Flow Meter Systems & Application Challenges: How do I measure?

In this blog feature we bring you some of the more interesting and topical flow meter systems’ application challenges posed to Titan Enterprises and the solution we provided. Don’t hesitate to send your flow metering application requirements to Titan, here.

Flow Meter Systems: How do I measure pulsating flows ?

Last month we covered pulsating flows in flow meter systems. This has made people ask what types of flow meter systems give the best results with changing flow rates. Pulsations in a flow line are usually caused by the pumping element. Piston, diaphragm, peristaltic and solenoid pumps can all induce quite serious pressure and flow pulses. Very few flow meters are able to measure these fluctuations accurately. To get best results it is therefore recommended to remove the pulsations near the pump with a pressure regulator and a pulsation damper. The pulsation damper is likely to be most effective at only one set of operating conditions so it is advisable to adjust this at your required operating flow. Should the pump speed change the system will be less effective. If it is not practical to install the damper, a length of flexible hose may reduce the problem.

How different types of flow meter compare when faced with pulsating flow conditions.

Flow Meter Type Effect of pulsating flow conditions
Mechanical flow indicators Variable area flow meters are likely to be unreadable as the float will bob up and down with the flow.
Low inertia turbine flow meters The lower mass of the turbine will allow the meter to accelerate and decelerate quickly. The Titan 800 series turbine has a step start-up time of less than 20 milliseconds and over a period of time will quite successfully give a reasonably accurate total.
Positive displacement flow meters Positive displacement flow meters such as the Titan oval gear meter range will give accurate readings as they take discrete pockets of fluid and transfer them through the meter. Care should be taken with some types of PD meters as hydraulic shock can damage the product.
Coriolis flow meters Coriolis meters are typically tolerant to pulsations as they measure the mass of the product passing through the device.
Vortex shedding Flow pulses in line will often render vortex shedding meters highly unreliable in pulsating flow conditions.
Ultrasonic flow meters Most ultrasonic flowmeters have a set cycle time and should this coincide (alias) with the flow pulsations errors will be recorded.
Electromagnetic flowmeters Most electromagnetic flowmeters have a set cycle time and should this coincide (alias) with the flow pulsations errors will be recorded.