THE HYDRAULIC ACCUMULATOR.
This useful and indispensable apparatus was designed by Sir William Armstrong. Its use was to secure a uniform pressure of water in a reservoir by weight so that however much or little of this water was used the pressure would remain constant.
ELEVATION.
Fig. 147.
In the first accumulator which is still in use the ram was attached to the foundation while the cylinder rose and fell as the pressure was utilized. The weights were annular in shape and were hung upon the outside of cylinder. In the modern types of accumulators the cylinder is stationary and the ram supporting the weights is made to rise and fall.
By means of a hydraulic accumulator a uniform pressure can be established and maintained on all parts of a hydraulic main or system.
PLAN AT BOTTOM.
Fig. 148.
The volume of water which is used intermittently for the purpose of operating presses—draw-benches for brass and copper tubing and the like is replaced by a pump or pumps which are started and stopped automatically by a connection between the accumulator and the throttle or belt shifter of the pump. The accumulator is used for a double purpose of maintaining a constant pressure and to store up any surplus force of the pumps. The friction loss in the transmission of power by water through mains is very small, as for example: It has been found that water under a pressure of 700 lbs. per square inch may be transmitted through well proportioned mains, one mile with a loss of only two per cent.
The useful work stored in an accumulator may be calculated by the following rule: Multiply the area of ram in square inches by the length of the stroke in inches by the pressure m pounds per square inch divided by 33,000 lbs. the equivalent of one H. P.
This represents the work done by one full stroke of the accumulator ram in descending from its highest position to its lowest.
Example. Required the work done by one stroke of a ram twelve inches in diameter, and a stroke of twenty-two feet, under a pressure of 750 lbs. to the square inch. Area of 12 ram = 113·097 square inches. No. of ins. in 22 ft. = 264. Then
113·097 × 264 × 750
————————– = 678·582 H.P.
33,000
Mr. Tweddel designed the accumulator shown in Figs. 147 and 148 to furnish the varying demand for water where only one appliance of this kind is used in connection with a hydraulic system of shop tools more especially where these tools are numerous.
The ram or spindle A is fixed top and bottom and acts as a guide for the cylinder B which slides up and down upon it.
VERTICAL SECTION.
Fig. 149.
This cylinder is loaded with weights marked to indicate the pressure which the accumulator will balance with those weights in use. The water is pumped into the bottom through the pipe C, and fills the annular space around the spindle. The entire weight of cylinder is raised by the pressure of water acting only on the area of the end of brass sleeve D D, which is only 1⁄2 inch thick all around the center spindle, and extends down through the bottom packing in cylinder, as shown in sectional view. Fig. 149.
A compact arrangement is thus gained and any reasonable, required cubical capacity may be reached by lengthening the stroke.
The accumulator is supplied by two pumps having plungers 13⁄8″ diam. by 31⁄2″ stroke, speed 100 to 120 rev. per minute.
When the loaded cylinder B reaches the top of its stroke, by means of a small chain it closes the suction cock E, which shuts off the water supply of the pumps.
To put in a new bottom packing, the cylinder is let down to rest on the wooden blocks G, and the spindle is lifted out of its tapered seat at the bottom by a tackle hooked into the eye-bolt at the top. To renew the top leather the bracket holding the top end of spindle A, has to be removed.
This accumulator (having only a small area) falls quickly when the water is withdrawn, thus producing a combined blow and squeeze, which is of great advantage in hydraulic riveting.
The Hydraulic Intensifier is a cylinder having two diameters, in principle very like the tandem compound engine. It is used for increasing the pressure of water in hydraulic mains, pipes, or machines, using only the energy of the pressure water to effect the change. But for this distinction a steam pump would be an intensifier. An intensifier worked the reverse way is a “diminisher” as a hydraulic pump usually is, giving a reduced pressure.
The intensifier is in some respects analogous to the electric transformer.
The intensifier as used in connection with hydraulic apparatus was patented in the year 1869 by Mr. Aschroft, but the principle upon which it works is very much older. Intensifiers are made both single and double acting.
PERCENTAGE OF THE TOTAL AMOUNT OF WATER TAKEN FROM THE RESERVOIR.
