Smooth Pump Operation Is Mark of Experience

Smooth Pump Operation Is Mark of Experience

The Volunteers Corner

Operating a fire pump involves more than the pump operator and the apparatus. It includes the men on the end of the hose line as an integral part of the operation. It’s no secret that a competent pump operator can make life more enjoyable for those at the nozzle end of the line.

The experienced pump operator works smoothly to provide water at desired pressures without sudden bursts of excessive power interspersed with drops in volume.

Hose lines should be charged smoothly so that hose crew can prepare for the buildup of pressure, and once water is flowing, the men on the line should have confidence that the pump operator will maintain that flow.

Operating at hydrant: When the pumper is hooked up to a hydrant and the first line is ready for water, open the discharge gate immediately with one hand and then slowly begin turning the micrometer throttle to increase engine speed and pump pressure. Before pump pressure starts, water will flow from the hydrant and through the pump into the hose line. Depending on the length of the hose line, allow a few seconds for the nozzleman to bleed the air out of the line before bringing the pump up to the proper operating pressure. The nozzleman can now open up all the way either where he has been waiting for water or after he has moved forward a few feet to an operating position.

If the pump is at draft, the operator should get 50 to 100 psi on the pump pressure gage before opening a discharge gate. As the operator slowly opens the discharge gate with one hand, he should start to rev up the engine with the other hand to maintain the pump pressure. When the gate is fully open, then the operator can start building up the desired amount of pressure.

If the pump shows a slight hesitancy in building up pressure, immediately cease opening the discharge gate and throttle up the engine slightly. In 9 cases out of 10— with no guarantee—the slight amount of air left in the pump during priming will be washed out and the pressure gage will rise. That’s the signal to resume opening the discharge gate while continuing to increase engine rpm. This little trick will save having to go back to priming the pump.

Two-handed operation: It may come as a surprise to some inexperienced pump operators, but pumping is a two-handed operation. I say this because trying to operate a pump with one hand is the most frequent failing I have observed during the many pump operator exams I have conducted. By keeping one hand on the throttle as you open the first discharge gate—and sometimes the second immediately afterward—you develop a smooth increase in flow and pressure and then maintain the desired pressure even while opening the second discharge gate.

When the operator charges the second line, he should keep his eye on the pressure gage and throttle up with one hand to maintain that pressure as he slowly opens the second discharge gate with the other hand. Remember, the pump cannot supply the additional amount of water required by the second line without an increase in the speed of the engine, which in turn increases the speed of the pump impeller, or impellers.

In the case of the second line, it is the slow opening of the discharge gate that averts a sudden thrust of pressure into the line and eventually at the nozzle.

Figuring the pressure: Another common failing among inexperienced pump operators is that they tend to take time out to figure the answer to the pump pressure problem while the hose crew is waiting for water. This frequently causes the nozzleman to have uncomplimentary thoughts about the pump operator.

When preconnected lines and booster lines are used, there should be no hesitancy by the pump operator because he should know what the pump pressures should be for these lines. These lines, even with automatic nozzles, should have definite rates of flow for initial attack. Inasmuch as their lengths remain constant, the friction losses can be figured once for all future use and to the friction loss, the standard nozzle pressure is added. The total of friction loss and nozzle pressure is the pump pressure. The only adjustment a pump operator has to make on the fireground is 5 psi per story, and that isn’t important until at least the third story.

When servicing long hand lines and master streams, the pump operator can start increasing pressure while working out his pump pressure. When the line has a fog tip, the operator knows he can increase the pump pressure to 100 psi just for the nozzle pressure. Then he can slowly increase pressure beyond that as he figures the friction loss. Finally, he adds the pressure needed to take care of back pressure and the loss in master stream appliances and Siameses.

Once a master stream is in operation, the pump operator should check his pump pressure computation. The easiest way is to start at one end of the layout and work toward the other. If he is supplying a ladder pipe, the operator might start with the friction loss in the multiple lines. Then he could add the friction loss in the siameses, the loss in the line up the ladder, the loss in the ladder pipe, the nozzle pressure, and finally the back pressure. In this way, he overlooks nothing.

Shutting down lines also should be done smoothly. Discharge gates should be shut slowly, and hose bleeders should be opened. Most important of all, the engine speed should be reduced by turning the micrometer throttle slowly. Never slam it shut.

No posts to display