By Paul Shapiro
One of the greatest challenges we face in high-rise firefighting is being able to develop the required pressure from fire department pump operations to provide sufficient flow to firefighters combating the fire. Basically when a fire protection system has a building pump and the fire department needs to take over the system, the department needs to match the system pressure. This can involve extremely high discharge pressures from fire department engines, which requires a specific pump operation known as tandem pumping. Tandem pumping involves putting two or more fire trucks in series to create higher pressures than a single engine can achieve on its own.
The type of hose needed for a tandem pump operation is either 2½- or three-inch hose because of their higher operating pressures. In fact 2½- and three-inch hose also come in a high-pressure construction that can be operated at up to 600 psi for tall buildings that can have operating pressures ranging from 350 to 600 psi. For safety reasons, these lines cannot be connected to the side of the engine where personnel are working whether it be a side-mounted or top-mounted pump panel because of a possible hose failure at the high pressures. The bottom line is that these discharge lines need to be connected to the officer side of the engine. Most engines do not have 2½-inch intakes on the officer side. And if they do, it’s usually just one. The problem is that this type of operation needs multiple lines, preferably three or four, to move the required flow at a reasonable friction loss.
Task Force Tips has a solution for this. It makes a variety of LDH appliances, from intakes to manifolds. One in particular is a four-inlet gated Siamese manifold that has 2½-inch couplings for the inlets and a large-diameter coupling to connect to the pump. The Siamese manifold comes with a choice of several types of couplings to fit the needs of the apparatus. The most common coupling used would be either a four- or five-inch Storz that can connect directly to the intake valves. All of TFT’s LDH appliances have a maximum operating pressure of 300 psi. That includes the manifold body itself as well as the Storz couplings. TFT also states that the 30-pound weight of the gated Siamese appliance attached to a TFT intake valve will be perfectly safe in relationship to the weight hanging off the valve itself. This valve comes with the choice of a pressure dump valve which can be adjusted up to 300 psi or completely turned off if needed. Note that the above mentioned pressure and weight ratings are based on using TFT products only, which includes a TFT intake valve. If another manufacturer’s intake valve is used, do not exceed its pressure and weight limitations.
With a 300-psi operating pressure, the gated Siamese manifold can be used efficiently in pump operations reaching 550 psi. Here’s the reasoning behind that. Remember that a tandem pump operation is multiple engines providing a high pressure. The engine pumping the highest pressure will be the one connected to the fire department connections. Let’s use a 550-psi system pressure as an example. The most efficient way to set up a tandem operation for a pressure this high is to use three engines. The first two engines will work together to create 300 psi. The first engine will pump 150 psi, and the second engine will pump 300 psi to the third engine. The third engine will have to pump 250 psi from its own power plus the 300-psi intake pressure to develop the 550 psi needed. At no time does the pressure exceed the operating pressure of the Siamese manifold.
PAUL SHAPIRO is director of Fire Flow Technology. He is a nationally recognized instructor on large-flow water delivery. He is also a retired engineer from the Las Vegas (NV) Fire Department. He has authored numerous articles for fire trade magazines. He has been in the fire service since 1981, is author of Layin’ the Big Lines, and produced the first in a series of videos on large-flow water delivery.