Q: What is a 鈥渉ydraulic ram鈥� as marked on 1:25 000 Ordnance Survey maps? One, in Ozleworth Bottom, Gloucestershire, consists of a buried water pipe running down a steep slope which emits regular pulses of sound at intervals of about a second.
A: Hydraulic rams are self-driven static pumps, designed to raise water from underground watercourses. They were first installed at the beginning of this century, primarily on farms. Many have fallen into disuse in recent years, as the mains water supply has reached more outlying areas, but with the advent of water metering some farmers are considering restoring old pumps. They are also being supplied as aids to developing countries.
The hydraulic ram was introduced commercially in 1774 by the firm of Green & Carter, which is still manufacturing rams at its works in Ashbrittle, Somerset. The rams can raise water more than 100 metres, or pump it a distance of 5 kilometres. They require virtually no maintenance, and can operate for 100 years or more.
Advertisement
A: The hydraulic ram is an ingenious form of water pump which uses the momentum of a relatively large flow at low head (vertical distance between source and pump) to raise a much smaller quantity of water against a greater head. The device was apparently invented by Montgolfier 鈥� he of hot-air balloon fame.
Effectively, the energy of a high-volume, low-pressure flow is used to drive a low-volume, high-pressure flow (see Diagram). Water entering through the large diameter inlet pipe spills through the pulse valve until the water velocity is high enough for the force acting on the valve to overcome its weight.
This closes the valve, and the sudden change in momentum results in a rapid increase in pressure, which forces water through the delivery valve and along the outlet pipe. Flow ceases when the pressure in the inlet chamber falls below that in the outlet and the cycle starts again, which is the reason for the pulsing sound.
The air vessel limits the rate of pressure increase, which could otherwise result in potentially damaging shock waves, similar to the water hammer that can be heard in household pipes.
A: When we farmed in Wales, from 1948 to 1960, the entire water supply for the farmhouse, three cottages and a herd of 60 cows was pumped by two hydraulic rams in the steep valley running through the middle of our farm.
The rams were installed around 1940. The larger of the two had a 10-centimetre drive pipe and pumped about 4500 litres a day to a reservoir on the hill more than 60 metres higher and 600 metres away.
A: Although I have no idea what a hydraulic ram is, it was discussed in 鈥減hilosophy of language鈥� lectures when I was a student. According to the lecturer, the Russians abandoned their machine language translation projects during the 1960s when an engineering document translated into English by a computer made constant references to 鈥渨ater sheen鈥�.