Here’s some pointers to finding the right flowmeter for your application
- Know your flow rate/ flow range. Perhaps this is obvious but you need an idea about what your flow rate might be to size the meter correctly. Not only the maximum and minimum but also the normal flow rate expected. Maybe there will be a unique flow rate at start up?
- What flow units do you want to use? Is that going to be litres, gallons or, maybe, a mass unit rather than a volume?
- What output do you need? Is it just a quick visual, an accurate 4-20mA you could use for control or maybe a high-end digital communications protocol like HART or Foundation Fieldbus.
- How well do you need to know it? In other words, to what accuracy and repeatability do you need the result? And, if that isn’t the same over the whole range of the meter or your application where would you prefer the accuracy to be? Oh, and don’t forget, accuracy costs – are you prepared to pay for it?
- Are there any size limitations? Straight lengths are just one component of this. Are there physical limitations to meter length, height, width or, even, weight?
- What connection type? Not just fluid but also electrical. Fluid: BSP; NPT etc male or female; flanged; wafer; plain pipe; Grayloc hub; Autoclave MP; there is a long list. Electrical: terminals; connector; gland; unusual cable size.
- Is the meter going to be installed in a Hazardous Area? Perhaps it’s a Safe Area anyway but in Hazardous Areas there are many ways to provide a flowmeter solution but it’s definitely not one solution fits all.
- Do you know your fluid?. Important properties like viscosity and density will have a fundamental influence on flowmeter choice. Add to that chemical compatibility and property change over time and it can become a limiting factor. Can the meter be installed so that the pipe is always full? Is there any entrained gas or particulate?
- What’s the pressure and temperature?. That’s not as easy as it seems! Pressure will refer at different times to the operating pressure, max or min, design rating and could be confused with pressure drop. External pressure rating is a factor for subsea installations; slight immersion or water jet cleaning might require specific IP or NEMA ratings. Temperature must be specified for the media and for the surroundings together with extremes due to location and process. Storage temperature range can be quite different. Humidity may affect storage limits and material choice.
- Have you any special documentation requirements? Standard paperwork might just include calibration certificates and an installation guide. There might be charges for material certificates. Paperwork may not even be offered – it could be all electronic. Specialist needs might encompass PMI, SDRL, MTR, SDS, FAT procedures, witness testing, data books and cert books.
All in all, Ask the Experts