High Rise, Big Water, Part 2

In this article, part two of this series on tandem pumping operations, I am going to show in depth how to take a standard tandem pumping evolution to a higher level to gain maximum flow.

Read High Rise, Big Water, Part 1

 

Tandem Pumping For Large Flows

The following is a list of considerations for large flows in a high-rise water delivery system from the engine to the nozzle.

  • The water supply.
  • The capacity of the apparatus in the evolution.
  • The friction loss in the tandem pumping discharge lines.
  • The correct pump discharge pressure for the engine pumping into the fire department connection (FDC).

Water Supply

The water supply problem is the easiest issue to overcome. It’s the same issues you would be dealing with a ground-floor level structure fire. The only difference is that all of the water will be going to one engine. Know your equipment and your areas, and be able to use a supplemental water supply with additional supply lines. I think it’s safe to say that most high-rise buildings are in an urban setting and will have the availability of hydrants. Moving the required flow may involve more than one hydrant and, in fact, could actually create the need for a relay pump operation.

Now here’s where to be proactive. If the first-in company does a size-up and thinks the fire has developed into a large-flow operation or has the potential to grow into one, consider establishing a large-flow water supply. This is obviously the first-in officer’s choice based on the information at hand. I would set up for at least a 2,000-gallon-per-minute (gpm) water supply. Remember, this is a goal to reach. It doesn’t mean you have to use the entire 2,000 gpm or that you will even be able to reach it-it’s just a goal. In most cases, using large-diameter hose (LDH) will bring that in with two hydrants.

Finally, here’s something to think about. What if your high-rise operation standard operating guidelines involved setting up a large-flow water supply every time? If you have the units and the means to get the water, then why not? This will definitely be a proactive move and, if nothing else, it would provide great training.

Pump Capacity of the Engine Connected to the Supply Lines from the Hydrants

In a tandem pumping operation, the required flow will be based on what the first engine in the tandem operation is capable of delivering. The reason being, all supply lines in the evolution are connected to the first engine in the tandem operation. That first engine moves water over to the additional engines involved with the tandem operation, which are used to boost the discharge pressure to match the system pressure of the building.

Most cities use engines with a pump capacity of at least 1,000 gpm and higher. Let’s take a worst case scenario for an example, which would be a 1,000-gpm engine. Remember, we are talking about the first engine in this tandem that is connected directly to the water supply through supply lines. It’s a proven fact that a centrifugal pump, which is what we use in the fire service, takes advantage of the incoming water under pressure and can actually pump more than what it is rated at. There’s no reason a 1,000-gpm engine can’t flow at least 1,500 to 1,800 gpm if it has the water supply to do it.

Another factor to consider is keeping the net pump discharge pressure on all the units in the operation no higher than 150 pounds per square inch (psi) if possible. Remember that pumps are rated to flow their capacity at 150 psi net pump discharge pressure. As the net pressure increases past 150, the capacity of the pump actually decreases. This should not be too difficult to maintain. Just be aware of it when determining the pump discharge pressures for the units in the operation.

Friction Loss in the Tandem Pumping Discharge Lines

Because high-rise pumping operations can require high pressures, you usually cannot use LDH, the best hose to use for moving water. In some of the lower buildings, LDH could work. There are two types of LDH with regard to pressure ratings. The most common, which is supply hose, is rated at 185 psi. Large-diameter attack hose is rated at 275 psi. So, if there were buildings that had system pressures that fell in line with this, then you could use LDH.

I mentioned that in a tandem pumping operation essentially one engine receives the entire water supply. Realistically, the amount of water that would be available to a single engine would probably average to no more than around 2,000 gpm. This amount of water is capable of being delivered through multiple 2½ or three-inch lines with minimal loss.

Smooth Bore Nozzle Rated at 50 PSI NP

System Pressure

65 PSI

100 PSI

HOSE

NOZZLE

NP

GPM

NP

GPM

150’ x 2.5”

11⁄8”

74

322

78

330

11⁄4”

60

357

64

369

Let’s take a look at an example. Let’s say we’re going to be using three discharges from engine to engine in a tandem pumping operation flowing 1,500 gpm. Because a tandem pumping operation requires the apparatus to be really close to one another for safety reasons, you can usually use 50-foot discharge lines to go from one pump to the other. If you divide 1,500 gpm by three discharge lines, you get 500 gpm per line. The friction loss in a 50-foot, 2½-inch hose is 25 psi. That’s not that high of a pressure to be overcome with engine pressure. I like three-inch hose for this type of operation because it has even better friction loss characteristics; 1,500 gpm divided by three three-inch discharge lines has an eight psi friction loss. Even if your department does not use three-inch hose, keeping four sections of three-inch hose on the apparatus for high-rise pumping operations would be very reasonable to accomplish.