| Height of fall in feet. | Elevation of discharge above delivery valve of ram in feet. | ||||
|---|---|---|---|---|---|
| 15 | 18 | 21 | 24 | 27 | |
| Percentage. | |||||
| 2 | ·0724 | ·0583 | ·0402 | ·0307 | ·0255 |
| 3 | ·1327 | ·1020 | ·0807 | ·0651 | ·0532 |
| 4 | ·1960 | ·1535 | ·1234 | ·1020 | ·0854 |
| 5 | ·2614 | ·2068 | ·1686 | ·1404 | ·1189 |
| 6 | ·3282 | ·2614 | ·2146 | ·1800 | ·1535 |
| 7 | ·3960 | ·3170 | ·2614 | ·2203 | ·1885 |
| 8 | ·4647 | ·3733 | ·3090 | ·2614 | ·2248 |
| 9 | ·5341 | ·4303 | ·3572 | ·3030 | ·2614 |
| 10 | ·6040 | ·4877 | ·4058 | ·3450 | ·2984 |
| 11 | ·6745 | ·5459 | ·4549 | ·3874 | ·3357 |
| 12 | ·7453 | ·6040 | ·5043 | ·4302 | ·3733 |
| 13 | ·8166 | ·6627 | ·5540 | ·4732 | ·4112 |
| 14 | ·8881 | ·7217 | ·6040 | ·5166 | ·4494 |
| 15 | ·9600 | ·7809 | ·6543 | ·5601 | ·4877 |
| 16 | — | ·8404 | ·7048 | ·6040 | ·5263 |
| 17 | — | ·9001 | ·7555 | ·6480 | ·5650 |
| 18 | — | ·9600 | ·8064 | ·6921 | ·6040 |
| 19 | — | — | ·8574 | ·7364 | ·6430 |
| 20 | — | — | ·9086 | ·7800 | ·6823 |
| 21 | — | — | ·9600 | ·8254 | ·7217 |
| 22 | — | — | — | ·8701 | ·7612 |
| 23 | — | — | — | ·9150 | ·8007 |
| 24 | — | — | — | ·9600 | ·8404 |
| Height of fall in feet. | Elevation of discharge above delivery valve of ram in feet. | ||||
| 30 | 35 | 40 | 45 | 50 | |
| Percentage. | |||||
| 2 | ·0181 | ·0112 | ·0063 | ·0027 | — |
| 3 | ·0441 | ·0326 | ·0243 | ·0181 | ·0132 |
| 4 | ·0724 | ·0560 | ·0441 | ·0348 | ·0281 |
| 5 | ·1020 | ·0807 | ·0652 | ·0533 | ·0441 |
| 6 | ·1327 | ·1063 | ·0870 | ·0724 | ·0608 |
| 7 | ·1640 | ·1327 | ·1096 | ·0920 | ·0782 |
| 8 | ·1960 | ·1595 | ·1327 | ·1121 | ·0960 |
| 9 | ·2285 | ·1868 | ·1561 | ·1327 | ·1142 |
| 10 | ·2614 | ·2145 | ·1800 | ·1535 | ·1327 |
| 11 | ·2947 | ·2425 | ·2041 | ·1746 | ·1514 |
| 12 | ·3282 | ·2708 | ·2285 | ·1960 | ·1704 |
| 13 | ·3620 | ·2994 | ·2532 | ·2177 | ·1896 |
| 14 | ·3960 | ·3282 | ·2780 | ·2395 | ·2090 |
| 15 | ·4303 | ·3572 | ·3030 | ·2614 | ·2285 |
| 16 | ·4647 | ·3863 | ·3282 | ·2835 | ·2482 |
| 17 | ·4993 | ·4157 | ·3535 | ·3058 | ·2680 |
| 18 | ·5341 | ·4451 | ·3790 | ·3232 | ·2380 |
| 19 | ·5690 | ·4746 | ·4046 | ·3507 | ·3081 |
| 20 | ·6040 | ·5042 | ·4303 | ·3733 | ·3282 |
| 21 | ·6392 | ·5340 | ·4561 | ·3960 | ·3486 |
| 22 | ·6745 | ·5640 | ·4820 | ·4188 | ·3688 |
| 23 | ·7098 | ·5940 | ·5080 | ·4417 | ·3892 |
| 24 | ·7433 | ·6241 | ·5341 | ·4657 | ·4097 |
| Height of fall in feet. | Elevation of discharge above delivery valve of ram in feet. | ||||
| 60 | 70 | 80 | 90 | 100 | |
| Percentage. | |||||
| 2 | — | — | — | — | — |
| 3 | ·0063 | ·0017 | — | — | — |
| 4 | ·0180 | ·0112 | ·0063 | ·0027 | — |
| 5 | ·0307 | ·0217 | ·0150 | ·0099 | ·0063 |
| 6 | ·0441 | ·0325 | ·0243 | ·0180 | ·0132 |
| 7 | ·0580 | ·0441 | ·0340 | ·0264 | ·0205 |
| 8 | ·0724 | ·0560 | ·0441 | ·0351 | ·0281 |
| 9 | ·0870 | ·0682 | ·0545 | ·0441 | ·0360 |
| 10 | ·1020 | ·0807 | ·0651 | ·0533 | ·0441 |
| 11 | ·1172 | ·0934 | ·0760 | ·0627 | ·0524 |
| 12 | ·1327 | ·1063 | ·0870 | ·0723 | ·0608 |
| 13 | ·1483 | ·1194 | ·0983 | ·0821 | ·0694 |
| 14 | ·1640 | ·1327 | ·1096 | ·0920 | ·0782 |
| 15 | ·1800 | ·1460 | ·1211 | ·1020 | ·0870 |
| 16 | ·1960 | ·1595 | ·1327 | ·1121 | ·0960 |
| 17 | ·2123 | ·1731 | ·1444 | ·1223 | ·1050 |
| 18 | ·2286 | ·1868 | ·1561 | ·1327 | ·1142 |
| 19 | ·2449 | ·2006 | ·1680 | ·1430 | ·1262 |
| 20 | ·2614 | ·2145 | ·1800 | ·1535 | ·1327 |
| 21 | ·2780 | ·2286 | ·1920 | ·1640 | ·1420 |
| 22 | ·2947 | ·2425 | ·2041 | ·1746 | ·1514 |
| 23 | ·3114 | ·2567 | ·2163 | ·1853 | ·1609 |
| 24 | ·3282 | ·2708 | ·2185 | ·1960 | ·1704 |
For explanation of these tables [see page 177].