not only for isolation purposes, but for ease of equipment removal or replacement, access to equipment, future installation of instrument devices.

Pipe is cheaper than valves.

What you describe is essentially a different form of isolation.

Spool can be very useful during construction and maintenence

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

Frequency of operation also factors into this; for isolation performed only every few to several years, the expense of valves may not be warranted, especially where the labour costs of performing and removing the isolation are not exorbitant. Other than for situations where operational considerations dictate the use of valves, why spend the extra money?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

Thanks Everyone for your answers! Really helpful :)

Quote (-ARK)

Could you please let me know what are your thoughts about the subject?

1/ Personnel
Statistically a spool piece (normally removed) is less prone to human error than a valve. Even if a valve is provided with a blind/spade or DBB (double block and bleed).
2/ Tradition
One considers a spool piece (normally removed) has the highest safety level (category I) as stated in HSG 253.
3/ First start
It is an industry practice to inserts a temporary strainer ("witch hat") to a spool piece during first start to protect a pump from carryed weld scales, debris and sand from upstream suction pipe.

Quote (-ARK)

I know that removable spool piece has been used in positive isolation in the industry for so long, specially on pump suction lines to prevent damage to the pump nozzle. But why??

Talking about a conventional horizontal centrifugal pump the spool pieces connected right to the pump nozzles provides pump maintenance without need to remove the pump. A spool piece makes maintenance easier and less labor-intensive:
- if you remove a suction spool piece you can briefly inspect/unclog/repair an impeller (otherwise you need to remove a pump)
- if you remove a suction spool pieces and disconnect a shaft coupling you can rotate a pump to take apart a shaft and internals (otherwie you need to remove a pump)
- if pipeworks provide an unacceptable level of stress to a pump flange you can remove an improper suction/discharge spool piece and make proper one (otherwie you need to weld in place (often prohibited))

Quote (-ARK)

Cant we just use a block valve and blind flange the main pipe and take out the pump?

Sure you can.
But after a couple of years from commissioning you are recommended to make sure technicians are far away from you. ))

Hi,
Probably good to read this memo about Process Isolation.
Spool piece is a quite inexpensive compared to a block valve .
In any case you need to install a blind flange to mitigate risk.
Pierre

• https://files.engineering.com/getfile.aspx?folder=fc6b2716-7784-4e64-88e1-8

Piping isolation remote from pumps can of course use spectacle pieces; cheap, secure, low labour cost to operate.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

Thanks again everyone.

Quote (shvet)

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