This article is the first in a two-part series on high-flow tandem pump operations for high-rise fire protection systems. In Part 1, I am going to discuss the basics on tandem pump operations with regard to delivering the required flow and pressure in a high-rise structure fire operation.
High-Rise Challenges
There are many unique challenges to fighting a high-rise fire that require firefighters to develop and deploy unique strategies and tactics. Probably the most important issue for high-rise firefighting is obtaining the required flow. The pressure restricting problems in a fire protection system have caused firefighters to come up with new tactics for creating the required stream. For the most part, this has been done by developing high-rise handlines to operate under low pressure. The two main issues that have been scrutinized are the diameter of the hose and the nozzle pressure. Both the diameter of the hose and the nozzle pressure must be able to reduce pressure requirements needed because of the low standpipe residual pressures. For the most part, the firefighters have been able to overcome this problem as much as possible with 2½-inch hose and 50 psi nozzles. However, for maximum flow based on a large volume of fire, there are issues that still need to be dealt with.
This article is based on being proactive with all things included with a high-rise pump operation. With regard to high-rise firefighting, if there is a confirmed fire, the water supply portion of the pump operation needs to be set up for a worst-case scenario, which would be a high-flow water demand. On a normal fire, the fireground is a little more forgiving when it comes to not maintaining the proper water supply volume. But when it comes to fighting a fire in a high-rise building, you basically get one chance to get it right simply because the fire department connections are the only way to get water into the standpipe. If a high-rise operation is not producing the required flow because it was set up for a standard high-rise operation, it could in some cases require units shutting down to obtain more water.
Codes and Standards
To help you understand the techniques on pumping large volumes of water to a high-rise system, I’d like you to take a look at the building codes for fire protection systems and how they work as well as look at the standard tandem pump operation. National Fire Protection Association (NFPA) 14, Standard for the Installation of Standpipe and Hose Systems, outlines pressure limitations for building fire protection systems that have a direct effect on how the fire department delivers water within the structure.
- System hydrostatically tested at no less than 200 psi.
- For a system pressure of 150 psi or higher, the hydrostatic test will be no less than 50 psi higher than the system pressure.
- The maximum allowed system pressure is no higher than 350 psi.
- Buildings with a single pump as well as express standpipes for multiple zone pumps can exceed 350 psi to meet the standards on tall buildings.
There are two basic sets of NFPA standards that affect water delivery. The first standard was in place until 1993 and the second standard, which is still in place, was put in place in 1993. Please note that structures with the pre-1993 standards were not required to upgrade to the post-1993 standards.
Pre 1993: The minimum requirement for water delivery is 500 gpm at 65-psi standpipe residual pressure from two outlets at the highest standpipe in the system. The pressure regulating device has a maximum pressure setting at the standpipe outlet of 100 psi.
Post 1993: The current code requires the same 500-gpm flow, but the minimum residual pressure is increased to 100 psi and the pressure regulating device now has a maximum setting of 175 psi.
The authority having jurisdiction (AHJ) can improve standards for their cities that supersede the NFPA. For example, Clark County, in Las Vegas, Nevada, requires a standpipe residual pressure of 125 psi.
High-Rise System with a Building Pump
Now let’s review the basic tandem pump operation and why it is needed. Should a combination sprinkler and standpipe system (with a building fire pump) in a high-rise building be overtaxed by fire or fail for whatever reason, fire departments must have the ability to take over the pumping of the system with fire department engines to adequately supply sprinklers and handlines.
Supplying an adequate amount of water to the fire floor in a high-rise building by fire department engines can be divided into two phases. The first phase involves all operations that are required to move the water from the city water mains to the engine or engines that will be supplying the system. The second phase involves all operations required to get the water from the fire department engine or engines into the fire department connection (FDC) of the fire building.
No Matter Which Floor
The fire department needs to pump the system pressure no matter what floor the fire is on. If the fire department needs to pump the system in a high-rise building, it will have to match the building pump pressure and possibly exceed it.
