replacement for an obsolete flowmeter
Troubleshooting device for verifying an existing flowmeter
Troubleshooting device for determining flow at various points in the fluid circuit
What about Cost?!
Surprisingly, the clamp-on style flowmeter is a more cost-effective solution than a gear style flowmeter. You can expect the costs to be about 60% of the cost of a gear flowmeter.
What's the Tradeoff?
The tradeoff for the simplicity and cost is that the flowmeter is not positive displacement, meaning that calibration at startup is critical. With a gear style flowmeter, variables such as viscosity and plumbing are not nearly as important, since each rotation of the gear equals a given volume.
Interested in a Trial?
Based on the success we have had in multiple applications, MHR now keeps a demo unit on hand at all times. If you are interested in a trial, reach out today.
Before the trial, it would be helpful to know:
Pipe OD and wall thickness
Fluid viscosity
Typical flowrates
Analog Input type (4-10mA or 0-10 VDC)
Contact Us for More Information!
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