Sprinkler Orifice Minimum Pressure

Not acceptable! More pressure is needed.

Get NFPA Standard 13, Standard for the Installation of Sprinkler Systems. Get the information from the professionals.

There are probably no professional licensed sprinkler designers, the person you want and need for the correct answer on CR4. There are many factors such as height of the sprinklers, hazards in the protected area, type of head, opening temperature of the head, etc.

Go to the Pro!

Good Luck, Old Salt

It's fine, as long as you never have a fire.

None of your units make any sense. Move the decimal point somewhere else.

A simple telephone call to the sprinkler manufacturer will answer this, and many more, questions. Do let the forum know how it went.

This what I found in Fire Protection Handbook

It sounds as though Anonymous Poster #1 has no idea that design guides and protocols for these systems actually exist. In this modern, globalised, Googlified world isn't that an amazing thing?

Yes, it is. More than a capacity of a mobile library, the only thing is "where to find and what to read" seems to be the basic and essential part to cross on every search.

Interestingly enough, all these Anonymous Posters who exhibit not the slightest bit of knowledge, or intelligence, all seem to have the capacity to find this forum (very likely by performing an internet search) before becoming totally and completely helpless.

I think the real problem is that much of the useful information is contained within standards, like the NFPA, and they don't give their livelihood away for FREE!!

I can hear Billy Preston now . . . .

https://www.youtube.com/watch?v=G_DV54ddNHE

Some are just helpless and some have good heart. Interestingly enough, asking questions even sometimes to like the dumbest thing to do is the first step to learning.

How do they manage to find us, seemingly effortlessly, and then become completely dependent on the fact that many, if not all, of us had to expend enough energy to find the answers they seek?

Oh, don't mind me. My marketing and events people are making requests even dumber than the most dull headed Anons today. They, too, are totally disconnected from reality.

I can't tell them how incredibly stupid I think they are, so I vent here.

And getting us smarter everyday, I mean that's the only difference.

It does seem a little odd. From Tyco data I agree pretty much with your 1.44psi for 30gpm. I suppose you could use a pressure reducer to limit it to 1.44psi, or supply from a header tank. But where is the 30gpm from? I don't have typical figures, but somebody on earlier post said 0.8gpm/ft² is high. High flow may not be a problem, unless you run out of water and still need to quench a fire at another sprinkler.

Also Tyco says, page 3

Sprinkler System Design NFPA 13 for ESFR Sprinklers based upon 45 psi (3,1 bar) design pressure, 169 gpm (640 lpm) with 12 sprinkler remote area

so if they think 45psi is typical, that's a much higher flow. Also I don't understand the last bit with 12 sprinkler remote area.

Perhaps somebody with experience can comment.

I am not sure what you are trying to, but the only sound advise you are likely to get will be based on you sharing your hazard data.

A system is designed based on the hazard (light, ordinary, extra hazard, etc).

An ordinary system will be designed based on 0.16gpm/square ft, covering 130 square ft/sprinkler head.

There are hundreds of exceptions, and factors that will change this.

This may help a little.

This gets stranger! Your chart might explain where AP got the 0.3gpm/ft² from, but it makes the Tyco reference to 45psi and 1.69gpm/ft² look even odder.

Do you know what the mm/min data under density is about?

Rainfall equivalent?

Yes of course I should have spotted gpm/ft^2 is a velocity.

no its not a velocity unit mm/min, its the depth of rain water to accumulate a standard container in mm/min.

But it's still a velocity. If you convert any of the gpm/ft² figures on the chart to mm/min, they agree (as I ought to have noticed before!).

A rain gauge collects rainfall over a known area, and puts it into a measuring cylinder or similar to read the volume, to increase the depth so improve accuracy. It's related back to the total area to get a rainfall velocity.

No, it's not.

You got it a bit off the racks.

Say there are 400 rain drops in a square inch and 250 rain drops in the other place just not so far away. Both cluster of rain drops fell at exactly the same elevation. Hypothetically, neglecting friction and crosswind effect.

Both cluster of rain drops will arrive the same time at the same ground elevation, agree?

Of course, at the same velocity.

However, if it happens both 400 drops and 250 drops are accurately captured in a different container, obviously, mm/min @400 drops would have greater than @ 250 drops.

I hope this clear out your misconception that mm/min is not a velocity (vector got magnitude and direction) or even speed. It simply denotes a depth of rain collection a standard size cross section container- and that happens to be a rain gauge or in simple terms " density" of rain water.

