NFPA 11 seems to let one bypass NFPA 20? 2

[ContractorDave]

We are overseeing a tank farm project where a low expansion foam system is being installed to NFPA 11. There are (4) tanks with (7) 550gpm chambers a piece. The system is calling for 4000 gpm@ approx. 120 psi which will mean in this case (2) 210 hp electric pumps. The design is to be fully manual. So here’s a twist thrown by NFPA 11: In Ch4 under 4.2 Water Supplies; 4.2.2 Water and Foam Concentrate Pumps;
4.2.2.1 When water or foam concentrate pumps are required for automatic foam system operation, they shall be designed and installed in accordance with NFPA 20.
4.2.2.2 Controllers in accordance with NFPA 20 shall not be required for manual systems.
Question A to 4.2.2.1: What if they are NOT automatic?
Question B to 4.2.2.2: I assume the controllers still have to be listed… just not designed or installed as per NFPA 20? What would be the guidelines then?
Sorry about the long winded explanation / question.

 

[riskengr]

Most of the foam system manufacturer's will provide a controller with their foam skid. The controller needs to operate more than the pump, as there will be a couple of motorized or solenoid valves on the skid as well.

Services provided include: Fire Protection Engineering, Emergency Response Planning, Fire Investigation and Process Safety Management.

 

[ContractorDave]

The foam system is bladder / proportioner type: the fire pump when operated supplies pressure to the foam tank which squeezes the foam concentrate bladder. Concentrate then goes to a calibrated manual proportioner which is basically a venturi mixing set-up. ALL valves are to be manually operated which include the ball valve from the foam tank to the proportioner, the ball valve from the fire pump discharge line to the foam tank, the proper 12" manifold valve to the tank out in the farm that needs the foam application... and then the fire pumps have to be started. All this presumably during an emergency. My "concerns" of how cumbersome this all appears have been "duly noted". Nonetheless, I am trying to have this installed as close to code as possible, as professionally as possible. The NFPA 11 vs 20 issue has caused some kerfluffel and I am trying to limit the fallout. Hence my post here looking for experienced and varied expert opinion.

 

[riskengr]

Most manual foam systems will include an instruction board mounted in the foam house. These can be quite extensive at most tank farms. as there may be multiple valves that need to be properly aligned in order to get foam to anyone tank.

Tank fires are very rare, which makes the cost of automation excessive. The standard allows the use on non-NFPA 20 controllers because they are way too complex to meet the simple need of starting and stopping the pump. The pump or foam skid. mfr should be able to recommend an approriate control/switch for the pump. Make sure the money is spent on having all valves/switches clearly identified (numbering, color coding, etc...) and have a good set of instruction permanently installed in the foam house (think bulletin board size, so multiple people can look at them simultaneously).

Services provided include: Fire Protection Engineering, Emergency Response Planning, Fire Investigation and Process Safety Management.

 

[ContractorDave]

Thx riskengr.
But I assume one still requires a 'listed' controller, whether or not one needs a controller as per NFPA 20?

 

[riskengr]

I spoke with a contact at one of the foam companies and they indicated that this is up to the Authority Having Jurisdiction.

As a minimum the switch/controller will need to be UL Listed electrical equipment. Also, expect that any old switch is not going to do. It's going to have to be in/on a red box and will probably be required to have a "power OK" light and possibly a "pump running light" (This what you normally see). The pump manufacturer should be able to provide an approved, Non-NFPA 20 controller.

Services provided include: Fire Protection Engineering, Emergency Response Planning, Fire Investigation and Process Safety Management.

 

[ContractorDave]

Thanks again. The AHJ will have his say.

 

[DavidCR]

I´m deling also with a bladder tank design to feed foam chambers so here is my thinking.

I think that NFPA 11 4.2 intention is as follows:

4.2.2 Water and Foam Concentrate Pumps;
4.2.2.1 When water or foam concentrate pumps are required for automatic foam system operation, they shall be designed and installed in accordance with NFPA 20.
i.e. it is refering to both the water supply (it must be NFPA 20) and the Foam pump (must be NFPA 20 also) when the foam feed is required to be automatic.

4.2.2.2 Controllers in accordance with NFPA 20 shall not be required for manual systems.
I think it refers only to foam pump systems (eg. a balanced pressure pump skid electric or diesel), in some cases the AHJ allows that the foam pump skid can be operated manually so a fully NFPA controller is not required.

In the case of a bladder system I think the water supply shall be NFPA 20 and the actuation could be manual with the option of using a hydraulic actuated ball valve to reduce the number of valves to open. Also could be fully automatic for example by using deluge valves actuated by the loss of pressure in the foam discharge device line.

There are bladder systems that keeps the bladder under pressure in stand by mode and others that don´t. I don´t know which is better and when.

http://www.williamsfire.com

manuals include some diagrams to ilustrate.

 

[ContractorDave]

Thanks David.

Is it your interpretation then that 4.2 is not relevant to the fire pump itself, but more to ancillary pumps that might be used in proportioner skids?

As for the hydraulically actuated ball valve on the concentrate line, I think that's the way to go also but the owner prefers to make it as unlikely as possible that the system ever be inadvertently operated.

 

[riskengr]

The primary heading for this section reads, "4.2.2 Water and Foam Concentrate Pumps". As a result, anything within the section (4.2.2.1 & so on) applies to both water and foam pumps.

An NFPA 20 controller is not required on a manually operated foam systems because there is no need for the monitoring of local or remote signal start signals/sensors, test timers and the redundancies and alarms associted with automatic starting. All of this would simply be a waste of money on a manually operated foam system.

I have been around numerous manual foam systems in 18 years and have never seen an NFPA 20 controller on the water pump of a manual foam system, except in those cases where the pump is a multiservice pump and also supplies automatic systems.

Services provided include: Fire Protection Engineering, Emergency Response Planning, Fire Investigation and Process Safety Management.

 

[ContractorDave]

Thanks Again riskengr.

I guess the last question would seem to be does it need to be a fire pump at all?