DUAL PUMPING
TRAINING NOTEBOOK
“What is dual pumping?” you might ask. One source defines it as the process by which a pumper receiving water from a hydrant supplies a second pumper with the residual hydrant pressure by connecting the suction intakes of the two pumpers with a suction line. (Residual hydrant pressure is the measure of the reserve capacity of a fire hydrant.)
You might say, “Wait a minute. That sounds like tandem pumping to me.” And you would be right. Many older textbooks on hydraulics and fire engineering call this procedure “tandem pumping,” and 1 always was taught that it is tandem pumping.
While researching 1 have found that tandem pumping now is defined as a short relay operation in which the pumper taking water from a supplysource pumps into the intake of a second pumper. The second pumper boosts the pressure of the water to pressures higher than pressures that would be possible with a single pumper while maintaining the required volume.
To clear up the confusion, 1 referred to the dictionary for the meanings of the words dual and tandem. Both these words match the given definitions.
IS IT RIGHT FOR YOU?
Following are the basic criteria to help you decide whether to use dual pumping:
- The gpm requirement exceeds that which can be produced by a single pumper.
- A hydrant capable of supplying more water than the first pumper can pump is available. (Keep in mind that a hydrant capable of a certain flow out of a 2’/z-inch port can flow a much greater amount out of a 4 ‘/2-inch port.)
- A second pumper is available or will be available.
- Other factors that may make dual pumping the best choice include:
- The position of the second nearest hydrant: It is on the same water main or is not reasonably near the emergency scene.
- The manpower, hose, or additional pumpers are not available to do a long hose lay to a second hydrant, even though the hydrant is on a separate water main.
- Very little, if any, additional equipment is needed.
- Additional hoselines can be placed into service without shutting off the hydrant or any of the hoselines that already may be flowing.
- The second pumper will be on site and its equipment will be available.
- Supply lines leading to a second hydrant are not needed; consequently, they will not impede traffic into, out of, and around the emergency scene.
Dual pumping is the best decision in many cases. It produces the highest gpm rate in the least amount of time and provides an uninterrupted flow of water. It eliminates the need to lay a hose to a second hydrant. All these factors add up to a safer, more efficient operation. Dual pumping makes good sense: If the water required to mitigate an emergency is available at a single fire hydrant and you know how to obtain that water, why not do it?
PREPLANNING/PRACTICE IMPORTANT
Before using dual pumping at an emergency scene, pump operators must understand the principles involved, be familiar with the technique, and know the basic criteria for its use.
For some structures or sites in your jurisdiction, dual pumping may be the best, or possibly the only, way that the required gpm can be obtained in the case of a major fire or other emergency requiring large amounts of water. Dual pumping should be part of your prefire or tactical plan for these sites. The technique should be used on the training ground first so that the pump operators can feel comfortable using it during an emergency.
Dual pumping is not difficult to learn, and it requires very little extra equipment. The equipment you now carry probably would be sufficient. The only equipment required is a means of hooking up large intakes between pumper 1 and pumper 2, which will vary from pumper to pumper.
Soft-suction hose works best. Although hard suction also works fine, it is much more difficult to handle. Some optional equipment that will make the operation easier includes large intake valves on one or both sides of the first pumper. If your department does not have a large intake valve, the following procedure can be used:
- Connect pumper 1 to the hydrant with large suction (to the 4’/2-inch port in most areas). Pumper 1 pumps the lines required.
- Use pumper 2 to position intake to intake with pumper l’s unused large intake. The distance between them should be a little less than the length of the connecting suction line.
- Connect the large suction line to pumper 2.
- Partially shut down the hydrant slowly as pump operator 1 adjusts the throttle to maintain discharge pressures until the compound gauge reads 0 to 5 psi. This is done so that when the unused large intake cap is removed from the opposite side there will be only 0 to 5 psi behind it.
- Remove the unused large intake cap on the opposite side.
- Connect the large suction line (from pumper 2) to pumper 1.
- Open the hydrant slowly as the pump operator adjusts the throttle to maintain discharge pressures. Pumper 2 now has all the residual hydrant pressure to use.
If pumper 1 has a large intake valve on the side receiving the water from the hydrant, this valve can be used to shut down part of the incoming supply instead of partially shutting down the hydrant as in step 4 and as in step 7 for opening it back up.
If pumper 1 has a large intake valve on the opposite side, steps 4 and 7 can be bypassed, although pump operator 1 may have to throttle up as this valve is opened to maintain discharge pres| sures. This by far is the easiest way to do this technique.
Once all involved practice dual pumping, they will find that it is a fairly easy technique, especially if the pumpers are equipped with large intake valves. Dual pumping can save time and energy by eliminating additional lines that must be picked up,cleaned, and loaded after the emergency has been mitigated. Firefighters probably will be very appreciative of the officer who issues the order Dual pumping’ instead of “Lay out.”
