Water meters, or measurers, are constructed upon two general
principles: 1, an arrangement called an “_inferential meter_” made
to divert a certain proportion of the water passing in the main pipe
and by measuring accurately the small stream diverted, _to infer_, or
estimate the larger quantity; 2, _the positive meter_; rotary piston
meters are of the latter class.
[Illustration: FIG. 603.]
[Illustration:
LONGITUDINAL SECTION.
TRANSVERSE SECTION.
FIGS. 604, 605.]
The distinctive difference between the two is, that the positive
meter measures water by means of a chamber alternately filled and
emptied. In most of these the flow of water ceases when, by any
derangement, the motion of the piston is interrupted. But neither the
motion nor the stoppage of the inferential meter has any effect upon
the water delivery, so that at times a large amount of water may
pass unrecorded. Another important mechanical difference is that the
motion of a piston meter should be slow, while that of the inferential
wheel is, and must be, rapid; this has much to do with their relative
durability.
Fig. 603 is a perspective view of the _Worthington water meter_, the
details of which are shown in the Figs. 604 and 605, the recording or
“dial” mechanism is also shown in Fig. 606.
The internal arrangement of the meter is shown in longitudinal section,
Fig. 604, and the transverse section, Fig. 605, on the opposite page.
[Illustration: FIG. 606.]
The plungers, AA, are closely fitted into parallel rings. The water
passes through the inlet and port I, and is admitted under pressure
into chamber, D, at one end of each plunger alternately, while the
connection is made between the chamber at the other end of the outlet.
Thus, the plunger in moving displaces its volume, discharging it
through its outlet. The arrangement is such that the stroke of the two
plungers alternates, the valve actuated by one admitting pressure to
the other. The plungers are brought to rest at the end of the stroke by
the rubber buffers, EE. One plunger imparts a reciprocating motion to
the lever, F, which operates the counter movement through the spindle
and ratchet gear as shown. Thus, it will be seen that the counter is
arranged to move the dial pointers once for every four strokes or
displacements, and that water cannot pass through the meter without
registration, for, in order to pass through, it must be displaced by
the plungers, and, therefore, recorded by the movement of the lever and
counter mechanism; nor can there be an over-registration, because the
plungers cannot move without displacing the fluid.
_To read the dial._ The counter usually registers in cubic feet, one
cubic foot being 7.48 gallons U. S. standard. When desired for special
services, counters are furnished reading in U. S. gallons, Imperial
gallons, and Hectolitres. This counter is read in the same way as the
registers of gas meters.
The following example and directions may be of use to those
unacquainted with this method:
[Illustration: FIG. 607.]
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.
[Illustration: 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
2-1/2 inches, inclusive.
TOOLS
VALVES
AND PIPING
[Illustration: FIG 609.—See page 348.]