Sprinkler Head Question

[ElectDesigner]

I know this is more of a mech/plumbing question, but here goes:

Why are sprinkler heads turned up whenever there is no ceiling and down when there is? (This is what I have seen in most buildings)

Just an example say you have a room that was used as an office (sprinkler heads down), later on - the ripped out the ceiling and converted it into a storage room (sprinkler heads now up). I just dont understand the whole coverage/spray pattern argument - are they saying that because the head is turned down , it is assumed there is nothing combustable above the ceiling.

 

[kwired]

Can't say I know for certain, but I would guess that in your example where the head orientation was changed, the head was maybe changed also and we now have a different spray pattern.

 

[nhfire77]

I know this is more of a mech/plumbing question, but here goes:

Why are sprinkler heads turned up whenever there is no ceiling and down when there is? (This is what I have seen in most buildings)

Just an example say you have a room that was used as an office (sprinkler heads down), later on - the ripped out the ceiling and converted it into a storage room (sprinkler heads now up). I just dont understand the whole coverage/spray pattern argument - are they saying that because the head is turned down , it is assumed there is nothing combustable above the ceiling.

It is a design and layout choice.

Uprights allow for greater flexiblity in layout of an open space. If it needs to be 1-12" of the roof, you can pipe straight up off a trunk.. A pendant would require the may require the use a elbow. This will cause a reduction in operating pressure at the head, throwing off your flow calcs, making the riser and main trunk lines bigger.

Pendant are good in drop ceilings for the same reason uprights are good in an open ceiling. No elbows= less friction loss.

There are plenty of buildings that actually require heads above the drop ceiling based on heights, fire loads etc. many ordinary fire loaded buildings may not, assuming most fires start below. This is another reason fire barriers, blocking, sealing etc is crucial. If the barrier isn't mantained the suppression system may become over loaded when fire breaks through into the sprinkled space below. (think las Vegas hilton hotel fire, 1980). Many systems are designed for a maximum of 12 heads operating, beyond that you loose water volume and flow. The heads require a minimum pressure to properly create he right size and amount of water droplets to absorb enough heat. A practical experiment for this is with garden hose and a camp fire. Adjusting the nozzle pattern and pressure will result in different extinguishment/confinement rates.

 

[nhfire77]

Another big factor: dry systems must completely drain, pendants would trap water.

 

[ElectDesigner]

It is a design and layout choice.

Uprights allow for greater flexiblity in layout of an open space. If it needs to be 1-12" of the roof, you can pipe straight up off a trunk.. A pendant would require the may require the use a elbow. This will cause a reduction in operating pressure at the head, throwing off your flow calcs, making the riser and main trunk lines bigger.

Pendant are good in drop ceilings for the same reason uprights are good in an open ceiling. No elbows= less friction loss.

There are plenty of buildings that actually require heads above the drop ceiling based on heights, fire loads etc. many ordinary fire loaded buildings may not, assuming most fires start below. This is another reason fire barriers, blocking, sealing etc is crucial. If the barrier isn't mantained the suppression system may become over loaded when fire breaks through into the sprinkled space below. (think las Vegas hilton hotel fire, 1980). Many systems are designed for a maximum of 12 heads operating, beyond that you loose water volume and flow. The heads require a minimum pressure to properly create he right size and amount of water droplets to absorb enough heat. A practical experiment for this is with garden hose and a camp fire. Adjusting the nozzle pattern and pressure will result in different extinguishment/confinement rates.

Thanks for the reply. Another reason i read was that in say for e.g. mechanical rooms where thes is a lot of piping running over the place, the upright provides better coverage against the obstruction as it is typically closer to the roof - hence higher.