I haven't got any misconception. Have you tried converting the gpm/ft² figures on the chart in #13 to mm/min? If you can't see they are both velocities (or speeds, to avoid getting deep into vectors) you should think about it some more.

You're getting in a tangle considering number of drops, it's irrelevant to the discussion. You don't even say they have to be same diameter, which they would need to be for your argument to make any sort of sense.

You also appear to think the mm/min is the velocity of individual raindrops. Typically 5mm/min? 5m/s would be more like it, 60000 x higher.

this is a philosophical post, that is unworthy of response.

I take that to mean you don't have answers to my points

The picture paints thousand words including your misconception.

Water precipitates average the same size of droplets and its pressure related and pressure is related to elevation.

Which one do you prefer?

No you prove to the forum at least AP/OP how did you arrive to mm/min as velocity?

Simple. Distance per time is by definition velocity. Please learn dimensional analysis.

Bah! you guys are just having good times on me. It's unfair.

Get a new job or hobby, whichever.

What else could it be? I can understand you might have to think about it to convince yourself that gpm/ft^2 is a velocity, but mm/min seems pretty straightforward.

It's the metric equivalent of GPM/ft^2.

Exactly. Also I assume a rain gauge is calibrated to read directly the depth of rain over the whole collection area, for ease of use.

Correct. And could therefore (and many times will) be used to verify the density of a fire sprinkler system.

AP seems to have disappeared, but I'm still curious about the apparent anomaly between the 0.3 gpm/ft^2 max on the chart, and the very low pressure required by the Tyco nozzle. The obvious answer is to use a smaller nozzle, or put an orifice or something inside, to give design flow at say 30 - 40 psi, in the area of mains pressure or a basic centrifugal pump.

Sprinkler nozzles are rated based on flow and pressure; their "K" factor.

With a K factor, one can determine what pressure to apply to the nozzle to achieve the desired water application density.

If Tyco has a nozzle that will flow .3GPM at less than 2 psi, I have no clue what that would be used for.

I have never designed a system that went over .4GPM/square foot, and the system pressure (static) was 175 PSI.

As I said earlier, a typical system is designed based on .16GMP/square foot, and uses "street pressure" (no fire pump required) of 45-65 PSI.

Now high flow fog type waterspray nozzles such as would be used on large outdoor transformers or propane tanks have higher K factors.

Yes, I know what the K factor is, and how to use it, it's on the Tyco data sheet. Sheet also gives maximum coverage area 100ft², but doesn't say anything about gpm/ft². We don't know why AP chose that particular data sheet, maybe that nozzle is used for situations (if any exist) where gpm/ft² hence total gpm are much higher than than those bandied about here, otherwise the pressure is so low as to be impractical.

Glad you don't understand it either . Presumably you wouldn't select that nozzle for your typical system, 16gpm at 45-65psi.

ESFR nozzles are designed to extinguish fire at earliest as possible. Fire Protection Hand book, typical application is for Extra Hazardous grp. 1&2.

You haven't commented on my #27, but leaving that aside, I had another look at the chart you posted in #5. For the duty you underlined, it gives a range of nominal K-factors, but the minimum operating pressure varies with K-factor, so the flow at minimum operating pressure stays nearly constant at ~ 125gpm, or 1.25gpm/ft² for 100ft². That's well above the sort of irrigation rates everybody seems to think is appropriate, so I'm still puzzled by it.

I think I can clear this up.

I studied the data sheet posted by the OP and now see what his high flow nozzle is for.

When protecting warehouse storage with racks, one will usually provide "in-rack" sprinklers as well as ceiling sprinklers.

With this particular nozzle, the in-rack sprinklers can be eliminated due to the ultra high flow of this nozzle.

The trade off is that the water supply must be much greater than ordinary.

OK thanks, it does say that in the Tyco data, I hadn't appreciated the significance.

We haven't heard from the OP/AP recently, but to help him, I think we can say that if he's designing for a conventional system as in your #13, 0.07 - 0.3 gpm/ft², he's looking at a completely wrong nozzle and should try again.

Someone said,

Rule # 1 If you're uninformed, refer and follow the code

Rule # if you are still in doubt, go back to rule #1.

The following questions below might be helpful:

What are the chances that NFPA people get mistaken on this?

What are the chances that you misunderstood the code?

I didn't say anybody was mistaken (apart from you) least of all the NFPA. I just pointed out some discrepancies between data in various posts. This is now explained (see #33) but if I hadn't pressed the point none of the other contributions covered it, and OP (if he's still around) would be none the wiser. I trust he is now, or at least better informed.