Valves for Ultra High Rise (>420 ft) Sprinkler/Standpipe system

[PEDARRIN2]

I have a project where I am designing the standpipe/sprinkler system where the standpipe valve on the top floor is about 555 ft above grade. At present, the system is being designed with two fire pumps in series where the upstream will feed the lower floors and be the suction source for the downstream pump which will serve the upper floors. I will be specifying PRV's to keep the actual sprinkler and hose connections within NFPA 13/14 requirements

However, when I calculate the pressures required for the 100 psi required at the top fire department valve with static and anticipated flow losses, I arrive at about 400 psi required at the base. I can find pipe/fittings rated for this pressure, but cannot find UL listed valves (butterfly, gate, check) which go up this high.

I have tried Nibco, Watts, Kennedy, Hammond/Milwaukee with no real luck. The closest they get is 350 psig. I have found some Crane valves
(gate and check) which meet the pressure rating, but are not UL listed.

I have a potential option of locating the downstream pump on an intermediate level, but the architect is extremely reluctant to give up real estate on upper floors.

Any ideas?

 

[TravisMack]

I believe the zurn/wilkins floor control valves (which also serve as a check valve) are rated for 400 psi.

https://www.zurn.com/media-library/web_documents/pdfs/specsheets/fv-zw4004-pdf

555' * .434 = ±241 psi. 100 psi at valve. ±7 psi for equivalent length of valve, 2½" nipple and welded outlet. This puts you at ±348 psi plus friction losses. Do you really have 52 psi of friction loss in your standpipe? Or is the 400 psi the pump churn values? If your residual pressure at the pump is 400 psi, are you using a variable speed driver to keep that churn pressure flat? Otherwise, your churn will be crazy high. The way I have always seen these is with a pump somewhere around the 28th floor. So, you have a low and high pump.

These tall buildings are always a fun challenge.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[stookeyfpe]

I don't know what codes for the Pedarrin 2 project are in effect but I'm about to start tests on a 66 story Residential high rise (626 feet to the highest occupied floor)and we required a secondary water supply on the roof and redundant fire pumps above the 34th floor per NFPA 14 (2010 ed.) and NFPA 20 (2010 ed.). 2012 IBC was in effect at the time of permitting.

 

[PEDARRIN2]

TravisMack - I am not concerned about the floor control valves where I will have PRV's to get the pressure down to "normal" levels. I am concerned about the valves on the level where the pumps are located (basement) and the standpipe isolation valves. The 400 psi I was initially using had both static and flow pressure drops. There was also some math errors in that number. When the math was done again, the flow pressure required is 346 psig. If I take out the flow friction, I am at 335 psig. But that is not including churn test pressure for two pumps in series. Without looking at specific pump curves, is a churn pressure of 15 psig a high number for two pumps in series (assuming both are in the basement)?

Stokkeyfpe - The Ohio Codes (ICC) were just updated last year, so it is based on the 2015 ICC codes. Due to seismic analysis, per the building code, I do not have to have a tank. I am designing to 2016 NFPA 20, 5.6. I am not sure what NFPA 14 will specifically require related to the height of the building. Please tell me what you are referencing.

This discussion may be moot if we decide to put the second fire pump on a higher level. The issue is this is an existing building which is being converted to residential and shrinks in floor plate as it gets to the top. The architect (typical) is very reluctant to give up space on the upper floors. He told us we can have all the space in the basement we want. I just want to have some ammunition that it cannot, or would be very difficult to be done.

Another issue is I have reference drawings from another project (almost across the street), which is taller (534.5 ft from street level) and that design had two fire pumps in series on the same floor level. So, it has been done. I just don't know how, yet.

As always, thanks for the help.

 

[stookeyfpe]

Pedarrin:

I'm suspecting the engineer of record has latched onto 2015 IBC Section 403.3.3 for secondary water supplies. This section was revised and the issue is it's not correlated to the NFPA 20 and NFPA 14 requirements for tall buildings. Section 403.3.3 states:

An automatic secondary on-site water supply having a capacity not less than the hydraulically calculated sprinkler demand, including the hose stream requirement, shall be provided for highrise buildings assigned to Seismic Design Category C, D, E or F as determined by Section 1613. An additional fire pump shall not be required for the secondary water supply unless needed to provide the minimum design intake pressure at the suction side of the fire pump supplying the automatic sprinkler system. The secondary water supply shall have a duration of not less than 30 minutes.

The second sentence is always applicable. The problem is all the designers read the 1st sentence and conclude that because the building is in Columbus, OH, Austin, TX or any other SDC Category A town that a secondary water supply isn't required. The fallacy is that 2015 IBC Section 403. requires the sprinkler system to comply with IBC Section 903.3.1.1 which requires the system to be approved, which in my jurisdiction is me or my counterparts.

My jurisdiction adopted the 2015 IBC last year and we're dealing with this on a 72 story mixed occupancy Group B/R/S-1 high rise. When we adopt a new building and fire code we update NFPA 13, NFPA 14, NFPA 20 and other commonly employed NFPA standards to the latest editions. The requirements in NFPA 20 were recently revised but even if you employ an older edition, a secondary water supply is required by NFPA 14 and NFPA 20.

NFPA 14 (2016 ed) Section 7.9.3 states:

7.9.3* For buildings with two or more zones in which any portion of the higher zones cannot be supplied by means of fire department pumpers through a fire department connection, an auxiliary means of supply in the form of high-level water storage with additional pumping equipment or other means acceptable to the AHJ shall be provided.

Herein lies the issue: these tall buildings are beyond the pumping capability of the fire department. As a result, a secondary water supply is required. For the mobile pumping apparatus (a.k.a, Engine or Quint in my town) we can supply 100 PSIG to the Class I standpipe hose valve that's about 32-35 stories above the lowest level of FD access. After that, centrifugal pumps are incapable of moving water while operating within the pressure limits of the pipe, valves and fittings.

It get's even more fun when you review Section 5.6 of NFPA 20 (2013 edition) because it requires the designer to base the design on the pumping capability of the responding fire department:

5.6.2 Fire Pump Backup. Fire pumps serving zones that are partially or wholly beyond the pumping capability of the fire department apparatus shall be provided with one of the following:

(1) A fully independent and automatic backup fire pump unit(s) arranged so that all zones can be maintained in full service with any one pump out of service.
(2) An auxiliary means that is capable of providing the full fire protection demand and that is acceptable to the authority having jurisdiction.

Obviously this brings up other issues like the dead load of the static water tank and the additional electric power demand on the emergency generator because it's required to carry the Emergency power load of 2 fire pumps. However, the client is bringing the hazard to someone's town and the local FD only has so much pumping capacity and the mathematics of centrifugal pump affinity laws necessitate these additional features to the firefighters and occupants.

I hope this helps to clarify the issues and how the cited 2015 IBC provision doesn't "connect the dots" back to NFPA 14 and NFPA 20.

 

[PEDARRIN2]

Stockeyfpe,

Good information. I had seen the NFPA 20 reference which will mean a duplicate fire pump assembly(ies) which will be automatically operated if the principle assembly(ies) fails to operate. We may have four fire pumps (a pair in series which is in parallel with another pair in series) or just two fire pumps, capable of supplying the entire building. We think we can keep things under the 350 psig for the valves and stuff. I don't have an issue with the fittings, because Victaulic has couplings rated that high.

I would hope complying with NFPA20 5.6.2 would meet NFPA 14 7.9.3. They both address the inability of the fire department equipment from reaching the top floors, but will have to address that with the AHJ. We are still very early in design so there is a bit of time to iron out the wrinkles.