Dismantling Joint and Magnetic Flowmeter Installation

[18815030]

Hi all,

It it more common to install a dismantling joint directly downstream (option 1) of a magnetic flowmeter or with 3x diameter spacing between the components.

Option 1 has maintainability advantages as you don't have to move an extra bit of pipe to access the flowmeter but may lead to inaccurate reading due to differences in internal diameters creating turbulence.

Let me know your thoughts

 

[Doug Hunter]

Does the dismantling joint have features which would disturb the flow? If not, I would think that you don't need the extra spacing. Even with disturbances, I think that they will cause effects more downstream, not so much upstream. You could always test both ways to be sure.

 

[swazimatt]

That is a question to the supplier of the flow meter. normally they just specify xDiameters of straight pipe upstream and downstream, a bend is probably more likely to cause turbulence than the irregularities of a dismantling joint (which won't be too different to the flanged joint between pipe and flowmeter)

I suppose it also depends on how accurate you need the results to be - laboratory experiment or just measuring flow from a pumpstation

 

[bimr]

Dismantling joints are normally used where the pipeline is mounted in such a way that it can't be easily pulled apart but you need to get access to a particular piece of equipment. For example if you had a flange mounted flow meter in a long straight piece of pipework it can be very difficult to remove or replace that flow meter. So you might put a dismantling joint on one side of the flow meter which will allow you to remove the flow meter relatively easily.

The flow meter tubes are more or less permanent and don't require regular replacement.

If you are worried about flow turbulence, just move the dismantling joint past the 2 times the pipe diameter.