Hydraulic Ram

Hydraulic Ram

The hydraulic ram is a pump which raises water without any external power for its operation. When large quantity of water is available at a small height, a small quantity of water can be raised to a greater height with the help of hydraulic ram.

History

1772- John Whitehurst is credited with inventing a non-self-acting ram pump in England.

1796- A Frenchman, Joseph Michael Montgolfier, had added a valve, which made the device self-acting, making the ram pump almost a perpetual motion machine when water supplies were steady.

1809- The first American patent was issued to J. Cerneau and S.S. Hallet in New York, but it wasn't until 1832 that information began spreading across the eastern states about the "simple pump that pushes water uphill using energy from falling water."

1843- H.H. Strawbridge of Louisiana claimed to be the first to put an American made model into use. His first ram, built entirely of wood, exploded, prompting a later model boasting "cross-bolts and rivets of iron." A cast iron ram soon followed.

1980- Richard Fleming developed and began marketing the Fleming Hydro-Ram.

Working principle

Hydraulic ram work on the principle of Water Hammer. Hydraulic shock (colloquial: water hammer; fluid hammer) is a pressure surge or wave caused when a fluid, usually a liquid but sometimes also a gas, in motion is forced to stop or change direction suddenly; a momentum change. This phenomenon commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe.

This pressure wave can cause major problems, from noise and vibration to pipe rupture or collapse. It is possible to reduce the effects of the water hammer pulses with accumulators, expansion tanks, surge tanks, blow off valves, and other features. The effects can be avoided by ensuring that no valves will close too quickly with significant flow.

Components of Hydraulic Ram

1. Supply Tank

2. Supply Pipe

3. Delivery Pipe

4. Air Vessel

5. Inlet Valve

6. Waste Valve

7. Chamber

Working of Hydraulic Ram

When the inlet valve fitted to the supply pipe is opened, water starts flowing from the supply tank to the chamber, which has two valves at B & C. The valve B is called waste valve & Valve C is called delivery valve. The valve C is fitted to the air vessel. As the water is coming into the chamber from supply tank, the level of water raise in the chamber & waste valve B starts moving upward. A stage comes, when the waste valve B is suddenly closed. This sudden closure of waste valve creates high pressure inside the chamber. This high pressure force open the delivery valve C. The water from chamber entre the air vessel & small quantity of water is raised to a greater height.

When the water in the chamber loses its momentum, the waste valve B open in the downward direction & the flow of water from supply tank start flowing to the chamber & cycle will be repeated.

Let

W= Weight of water flowing per second into chamber

w= Weight of water raised per second

h= Height of water in supply tank above the chamber

H= Height of water raised from the chamber

q = Discharge of delivery pipe

Q= Discharge through supply pipe.

The energy supplied by the supply tank to ram

= Weight of water supplied × Height of supply water = W × h

Energy deliver by ram = Weight of water raised × Height through which water is raised

= w × H

Efficiency of hydraulic ram =  h = Energy deliver by ram / Energy supplied to the ram

Efficiency = w × H / W × h

Or Efficiency = q × H / Q × h

The above expression of efficiency was given by D’Aubuisson & hence known as D’Aubuisson efficiency.

Rankine gave another form of the above efficiency. According to Rankine “Weight of water (w) is raised to a height of (H-h) & not H. The water is initially at a height of h from the ram & hence the water is only raised to a height equal to (H-h)". Hence according to Rankine-

Energy deliver by the ram = w × (H-h)

Energy supplied = (W-w) × h

Efficiency  = w × (H-h) / (W-w) × h

Or Efficiency = q (H-h) / (Q-q) × h

Advantages of Hydraulic Ram

1. No moving parts.

2. No power requirements.

3. Inexpensive.

4. Quiet pumping continuously over a long period.

5. Pollution free or “Green" pump.

6. Simple construction and easy to install.

7. Only initial cost and very low or negligible maintenance cost.

Disadvantages of Hydraulic Ram

1. It can pump only one tenth of the received water volume remaining being wasted through waste valve.

2. It must have a continuous source of supply at a minimum height of not less than 3 feet or 91 cm.

3. It cannot pump viscous fluids to a greater height. Usually used for pumping drinking water or potable water.

Notes- 

An alternative to the hydraulic ram is the water-powered pump. It can be used if a high flow rate at high head ratio is required. A water-powered pump unit is a hydraulic turbine coupled to a water pump. The motive power needed by the pump is generated by the hydraulic turbine from the available low head water energy.