Minimum water supply required for NFPA 30 project

[SprinklerDesigner2]

So that you all know I feel I am not competent when it comes to NFPA #30 and I have hired an FPE to help with the design criteria for this project. That said I am not looking for any specific design criteria as I will probably be getting that on Friday or early next week.

What I am asking of those who do have some experience is does it look like we will have enough water given the following:

1. Water supply is 1,250 @ 100 psi fire pump from city connection. At churn we had 170 psi, 1,250 gpm @ 140 psi and 1,900 gpm @ 110 psi. Very flat curve and I recognize the 1,900 gpm is over the 150% but that is what I got.

2. Building is bent metal purlin 24'-0" eave and 31'-4" at peak.

3. Commodity stored on back to back racks without shelves sine three and some four tiers high. Looks like we can expect storage 20' high.

4. There is a list of 530 chemicals being stored and just a small representative sample is provided below:

Looks like lots of required information is missing from that list but that is what I got and this is why I hired an experienced FPE to make sure I don't step in it.

From my amateur status going over NFPA #30 it appears the pump can't deliver enough water. I am not looking for any sort of definitive answer, like I said I will have that at the end of the week, but do you tend to agree with me from what your experience tells you?

Thanks.

 

[SprinklerDesigner2]

I received the design criteria just a few minutes ago and it appears we're going to go with NFPA standards. Note that everything is foam.

Ceiling Density: 0.30 gpm/sq.ft. over 3000 sq. ft. due to drum storage OR 0.30 gpm/sq.ft. over 2000 sq.ft. based on smaller containers (<5-gal.)

In Rack Arrangement: Only at longitudinal space (center of rack), spaced no greater than 10 ft. apart, staggered vertically throughout the rack. However, if the containers are of the “relieving style”, then in-racks are only recommended on every other level.

Foam Duration: 10 minutes

Something else to note is that if you choose to go with a pre-primed foam system, NFPA allows you to reduce the ceiling areas (3000 to 2000 for drums and 2000 to 1500 for smaller containers) and allows you to calculate the demand based on 3 sprinklers per level operating for 3 levels rather than 6 per 3 levels. These together reduce the demand significantly, keeping the water demand well below what is already provided.

There is drum storage so it will be the .30/3,000 but that could be a challenge with a 1,250 gpm pump.

As I said I just now got this so what about the pre-primed foam? I think I know what is involved but I *think* it has more to do with maintanence of the pre primed system.

Welp, time to start reading up!

 

[LCREP]

Foam and in-racks what a surprise.... the pre-primed foam is hard on the pipe. Do not forget the test header to test the foam at the required sprinkler demand.
Check with the local environment folks regarding the foam discharge test, some will permit discharge onto the ground, others want it into a tanker$$$$$$. The fun begins......I always liked these jobs...bring a camera to video the test.....

 

[stookeyfpe]

Ensure the electrical engineer has provided the required ampacity and correct number and size of conductors (and properly sized conduit) for any required foam concentrate pumps and understands these are required to comply with NEC Article 695 and NFPA 20.

 

[TravisMack]

Yeah...0.3/3000 plus 3 levels of in-racks for 18 sprinklers total is going to be challenging with a 1250 gpm pump. FM used to only let you use 120% of rated capacity (vs 150% allowed by NFPA). You may need to look at some things that can help reduce your demands if they are available.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[SprinklerDesigner2]

Travis,

The owner has elected to go with NFPA standards not FM.

With AFFF a pre-primed system doesn't appear to be any great issue and by so doing "NFPA allows you to reduce the ceiling areas (3000 to 2000 for drums and 2000 to 1500 for smaller containers) and allows you to calculate the demand based on 3 sprinklers per level operating for 3 levels rather than 6 per 3 levels. These together reduce the demand significantly, keeping the water demand well below what is already provided."

I think the table used was TABLE 16.5.2.1 Design Criteria for Sprinkler Protection of Single- and Double-Row Rack Storage of Liquids in Metal Containers, Portable Tanks, and IBCs. It appears we will need 500 gpm hose but without knowing for sure what table was used I suppose it could be 250. Good thing is with pre-primed and the reduced areas 500 vs 250 isn't going to make much of an impact.

.30/2,000 with a total of 9 in-rack sprinklers isn't bad with the 1,250 gpm pump.

