Critical piping

[sadanand091]

How is critical piping defined?
How is it differentiated from Non-critical piping?
What code is used for the design of Critical piping?
How are allowable stress values different for these two types?

 

[XL83NL]

What is critical piping acc. to you? May sound like a dumb question, but without a clear definition, it can mean anything to anyone. So its up to you to decide whats critical.
PS: B31.1 doesnt differentiate in critical as it dont knows critical piping.

 

[EmmanuelTop]

In one of the companies where I worked, non-criticality (and hence no flexibility analysis was further required) is assigned to a piping system which:

- Duplicates, or replaces without significant changes, a system operating with a successful service records;
- Can readily be judged adequate by comparison with previously analyzed systems;
- Is of uniform size, has no more than two points of fixation, no intermediate restraints.

The non-critical lines usually are:
[ol 1]
[li]Non-hydrocarbon lines such as air and utility water[/li]
[li]All lines which discharge to atmosphere including fire case relief and vent lines (excluding other relief and vent scenarios)[/li]
[li]All lines within skid mounted packages (which are the responsibility of package vendors)[/li]
[li]All small diameter piping (40mm and below) unless subjected to surging such as relief and blowdown[/li]
[li]All piping connected to open drains[/li]
[li]All piping connected to closed drains[/li]
[li]Lines that have similar configuration or mirror image to those that have been analyzed and satisfy the pipe flexibility.[/li]
[/ol]

Classification of the remaining piping systems considers: service conditions, size, and temperature range - into Class I and Class II of critical piping. But, as others have said, the term "critical" can be applied based on many different criteria.


Dejan IVANOVIC
Process Engineer, MSChE

 

[sfitzgerald9]

B31 codes and API codes would be a good place to start. Not very clear on what your application is here. Is this clean room piping or large diameter gas piping?

 

[sadanand091]

@sfitzgerald9,
I am working on a boiler piping

 

[BigInch]

Can also involve,
Failure potentially causes excessive monetary, property, or environmental damages, or loss of life.
Failure causes excessive damage to company brand, or excessive stock price decline.
Reduces sales by more than 25%.
Causes failure to supply contracted quantity.

 

[MJCronin]

There is no one, uniform definition of a critical piping system. It depends on the type of plant under consideration and the function and operation of that piping system.

In a nuclear power plant, designers use a gradient of importance for critical systems. They have three ASME Safety Classes (1,2,3) designations plus non-critical piping.

This may help:

https://mceer.buffalo.edu/publications/workshop/01-0002/presentations/Antaki-2.pdf

MJCronin
Sr. Process Engineer

 

[racookpe1978]

I cannot see any boiler piping of any size being judged "non-critical": high temperature, high temperature changes from shutdown, high pressures, high importance to the plant, high stored energy if broken and while failing, high price to fit, repair, install, and NDE; high price material to replace, high potential for failure if stress analysis is wrong, etc.