Questions and Answers
NOTE—Readers are invited to send in questions, which will be answered in the order received. Names are omitted from questions unless otherwise specified
Discovering Fire When Responding
To the Editor:
The writer would like data on the following questions, on making a run to a fire and on the way discovering another fire; also as to the duties of the man in charge of the company in handling the situation.
- What would be the proper thing to do in case a box alarm came in from the outskirts of town, and in responding to the alarm another fire was discovered in the outskirts?
- If the alarm came in for the same fire as above, and a fire should be discovered in the business district, what should be done?
- A centrifugal pump would not take suction on account of a cracked discharge valve. Pump was primed with the booster tank of water to seal the crack long enough to create a vacuum. There has been a lot of comment on this incident, but we would like to have your opinion on the matter. Was the driver right or wrong?
Answer: 1. The action of the company officer would depend entirely on conditions encountered. If there were a severe life hazard at the fire discovered enroute to the box alarm, then the officer in command of the company should immediately stop at the fire, and put his company in operation. At the same time he should direct one of his men to communicate with headquarters and notify them what action had been taken so that the original fire could be covered, by another assignment.
On the other hand, if the second fire discovered were either a minor one, or represented no life hazard, then the proper procedure would be to drop one man off at the second fire so discovered and the company proceed on to the box from which the alarm was transmitted. The man so left would send in an alarm from the nearest box and take whatever action he could alone until the arrival of apparatus.
Answer 2. The same would apply in the situation where a fire was discovered in a business building while responding to an alarm as in quesiton 1.
It is merely a question of judgment—which action would be deemed the better.
Answer 3. The situation described in your question is not clear. A broken discharge valve on a pump should not interfere with the primer taking suction.
This much may be said, however, if the use of the water in the tank served to prime the pump, and it operated satisfactorily thereafter, the operator of the machine deserves credit for using his head.
Drafting and Siphoning
To the Editor:
Will you be kind enough to answer the following question: What is the difference, if any, between drafting and siphoning, in regard to the height water can be lifted?
In siphoning water are we governed by atmospheric pressure as in drafting?
Would it be possible to siphon water 100 ft. or more in a layout such as shown in the diagram herewith?
Answer: There is a slight difference between drafting and siphoning of water in regards to the height the water can be lifted. It can be lifted a little higher by siphoning than by drafting due to the fact that in siphoning a complete vacuum is more nearly approached.
With pumping, there is always a possibility of leakage of air in the pump from the discharge side to the intake side, with the result that 28 feet is about the maximum water can be lifted by an ordinary fire engine.
However, we are governed by atmospheric pressure in siphoning as well as in drafting.
All we do in either case is to create a vacuum within the suction line, and the atmospheric outside pressure forces the water up into the suction line to such a point as to balance the vacuum. In other words, when we exhaust the air from a line or create “suction” therein, we have a pressure much less than atmospheric pressure. Having less pressure within the suction line than we have on the outside, these pressures tend to equalize themselves by the atmospheric pressure forcing water up into the suction line.
No, it would not be possible to siphon water 100 feet or more by such an arrangement as you show in your diagram. Even if there were no gases or vapors present in the water which would tend to reduce the vacuum, it would not be possible to lift water more than 33 feet, at approximately sea level.
Relaying at a Fire
To the Editor:
The accompanying sketch is a layout test that resulted from a discussion in the method of re-laying water at a fire. An answer from you would be greatly appreciated.
A fire occurs in a shed 15×30 feet, one story frame (no exposure), occupied by a carpenter as shop and storeroom. It is located 2,750 feet away from a hydrant fitted for 2 1/2“ hose.
Two engine companies respond with pumping engines and hose wagons equipped with 69 lengths of 2 1/2″ hose.
Fireman A. Claims:
- A 1 1/8 inch nozzle, 54 lbs. nozzle pressure, with 275 G.P.M. will be sufficient to handle the fire.
- That the layout in the sketch is proper as four lengths of hose should be held in reserve so as to replace any length that a coupling might blow off of.
- That the fire engine should be placed 8 lengths away from the hydrant so as to make use of the 80 lbs. hydrant pressure, thereby reducing excessive pressure on the discharge line to second engine.
Fireman B. claims:
- That a Y-connection should be used near the fire with two lead lines with 1″ nozzles.
- That all the hose should be used and none held in reserve.
- That the first engine in a relay should be connected to the hydrant with the suction connection 4 1/2“ size regardless of hydrant pressure.
Answer: In answer to the first question any answer given would be nothing more than a conjecture. A single good stream such as you would get from nozzle at 54 lbs.
pressure might be far more effective than two 1″ streams from lines fed by Y-connection. On the other hand, the two separate nozzles might be better in the event that fire was burning in partitions where it would be necessary to cover more than one point at once.
With reference to the second answer, the practice suggested by fireman A would probably be the better of the two, because in layouts of this type, where excessive pressures are apt to be encountered, there is possibility of hose lines bursting. Very often the lines used in suburban sections are not capable of withstanding high pressures, due to the fact that they are never subjected to such pressures and may not show any inherent weakness due to age or abuse, until high pressures are encountered. For this reason burst hose is very likely in such a layout, in the suburban districts.
In answering the third problem, A also gives the better practice. There is no reason why the full benefit of 80 pounds at the hydrant should not be secured by making parallel layouts as is shown. Were the engine placed at the hydrant, then the pressure at the discharge side would be so much greater, with the result that the hose on the discharge side near the pumper would be under greater strain.