CONSTRUCTION AND OPERATION OF TWO TYPES OF HYDRANTS
Concluding Installment of a Series of Articles Started in the February Issue— Outstanding Features of Design Explained
ON many occasions, particularly in the outlying sections or rural areas, the fact has been demonstrated that efficient and expensive fire apparatus is useless unless supported by an adequate water supply. As it is not always practical or feasible for pumpers to draft water from ponds or cisterns, means are provided for obtaining a supply of water from the city distribution system. Hydrants are installed to provide Fire Departments with a physical means of connecting their suction lines or the hose lines to a dependable water supply.
There are many types of hydrants in common use. Two are described in this concluding installment.
The O’Brien hydrant (A. P. Smith Manufacturing Company, East Orange, N. J.) has a large diameter standpipe to cut down the frictional resistance. The manufacturers claim that a standard type two-nozzle hydrant was tested under a delivery of 250 gallons per nozzle, and the friction loss was but 1.7 pounds.
The drip valve of the hydrant is so correlated with the main stem that the moment the main valve is closed, the drip valve opens. The action of the drip valve is positive.
A good size packing box is provided. Where the spindle passes through the packing box, it is bushed with bronze so that it will give unfailing service.
When the hydrant is once set, the standpipe section need not be disturbed in order to make any repairs that might be necessary to the inner parts. All that is required is to remove the bonnet and top and to insert a wrench designed for that purpose. Every inner part, including the valve seat, can be removed in one operation. When the necessary repairs have been made, the parts can be replaced with the same wrench.
The spindle nut mechanism of the Waterous hydrant (Waterous Fire Engine Works, St. Paul, Minn.) is not exposed to water due to the locating of the packing gland (4).
The drain is in reality a piston valve or plunger that floats between a bronze cross bar (23) on valve rod and upper valve washer. When the hydrant is opened, the drain plunger (19) moves downward and closes the drain opening. When the hydrant is closed, the plunger moves upward and uncovers the drain. Downward movement of the plunger is caused by the cross bar, and the upward movement by the upper valve washer. A bail at top of plunger encircles one arm of the cross bar and prevents loss of the plunger when the hydrant is disassembled.
To remove the valve seat and drain, the bolts (17) are unscrewed, and the jamb nut (2) and spindle nut (1) are removed. The top (3) is now taken off. This exposes the valve rod (21) and the interior of the hydrant. The valve seat wrench is now inserted over the valve rod and lowered into the standpipe until the wrench reaches the valve seat (18). With the aid of a bar in the upper end of the wrench, the seat can be unscrewed and the hydrant rod removed with its seat, valve and drain mechanism. When these parts are taken out, renewals or repairs can be made without difficulty.
To replace, the valve, valve seat and drain are all assembled on the hydrant spindle and lowered into the standpipe until the bottom is reached.
The valve seat wrench is used to tighten the seat securely in place. After the seat is in place, the top is placed in position, the bolts tightened and the spindle nut and jamb nut screwed into their places. The hydrant is now ready for use.
The hydrant valve is designed to open and close slowly to avoid water hammer. The valve is made of leather and the manufacturers claim that the leather is protected against rapid deterioration.