There are one-way check valves located where the FDC enters into the system and after the building pump on the discharge pipe, both on the discharge side of the building pump. Because of these one-way check valves, if the pump is running but not doing the job (producing the pressure or gpm), the only way the fire department can enter into the system to take over is to exceed the building pump pressure. Either the building system pressure does the job or the fire department engine does. As a rule, they do not work together. If the building pump is not running, there will still be system pressure up against the check valve that will have to be overcome by the engine companies.
If the building pump should fail to provide the required pressure for whatever reason, the fire department engine will still have to pump the system as though the fire problem is on the roof. Yes, at the highest pressure. The reason for this is simple: A building fire pump does not have the capability of controlling its engine pressure over a wide pressure range as would be needed to provide the proper pressure to all the floors in a multistory building. Therefore, the building pump is designed to pump to the highest point in the building. Because of the potential of high pump pressures in the system, there needs to be a way to reduce the pressure at the lower floors to provide the proper pressure to the handlines. This is done through different types of pressure regulating devices. These devices are designed to reduce the building pressure to the proper pressure on the floor it is in service on.
Tandem Pump Operation
A tandem pump operation is nothing more than a relay pump operation, which involves one engine pumping water to another. The reason for a relay is to move water from a water supply to an engine through hose when the water supply does not have enough pressure to do it on its own. These operations are usually done over a long distance.
In a tandem pump operation, the purpose for its use is to develop more pressure than a single engine is capable of doing, or at least doing efficiently. These engines are placed close together with the goal of only using 50-foot sections of hose between them.
Procedures for High-Rise Pump Operations
The following procedures shall be accomplished when given the order to pump the system of a high-rise building.
- A water supply shall be established.
- The engine or engines that will be supplying the FDC shall be spotted in such a position to accommodate the following objectives:
- A minimum of two discharge lines shall be used to make the connection from the discharges of the engine to the FDC.
- The engine shall be spotted with the pump panel away from the fire building to help protect the engineer from falling debris.
- The discharge lines supplying the FDC and other engines in the operation shall be connected to the discharges opposite from the pump panel, allowing the engineer to stay clear of the lines in the event of hose failure. If the pump panel is top mounted, there still needs to be a safe side clear of hose for the operator and anyone else who needs to have access to the unit.
- After all lines are connected, the system pressure should be determined and the engine pressure of the engine supplying the system should be set at 50 psi below the system pressure. Setting the engine pump discharge pressure 50 psi below the building system pressure will allow the building pump to stay running and do the job as long as it can. A pressure drop in the system of more than 50 psi is a good indication of a substantial amount of water flowing, which in turn is a good indication of a drop in residual pressure that could affect the flow to the handlines. It might also be an indication of pump failure. It’s at this point the fire department engines should take over the building system.
- Once the fire department engine is set up and pumping its required engine pressure, it should be determined whether or not the engine is flowing water into the system. At any time, the engine should start flowing water whether it is initially after the engine goes into operation or at any time during the incident. Or, if the firefighters inside request more pressure, immediately pump the system pressure. Command should be notified after the initial hookup, whether or not the engine is flowing water, and at any time during the incident if water should start flowing.
- One method for determining whether or not water is flowing from the fire department engine into the FDC is to gate down the discharges being used. If the lines are static (water not flowing), the pressure on the discharge gauge will not change. On the other hand, if there is water flowing from the engine into the FDC, the pressure on the discharge gauge will change when the discharge is gated down. It should be noted that a minimum flow from the engine may not show as a residual pressure with the shutdown of one discharge. Therefore, when doing this check, all discharges should be gated down one at a time to determine if the engine is flowing into the system.
