Portable on-site checkmetering
When a flowmeter in operation has to be verified it usually has to be uninstalled from its location and transported to a facility where the necessary verification or checkmetering can take place. However, with an on-site verification device this task is made much faster, easier and at a fraction of the cost. When using the right meter, the result can even be as accurate as any off-site verification.
Off-site vs. on-site verification
In order for these plants to operate efficiently, the plant manager needs to be certain that each flowmeter is operating 100% correct. Upon delivery, meters are usually calibrated and therefore, the operator can be sure that they measure correctly. However, if the flowmeter operates under very harsh conditions, if it has been running for hours on end or if the plant operator simply questions a meter's performance, it can be necessary to check that the meter is still running exactly the way it is supposed to.
Doing this can be very time consuming and difficult because it often means that the equipment has to be removed from its location and sent to a factory for testing. Such an operation requires that the plant needs to be shut down in order to uninstall the device, which means lost production time, hours of hard work and ultimately, loss of money.
In a situation where it is expensive and takes a lot of time to uninstall a meter, it can therefore be very beneficial to perform an on-site verification of the flowmeter instead. When performing such a task, a portable measurement device is used to verify the performance and accuracy of the flowmeter. This allows for the verification to take place while the meter is in operation, which is clearly a benefit for the plant operator because a temporary shut-down becomes unnecessary.
However, if such a verification process has to prove itself useful to the customer it has to offer the same benefits as an offsite verification. This means that it has to be just as accurate and reliable.
Among the various options typically used for verification today, one product is of particular relevance to the water and wastewater industry: the clamp-on checkmetering kit. Since the meter is based on the ultrasonic flow measurement principle, it comes with functionalities that other flow technologies have difficulties with. First of all, it can be used to measure practically all conductive or nonconductive clean or moderately aerated liquids or liquids with suspended solids. This basic feature makes it possible to verify or check the performance of existing meters located at any given water and wastewater plant measuring for instance raw sewage, effluent or fresh water. Other application areas include temporary leak detection in large intake or distribution pipes in the irrigation industry.
Accuracy is typically around 0.5-1% and the repeatability on the better side of 0.015% making it deal for verifying high precision measurement tasks such as the addition of chlorine to drinking water.
Dual mode of operation
One of the most significant advantages, however, is that the meter has two modes of operation: transit time and Doppler.
Transit time operation is the preferred mode for relatively homogeneous liquids because the ultrasonic transit time pulses require a trouble-free passage of the pipe in order to deliver a signal that can be processed. Homogeneous liquids are found in primary sludge, mixed liquor or drinking water applications.
Doppler operation, on the other hand, relies on solids or debris in the liquid to offer a precise signal and hence, is the preferred measurement method for liquids with extensive suspended solids or aeration. Such conditions are typically relevant for measuring thickened and digested sludge.
The system can be set up to automatically switch from one mode of operation to the other as conditions change eliminating the need to alternate between meters. As the above examples illustrates, the dual mode capability enables an operator to use the checkmeter on almost any application at a water and wastewater plant because its operation can be adjusted and optimized to the specific measurement tasks regardless of aeration and solid percentages. In enables verification of any brand or type of flowmeter based on the traditional flow measurement principles including electromagnetic, ultrasonic, orifice or rotary piston technologies.
Portability ensures versatility
The last factor adding to the versatility of this particular checkmeter is its portability. The kit is battery-powered and comes with a selection of transducers that fit the most common pipe sizes and types within the industry. Since the kit is of the clamp-on meter type, it utilizes external transducers that can quickly and easily be installed on the outside of the pipe. This allows the meter to be transported from one installation to another facilitating the performance of surveys and monitoring of temporary or permanent flowmeter installations.
On-site verification a powerful tool
So using an on-site clamp-on ultrasonic checkmeter to verify the performance of existing meters, has several benefits for plant operators and managers in the water and wastewater industry. The most persuasive one being, however, that it offers an inexpensive and easy way of verification without having to perform a costly and time-consuming off-site verification.
- Brian Roughan