Short Cuts and Gadgets
EXHAUST PIPE PROTECTION FOR FOREST AND FIELD FIRE FIGHTERS
Under given conditions, exhaust pipes of trucks may reach surface temperatures of 1,200 deg. F., which is sufficiently high to ignite grass or similar vegetation which might come in contact with the pipe. A simple and quite popular method for eliminating this possibility of fire is to change the standard exhaust line so that it enters a vertical pipe or riser mounted on the rear of the cab, the top of the exhaust being slightly higher than the roof of the cab. A length of 8 to 10 in. irrigation or similar sheet metal pipe is slipped over the vertical section of the exhaust line to permit air circulation between the exhaust pipe and shielding tube. The shielding pipe seldom reaches temperatures which are uncomfortably hot to the hand.
This type of termination of the exhaust is best from the standpoint of safety since ejected carbon must travel the maximum distance through air, partially cooling it before reaching ground. An exhaust line placed in the vertical position is not a substitute for a spark arrester but it does keep the line clear of contact with vegetation and the possibilities of fires through contact. The tractor spark arrester is an ideal unit for vertical mounting on all types and sizes of automobile engines.
(From Forester Fire Protection News, July, 1944)
PRACTICAL TRAINING AID
In the July, 1954, issue of FIRE ENGINEERING there was published an interesting article by Charles A. Key, Specialist in Property Protection, Tennessee Valley Authority, entitled “Low Cost Training and Rating in TVA Fire Suppression.”
The author dwelt at length on the wisdom of practical field training and showed how at TVA this could be accomplished without having to purchase or build elaborate, costly training facilities such as deep pits and tanks.
In his article, Mr. Key referred to a substitute for the old style field pits, devised by a fire fighter at the Kingston Steam Plant.
This consisted of 55-gallon oil drums split lengthwise, after which the halves could be laid end to end in a rectangle, partially filled with water and an inch or two of oil or gasoline, which then could be ignited to make interesting training fires.
The same half-drums could be made into double or triple-deck affairs by adding angle-iron legs.
In the article we failed to show pictures of these improvised gadgets—an omission which is now rectified. Herewith the picture of the units “at work.” And further thanks to Brother Key.
RELIEF VALVE “RELIEVES” RELAY
Too often in our relay operations we have had the unpleasant experience of hose bursting at the most inopportune times. In by far the majority of cases this was due not to hose defects nor normal operating pressure exceeding a safe figure (hose annually tested at 200 lbs.) but due to intermittent pressure surges in the lines when nozzles were shut off. This was particularly true where more than two pumpers were used in the layout.
As is the case of many other departments, we have for some years past leaned towards the installation of relief valves for controlling devices, even on centrifugal pumpers. Although they seem to have stood the test of time better than governors and are a greater asset in most drafting and hydrant operations, relief valves have certain inherent limitations in relaying operations. They, of course, do not affect motor speed but merely keep the pumper from exceeding a set pressure (when lines are shut down) by bypassing water from the discharge side back to the suction side of the fire pumps, thereby keeping the load on the motor and preventing its speedup with resultant increase in pump speed and pump pressure. This bypassing action has the same effect as if the discharge were constant. If nozzles could be kept open continuously or somehow water constantly discharged from the lead pumper, we would not have this problem, but such is not always practicable nor feasible.
It is characteristic of centrifugal pumpers to take full advantage of the pressure at which water is delivered to them and for the discharge pressures to be increased accordingly. Unless properly controlled, such build-up is inevitable when water ceases to flow if any single unit in the layout is equipped with a relief valve or governor which is: (a) not in operative condition, (b) not properly set, (c) slow in functioning.
It has been found that many relief valves have their settings affected by variations in intake pressure. Also there is always a momentary surge of pressure until the spring tension in the pilot valve is overcome and water under pressure pockets behind the head of the piston of the relief valve proper.
Generally speaking, the relaying of water is a devious and complicated operation with pumpers frequently out of sight and sometimes out of touch with one another. There is frequent “jockeying” with throttles and relief valve settings with quite a time interval before things are properly balanced throughout the relay set-up.
Because of the foregoing operating difficulties in relay work, our Supervising Engineer’s Staff recently devised a novel method by which water could be kept flowing in a relay stretch, by converting a Ross Relief-Valve from an older pumper into an “External Dump Valve,” set to operate when nozzles are shut off and pressure on the intake side builds up as a consequence thereof.
As shown, the head of the relief-valve proper is attached to a flange with a 3″ intake and a 2″ discharge pipe, both of which are fitted with adapters threaded for 2 1/2″ hose. The discharge pipe, however, instead of returning the water to the suction side of the pumper, dumps it to the ground near the pumper. If this is undesirable, a 50-ft. length of 2 1/2″ hose can be attached to carry it to a distant point. The threaded feed pipe is connected to an unused suction inlet of the lead pumper by means of a 4 1/2″ by 2 1/2″ double female fitting. When first installed and until pressures are balanced throughout the relay, the valve is set at a figure high enough to prevent its operation. Then, when water is flowing from the nozzles, the setting is gradually lowered until the intake pressure overcomes the setting of the valve and water is dumped to the ground. The setting is then raised 20-30 lbs. above this figure and locked by means of a key. Water then ceases to dump to the ground until pressure on the suction side rises as will occur when nozzles are shut off. When nozzles are again opened, the intake pressure drops and valve closes. With this device the relief-valves or governors can be cut out on all but the lead pumper in the relay. The valve could also be used on a dischargegate employing a 2 1/2″ by 2 1/2″ double female coupling but not only would this give us one less outlet for our lines but the valve itself is more sensitive at lower pressures such as we have on the suction side.
A practical demonstration of the efficiency of the valve was recently given before top officials of the department at New York’s Idlewild Airport, in a sixpumper relay laying over a mile of hose. As a result, one of these valves has been made by the N.Y.F.D. Shops for Idlewild and another for La Guardia Airports, at both of which relaying is a frequent operation. A third valve is carried by the staff of the Supervising Engineer, which covers all major alarms and unusual operations in this city—particularly the relaying of water.
(Submitted by Lt. Thomas Ryan, Asst. Supervising Engr., N.Y.F.D.)
FOR BALKY STANDPIPE CONNECTIONS
Often engine companies connecting hose lines to standpipe or sprinkler Siamese connections are confronted with the problem of swivels on these connections that won’t turn.
This is due to the fact they they are constantly exposed to the elements and some building superintendents don’t give them the attention they deserve.
This can be overcome in either of two ways:
- Stretch the hose so that the female end is taken to the Siamese. Place a double male into the defective swivel, and connect the female butt of the hose to the other side of the double male. A double female is then used on the pumper outlet.
- Stretch the male end of the hose line to the Siamese. Connect the double male to the defective swivel; connect a double female to the double male and then connect the male butt of the hose to the double female.
WILLIAM E. CLARK, Captain Eng. 243, NYFD