- If there is an actual fire, additional engines can be requested to duplicate the original pump operation using a separate FDC bank if available. This will provide reliability for supplying the system as well as additional gpm if needed. The clappers in the inlets of the FDC that are not being used can leak under pressure, which will cause pressure buildup in the inlet if the cap is left on. This can be a problem for firefighters who are trying to remove additional caps to add more lines to the FDC. For this reason, all caps should be removed from the FDC before the initial pump operation is set up.
- A minimum of two discharge lines shall be used to make the connection from the discharges of the engine to the FDC.
- Another method for providing reliability to the pump operation is to add an extra engine in the primary pump operation. If a single engine is all that is needed to create the system pressure, add a second engine in tandem for backup. If a tandem operation is initially set up, add an additional engine, again for back up.
- Pumps need to circulate water to keep from overheating. If the engine is throttled up but is not flowing water into the FDC, open an unused discharge and its corresponding drain valve. This should flow enough water to keep the pump cool.
The Required Hose
The high system pressures created by the taller buildings can require pressures higher than what the standard hose is rated for. Most of the 2½- and three-inch hose in service today have an annual service test pressure of 400 psi. The rule states that the maximum allowed operating pressure for hose should be 10 percent less than the annual service test pressure. So what does this mean? The 400 psi test pressure hose can be operated at 360 psi. Always consult with the manufacturer to determine what is safe for their products. For system pressures higher than what the standard hose can be operated at, special high-pressure hose should be used. It is not uncommon to have system pressures more than 350 psi. Several hose manufacturers make high-pressure hose capable of pressures up to 600 psi.
It is essential that the hose used for high-rise pump operations not be used for normal operations. The reason for this is simple: Hose can get slight cuts, abrasions, and burns that may not burst under normal operating pressures, but this may not hold true for a high-pressure operation found in high-rise pump operations.
Intake and Pressure Dump Valves
If the incoming pressure to the intake pressure dump valve exceeds its maximum setting, a significant amount of pressure above that point will be expelled through the pressure dump valve instead of contributing to the required engine pressure. Additionally, there is a chance the maximum pressure limitations to the valve body itself will be exceeded, creating an unsafe situation. Consult with the manufacturer of your valve for pressure limitations. This doesn’t mean they can’t be used. For example, if units with a 300-psi intake valve and pressure dump valve ratings are involved with a 500-psi operation, it doesn’t mean that the valve will have the full 500 psi going through it. The pressure needs to be divided between the engines so that the pressures do not exceed the valve capabilities.
For example, a tandem pump operation is being set up to provide a 500-psi system pressure using three engines. These engines are equipped with a 300-psi rated intake valve both for the valve body and the pressure dump valve attached to it. The first engine pumps 150 psi to the second engine. The second engine pumps 300 psi to the third engine, and the third engine pumps the required 500 psi to the system. At no time does the pressure at any of the intake valves exceed the maximum allowed 300 psi. It is important to max out the adjustment of the pressure dump valve to keep from losing discharge pressure. Some pressure dump valves are capable of being turned off.
Most engines also have built-in pressure dump valves on the steamer intake pipe, which need to be dealt with if overpressurized. The easiest way to do this is to cap off the dump port with a 2½-inch cap. The dump port will have a label on it that says “DO NOT CAP.” If the port is capped, the dump valve will not work. That is exactly why we are capping it. Capping it will not damage the dump valve. It will, however, eliminate water hammer safety at that point, again because it will not activate. This should only be done if there is no other way to create the required pump discharge pressure.
Water Delivery
As you can see, tandem pumping for a high-rise fire protection system is rather technical. It also goes against the grain with regard to the fireground hydraulics we are taught for calculating, for lack of better words, ground-level water delivery hose evolutions. Fortunately, the statistics are on our side with regard to a high-rise fire being a low-flow operation, which more than likely will be handled by the building fire protection system without fire department intervention or no more than a basic tandem pump operation, as discussed in this article.
However, high-rise fires can and have developed into a large-scale fire operation demanding large flows for extinguishment. Part 2 of this series will discuss operations for achieving maximum flows if that unexpected fire does happen.
