5 replies to this topic

[shan]

Hi Everybody,

Usually, utility supply headers are straight lines. Sometime, people design ring headers for fire water and instrument air. I understand ring shape header has advantage of provide supply from both sides and pressure equalization. Other than these, are there any other benefits to build a ring header?

Regards,

Shan

[katmar]

With the correct valving you can isolate a section of a ring for maintenance, while the rest remains live. In a straight line header everything after the valve would be isolated.

Theoretically a ring header could be made of a smaller diameter pipe than a line header, but it would likely be much longer. This factor, plus the extra valves required to take advantage of the facility to isolate sections, would probably make the ring header more expensive.

[Erwin APRIANDI]

If I'm not mistaken the reason why ring header is prefer for fire water distribution is a matter of reliability, as what Katmar has said

"With the correct valving you can isolate a section of a ring for maintenance, while the rest remains live. In a straight line header everything after the valve would be isolated."

and there in case of fire and some leakage occur from one other source end, the other source can still supply to the rest of header.

This ring application is also used for aviation fuel distribution system to ensure equal pressure and better reliability

[kkala]

The main advantage of the rings in fire fighting system has been pointed out by katmar & erwin.apriadni: you can isolate (say) half ring for maintenance, while it is still possible to send firewater everywhere in need through the remaining fire fighting network. In this sense the two parts of each ring should be of equal diameter; and not far from each other, so that each individual part can cover the same equipment inside the ring. In a refinery the peripheral fire water loop contains numerous smaller rings for this purpose. This may be according to NFPA recommendations (but I have not read it explicitly), separating the whole field into areas; whole fire water flow should be adequate for one area at a time.
I have not heard of pressure equalization in fire fighting, although two water supply points could give a bit higher total flow (at the required pressure) than the design flow.
Mentioned advantage of ring headers are also valid for other utility systems (e.g. instrument air).

Note: For big petroleum tanks (say dia=45 m or higher) two independent access roads for fire fighting vehicles are recommended, but this does not concern the ring.

Edited by kkala, 22 July 2011 - 07:31 AM.

[shan]

The main advantage of the rings in fire fighting system has been pointed out by katmar & erwin.apriadni: you can isolate (say) half ring for maintenance, while it is still possible to send firewater everywhere in need through the remaining fire fighting network. In this sense the two parts of each ring should be of equal diameter; and not far from each other, so that each individual part can cover the same equipment inside the ring. In a refinery the peripheral fire water loop contains numerous smaller rings for this purpose. This may be according to NFPA recommendations (but I have not read it explicitly), separating the whole field into areas; whole fire water flow should be adequate for one area at a time.
I have not heard of pressure equalization in fire fighting, although two water supply points could give a bit higher total flow (at the required pressure) that the design flow.
Mentioned advantage of ring headers are also valid for other utility systems (e.g. instrument air).

Note: For big petroleum tanks (say dia=45 m or higher) two independent access roads for fire fighting vehicles are recommended, but this does not concern the ring.

Thank you Kalmar, erwin.qpriand and Kkala. Your opinions on reliability improvement of ring utility header make sense.

[Vimalesh Agnihotri]

thanks to all for valuable information.