Spec Break

[C4Reactor]

All,
In designing a piping system with variable pressure rating, what is the consideration when specifying the piping spec break? Must there be a valve at every spec break? Is there any code on this?

Thanks

 

[dcasto]

You can declare a spec break anywhere you like, but how would you maintain the change without a control or hand valve? You could protect the system at different pressures with either mutiple or a resetable relief valves as an option, or just have the various pressure producing points have a relief valve for the variable pressures.

 

[SooCS]

Try API RP 14E, it gives a very good guide in piping system design for offshore industries but is very applicable for onshore as well.

Best of luck.

 

[aliansari]

Spec break is required to be defined when,

1. Operating parameters are changed like pressure and temperature. Let down pressure control valve is an example where rating of the downstream flange is determined by the specified pressure in the line after the let down. Important to note that the low pressure side must be protected by a safety relief device to avoid over pressure due to control valve malfunction or physical blockage,

2. Changing the chemical characteristics / composition of the fluid handled. For example, piping material change is essential and must be shown as a spec break on the P&ID at and downstream of a mixing tee where 98% sulfuric acid is diluted with water, for regeneration of demineralizers.

Bottom line is, there is always a fitting (valve, tee or an injection quill) downstream of which, illustration of the spec break is to be shown.

Ali Ansari

 

[MortenA]

one of the situation where i could envisage a spec break with out a valve could be after a gas blowdown valve, where imediately following the valve a cold spec pipe could be used, and after a certain distance of pipe you could switch to a normal pipe.

Best Regards

Morten

 

[C4Reactor]

Thank you all for being all the comments. Its has been very helpful.