Another consideration is purchasing a Siamese intake appliance that has multiple gated 2½-inch inlets. This appliance could be attached to the six-inch intake on your apparatus. In fact, you could also put one of these on a front suction, which would really give you plenty of lines. With a little creative thinking, this could be set up to receive six lines. This would reduce the friction loss in the discharge lines to practically nothing.

Raising the Required Pump Discharge Pressure to Overcome Friction Loss

So far the only things that have changed for putting together a high-flow tandem pumping operation are the water supply and the multiple discharge lines. What about the required pump discharge pressure? We know that we are supposed to pump the system pressure, but that’s based on a 500-gpm flow. For a fire that only requires a small flow, such as one or two lines, matching the system pressure on the engine’s discharge gauge will more than likely be enough. For a large flow requirement, you are still going to match the system pressure within the system itself but the engine pumping the FDC needs to increase the discharge pressure higher than the system pressure requirement to overcome friction loss in the discharge hose going into the FDC. If this is not done, as more handlines continue to open up in the high-rise, the system pressure will drop. The pump operators need to actually maintain whatever pump discharge pressure they are using. By doing this, the system will, for the most part, maintain its pressure while allowing additional handlines to be connected to additional outlets. The only thing that will end the addition of handlines is if you run out of water from the water supply or if you max out the throttle or engine governor on the engines.

At the beginning of this article, I talked about all systems being hydrostatically tested. As a refresher, any system up to 150 psi is hydrostatically tested at 200 psi. Any system pressure higher than 150 psi is tested at 50 psi higher than the system pressure. What this means is that, when the system was first installed, it was able to withstand the above-mentioned pressures. As you know, we are dealing with systems that are decades old in some cases and the question arises, should we really be pushing our luck with increasing the pressures past system pressures?

Let me answer this question with a question: If we need more water and without it we are going to lose the battle, should we chance it? If you choose not to chance it, then the fire attack will have to be done with inferior flows. It may or may not be enough. This is a decision that the incident commander (IC) needs to make on the fireground.

In researching this particular issue, I’ve dealt with many fire protection engineers and, more importantly, fire protection system contractors. The large majority have said that they would take the extra risk because it would probably withstand the pressure and, if there was a failure, it would most likely be a leaking joint connection vs. a catastrophic failure in the pipe itself. Again, this is the IC’s decision. If you choose to do so, I would recommend increasing the pressure between 15 and 25 psi and seeing if that satisfies the water demands. As mentioned, multiple lines between the engines and the FDC will keep the friction loss to a minimum. Establish a minimum of four lines if possible.

Some of the increased pressure will not even make it to the nozzles in use because it will be eaten up in friction loss in the lines going to the FDC. This is because an increase in pump discharge pressure through the discharge lines to the FDC means that the flow is being increased. As the flow is increased, the friction loss in the FDC hose and the handlines is increased as well as the plumbing in the fire protection system itself. So even an increase of 25 psi pump discharge pressure will not mean an increase of 25 psi to the nozzle. It is possible to only see half of the 25 psi or less go to the nozzle itself. We did a flow test to simulate a high-rise system using an engine company. Two separate flow pressures were tested, 65 psi and 100 psi, with both based on a 500-gpm flow rate. In other words, after flowing 500 gpm, the above-mentioned pressures were the residual pressures just as the National Fire Protection Association (NFPA) calls for. Below is the chart that reflects the outcome of these tests.

As you can see, the largest gain in nozzle pressure was four psi with a flow gain of 12 gpm. A large majority of the apparatus in service today are equipped with electronic pressure governors, which, when left in the psi mode, will automatically maintain the set pump discharge pressure. The problem using it in the psi mode when pumping engine to engine is that the units have the potential to react from each other a lot, creating a revolutions-per-minute (rpm) hunting situation where the rpm are fluctuating up and down too much. If the governor is set in the rpm mode this will not happen, but the operator will have to monitor the pressure and react accordingly. You might want to even try keeping the engine connected to the FDC in the psi mode. This would allow the system pressure to be maintained and might not create the rpm hunting, since the other pumps will be in the rpm mode. I recommend doing some drills to get a feel for what will happen in both modes; then go with what works best for you.

Duplication of the PumpING Operation

Another alternative for a big water pumping evolution is to simply duplicate the first pumping operation. Of course, more apparatus will be needed as well as FDCs. The key to using a duplicate pumping operation is to use two separate FDCs for maximum results. Not all structures have this. If you duplicate an operation using one FDC with four inlets or less, each evolution will only be able to use two. This means that the friction loss from the engine to the FDC could be too high, which could greatly hinder the flow.

First Set: Test One.

