MOVs and GBS

[Hydrotreaters]

Hello Guys!

Just want to solicit you rexpert opinion on MOVs (motor operated valve) and GBS (maual valves with positional switch). When do you use an MOV and not GBS, or GBS and not MOV? The installation of MOVs and GBS is part of the automation of our mogas blending (in-line blending); we want to optimize our cost and one of the options is the use of GBS instead of MOV as MOV is more costly. Thank you!

 

[TD2K]

Some factors to consider are:

do you need to be able to close the valve for emergency isolation? If yes and it's in a fire zone, the valve and electrical cables should be fire proofed.
Size? Big valves are slow to operate, Operators don't like to have to open and close them.
How frequently the valve has to be operated. Ties into size. A manual valve that has to be operated once a year will be viewed differently from a valve that has to be operated each shift.

 

[hacksaw]

for a blending operation with occasional product switches valves with limit switches are fine, but if you have a lot of product changes ( more than one valve every few days) then you need to consider automatic valves. It is a reliablity issue, limit switches are not considered adequate primary safety device unless they are self checking and tamper proof.

use of MOV's is a big question mark if your are blending gasoline; they'd be very expensive and are notoriously difficult to configure for "fail-safe" modes.

 

[MortenA]

You normally cant use MOV's for emergency vales (assuming that they either must open or close on failure). Because that the motor usually wont work if the power disappers.

Usually ESDV's are hydraulic or pneumatic with a spring to open or close on failure.

Re manual or actuated valves: This must depend on your plant layout and your avaiability requirements. It seems pretty obvous to me that if you have a large plant and require the valves to be operated manually, then you must be prepared to wait while the operators move out there. You will also require more people then Assuming that you are in the middle east this might not matter much.

Best regards

Morten

 

[Hydrotreaters]

Thank you guys for the responses.

we will be blending 4 grades of gasoline, usually one grade a day or more frequent depending on the product demand/liftings.

we'll be using MOVs to minimize human intervention and do the blending faster (i.e. without waiting for the operator to open/close a valvein another location).

the capacity of our plant is 180 KBPSD.