What I was told by the AFFF people is pre-priming consists of filling the system when testing the proportioner through the test header and we're done.

Before the tenant came with the flammable liquids we were going to go with an K16.8 ESFR system; 2 1/2" grid with 4" mains and 6" riser. I can't find a reason we couldn't use the same pipe (Dynaflow) arrangement just change heads. Pipe size wise I am way over designed if we go that way and in the future if the tenant ever moves out converting the system to ESFR would be as easy as modifying the riser manifold and changing the heads.

This all said I am still going to oversize the tank because preliminary calculations show I need 90 psi when I have about 150 psi available and we all know what that does. I will do a demand calc and base the quantity of concentrate on that.

 

[TravisMack]

I believe NFPA 16 is the foam standard. In that, you have to do a supply calc and size your foam concentrate based on the supply calc. Also, you are going to have to have your sprinklers discharge no more than 20% of required. So, if you have 30 gpm / sprinkler minimum demand, you are limited to 36 gpm on your demand calc. If you are way over-sized, you may be exceeding that requirement.

If I recall correctly, the 20% max is so that you provide a uniform foam distribution over the design area.

I design about a dozen or so foam systems every year. They are always challenging in getting that 20% limit.

On a different topic, the really fun part is when you are doing foam grate nozzles in an aircraft hangar. They are limited to 40-45 psi. It gets to be a real pain trying to balance those suckers out. I've spent DAYS trying to balance and grate nozzle system with the overhead and keeping everything within those parameters. I have found some better ways to do it, but I still remember that first one. It was a nightmare.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[SprinklerDesigner2]

Travis,

Yep, all of that and from what I gather I'll have to incorporate a pressure reducing valve on the system which will be only the second time in 40 years I've had to do that.

http://www.chemguard.com/pdf/fire-suppression/datasheets/d10d03129.pdf

NOTE 1:
If normal water supply pressure to actuator operating the valve is above 120 psi (8.3 bar), a water regulator (Part Number 7001) Is recommended to reduce actuator inlet pressure so that it does not exceed 120 psi (8.3 bar). Excessive water inlet pressure to the actuator can cause damage to the valve stem.

At churn I have 170 psi at the flange and spigot so there you go. Work so hard to get all the pressure I can get then this comes along.

 

[skdesigner]

SprinklerDesigner2,

Note 1 in the datasheet is referring the concentrate control valve's actuator (the water motor that opens the valve automatically upon system activation, allowing foam concentrate to flow to the proportioner), not the entire system. The water regulator is a small device (likely 1/2") that sits in the normally-unpressurized supply line and prevents pressure higher than 120 psi from hitting the actuator. The rest of the system devices should be rated for a minimum of 175 psi. Confirm with Chemguard of course, but don't make a mountain out of the proverbial mole hill.






R M Arsenault Engineering Inc.

http://www.rmae.ca

 

[SprinklerDesigner2]

skdesigner,

I wasn't sure and yes, will confirm with chemguard.

 

[stookeyfpe]

You do understand that everything you are designing for is predicated on the container's material of construction, it's ability (or inability) to relieve pressure, and the water solubility of the liquid? Yes? You further understand I witnessed aerosols in your intial posting. Your design for that is silent. No problem, just asking.

Look, I am glad your got the gig but everything I've seen in the posts has failed to mention all the things I identified. Everyone is all excited about AFFF but I have read little about your design. It sounds good.

Just be careful. AFFF foam, like ESFR or K 25.2 are not fire protection saviors.

I am also a AHJ so I am sensitive to these issues.

 

[SprinklerDesigner2]

Stockey,

Rest assured there is no way I would attempt to assign any sort of design to anything having to do with flammable liquid storage. No way, no how... not with a ten foot pole.

The owner has retained the services of an FPE and as for the design blow is a screen capture of the last email:

Large company and generally they follow Factory Mutual but in this case, it's a rather small project with the building itself only 20,000 sq ft, they decided to go with NFPA standards. The Options were sent to the owner by the FPE and the owner made the decision to follow NFPA standards. There are drums so it's a pre-primed system .30/2,000 with 3 sprinklers operating for 3 levels of in-rack sprinklers.

As Clint Eastwood said in one of his Dirty Harry movies "A man has to know his limitations" and I certainly know mine. If it was up to me the only way I would touch this project is to retain the services of an FPE and I wouldn't care how much it took money wise...