PROTECTING FRONT-MOUNT PUMPS DURING FRIGID WEATHER
Manufacturers Offer Suggestions for Preventing Freeze-Ups in Winter Weather
ONE of the problems which operators of front-mounted fire pumps have to contend with during winter weather is that of freezing.
A member of a volunteer fire department in one of our larger states reports that on numerous occasions he has encountered the problem of freezing of front-mounted fire pumps while the apparatus was en route to a fire. He cited a case which came to his attention in a small village in mountainous area in which six pumpers responded to an alarm, four of them being called under mutual aid agreement.
Five of these pumpers were equipped with front-mounted pumps, and traveled from two to fifteen miles in the tenbelow-zero temperatures to reach the scene of the fire. None of these five was able to pump, due either to being frozen on arrival or to being so cold that water from ponds froze on contact with the pump.
This volunteer, who, incidentally also is a member of a state insurance rating organization, asked this Journal to study the problem and come up with answers that might help alleviate what he terms a serious problem. He points out cases where extreme difficulty was experienced in maintaining engines above safe minimum operating temperatures while responding to rural alarms in sub-zero conditions. For this reason he wonders if by-passing of engine coolant through a pump jacket would be an adequate solution. Also, he adds, that it might be noted that while the NBFU standards (No. 19) for fire apparatus specify that gauges shall be protected from freezing, there is no similar specification regarding pumps.
The editors, acting upon the request, made contact with manufacturers of front-end pumps, asking for their advice and suggestions. All were most helpful, and from among the data submitted the following are offered for such help as they may afford our readers.
One manufacturer had this to say: “Front-mounted pumps are naturally more sensitive to the effects of cold temperatures than are midship-mounted pumps, as the former are subject to a blast of cold air as the truck is driven over the road, while the latter are given considerable protection by the truck engine and cab and, in addition, receive some heat from the exhaust, especially where so-called heater pans are employed to retain some of the heat from the exhaust pipe within the pump compartment. There is no reason, however, why front-mounted pumps cannot be made to function properly in cold temperatures, if proper measures arc taken to maintain the pumper in a state of readiness at all times.
“The pump should be completely drained of water after every use, and suction and discharge caps, fittings and gaskets wiped dry before they are reassembled. The line from the booster tank to the pump should also be kept dry and, if operation from the booster tank is desired, the shut-off valve between the tank and the pump should be located close enough to the tank so that water at the valve cannot freeze. If the pump is furnished with a discharge check-valve of the disc type, this valve and its seat must also be wiped dry as otherwise a small amount of water between the valve and its seat may freeze and effectively shut off the discharge from the pump.
“Some fire pumpers have priming devices located so that the line from the pump to the primer cannot be drained following priming operation, until pump operation ceases. In such a case, this line could freeze during pump operation when the atmosphere temperature was below freezing, and might remain frozen and prevent priming at a subsequent alarm. It goes without saying that this is an important point, and it might be easily overlooked by a volunteer fire department. We would suggest that any department operating any pumper in the winter time make sure that the priming device will function after the truck is returned to the fire station, and that the line from the pump to the primer will not remain full of water during the next run.
“Means of keeping portions of the pump warm utilizing engine exhaust gases or circulation of engine coolant will be of assistance in preventing pump freeze-up; however, they in themselves are not enough to guarantee functioning of the pump.
“As a matter of interest, we performed the following experiment in an experimental truck on a January day, when the temperature was approximately 20½ below zero. The pump was first filled with water, then drained. The truck was then driven several miles at speeds up to 40 MPH and, when it arrived back at the factory, we were able to engage the pump clutch and turn the pump over without difficulty; also, the pump was primed satisfactorily.
“We did not pump water from draft, as a satisfactory supply of water was not available; however, we do not believe that we would have had any difficulty in doing so. We did experience some difficulty in removing the suction cap, because of water frozen at the suction gasket. Incidentally, our pump includes provisions for circulating engine coolant around the pump suction eye.
“We are of the opinion that water would not freeze immediately upon contact with the pump during the priming operation under any operating temperatures which might be met in the continental United States, especially if the pump impeller was rotated during the priming operation in order to churn the water as it entered the pump chamber.”
Another manufacturer writes that they have recognized this trouble for some time and several years ago took the necessary steps to overcome the objection, by building what is termed a “truly frost-proof pump.” In this unit water at engine temperature constantly circulates from the engine cooling system through the cored suction head of the pump. It is a “closed system” with no possible loss of radiator water or antifreeze, according to this manufacturer.
Still another company has this to say: “With the pump and lines thoroughly drained and no time lost in starting the pump delivery, there should be no such difficulty. Our maintenance manual particularly calls attention to the necessity of always keeping the pump and lines drained. All installations that we make properly locate the drain valve so that piping, in addition to the pump, will drain completely.
“There is the possibility, of course, that in local installations many have been made with the pitch of the suction line not properly planned; consequently, the lines not draining properly may freeze under severe weather conditions. Our latest type front-mount incorporates a feature whereby the engine coolant is by-passed through an adapter casting which provides sufficient heating to preclude the possibility of freezing under such conditions. We can provide a heating system for delivering the hot exhaust gas through a jacket around the priming chamber as a protective against freezing.”
Poorly Heated Fire Stations
One point that has come to the attention of the Editors is the effect of poorly heated fire stations upon front-mount pump’s.
In many of the smaller, unattended fire houses, particularly in the intemperate weather areas, the piece of apparatus is housed with its front-end pump close to the station door. Lack of insulation against the weather frequently cools the unit so that it is difficult to start the pump, even in the fire house. In other words, the pump is chilled before the apparatus ever leaves the station and freezing en route to the fire is made just that much easier.