Change-Over and Hot-Tap Hookups
“It can’t be done” is the reaction I get when I tell people how our fire department has been using change-over and hot tap in pumping operations for five years. In the Ventura County, Calif., Fire Department, these evolutions have proved to be real time-savers in getting water on fires.
Whether one of our engines stretches a line from fire to hydrant or lays a supply line from a hydrant and uses a 1 1/2-inch live line after taking a position at the fire, the pump operator immediately pumps from the booster tank. Our booster tank sizes range from 750 to 1000 gallons.
First, I will explain how we do a change-over. Our pump operators charge the hose line by pumping from the booster tank as soon as the pumper is positioned at a hydrant, and then they connect a 12-foot, 2½-inch soft suction first to the hydrant, and then to the 2 1/2-inch gated suction inlet. The tank-to-pump line has a clapper valve on most of our pumpers, so all the pump operator usually has to do is open the 2½-inch suction gate and adjust the throttle to maintain the desired pump pressure.
If there is no clapper in the tankto-pump line, then we make a changeover. During this evolution, the pump operator maintains the desired pump pressure. He does this by closing down the tank valve until there is slight drop indicated on the compound gage-usually a hair below zero. Then he starts to open the suction inlet gate, maintaining the same compound gage reading, until the tank valve is closed all the way. This leaves the 2½-inch intake gate about halfway open. Watching the pressure, gage to maintain his pump pressure, the operator reduces the engine speed while opening the inlet gate all the way. Now he is safely pumping from the hydrant.
With a 2½-inch line from a wetbarrel hydrant, we want more potential flow in case we have to run more lines from our pumper. At this time, we connect our large soft suction to the steamer outlet of the wet-barrel hydrant and lay the other end of the soft suction at the operator’s panel.
Hot tap procedure
We are now prepared for the hot tap-tapping into a working pump with an additional supply of water. This procedure permits the removal of the 4 1/2-inch pump inlet cap while pumping so that the large suction hose can be coupled to that inlet. If the engine has a 4 1/2-inch gated inlet, the hot tap is unnecessary as the pump inlet cap can be removed without affecting the pump.
To connect the large suction to a pump inlet that does not have a gate, the pump operator slowly closes down the 2½-inch inlet gate while throttling up the engine to maintain the desired pump pressure. His goal is to bring the compound gage reading down to zero and maintain the pump pressure by coordinating the closing of the 2½-inch intake gate and the throttling up of the engine.
When the inlet pressure is stabilized at zero and the engine is at the proper speed to maintain the desired pump pressure, the operator slowly loosens the 4½-inch suction cap. As the cap nears the end of the threads, there is a distinct feeling of suction.
Large suction connected
With the large soft suction coupling in one hand, the cap is removed and the coupling is connected to the pump intake. The 2½-inch inlet gate can now be fully opened as the operator adjusts the engine speed to maintain the pump pressure. Now the 4½-inch hydrant valve can be opened as the pump operator maintains the desired pressure.
If a pump operator prefers to connect the large soft suction immediately instead of making the change-over, he charges the hose line going to the fire with booster tank water, slowly closes down the tank valve while maintaining the pump pressure, and hooks up the large suction as previously described.
From the time we stretch the first hose line, we do not have to stop pumping and we do not lose water as we hook up to a hydrant. These are quick, safe ways to get water on the fire immediately and also gain a hydrant supply without interruption.