trapped water in preaction system

[MTuWThFriFriFri]

Hello,
I am assigned Single Interlock Preaction System Design at Army Garrision Oversea. The Spec was pre written before the system design. The reason of Preaction System in the Spec is in question. The building has no valuable equiptment. There are 15 jail cells over 13,000 sq.ft. free standing Admin Building. There is suppose to be no heating provided in the building except at the riser room during winter time. Temperature falls -20 degree. The building is not heated and there are approximately 110 pendant sprinklers to provide proper coverage below deop ceiling at office areas. I am not as familiar with selection of pendant sprinklers in preaction systems. What is common practice s in the east cost? I am assuming weather is just as cold in east coast. What's likelyhood of installing wet pendant sprinklers instead of dry sprinklers in preaction systems? Do wet sprinklers truely crack as trapped water in arm over drop subject to cold weather? There is a huge budget difference between two type of sprinklers. Beside, with all dry pendant sprinklers, I am not confident the intension of preaction system in the project specification is well served. Any feedback will be appreciated.

 

[ChrisConley]

That is a bad a$$ jail. Unheated jail cells to -20F?

 

[TravisMack]

If you have a double interlock preaction system, then pipe it like a dry system with slopes and dry pendent requirements. No gridded double interlock preaction systems. The only way to do std pendents is if the pipe and heads are in a heated area. It does not sound like you meet this criteria.

If single interlock or non interlock, I don't believe you need to slope, but am not positive without looking it up. However, you can grid a single interlock system. You will still need dry pendents if you are in unheated areas.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[NJ1]

Damm. Jail with no heat and a pre-action systems installed sounds like a great forced vacation.
First of all what is your responsibility or scope?

Then we can help you. Are you a designer, estimator, project manager, etc.

 

[MTuWThFriFriFri]

Hi NJ1,I am happened to be a designer.

 

[NJ1]

Well the only reason to install a preaction system based on your info that I can think off is to avoid accidental discharge cause by inmates but other than that I see no reason why to install a preaction sprinkler system

 

[cdafd]

So are they using some type of detection to trip it???

 

[NJ1]

Well since it is a jail and is supervised at all times Most likely is to be tripped manually I guess.

 

[cdafd]

Jail / admin building

 

[pipesnpumps]

You really should question single interlock, because any spurious trip of the detection system (without a corresponding fused sprinkler head) would fill the pipe and then it could freeze in the piping.. This would happen reGARDless of dry pendents or no dry pendents..

Why not go double interlock? But don't forget about institutional heads.. I would doubt they make dry pendent institutional heads?? You got yourself a real interesting one there. Good luck.

I would push back politely. Buildings owners/users are building owners/users, regardless if they are a private company or the Army.. They "think" they know what they want to meet their operational goals for the facility, but they don't have the expertise to decide the types of sprinkler system to be used.. Sometimes they might decide these kinds of things anyway, because they feel like they have to put their thumbprint and get the best/fanciest/most advanced system; They saw it at a tradeshow, etc.

For basic conformance to UFC 3-600-01, my wetpipe system checklist might be somewhat useful for the other parts of your system:

http://files.engineering.com/getfil...t_Pipe_Sprinkler_-_DoD_-_Eng_Plans_Review.pdf

 

[MTuWThFriFriFri]

Thanks pipesnpumps for your input. I am worried the pumped in moisture in the piping condensed at the pendant sprinklers might freeze up and damage sprinklers when weather gets cold. Humidity is high during summmer and temperature falls -20F during winter time.

 

[cdafd]

nathanjung:::




So are they using some type of detection to trip it???

 

[MTuWThFriFriFri]

cdafd,
Spec is Single Interlock Preaction w/Electric Actuation

 

[cdafd]

So smoke detectors to trip the electric actuation ???

 

[chillylulu]

Pre-action systems are a very good solution for jails. A common misconception about institutional heads is that they are tamper proof. The escutcheon is, but the heads actually seem to break apart easier. They are designed so that you cannot hang any-(thing? body?)from them.

Detection can be placed behind a service grill, the biggest problem is that you usually only have one detector per cell. A delay can be included in the alarm / detection system. Systems can also be controlled remotely, from a control room.

Preaction systems in jail cells are not overkill or overspec. They are preferred.

Most cell protection is sidewall type sprinklers. Depending on the service shaft / building design you may be able to avoid dry heads and still provide proper drainage.

Smoke detectors are ok, VESDA is better.

You should also have more than the usual compliment of spare sprinklers for two reasons:
1. The guards will have to have a couple to take apart - they need to be able to find every piece that comes off the sprinkler head. They usually make a board with all the parts on it.
2. They will go through several extra in the first 6 months.

BTW - one jail I know of lets the cell fill up with a couple of feet of water (allegedly.) Claims to have stopped tampering issues. Makes for a good story.

-20°f sounds incredible for a normally occupied location.. are you running pipe outside the building envelope?

Good Luck!