Is there a problem with installing the flow meter at the front end of the fan?
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It is well known that most flowmeters require a certain length of straight pipe section during installation; generally, the installation is carried out according to the dimensions specified in the manufacturer’s calculations. However, due to timing issues between the pipeline installation and the procurement of the flowmeter, the calculations are not available at the time of piping installation, so in most cases, a straight pipe section of ten units in front and five units behind the flowmeter is provided as a practical approach. The straight pipe section is a parameter that most designers pay attention to, but there is another issue: are there any requirements regarding the installation location of the flow meter? For example, does the location of the flow meter – whether it is installed in front of or behind the valve, in front of or behind the equipment, etc. – have an impact on its measurement? Are there any regulations regarding the installation of various types of flow meters? A current project is facing a situation where there is an air supply duct through which air is delivered to the equipment using a fan. The diameter of these ducts is quite large, ranging from DN500 and up to DN1200. Due to cost considerations, insertion-type Anubas, Probas, thermal mass flow meters, and similar devices are generally used to measure the flow rate in these ducts. The pipe at the upper end of the fan is connected to the atmosphere, while the pipe at the lower end is connected to the equipment. However, the section of pipe from the fan to the equipment is quite short, and sometimes the required straight pipe length cannot be achieved. Therefore, some people have suggested installing the flow meter on the pipe at the front end of the fan. Will such an installation affect the measurement accuracy? Are there any other requirements?
Take a look at the installation specifications for automated instruments, GB 50093.
Is the front end of the fan a negative-pressure duct?
It is best not to do so; the flow meter should be installed in a location where the pressure is stable, usually in front of the valve and behind the pump. Installing it in front of the fan will affect the measurement values
1. It is best to install it at the outlet, as this ensures more stable parameters. 2. Manufacturers generally provide instructions regarding the location before and after the valve. 3. Our usual advice to customers is that if the pipeline on-site does not meet the requirements for a straight section, the installation can be carried out by making an opening 2/3 of the way along the straight section and 1/3 of the way from its end. 4. When installing, it is best to align the insertion point in the direction of the fan blades.
If there is enough straight pipe section at the front of the fan, it can be installed in that area. If a magnetic flowmeter is chosen, temperature and pressure compensation must be carried out ； We generally recommend that customers choose plug-in thermal mass flow meters. You can consult us for details. Thank you!
Installing it in front of the fan will affect the measurement values