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Sequence of Pressure and Temperature Instruments

02/08/2017 4:17 AM

Downstream of any equipment e.g. a pump, we have a pressure and temperature instruments. Is there any sequence of installing them or we can have them in any sequence?

If sequence is there, what is the reason for it?

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#1

Re: Sequence of pressure and temperature instruments

02/08/2017 4:23 AM

I don't think there are any particular issues about that. It could be interesting and/or amusing to see reasonings otherwise, but some "professor" somewhere might have some.

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#4
In reply to #1

Re: Sequence of pressure and temperature instruments

02/08/2017 7:53 PM

I should, though, add that installation geometry for flow instruments is more important. Thermowells in particular, and perhaps pressure ports in some cases, may need to be located some distance away from flow sensors, to minimize turbulence.

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#6
In reply to #4

Re: Sequence of pressure and temperature instruments

02/09/2017 12:17 AM

I think the general point is if they affect each other then the effect should be allowed in the layout.

Pressure devices in my experience are just a side branch - small with just a small eddy effect on the flow.

Temp devices again in thermowells or other will create different eddies. Technically these eddies might impact the pressure measurement but not to the extent that is significant or measurable on an industrial plant.

So probably Pressure then Thermowell. This also seems sensible if the PI is there to indicate the performance of the pump (in an installation downstream of pump) and so you would want it as close as possible to the pump outlet.

BUT if you have some lunking great device then think about what you are trying to measure and ensure that you can measure those things without impact.

Overall I would be surprised if it had an impact and in 20 yrs have never worried about the order.

HOWEVER double plus agree with Tornado that flow elements are very different and have critical rules for the installation of other meters, elbows tees etc.

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#2

Re: Sequence of pressure and temperature instruments

02/08/2017 5:23 AM

If there is one, it will be contained within a design document called "Process Description" or similar. The Process Engineer who wrote it will have given the reasoning.

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#5
In reply to #2

Re: Sequence of pressure and temperature instruments

02/09/2017 12:10 AM

You must have read better Process Descriptions than me gunga din!

And as a Process Engineer i think I may have been guilty of frequently just setting rules. But it would be nice to get justifications for things like this when there appears no reason!

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#7
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Re: Sequence of pressure and temperature instruments

02/09/2017 9:10 AM

Perhaps the one exception to that being Coriolis flow sensors.

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#3

Re: Sequence of pressure and temperature instruments

02/08/2017 9:08 AM

I prefer to install the most difficult one to reach first. Often the easy to reach sensors block access to that one pain in the a$$ sensor.

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#8

Re: Sequence of Pressure and Temperature Instruments

02/10/2017 7:37 PM

Generally, Pressure gauge should be install first after the pump follow by the temperature sensor. Pressure switch should be install slightly far away from the valve to avoid water turbulence which will effect the pressure gauge reading. The distance should be 2.5 time the diameter of the pipe. If you are using a 100 mm diameter pipe, your pressure gauge should be 250 mm distance from the valve

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#9
In reply to #8

Re: Sequence of Pressure and Temperature Instruments

02/13/2017 11:22 AM

I don't know if I totally agree about pressure followed by temperature. If it is a pressure critical application, I might want (if allowed only one transmitter each) the pressure nearer the important application of pressure. Just sayin'.

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James Stewart (2); PWSlack (1); redfred (1); Simon Wan (1); simonsd (2); Tornado (2)

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