What Size Handline Should Be Used In a Highrise Fire?

What Size Handline Should Be Used In A Highrise Fire?

The purpose of this document is to provide information that will help firefighters in making a decision on what size handline is to be deployed in a highrise fire.

There are four basic components for a high-rise handline operation. They are the hose, the nozzle, a 2.5 x 2.5 gated wye, and a in-line pressure gauge.

HOSE AND NOZZLE

Choosing the proper hose and nozzle combination needs to be based on delivering the required flow for fire attack using low system operating pressures. The reason for this is simple. High-rise fire protection systems are limited in operating pressures because of elevation, friction loss in plumbing, pressure reducing devices, and probably the most concerning issue, system pressures. established by NFPA, which is the codes that high-rise fire protection systems are designed from.

 

There are two basic sets of standards that have been put in place by NFPA that can effect water delivery. The first standard was in place until 1993 and the second standard which is still in place started on 1993. Please note that structures with the Pre 93 standards were not required to upgrade to the Post 93 standards.

 

PRE 1993 The minimum requirement for water delivery is 500 GPM at 65 psi standpipe residual pressure at the highest standpipe in the system. The pressure restricting device has a minimum allowed residual pressure at the standpipe outlet at of 100 psi and a maximum of 175 psi. The pressure reducing valve has a maximum static pressure of 175 psi at the standpipe outlet.

 

POST 1993 The current code requires the same 500 GPM flow but the minimum residual pressure was increased to 100 psi. The pressure restricting device pressure setting of 100 psi is not required and the pressure reducing valve static pressure setting remains at 175 psi.

 

NFPA also requires a minimum flow of 150 GPM on attack lines. It makes no difference whether the fire attack is taking place in a single-story structure or a multi-story structure.

 

Because of the above-mentioned pressure issues in fire protection systems most fire departments have opted to exclusively use 2 ½ “ handlines with smoothbore nozzles for all fire scenarios big and small. The true fact is that the 2 ½ “ handline will provide the most water every time. However along with the positive flow capabilities of this line there are also negative deployment and kinking issues that have to be dealt with because of the size of the hose itself.

 

The low standpipe residual pressures mentioned above have been misleading causing firefighters to to assume that smaller handlines such as

1-3/4” and 2” could not be used because of the higher friction loss these lines possess as compared to the 2-1/2”. Let’s analyze the true pressures that can be expected in a high-rise fire protection system.

 

Again, fire protection systems are based on a 500 GPM flow capability and after flowing 500 GPM the residual pressure will need to be either 65 psi, 100 psi, or 125 psi depending on when the system was built. The true fact is that if 500 GPM is not flowing, which it would not be with the initial handline deployment, the residual pressure will actually be higher. The following chart will illustrate this. Actual flow tests were conducted at the Binions Horseshoe Hotel using 1-3/4” 1.88”, 2”, and 2-1/2” hose all at 150’ in length. Here are the results.

 

Binions Horseshoe Hotel in Las Vegas.

This is a 500 GPM / 65 psi system.

FIRE PROTECTION SYSTEM STANDPIPE

RESIDUAL PRESSURE FLOW TESTS

                                                                                                                                     

                                                                                                                                  SRP    STANDPIPE RESIDUAL PRESSURE 

                                                                                                                                               GPM    GALLONS PER MINUTE

                                                                                                                                                    NP    NOZZLE PRESSURE

 

                                                                                                                                     SYSTEM SPECIFICATIONS     500 GPM @65 PSI SRP

                                                                                                     1.75”HOSE X 150’              SRP 100                    GPM 188       TIP 1”             NP 40

 1.88” HOSE X 150’             SRP 98                      GPM 210       TIP 1”            NP 50

 2” HOSE X 150’                   SRP 92                      GPM 222       TIP 1”            NP 56

 2.5” HOSE X 150’                SRP 88                      GPM 301       TIP 1-1/8”      NP 64

 

As you can see the standpipe residual pressures increased significantly and all flows exceeded the NFPA minimum handline flow of 150 GPM as well. The size of the hose in the high-rise pack should reflect the requirements of the fire and the system pressure.. The GPM needs to match the BTUs and the diameter of the hose needs to be able to overcome the system pressures. In order to have the luxury of an easy to deploy 1-3/4” or 2” handline, a 2 ½ “ hose pack needs to be brought into the structure as well just incase its use is warranted. .

 

Low-pressure nozzles are a must in a high-rise operation even with the higher residual pressures which were indicated in the chart. Remember system pressures are going to be low so lowering the nozzle pressure from the standard 100 psi to a much lower pressure in the range of 40 PSI to about 60 psi greatly improves water delivery capabilities.

 

The following chart shows examples of the Combat Ready 1-3/4” and 2-1/2” hose packs with their accompanying nozzles and their approximate flow capabilities in three different system pressures, 65 psi, 100 psi, and 125 psi.

 

1-3/4” x 150’ with a 15/16” smooth bore tip and a 185 GPM fixed gallonage combination nozzle @ 50 psi nozzle pressure

65 psi system           100 psi system         125 psi system

185 GPM                     191 GPM                   198 GPM

105 psi SRP              120 psi SRP              135 psi SRP

 

2-1/2” x 150’ with a 1-1/8” smooth bore tip and a 250 GPM fixed gallonage combination nozzle @ 50 psi nozzle pressure.(both were identical in flow)

65 psi system         100 psi system        125 psi system

300 GPM                330 GPM                 335 GPM

90 psi SRP             110 psi SRP              135 psi SRP

 

Not all standpipe outlets are user-friendly in regards to connecting hose and gated wye appliances to them. Because of this a short 15 foot section of either 2-1/2” or 3 “ hose should be used to connect the high-rise pack to the standpipe outlet.

 

GATED WYE

A 2-1/2” x 2-1/2” gated wye should be connected to the end of the short section of hose leading from the standpipe to allow two handlines to be connected from one standpipe outlet.

 

2-1/2” INLINE PRESSURE GAUGE

The 2-1/2” pressure gauge is connected between the gated wye and the short section of hose leading off the standpipe outlet.The purpose of the

in-line pressure gauge is twofold. Part of the high-rise deployment procedure requires a flow test of the hand line before commencing with the fire attack to determine if the required handline pressures can be met from the system which in turn will help decide what size line can be used. The other thing the in-line pressure gauge can do is help to dial in the required pressures for the handline. For example let’s say you’re using Combat Ready 1-3/4” hose and the required pressure for that line to flow 185 GPM with the 15/16 smoothbore is 105 psi. This can be noted with a label on the side of the gauge body so if an adjustment is needed at the standpipe a firefighter simply adjusts the standpipe outlet valve to the required pressure. The same can be done for the 2 ½ “ line.