Spacer VS Spectacle blind without blind

[Jack Nicholson]

Hi.
What is a difference between spacer and Spectacle blind without blind (blind removed), as attached in following picture:
Why we use a sapcer in pipeline? I think the process wise usage of these two equipment is the same.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1476962909/tips/Spacer_wfmobl.bmp[/url]

 

[DSB123]

First of all - never heard of a sapcer!!! A spectacle blind may be turned to either blank the line or open the line for flow. A spacer whould either be a blank spacer or an open spacer - so you need both open and closed spacer. Whereas a spectacle blind is basically an open spacer and a closed spacer connected together so you can spin thit around depending on whether you want the line blanked or not. Process wise the two items you indicate are not the same. The spacer allows fluid flow whereas the spectacle blind may or may not allow fluid flow depending on which side is installed in the pipeline.

 

[MickMc]

It is down to a matter of weight as typically a figure 8 is used in sizes where it is practical to operate that is to turn it in position to open or closed and where impractical a single blind or spacer is used.

Pressure rating is a factor here as the higher the Class the bigger/thicker/heavier the components will be. Typically for Class 150 spades/spacers will be used from NPS 14 and above and the higher the class lower NPS.

 

[LittleInch]

"What is a difference between spacer and Spectacle blind without blind (blind removed), "

In practice - no difference, but without some sort of context it's difficult to say.

I can only surmise that the graphic is used when comparing one state ( piping with a blind installed) to a different state where the blind is removed, but a spacer inserted in its place. or a part of a sequence of actions or actions required to move from an isolated case to a normal operational state.

the two boxes I assume you highlighted are NOT a spectacle blind, but two separate bits of metal. It looks very similar, but if you look closely, the spacer has a little line coming from it at the top, the spectacle blind doesn't....

Why do you use a spacer? So that when you want to install a blind, the gap between the flanges is there and you don't have to force pipe apart to insert it or close up the space when you remove it.

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

 

[Artisi]

DSB123: You may not have heard of a sapcer but can you please advise what a whould and a thit are ?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

Ouch!

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

 

[georgeverghese]

Maybe the earlier symbology indicates the there is normally a spacer (or a blind) at this location, and that either (the blind OR the spacer ring) should not be removed.

While the latter symbology indicates that a spec blind is normally at this flange.

 

[europipe]

a thit is a bhreast

 

[pennpiper]

This appears to me to be only one Company's Symbol Legend. If you work for that company you know and understand what they mean, if you are a Client having that Company do a project for you then they will teach you what the Legend means, and the rest of us do not need to worry about what each symbol means.



Sometimes its possible to do all the right things and still get bad results

 

[saplanti]

If they have the same thickness they are the same. However spacer length (thickness) may change with the need for required space of the connected equipment. If equipment requires a space for dismounting a kind of spacer is needed. Sometime it might content a pipe in a length and a flanges on each end.
I trust this is sufficient.

 

[moltenmetal]

samplanti has it right- a spacer is a disc of flange material with a hole through the middle, inserted wafer-style between flanges, similar to a flushing ring used with instruments. It may be required to provide removal clearance, or just to take up space in a line which has been shortened for some reason i.e. by replacing a long pattern valve with a short pattern valve or a flanged instrument (flowmeter etc.) of different dimension, or any number of other reasons. These are VERY common in lined piping, where it is not feasible to make a spool shorter than a certain length. Unlike a spectacle blind, it is never intended to be used to block flow. Generally a flanged spool wouldn't be referred to as a spacer. You'd only indicate the spacer on a P&ID if it serves some process function.

 

[MickMc]

In my experience a spacer's function is to maintain the space required to insert a blind in order to positively isolate the line both being the same thickness normally to ASME B16.48. This would be on the P&ID whereas I would not imagine that any used as 'pup piece' would be.