If the pointer is between two figures, the smaller one must invariably be taken; suppose the pointers of the dial stand, as shown in Fig. [606]; starting at the dial marked 10 cubic feet, we get the figure 4; from the next marked 100 cubic feet, the figure 7; from the next marked 1,000 cubic feet, the figure 8, and from the next marked 10,000 cubic feet, the figure 6; the reading is 6,874 cubic feet. The pointer on the 100,000 cubic foot dial being between the 0 and the 1 indicates nothing. By subtracting the first reading taken from that taken at the next observation, the consumption of water for the intermediate time is obtained.
A steam trap is an apparatus to remove the water of condensation from steam pipes for heater coils and radiators without permitting steam to escape; the steam trap is also used to remove the water of condensation or entrained water caught in steam separators, located near the steam engine in the connecting pipes between the engine and boilers.
The problem of saving the water of condensation without allowing the escape of steam is a difficult one, in view of the early wear of the valves and the valve seats.
Fig. [607] represents the Anderson improved steam trap. This trap shows at all times what it is doing by the position of the water in the glass gauge attached to the side of the trap and in front. The water of condensation enters at the upper right-hand side, A, Fig. [608], where all scale and dirt from the pipes are caught in the settling chamber which contains a strainer. This strainer can be lifted out with its contents of dirt and scale and replaced in a few moments by unscrewing the plugs, shown in Fig. [607] just above the inlet. The discharge is connected at the lower left-hand side. The bonnet which contains the valve float and lever can be removed without breaking any pipe joints, or the valve and seat may be removed by simply unscrewing the cap, H, at the lower left-hand side without disturbing the bonnet at all. It will be understood that this trap does not dump, but the discharge of water is regulated by a ball float and valve, hence there are really but two working parts to this trap, viz.: the ball float and valve. Water is permitted to pass this trap as fast as it comes along, and no considerable quantity ever accumulates within this trap at any one time.
Fig. 608.
The sectional view, Fig. [608], gives a fair idea of the interior of this trap, being a longitudinal section on center line. The by-pass valve, C, so-called, is not a valve, but is simply a threaded stem and is used to hold up the float in emptying the trap. To blow out the trap this by-pass is screwed in as far as it will go without forcing, same motion as in closing a globe valve. When the water has been discharged, this by-pass is unscrewed to its former position, which permits the float to drop, closing the valve when the reservoir fills with water, to its normal position.
With three inches of water in the glass the valve is closed and sealed so that no steam can escape. The dotted line represents the water level. The sediment chamber, E, prevents dirt and scales in the pipes from getting into the valve.
The ball float is made of seamless copper with heavy bands to prevent the ball from collapsing under high pressure. These traps work on all pressures from 150 pounds pressure down, and are also made for higher pressures in special cases—will work against back pressure and with exhaust steam alone—are made in seven sizes, i.e., from 1⁄2 inch to 21⁄2 inches, inclusive.