Isolation Valve on oil/water bridle

[asghar]

How much is it important to have isolation valves on the main lines feeding the bridle on which level switches and LG are installed which have their own isolation valves.

Plant operation reasons out that since the liquid in the bridle remain stagnent therefore becterial growth causes corrosion and that is why recent leak in the bridle has occured. It is to note that the bridle has a 1/2" vent and 1/2" drain.

I agree to the point that it is a good engieering practice to have isolation valves for maintenance ease but the captioned logic does not click.

Your expert opion will add to my knowledge.

 

[saxon]

ashgar, One question; Without bridle blocks, How do you clean and maintain the bridle without shutting the process down? Remember, down time is money!

Hope this helps.
saxon

 

[asghar]

Saxon, You have a point. Thanks

 

[jsummerfield]

Consider locking or car sealing the main valves open. Often the process control and safety shutdown level instruments have separate connections. If both are on the bridle, isolating the bridle eliminates all level measurement. After routine instrument testing it is easy to leave a valve blocked in with no indication that this occured. This is a serious concern when the technicians or operators block the bridle instead of individual instrument.

John

 

[asghar]

John, The way I look at it is that the extreme switches, LSHH and LSLL, should be independently installed on the vessel.

In my case where the existing system has all the switches on the bridle, I was little hasitant to install isolating valves just because of the reason you mentioned.

However, Saxon's point has some weight and should be given due consideration unless there is some other complling reason not to install isolating valves.

Any way you have highligted a good point, thanks for the input