Two 2½-inch handlines 150 feet long with 11⁄8-inch tips connected to a gated wye, which was connected to the standpipe outlet

Total gpm 476

Two Handlines

11⁄8-inch Tip

40 PSI NP

238 GPM

Standpipe Residual Pressure 65 PSI

Building Pump Residual Pressure 170

First Set: Test Two.

Single 21⁄2” handline 150’ long.

11⁄8” Tip

265 GPM

50 PSI NP

Standpipe Residual Pressure 80 PSI

11⁄4” Tip

345 GPM

56 PSI NP

Standpipe Residual Pressure 74 psi

First Set: Test Three.

Total GPM 992

Four Handlines

11⁄8” Tip

44 PSI Average NP

248 GPM

Average standpipe residual pressure 48 psi

Building pump residual pressure 165 psi

(Table by author.)

The diagram above shows three different types of tandem pumping operations that can be used to get high flows. They are pumping at system pressure, pumping 20 psi higher than system pressure, and somewhat of a duplication of operations. Two separate engines, 5 and 6, are pumping into the FDC with two separate tandem pumping operations. Engine 2 is supplying more water to engine 3, which is the first engine in the existing tandem pumping operation with engines 4 and 5. There are three engines involved with the second tandem pumping operation, engines 1, 7, and 6. Engines 1 and 7 have hydrants. As you can see, there are many variables that can be used.

The Riviera Hotel High-Rise Flow Tests

On June 9, 2015, a series of flow tests were conducted at the Riviera Hotel in Las Vegas, Nevada, with the Clark County Fire Department; Las Vegas Fire and Rescue; Fire Flow Technology; and Desert Fire Protection, a major sprinkler contractor in Las Vegas. The purpose of these flow tests was to see what the best options were for developing a maximum flow scenario in a high-rise structure. Part of these tests involved using the system pump only, and the other part involved a tandem pumping operation with two engine companies for discharging water into the building.

Guidelines were set up for conducting these tests to ensure that the operation would be as safe as possible and as accurate and realistic as possible. All system pressures were strictly adhered to. All flows were delivered through 2½-inch handlines with 11⁄8-inch tips with the exception of one, which used a 1¼-inch tip. It was decided that we would only count the flow delivered by a handline if the stream it was producing was considered to be adequate for firefighting. We went no lower than 40 psi nozzle pressure.

FIRST SET

The first set of tests conducted were done without fire department intervention in the system. Basically, we allowed the building pump to deliver the flow. We wanted to accomplish three goals with this portion of the testing.

Test One: see how much water one standpipe outlet could produce by running two 2½-inch handlines off one standpipe outlet on the top floor. These lines were connected to the outlet via a 2½-inch à— 2½-inch gated wye.

Test Two: a maximum flow from a single outlet with one 2½-inch handline.

Test Three: a maximum flow from a multiple outlets from three standpipes with 2½-inch handlines.

SECOND SET

The second set of flow tests was conducted with fire department intervention into the system. Two single-stage 1,500-gpm engine companies were used in a tandem pumping operation pumping into four inlets on the FDC. The goal for this test was to see how much water could be delivered out of the standpipe system in workable firefighting streams while keeping within the pressure parameters of the system. The system itself has a 1,000-gpm pump with a churn pressure of 180 psi, which is based on NFPA standards that this system followed. In addition, it has a hydrostatic pressure of 230 psi, 50 psi above churn pressure.

Two five-inch supply lines were brought in from one hydrant. Four 2½-inch discharge lines 50 feet long were stretched between the two engines and from the second engine to the FDC. A special intake valve, designed by Task Force Tips, allowed us to run all four discharge lines from the water source engine to the engine pumping into the FDC. One of the problems that we noticed in preparing for this test was that most engines are not designed to allow multiple 2½-inch supply lines to be taken in on the officer’s side of the unit. Remember, the lines used in a tandem operation can be quite high in pressure so they should not be brought into the pump panel side for safety reasons. The specially designed intake valve eliminated this problem. In fact, if an engine has a front or rear intake it could theoretically bring eight lines. It sounds like overkill, but if the pump operation happens to be set up in the debris field there is a good chance that those lines could be cut by falling debris. Running extra lines between the units would allow for the best chance of an uninterrupted water supply if a line was ruptured.

Test One: The first portion of these tests involved the tandem pumping operation throttling up to the 180 psi system pressure. The pump discharge pressure was maintained throughout the evolution. In other words, after initially throttling up to the required pressure, if that pressure dropped because of an increasing amount of flow from the system, pump operators would actually maintain the required pressure by throttling up, thus allowing for a maximum flow. An engine with an electric governor would do this automatically in the psi mode, but our engines did not have pressure governors.

Test Two: The second portion of the series again involved a tandem pumping operation, but this time the required pressure was increased from 180 to 200 psi. So we did pressurize the system past the system pressure itself; however, we did not go past the hydrostatic pressure limitations.

