Pump

The Hydraulic Ram.

This is an apparatus devised to utilize the energy of a water supply at a low head, to pump up part of this water to a height greater than that of the supply head. It consists of an inclined supply pipe leading straight into a valve box which is fitted with a waste valve opening inwards, and a delivery valve opening outwards. This valve discharges the water into an air vessel from which it is delivered in a steady stream to the discharge pipe.

The action of the ram is as follows: The waste valve being opened, water is free to escape, and flow is set up along the sup ply pipe. The velocity of flow increases under the influence of the supply head until the dynamic pressure on the under side of the valve becomes sufficiently great to overcome its weight. The valve now closes rapidly and the sudden check to the momentum of the supply column causes a rapid increase of pressure in the valve-box until this pressure becomes sufficiently great to open the delivery valve. Water then escapes through this valve into the air vessel, compresses the air, and flows away along the rising main. As soon as the momentum of the supply column is

destroyed the delivery valve closes, the water below the valve partaking of the backward motion thus instituted. This motion, once set up, can only be checked by a reduction of pressure in the valve-box below that corresponding to the statical head of the supply, and consequently the pressure in the valve-box is re duced rapidly until at some instant the waste valve reopens, and the whole cycle of operations is repeated. The efficiency of the hydraulic ram falls off as the ratio of the delivery head to the supply head is increased. When this ratio does not exceed about 4 1, the efficiency may be high as 75%. If the ratio is increased to 20 : I the efficiency does not exceed about 25%.

A pumping device known as the "Hydrotomat" has been re cently introduced which also utilizes a large quantity of water under a low head to raise a portion of itself to some greater height. This works by alternately compressing and exhausting air in a series of containers.