Spectacle Blind 2

[happyam]

Spectacle blind are used for easy change-over when physical isolation of pipe is needed.

But I always have a question in mind, how can we remove the old gasket as well as adding a new gasket within the limited working space?

Many thanks!

 

[MikeHalloran]

There seems to be a tacit assumption that gaskets will seal but not stick and not fracture, and that flange spreaders will be available or unnecessary.

So I'd have to assert that the change-over is easy only from the perspective of the guy who doesn't have a wrench in his hand.



Mike Halloran
Pembroke Pines, FL, USA

 

[TGS4]

What, specifically, is your issue? There are many on this board that have done what you are discussing.

MikeHalloran - good one!

 

[zdas04]

Sounds like you are using paper gaskets. STOP. Using anything but a spiral wound gasket (also called Flexitallic Gasket) on a spectacle blind is a very bad idea. Paper gaskets (even without gasket compound) have a tendency to stick to the flange face and can be impossible to scrape out in the limited space allowed for the spec blind. Flex gaskets solve that problem and result in a better seal. The cost difference is an illusion, and if a $30/hour mechanic or fitter has to spend an extra 20 minutes scrapping a flange with a $10,000/day crew standing around waiting for the isolation to be complete, you just burned a lifetime of savings on less expensive paper gaskets.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[ConstantEffort]

An additional assumption is that there is some flexibility in the line. If there is spec flange is installed on a straight shot between two anchors, happyam is probably right. Put in a turn or two and some perpendicular pipe to bend and it can be done.

.... says the guy without a wrench in his hand.

 

[btrueblood]

As a guy with the wrench occasionally in his hand (or at least sitting uncomfortably close to those with wrench(es) in hand(s)), I usually spend the money for a valve instead of using a blind, if the blind is going to be used more than once every few years. We've also been using a thin film of silicone grease on all of our pipe flanges, which greatly eases the seperation of gasket from flange face (well, but we also use gaskets that don't react to silicone, i.e. most rubbers and polymers except silicone rubber).

 

[happyam]

I am sorry for my naive question and please forgive me as I am new to spectacle blind.
As Zdas04 said, a contractor used paper gasket. When I saw the paper gasket, I just wonder how can the change-over be done efficiently. Therefore, I come here and seek for your expert advise. Apart from the gasket problem, another headache problem is that I find corrosion on the blind side of the spectacle blind. In the isolation state, the corroded blind surface should lead to leakage even all the rust are removed.

By the way, I do think that spectacle blind and valve serve different purposes. As spectacle blind provide guaranteed isolation whereas valve does not.