5 replies to this topic

[nguyenmd147]

I'm not very familiar with flow instrument in general, therefore apologize if any of the question are weird (and silly). 

Flow measurement (high chance) is a flow element / restricting orifice sending 2 signal  to 2 pressure differential transmitters, to measure  a Hot Oil (therminol 55)  flow in 8" pipe to a heat recovery unit. The design is 2 transmitters, 1 for alarm and 1 for display in LCP.

So my question

1) If we gonna set up 2 transmitters, is there will be any significant pressure difference when the fluid spilt up to each transmitter?

2) If we use another type of flow measure (Coriolis, ultrasonic), by any chance the changes in arrangement are make the problem 1 disappear?  

 

 

The design looks like the pic in attachment . The transmitter are 5 valve manifold.

(Note : The original design was 2 different FE in 2 places for each signal, but the requirement from our clients they have to be separated at least 2m within each other, so its will take significant space. )

Attached Files

•  flow meter.png   26.49KB   0 downloads

Edited by nguyenmd147, 02 December 2023 - 12:43 AM.

[Pilesar]

I will give a general answer since I don't fully understand your question (due to no picture and undefined acronyms)... It is good practice to have independent indicators for control and for automatic interlock. This is to try and provide a safeguard from misleading control indication. The two indications might nominally measure the same process variable in the same location. The goal is not for the measurements to be identical, but for each measurement to be accurate. Measurement indications are calibrated separately and will often differ slightly with each other while still within the accuracy range of the measuring instrument. The two measurements can be significantly different if at least one measurement is not accurate. This problem will not disappear since it is inherent in the concept of independent measurements and provides the safeguard. So my answers to both your questions are 'no' for normal operation.

[nguyenmd147]

I will give a general answer since I don't fully understand your question (due to no picture and undefined acronyms)... It is good practice to have independent indicators for control and for automatic interlock. This is to try and provide a safeguard from misleading control indication. The two indications might nominally measure the same process variable in the same location. The goal is not for the measurements to be identical, but for each measurement to be accurate. Measurement indications are calibrated separately and will often differ slightly with each other while still within the accuracy range of the measuring instrument. The two measurements can be significantly different if at least one measurement is not accurate. This problem will not disappear since it is inherent in the concept of independent measurements and provides the safeguard. So my answers to both your questions are 'no' for normal operation.

 

@Pilesar 

Thanks you for your respond. If you don't get any specific unclear words, tell me and i'll try to explain it more clearly. 

I have updated the image.  I am only checking for a new intern in charge of buying and design this, as myself don't really work directly with flow instrument. 

I can provide a hook-up drawing for a bit more detail. 

For a more clear picture, one suggestion is at the connector to transmitter just get a short tee + a short tube for another transmitter (hence why the pressure drop concern). Another using another tube (about 2-3m) with same hook-up for another transmitter, but the clients really don't like it. 

Attached Files

•  hook-up for flow meter.png   119.99KB   0 downloads

Edited by nguyenmd147, 02 December 2023 - 01:01 AM.

[Pilesar]

If I understand your setup, the fluid pressure seen by the two transmitters will be the same. The split does not matter as the transmitters do not affect each other. Prove it to yourself by configuring each transmitter location as if it were the only one. Will it sense the pressure? If so, then the installation is acceptable. There is zero flow rate in the sensing line so an additional tee in that line has no hydraulic consequence. 

[Pilesar]

I would place the two transmitters side-by-side about a hands-width apart.

[shvet1]

Nothing special, common design as per my experience. This control system has totaly independent ESD and DCS and stays safe in case of any failure of DCS.

 

FICA-6121A - control loop via DCS

F - flow

I - indicate

C - control

A - alarm at low set

 

FZA-6121A - trip loop via ESD

F - flow

Z - other action type (usually emergency switch)

A - alarm at low low set

 

Find cause and effect diagram for details.

 

For info

ISO 10628; ISO 14084; ISO 14617; ISO 15519; ISA-5.1; PIP PIC001

Edited by shvet1, 04 December 2023 - 12:35 AM.