Everything about Hydraulic Ram totally explained
A
hydraulic ram is a
cyclic water pump powered by
hydropower. It functions as a hydraulic transformer that takes in water at one
hydraulic head and flow-rate, and outputs water at a different hydraulic-head and flow-rate. The device utilizes a phenomenon called
stagnation pressure, also known as
water hammer, that's based on
Bernoulli's principle. In operation, a portion of the input water that powers the
pump is lifted to a point higher than where the water originally started. The hydraulic ram is sometimes used in remote areas, where there's both a source of low-head hydropower, and a need for pumping water to a destination higher in elevation than the source. In this situation, the ram is often useful, since it requires no outside source of
power other than the
kinetic energy of water.
History
In
1772 John Whitehurst of
Cheshire in the
United Kingdom invented a manually controlled precursor of the hydraulic ram called the "pulsation engine". The first one he installed, in
1775 at
Oulton, Cheshire, raised water to a height of 16
ft (4.9
m). He installed another in an
Irish property in
1783. He didn't
patent it, and details are obscure, but it's known to have had an air vessel.
The first self-acting ram pump was invented by the Frenchman
Joseph Michel Montgolfier in
1796 for raising water in his
paper mill at
Voiron. His friend
Matthew Boulton took out a British patent on his behalf in
1797. The sons of Montgolfier obtained an English patent for an improved version in
1816, and this was acquired, together with Whitehurst's design, in
1820 by
Josiah Easton, a
Somerset-born engineer who had just moved to
London.
Easton's firm, inherited by his son
James (
1796 -
1871), grew during the
nineteenth century to become one of the more important engineering manufacturers in the United Kingdom, with a large works at
Erith,
Kent. They specialised in water supply and
sewerage systems world-wide, as well as land
drainage projects. Eastons had a good business supplying rams for water supply purposes to large
country houses, and also to farms and village communities, and a number of their installations still survived as of 2004.
The firm was eventually closed in
1909, but the ram business was continued by
James R Easton. In
1929 it was acquired by
Green & Carter
, of
Winchester,
Hampshire, who were engaged in the manufacturing and installation of the well-known
Vulcan and
Vacher Rams.
The first
US patent was issued to
J. Cerneau and
S.S. Hallet in
1809. American interest in hydraulic rams picked up around
1840, as further patents were issued and domestic companies started offering rams for sale. Toward the end of the 19th Century, interest waned as
electricity and electric
pumps became widely available.
By the end of the
twentieth century interest in hydraulic rams has revived, due to the needs of sustainable
technology in
developing countries, and
energy conservation in developed ones.
Construction and principle of operation
A hydraulic ram has only two moving parts, a spring or weight loaded "waste"
valve sometimes known as the "clack" valve and a "delivery"
check valve, making it cheap to build, easy to maintain, and very reliable. In addition, there's a drive pipe supplying water from an elevated source, and a delivery pipe, taking a portion of the water that comes through the drive pipe to an elevation higher than the source.
Sequence of operation
Initially, the [4] waste valve is open, the [5] delivery valve is closed. The water in the [1] drive pipe starts to flow under the force of
gravity and picks up speed and
kinetic energy until it forces the waste valve closed. The
momentum of the water flow in the supply pipe against the now closed waste valve causes a
water hammer, raises the pressure in the pump and opens the delivery valve [5], so some water flows into the delivery pipe [3]. Since this water is being forced uphill through the delivery pipe farther than it's falling downhill from the source, the flow slows down and when it reverses the delivery check valve closes. If all water flow has stopped, the loaded waste valve reopens against the now
static head, allowing the process to begin again.
A pressure vessel [6] containing air, cushions the hydraulic pressure shock when the waste valve closes, and it also improves the pumping efficiency by allowing a more constant flow through the delivery pipe. Although, in theory, the pump could work without it, the efficiency would drop drastically and the pump would be subject to extraordinary stresses which would shorten its life considerably. This air is under pressure and is gradually dissolved in the water until none remains. One solution to this problem is to have the air separated from the water by an elastic diaphragm, (similar to an
expansion tank); however this solution can be problematic in developing countries where replacements are difficult to procure. Another solution is to have a mechanism such as a
snifting valve which automatically inserts a small bubble of air with each pump cycle.
(External Link). Another solution is to insert an inner tube of a car or bicycle tire into the pressure vessel, with some air in it and the valve closed. This is in effect the same as the diaphragm, but is implemented with more widely available materials. The air in the tube cushions the shock of the water the same as the air in other configurations does.
The optimum length of the drive pipe is 5 to 12 times the vertical distance between the source and the pump, or 500 to 1000 times the diameter of the delivery pipe, whichever is less. This length of drive pipe typically results in a period between pulses of 1 to 2 seconds. A typical efficiency is 60%, but up to 80% is possible. The drive pipe is ordinarily straight but can be curved or even wound in a spiral. The main requirement is that it be inelastic, strong and rigid as otherwise it would greatly diminish the efficiency.
Common operational problems
Some common operational problems are intrusion of air into the drive pipe, blockage of the intake or valves with debris, knocking due to too little air in the pressure vessel, and freezing in winter.
Further Information
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