FAMA Forum: Pumping Considerations for High-Rise Firefighting

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As a member of the pumps and plumbing task group within the FAMA technical committee, NFPA 1901, Standard for Automotive Fire Apparatus, Pumps and Plumbing Subcommittee, and in my role as North American sales manager for the Darley Pump Division, I am frequently presented with opportunities to answer pump-related questions and participate in discussions.

High-rise pumping discussions are often quite noteworthy and insightful given the significant diversity in standard operating procedures (SOPs) from one city to the next. While there are several different methods, there are some basic considerations that remain constants in preplanning and preparing to take on the challenges presented with the possible occurrence of a fire, for example, on the 70th floor of a high-rise.

UNIVERSAL HIGH-RISE PUMPING CONSIDERATIONS

Lift Station Failure: Lift stations are permanently installed fire pumps designed to work as booster pumps through a building’s standpipe system, boosting incoming pressures provided from apparatus on the ground through the fire department connection (FDC). These pumps are covered in NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection. The need for apparatus capable of high-pressure pumping operations in a city stems primarily from the potential failure of the lift station operation or other catastrophic failure of these NFPA 20 pumps.

Hydraulic Calculations: In the event the lift station fails, the height of the building is most commonly measured by the number of stories of the building. This is the major initial consideration. For simplicity of deducing the height, a typical rule would be to use 10 feet per story.

The weight of water column in a standpipe turns into a resultant back pressure at the ground, expressed in pounds per square inch (psi), that will need to be overcome before supplying any subsequent firefighting pressures. In the example of a 70-story building provided above, the pumps would need to overcome a backpressure of 303 psi.

The next consideration in sizing and specifying the proper pumps for the job is the projected friction loss in the standpipe itself based on the incoming flow rate and the friction loss coefficients of the piping. These vary depending on the required performance in both pressure and flow needed at the nozzle. Again, when specifying the equipment necessary, we are typically considering an event at the top of the tallest building in a city and the worst-case scenario to determine performance requirements on the ground. Many metro cities with building heights in the 70-story range specify a pump performance requirement of 600 psi at 600 gallons per minute (gpm) for high-rise pumping.

METHODS OF HIGH-RISE PUMPING

Single-Stage/Relay Pumping: Relay pumping is likely the most commonly used approach across the board in cities encompassing mid to major metro classifications. Relay pumping occurs by feeding one pumper, which will be deploying the lines into a standpipe, from a second pumper connected to the water source and acting as the supply pumper. Both pumpers will be operating at or nearly at the highest firefighting pressures each respective pumper can produce, typically around 250 to 300 psi. Then the incoming pressure from the first pumper is boosted incrementally with the pump on the second truck to enhance the pressures delivered to achieve the necessary operating pressures, typically 500 to 600 psi. The benefit here is that standard pumpers equipped with single-stage pumps can respond and serve the operational need when equipped properly.

Two-Stage or Multistage Pumps: Two-stage or multistage pumps essentially act as booster pumps, building pressure in multiple impellers inside of an individual pump, typically capable of creating a second-stage pressure of 600 psi or more. The use of these pumps on scene is a net positive in the ability to respond with a single piece of apparatus to a high-rise fire. Though the initial cost of the two-stage pump may be slightly higher, the efficiency and consistency of operations afforded by a two-stage or multistage pump justify the initial cost. These benefits have led to their increasing popularity in the SOPs in mid to major metro departments that are seeing upward development in their municipalities. Two-stage pump use has been a longstanding SOP in many of the largest North American metro cities.

Compressed-Air Foam Systems (CAFS): CAFS present a unique opportunity to overcome one of the main factors in high-rise pumping mentioned above. With CAFS, we have taken droplets of water and turned them into bubbles, essentially taking a majority of weight out of the water column that would otherwise be present resulting in backpressure. There is also significantly less friction loss in the surfactant as it rises through the standpipe. From an operational perspective and to realize the gains provided with CAFS use, draining the water from the standpipe is a necessity. Once this is completed, CAFS allows for delivery of the surfactant to the heights at much lower operating pressures. Depending on building heights in the city and other operational considerations, many departments using CAFS in their high-rise operations are still coupling CAFS with a two-stage pump.

Separate Engine-Driven Pumps: Commonly mounted on trailers or purpose-built, separate engine-driven single-stage pumps have been used in similar manners to a full pumper. Depending on specifications, these units can work as both the “feeder” pump and the “delivery” pump in relay pumping operations. These are often pulled by a multipurpose vehicle and can provide benefits in housing developments where space is limited or in other tight areas and can be specified to carry tactical equipment required for high-rise firefighting operations.

ADDITIONAL CONSIDERATIONS IN SOPs AND SPECIFICATIONS

High-Pressure Hose: Another major element is safely delivering this highly pressurized water from the truck to the FDC. The most common discharge hoses are rated at 250 psi with a burst pressure of 500 psi. It’s important to remember the pressures being produced are beyond standard burst pressures and could cause unsafe conditions without the proper considerations regarding the hose. High-pressure discharge hoses need to be specified to ensure firefighter safety.

Plumbing Component Considerations: When specifying your equipment to operate at high-rise pressures, you will need to take care in specifying the full system, specifically that the plumbing and valves and other waterway components you intend to use for pumping at high pressures are rated to handle the pressures you specify. Single-stage pumps are rated and tested according to NFPA 1901 testing requirements ranging from 150 to 250 psi. As a result, many manufactured components are built to withstand the same. If it is your SOP to use a product in relay pumping, specify accordingly to prevent failures or damage to critical components at critical moments.

In the event you are evaluating an approach to high-rise firefighting for new construction in your area or you are reevaluating your tactics in a city of high-rises, work closely with your fire department’s operations and training personnel and seek out specialists in engineering and sales departments of the FAMA member companies with whom you are working. Solicit other department contacts from FAMA member companies to network with concerning your use cases and SOPs. There are a lot of well-versed individuals in the industry with extensive past experience who are willing to pass along their prior knowledge and expertise. Good luck in building a safe and efficient apparatus suited to your department’s needs.

FAMA is committed to the manufacture and sale of safe, efficient emergency response vehicles and equipment. FAMA urges fire departments to evaluate the full range of safety features offered by its member companies.


JASON DARLEYis the North American sales manager for the Darley Pump Division of W.S. Darley & Co.

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