Spectacle Location 1

[0123654789]

In piping model, a spectacle which is on a removable spool, is connected to an tube&shell heat exchanger nozzle directly.

My question is: is this configuration wrong? during maintenance, the removable spool including this spectacle is removed, how to prevent fluid inside piping come out?

even there is a valve before this spool, it still can not prevent fluid leakage completely.

Should we put the spectacle before the removable spool?

thanks for your reply.

 

[jte]

Well, spills happen. You just can't drain everything perfectly, and as you noted, single valves frequently leak a bit. That's what kiddie pools are for. Really. Nothing can be drained perfectly. If you're really concerned about it, instead of a blind-spool-valve setup why not go with a blind-spool-double block and bleed setup. Though... normally you'd just go exchanger-double block and bleed.

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If you're concerned with emptying the entire pipe on the far side of the single valve if it has a slow leak, why not just remove the spool, then blind the valve? Which also brings up the question of why you have a spec blind between the exchanger and removable spool? When you remove the spool, what's keeping the spec blind in? And why would you want to blind the exchanger when you have removed the spool?

jt

 

[0123654789]

jte,

thanks for your reply.

the spectacle location is exactly the same as P&ID sequence, I think it is for hydrotest to isolate heat exchanger.

If we blind the valve, that means we need put another spool between removable spool and spectacle+valve. that is: exchanger - removable spool - pup - spectacle-valve. how is it?

 

[jte]

Here’s what I’m visualizing:

In service:
(shell or channel) ---||-------(removable spool) -------||X||---------(pipe)

Out of service. Close valve, remove spool, put a standard blind flange on the valve. No spec blind:
(shell or channel) ---| ||X||---------(pipe)

How often is the exchanger going to be hydrotested? Shouldn’t be really frequent… If a hydro is required… remove the spool and put a blind on the shell or channel flange. Or is this a high pressure exchanger and blinds are hard to come by? Class 900 or higher?

jt

 

[0123654789]

on your out of service, you mean adding additional flange and bilid to valve on site?

my visualization is like this:

In service:
exchanger-||---(removable spool---||---(pup)---|?|X||---(pipe)

Out of Service:
exchanger-| |---(pup)---|?|X||---(pipe)

?=spectacle

 

[jte]

Yes. The site maintenance folks will have blind flanges. They will close the valve, drain the exchanger and pipe (you do have drain connections with valves, right), remove the removable spool, install a normal blind flange on the valve. Done.

The exchanger is now positively isolated from the process related to that pipe, and a small leak of the valve will result in a few gallons (depending on pipe size)collecting between the gate of the valve and the blind. When the time comes to put the spool back, the process is reversed. Maintnance should anticipate the possibility of a bit of liquid trapped between the gate and the temporary blind and place a kiddie pool under it when the nuts are loosened.

Spec blinds serve a purpose; I just don't see it in your application.

jt

 

[0123654789]

In service ? is a open spectacle, and out of serve ? is a closed spectacle. maintenance don`t need provide blind flange in this way

your point makes sense for me if it is normal for maintenance folks have spare blind flanges on site.if so, should piping group note this material on IFC ISO? otherwise, how do they know to prepare it?

 

[jte]

Well, the operating plant that I spent several years at knew that they would need hundreds of blind flanges for a unit shutdown and the pallets would be delivered to the unit a week or so in advance of "oil out". Sooner or later you'll have to let the plant's maintenance folks walk on their own. You cannot provide every blind point with a spec blind.

Have you spoken with the plant's maintenance supervision? They don't bite. Well, not hard anyway...

jt

 

[0123654789]

Thanks so much, jte! you have much more experience in operating plant than me, and your solution works on maintenance.

The spectacle is shown on P&ID. As a piper, I only can decide its location to fit process requirement. That's why I asked the spectacle location.

anyway, I learned some maintenance knowledge from you. thank you again!