flow meter

[bob4]

Hi All, I'm building a compact flow, pressure and temperature unit to handel max 200litre @ 250Bar and max temp 120DegC of hydraulic oil. looked at the turbine wheel type and i think that there too big and heavy. what if i used two pressure transducers, I could get my pressure reading from the first and providing i have some sort of restriction between the first and second pressure tranducer I could measure the drop and work out the flow. I know that the viscosity will alter the flow but how acurite do you think it would be?

 

[JLSeagull]

What is the flow rate? You mention the volume but not the time period.

An integral orifice transmitter may be suitable for lines smaller than one-inch. This has a differential pressure transmitter across a small honed orifice run. Micro Motion and other Coriolis meters are suitable for small flows.

A flanged flow orifice is suitable if the flow is 200 liter per minute.

Depending upon the flow rate, these could all as big as a turbine meter.

 

[bob4]

The flow range can be anywhare from 30 to 160 L/min. I was trying to get the whole unit as compact as possible.

 

[BigInch]

Why not try an ultrasonic strap-on? Would it fit on your line size?
-----------------------------------------------
Viscosity should change that much, unless there is a big temperature change.

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[bob4]

It would be nice if I could make the whole unit out of 25mmID SS or some thick walled aluminium tube. weight and size are the most important factors.

 

[danw2]

120°C is likely to fry the DP electronics on an integral mounted orifice. Meter body temp limits are usually around 110°C. Maybe someone makes a higher rated body, if not, DP might have to be remoted with impulse tubing, if the size and weight are acceptable.

Assuming your line size is 25mm (1"), there are averaging pitot tubes (Midwest, Preso, Annubar) that might take 250 bar. The spec sheet I have only shows scehdule 40, which is not enough, but I'm sure they make schedule 80 units.

The transmitter to pitot tube plumbing could be tubing with compression fittings. The flow tube isn't much more than what you describe - SS tube with a couple 1/4" nipples for high side and low side ports.

Generally, measuring both sides of primary flow element with gauge pressure transmitters and subtracting the two for a DP is not a good idea, because the error, a percentage of full span at the high pressures you are working at, overwhelm a small DP value.

If the error on one side goes positive and the error on the other side goes negative, you can actually get a 'differential' subtraction with a flipped sign that indicates the flow is in the opposite direction.

Turbine meters can have remote mounted electronics. When you said a turbine was too large, were you referring to the flow tube or the electronics part? Is your concern for size where the flow tube has to fit or the entire package?

Dan

 

[bob4]

Thanks Dan, I've been asked to make up a compact test kit for service engineers. There's loads more tranducers and thermocuples in the kit and i'm trying to keep the weight and size down. I expect a normal working temp of 65-80degC and 70-130Lpm flow. Most standard units seam to be around $900usd(£500stg).

 

[jmw]

Visit Flow Technology Inc (Phoenix I think,)
They produce turbines and PD meters.
Their meters for hydraulic duty are used in subsea assemblies so you can be sure they are reliable.


JMW

http://www.ViscoAnalyser.com