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Use of Sight Glass on Drain Lines

Use of Sight Glass on Drain Lines

Use of Sight Glass on Drain Lines

Dear All,

I would like to seek your views on the use of sight glass elements on drain lines downstream the drain valves. Are there are any integrity issues associated with their use. Some operational experience recommend their use to monitor drain valve's passing / inadvertent opening.

Appreciate your feedback from your experience on such design element.


RE: Use of Sight Glass on Drain Lines

To me nothing wrong with them , make sure the glass and gasket are compatible with your chemicals & Operation conditions (P&T).
My view

RE: Use of Sight Glass on Drain Lines

I recommend the operator visually inspect the sightglass prior to draining, and then proceed with draining only if sightglass is not defective.

A frequent, safe draining, like water, could be built into the procedure. A non-frequent, hazardous draining might require a time/date sign-off the sightglass is not defective.

Good Luck,

RE: Use of Sight Glass on Drain Lines

Sawsan, what is the purpose of these sight glasses? How do sight glasses monitor a drain valve position? I don’t understand what you get out of them other than confirmation draining is complete. They usually aren’t great at confirming valve leaks unless the liquid trail happens to run across the glass plate.

My experience for reliability is that if these are mounted in clean service, they are usually fine (though if the liquid is clear it can be quite difficult to see if there is liquid or not).

If mounted in a dirty service, they seem to collect debris and usually get coated, requiring periodic cleaning or change outs.

RE: Use of Sight Glass on Drain Lines

Add a wherl inside so you can see the flow.

But after 5 years you need to change the class

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Use of Sight Glass on Drain Lines

I worked on facility where process fluids are prone to polymerizing so we used sightglasses widely for draining purpose. A sightglass was installed just downstream of drain valve. It was useful when drain valves are prone to clogging by polymer/debris and there is no other safe or reliable way to check if a vessel/pipe to be drained is emptied. Based on sightglass an operator made the decision if a drain valve should be cleaned manually or purged.

The same for drain valve tightness - a sightglass helped to make sure it is not leaking.

A sightglass was extreamly helpfull for the purpose of emergency emptying of process vessels containing fluids prone to clogging.

Sightglasses are prone getting dirtied so it is essential to have means for safe and prompt disassembling of a glass for cleaning.

RE: Use of Sight Glass on Drain Lines

Most sight glasses I've seen are in some fouling service or other, and they are usually covered in some crud, making it useless.

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