Fire water main header thermal PSV needed? 1

[gl99]

Our project designed one aboveground fire water system, I have one question about thermal PSV protection for the firewater main header (no insulation, max ambient temperature =30C, max). I understand water expands when temperature increase and thus thermal PSV need. But, I checked other projects, there are not thermal PSV provide on the underground header. But as I think there are always have some section is above ground. Same time, I did not find any standard or design guide about this. Please help me figure if this thermal PSV need?
Thanks,

gl

 

[pennpiper]

Lots of missing information!
1. Where geographically, is this facility located?
2. Is this primarily an indoor facility?
or
3. Is this an outdoor facility?
4. What is the material of this Fire Water system?
5. Is this installation fed by an offsite municipal Fire Water system
or
6. Is this system a stand alone system with a dedicated Fire Water Storage tank, two or more dedicated Main Fire Water Pumps with a supplemental "Jockey" pump to maintain system pressure?

You may ask why do I want all that detail? Well, the answer to your question is in the "Details".


prognosis: Lead or Lag

 

[gl99]

Pennpiper,
Thanks, I list detail in below
1. Where geographically, is this facility located?
This is for one tank farm
2. Is this primarily an indoor facility?
or
3. Is this an outdoor facility?
outdoor
4. What is the material of this Fire Water system?
steel pipe in 150#
5. Is this installation fed by an offsite municipal Fire Water system
or
6. Is this system a stand alone system with a dedicated Fire Water Storage tank, two or more dedicated Main Fire Water Pumps with a supplemental "Jockey" pump to maintain system pressure?
Jokey pump used to maintain the pressure

 

[pennpiper]

Question #1 is intended to get the "Geographically Location" not the facility being protected.

A correct answer might be Siberia or Sahara or Singapore, or South Africa or somewhere else, you know the "Geographically Location". Where is this plant?

prognosis: Lead or Lag

 

[gl99]

We are in North Americam

 

[cvg]

i think operating conditions might be more useful such as min/max temperature. North Americam is a large country
schematic / P&ID and profile along with elevations and normal operating pressures

exterior systems see a lot more expansion and contraction
pressure can be reduced by leakage back through check and gate valves to the tank
underground pipes usually don't experience large temperature fluctuations

 

[gl99]

Can we count on the check valve leakage to eliminate the thermal PSV in FW main header? In PSV sizing, we do not consider any credit from check vale leakage, right?

 

[pennpiper]

Now THAT really pins it down.
It is some where between Prudhoe Bay, Alaska and Key West, Florida.

You need to get a copy of the NFPA Standards and study the section on Tank Farm Fire Protection Criteria. Base your decision on NFPA and what ever the facility's Insurance Fire Risk Agent says.





prognosis: Lead or Lag

 

[bingbingwang]

yes, you need a PSV.

Get help and return with helps!!.

 

[TD2K]

If heat gain to the piping system results in overpressure due to the expansion of the water because it has no where to go then you need to provide overpressure protection or address the overpressure issue somehow.

Your system is above ground in a hot climate so solar heating will definitely occur. Since firewater system typically have isolation valves to be able to isolate a damaged portion of the system, if a section is blocked in, how are you going to prevent overpressure? On a firewater system, sections are not normally blocked in because of safety concerns so blocked in legs are not going to be a common situation and for a section that can be blocked in, thermal relief valves are one option, other options would be procedures to call for the blocked in section to be drained.

You're going to need to look at your system and its design and decide if thermal expansion needs to be protected against and then decide how to do that. I can't say from what you have posted whether it's an issue or not. I'll point out that thermal relief valves have long term maintenance costs associated with them, they need to be pulled and tested on a schedule.

 

[rconner]

I guess only other thing I could add is if any of that aboveground piping is subjected to sunlight, and at 30 degrees C "max ambient temperature" with no flow, I've got a sneaking suspicion pipe and contents could well get to even a somewhat higher temperature than that!

 

[TD2K]

I love drive by posters.