Comments on the Flow Tests

We noticed several interesting points with the flow tests. All of the building pump tests we did surpassed what we expected. The flow test with the two 2½-inch lines from one outlet using a gated wye that flowed 476 gpm was a lot more than we expected. The NFPA standard calls for a total of 500 gpm being flowed from two outlets. We did the 476 gpm from one outlet.

The single 2½-inch handline also impressed us. If you go back into the archives, you will see that the reason the 65 psi standpipe residual pressure was chosen was because it would supply 100 feet of 2½-inch hose with a 11⁄8-inch smooth bore tip at 50-psi nozzle pressure flowing 265 gpm. I would venture to say that most high-rise handlines are set up for this exact scenario, and the real truth is they are robbing themselves of a lot more water if the line was intended to be a high-flow line, or should I say higher than 265 gpm. Again, we flowed 345 gpm with a 150-foot handline using a 1¼-inch tip.

The final flow test for maximum flow with multiple 2½-inch handlines is probably the most impressive test we did for the entire series. We pumped 992 gpm from a building pump that’s rated to flow 500 gpm with a 65-psi standpipe residual pressure. We just about doubled that. The thing to remember is that multiple standpipes increase the flow from the pump.

This system is the worst-case scenario for an NFPA fire protection system. It’s a pre-93 building rated to do 500 gpm at 65 psi residual pressure. We conducted our flow tests to the hydraulically most remote part of the system, the roof.

Second Set: Test One.

A maximum flow through multiple handlines from three standpipes using a two engine tandem pumping operation. The second engine in the operation matched the building system pressure of 180 psi.

Total GPM 952

Four Handlines

11⁄8” Tip

40 PSI Average NP

238 GPM

Average Standpipe Residual Pressure 60 psi

Pressure at the inlet of the FDC 180 psi PDP of the second engine 180 psi PDP

Second Set: Test Two.

A maximum flow through multiple handlines and a portable master stream from three standpipes and a two-engine tandem pumping operation. The second engine in the operation had a PDP of 200 psi.

Total GPM 1315

Four Handlines

11⁄8” Tip

40 PSI Average NP

238 GPM

Master Stream

13⁄8” Tip

42 PSI NP

363 GPM

Average Standpipe Residual Pressure 55 psi

Pressure at the inlet of the FDC 175 psi PDP of the second engine 200 psi PDP

(Table by author.)

The second portion of the flow tests conducted from a tandem pump operation was also an eye-opener. The flows were 952 gpm at 180 psi and 1,315 gpm at 200 psi. When a department engine pumps a specific pump discharge pressure (PDP) there is no guarantee that it will be the same as the system pressure it is trying to match.

The reason is that the only indicator for the engine PDP is at the pump panel. There is discharge hose and an unspecified plumbing configuration before the standpipe that could create pressure loss and cannot be accounted for. It appears that when we did the 180-psi operation, we were probably very close to the 180 system pressure since the flow was very close to the max flow on the building pump. The flows were 992 gpm with the building pump and 952 gpm from the engine.

Had this been a real fire and we needed more water, an additional supply line from the second hydrant could’ve been established into the evolution. It could have been connected to either engine in tandem.

One interesting thing to note about fire protection systems and the rated capacities of the in-house pumps is that these pumps are rated to get a specific gpm, but requirements for delivering the flow do not always allow for working fire streams to match the rating. The building pump for this system was rated at 1,000 gpm. When the system was tested, the water was discharged through three 1¾-inch smoothbore tips with a nozzle pressure of 15 psi. The 15-psi nozzle pressure will not produce a firefighting stream. It’s almost like having an open butt discharge flowing the water. Again, we used actual 2½-inch handlines with 11⁄8-inch tips and required a workable stream for the flow from the specific line to count in our tests. It’s one thing to produce a lot of water, but if you can’t use it, then it doesn’t matter how much is delivered.

Realistic Training

It’s important to remember that the information taken from these flow tests is really unique to this building only with regard to the exact numbers. However, it does reflect a pattern with regard to what you can expect from a high-rise building. I hope the information in this article has been helpful for you. Remember, in a high-rise fire we are already starting behind the eight ball with regard to water delivery. The techniques presented in this article have been proven on the fireground and are relatively safe to undertake.

Don’t expect miracles with regard to several thousands of gallons of water per minute. For the departments that have high-rises in their cities, start coming up with a plan for flowing big water in a high-rise structure. Start with your fire prevention bureau. Contractors of fire protection systems are also an excellent resource because they design and build the systems. There is a lot involved with an operation like this, and there’s a really good chance that you may only go to one actual high-rise fire in your career-if that. That is why it is extremely important to conduct realistic training on a regular basis.

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