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Join Date: May 2011
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Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

03/13/2017 12:36 PM

hello everyone

please clarify

1.whether Integral type manifold or Traditional type manifold to be chosen for DP type flow transmitters.

2.whether it depends upon the process fluid to choose the type of manifold for DP type flow transmitters.

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#1

Re: Selection of manifold Integral or Traditional type for DP type flow transmitters

03/13/2017 1:17 PM

Maybe you could offer us a little bit more information about your application?

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#2

Re: Selection of manifold Integral or Traditional type for DP type flow transmitters

03/13/2017 1:54 PM

You mean like this one for Rosemount?:

I suspect there are distinct advantages to using integral manifold when possible for best results. Obviously, your best source of information will be the various OEM's for this type of instrumentation.

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#3

Re: Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

03/13/2017 4:30 PM

A1) It depends upon the application, which has been withheld from the forum.

A2) It depends upon the application, which has been withheld from the forum.

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#4

Re: Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

03/13/2017 8:59 PM

Mohsinhamid,

I could say the following:

Traditional or integral manifold would be application dependent, shall be very important the instrument installation detail defined during the detail engineering phase.

I have seen Dp transmitters with three or five valve manifolds, even I saw several Dp transmitter with manifold without bypass, of course, this were due safety issues.

By other hand if you are replacing a transmitter with traditional manifold, the practical would be that the new one arrived with the same traditional manifold in order to avoid impulse line modification.

Regards

JP

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#5

Re: Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

03/14/2017 8:24 AM

you may want to remove the instrument for repair or replace, and leave the impulse piping intact, and isolated, for separate manifold. Also sep. manifold can allow instrument replacement of different manufacture.

Fewer field connections on an integral manifold, so less risk for failure, less expensive to install, slightly.

process fluid not a factor, if both have similar ratings and port configuration.

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#6

Re: Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

03/14/2017 10:27 PM

James Stewart's #2 post shows a Rosemount coplanar 5 valve manifold that connects to the two ports of a DP transmitter to the process piping/impulse tubing. It was the first shift away from a 4 decade industry standard since the 1940's, when pneumatic, then analog DP transmitters, and then smart DP transmitters used an industry 2 1/8" center-to-center flange mounting for a manifold valve.

The center-to-center dimension for the process ports (the holes in the center) were the same for all brands, all models from the pnuematic era on the left to the smart era on the right until the coplanar. The four threaded holes above and below the process port are for the bolts that hold the flanged manifold valve to the process heads.

A flanged 3 valve manifold. The flange bolts to the process heads shown above (the pneumatic transmitter has 'footballs', 1/4"-to-1/2" NPT threaded adapters, those would be removed for a flanged manifold valve)

The process piping connects to the NPT threaded connections on the side you can not see above:

My concern about coplanar venting gas in liquid line. Air or gas needs to be vented from the impulse lines in a liquid application.

The process head below shows a typical vent that is mounted on the side of the process head, above the center line, because air/gas rises above the liquid. The side vent is circled in red.

Here's a side vent. The hex head is a needle valve that opens or closes a channel to the vent hole, circles in red:

This red arrow in the graphic below shows the air/gas vent path when the side vent is opened:

That configuration shown above definitely works for the gas entrainment I've dealt with. I'm sure the coplanar works, but I'm always suspicious that gas can get trapped above the elevation of the vent, in the pressure chamber in the transmitter itself where the measurement is made. The coplanar side vent is shown below.

The fora have not been plagued with complaints of error low pressure error due to gas entrainment, but it's always made me wonder.

I had a couple drinks with an Emerson product guy a decade ago at an ISA show and he said that the coplanar design was really cost driven; it does not need the flange at right angles to the valve body that the traditional valved manifolds need. A coplanar can be machined from plate stock. Bar stool opinion or the truth? I don't know.

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#7
In reply to #6

Re: Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

03/15/2017 9:43 AM

Nicely done, and well thought out!

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#9
In reply to #6

Re: Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

04/19/2017 2:58 PM

I heard somewhere that the rationale for the coplanar design was to relocate the sensing capsule in such a way that it would not be subjected to as much flange bolt stress. This is (ostensibly) one of the reasons the coplanar transmitters have much better calibration stability, especially as ambient temperature drifts, than the legacy capsule/flange design.

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#10
In reply to #9

Re: Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

04/19/2017 3:04 PM

interesting thought, good point.

Stay dry!

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#8

Re: Selection Of Manifold Integral or Traditional Type For DP Type Flow Transmitters

03/16/2017 10:48 AM

Thanks all for your valuable inputs.

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Users who posted comments:

Instruments-guy-SAV (1); Iris (1); James Stewart (4); mohsinhamid (1); PWSlack (1); rwilliams (1); tonykuphaldt (1)

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