A Simple Explanation of the Construction and Operation of Fire Hydrants
This is the third section of an article which describes some of the more common makes of fire hydrants.
FIRE engines had arrived, had performed the required tasks, and had departed. Near hydrants from which water was obtained were tell-tale pools of water. The passers-by did not deem them worthy of a second glance. The miniature lakes, to the trainedfire-fighter, represented a complete story.
They revealed that fire companies upon arrival at a fire scene, had no trouble in finding a plentiful supply of water, for hydrants near the property were in good operating condition.
Hydrants are always assumed to be ready for service, but very often they are not. Either because of defects in mechanical construction or design, or through lack of proper installation or maintenance, the mechanism fails to function properly. During the cold season, improper drainage of water which remains in the barrel, results in an ice jammed valve.
Such conditions can be corrected through a proper understanding of the construction and operation of fire hydrants so that hydrants that are not properly installed will become a rarity. One is less apt to mistreat a mechanism if one thoroughly understands its construction.
In the previous issue, mention was made of the proper installation of hydrants, the use of the drip valve, and anti-freezing compounds. Three of the many hydrants in common use were described. This article continues with the description of other hydrants so that the fire department officer will be in a better position to advise city officials, if called upon to do so.
The Darling Hydrant (Darling Valve & Mfg. Co., Williamsport, Pa.), has been designed so that inspections and repairs can be made with ease. The manufacturers claim that one man on an inspection tour can quickly and easily take all the working parts of a Darling hydrant out through the top of the barrel so that he can see the mechanism and know whether there is immediate need of repair.
The inspection is made by removing six bolts. The thrust plate and packing plate are released by unscrewing the operating nut on the valve rod. A few turns with a seat wrench permits the removal of all internal parts, including main valve seat and drip valve seats.
When the operating nut is turned to permit the flow of water into the hydrant, the hydrant valve is lowered and at the same time the drain openings are closed by the drain valve.
Extension sections are provided from six to sixty inches long so that the hydrant can be raised to the required level, due to change in street grade, without using new internal parts and without having to disconnect the hydrant from the base line.
The Corey hydrant (Rensselaer Valve Company, Troy, N. Y.) is operated on the knuckle joint principle. In opening the hydrant it is only necessary to give the spindle about four turns. However, the operator should continue turning the spindle until the gate is open so that there will be no obstruction to the flow of water. In closing, the first turn of the spindle moves the valve nearly two inches. After this the speed of closing decreases and the amount of power applied increases. The last turn of the spindle only moves the valve about one-eighth inch.
The drip valve consists of a holder, a cup shaped molded piece of specially prepared rubber, a washer and a bolt. The holder is threaded and moves up and down on the spindle as the hydrant is operated. When the hydrant is closed, the rubber is in the upper part of the barrel and moves to the lower part of the barrel when the hydrant is opened.
About one-half of a turn of the spindle is required to take up the elasticity of the rubber valve before the water will flow into the hydrant.
The manufacturers claim that this hydrant delivers a solid stream of water the full size of the valve opening as the operating rod is not in center of the barrel. A deflector at the top of the hydrant turns the water, as it rises in the standpipe, out into the hose nozzle outlets.
Interior working parts can be removed by taking out the hydrant head bolts.
When closed, the gate is held in position by the half-ball ends of the arms running in grooves in the back of the hydrant. These arms form four solid braces between the back of the hydrant and the gates.
Kennedy “Safe-fop” Hydrant
A special breakable section has been incorporated in the design of the Kennedy “Safetop” hydrant (The Kennedy Valve Manufacturing Company, Elmira, N. Y.) as a protection against possible damage by impact from trucks and other vehicles.
Near the ground line of the hydrant is the safety section which under normal conditions serves as a part of a one-piece standpipe and stem. Should the hydrant be damaged as the result of a collision, it is only necessary to replace the breaking ring and a stem coupling.
The standpipe and stem are in two sections abutting each other slightly above the ground line. The two standpipe sections threaded at their abutting ends and a correspondingly threaded breaking ring holds the two sections in alignment. The two stem sections are held in proper position by a coupling which is secured to each section by a large pin. During normal operation of the hydrant, this coupling acts as part of the stem. In case of accident, both the ring and the stem will break at the groove provided.
The hydrant nozzles can be made to face in any desired direction by backing the breaking ring in a quarter or half turn, rotating the nozzle head to the new position, and then tightening the breaking ring until it becomes locked.
In case of a break, the water pressure in the main holds the valve firmly against its seat.
The manufacturers claim that a hydrant which has been damaged by a truck can be replaced in eleven minutes at a nominal cost.