Orifice meter up/down stream straight pipe 1

[0123654789]

good day,

An orifice upstream straight pipe length requires 5D, I put a PI in upstream 4D. Is it ok?

thanks.

 

[racookpe1978]

Think about it: If I understand your description, you have a single, very long straight pipe.

At point 0, you have a pressure tap mounted in the side of the pipe.

At point 4D, you have a flow orifice.

A standard static pressure tap has no flow into or out of it, and its (very small) hole doesn't stick into the fluid flow path. So how could the pressure tap significantly affect the orifice flow, which will be at the centerline of the pipe?

Now, you do need to make sure there is a straight section of pipe downstream of the orifice plate before the next bend, and the pressure tap should be in a bend itself.

 

[dcasto]

no. First off, 5D upstream is not acceptable. If it were, the tap will create an eddy that will give a false reading.

Get the API MPMS chapter 14 for designing orifice meters.

 

[0123654789]

sorry, 5D is not a real thing, I used it as a number presents straight pipe.

my question is: the distance between PI and orifice, is shorter than the length required by the orifice meter up/down straight pipe.

I agree with racookpe1978. Is there any other opinion?

Thanks!

 

[zdas04]

I wouldn't accept it in a meter that was measuring my gas. I have to wonder why you have a PI 4D upstream. If you are using it for a static pressure in the calculation then there is simply nothing right about it. If you are using it for walk-up indication then the problem is less.

It all comes down to what you are using the meter tube for. If it is used for plant control then the PI is fine. If you are using it for custody transfer then you have to conform to the minimums in AGA 3 (which is the same as API MPMS Chapter 14)--they are not negotiable at all. If the book calls for 5D in a 6-inch Sched 40 pipe, then you cannot have any part of a purtabation in the flow within 30.34 inches of the upstream face of the plate. Some people would claim that the distances are based on the OD of the pipe, but I don't find support for that in the code.

David

 

[BigInch]

Neither would I. 5D MINIMUM is for a pump. For a meter you need at least 10 D AND straightening vanes.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[JLSeagull]

http://www2.emersonprocess.com/en-U...nditioning-Orifice-Flowmeter/Pages/index.aspx

 

[0123654789]

please ignore how many Ds for up/down stream straight pipe, it could be from 2D to 20D even more.

My PI is for plant control, I put it within distance required by orifice meter up/down straight pipe. otherwise, it is too high to access.

 

[zdas04]

Can't you take the signal off the Static tap on the meter?

David

 

[BigInch]

Now you say ignore it.
Then WHAT is your question?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[0123654789]

please bear with my grammar.

my question is: is there problem putting a PI in the orifice meter upstream straight pipe?

 

[BigInch]

No, but accuracy of the reading and the proportionality of pressure to flow may be another story, if you don't do it right.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[pennpiper]

Except for only certain situations I do not allow anything upstream for 20 diameters and nothing downstream for 5 diameters.
That goes for PI's also.

 

[0123654789]

does this PI cause flow turbulence and affect the accuracy of orifice measurement?

 

[BigInch]

That's the general idea.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[hacksaw]

A properly installed pressure tap is perfectly acceptable in routine flow measurement and custody transfer. Never had a problem.

Upstream tap is less affected by the meter, while the downstream tap should be located beyond the vena contracta and preferrably 20 D or so, however, in common plant installations this rule is not always possible to implement, so you take what you can get.


Most meter manufacturers have recommeded upstream runs as do the meter standards.

 

[BigInch]

That's confused things. "Properly installed" does not usually equate to, "take what you can get".

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[hacksaw]

The design of static pressure taps is a discipline unto itself, flow meter installations in an operating environment with the constraints imposed by equipment layout and piping is forced to deal with far more practical issues. It is there that the decisions involve engineering trade-offs.

Meter stations often with provision for testing, inspection, flow conditioning, etc. are another mater because of the need for contactural accuracy.

good day

 

[JLSeagull]

Perhaps the upstream tap may not be affected BY the meter for the pressure measurement. However, the upstream tap could affect the meter that needs a consistent flow profile.

The downstream tap should be located beyond the vena contracta but not 20 D downstream. Nothing more than six diameters downstream should cause concern.

 

[rgvrider]

It'll also depend on the relative size of the pipe ID compared to the pressure tap diameter.

As others have said, the closer any disturbance is to the orifice, the greater the inaccuracy of the reading. Given the lack of information, you will need to make the decision on the size of the disturbance and whether it will have a 'real' effect.