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3.13 Hydraulic Ram

Technical Description

Hydraulic ram technology uses the power of falling water to force a small portion of the water to a height higher than that of the source. The ram operates according to well-known hydraulic principles, with the total force required to elevate a given volume of water being that which is greater than the sum of the forces created by the vertical distance which the water has to be elevated (or the static head) and the resistance offered to the flow within the suction and delivery pipes (or the friction head). In the Village of Baugha Ghuma in the Palpa District of Nepal, the source of water is a small stream, Bhulke Khola, having a dry season flow of about 8 l/sec (500 l/min), located about 1.5 km downhill from the village. The bed of the river at the point of abstraction is concreted (30 m length by 3 m width). A weir diverts a portion of the river flow to a stone masonry intake, which is fitted with two square outlet structures at the bottom. Each square hole serves as an anchor point for a bundle of four 63 mm diameter HDPE pipes, which feed into two 200 mm diameter vertical rolled steel stand pipes, each 5 m in height. Two 7.6 cm galvanized iron pipes, 60 m in length, connect to the vertical stand pipes and form the driver pipes which are directly joined to the ram pump body. The ram pump body is fitted with two impulse valves, one allowing water to flow to waste and one allowing water to flow to the delivery system. Two 10 cm diameter ram pump sets are housed in a pump house. The pumps have a working head of 20 m and a delivery head of 185 m.

Water is abstracted from the river at the weir and is delivered to the pumps by the driver pipes. The driver pipes are angled at 11.3o, providing water to the pumps at a rate of 4.5 l/sec (27 l/min). Water flows through the pump body until such time as the overflow impulse valve is forced closed by the water pressure. The sudden cessation of flow through the overflow impulse valve forces the water through the second impulse or delivery valve, directing the water into an air chamber, which, in turn, forces a portion of the flow to be propelled upward through the delivery pipes into a 2 m3 storage tank. This releases the pressure in the air tank, causing the delivery valve to reseal and again directing the flow through the overflow until such time as the overflow impulse valve is forced closed by the water pressure. The daily output of this pumping system is 39 000 l, which is dispensed through taps serving 14 households within a 2 400 m distribution system (consisting of 1 600 m of 50 mm diameter HDPE pipe and 800 m of 40 mm diameter HDPE pipe) at a rate of 0.45 l/sec.

Operation and Maintenance

To prepare the pump for operation, the valves at the source must be open so that water fills the drive pipe and pump body. When the pump body tank has been filled for several minutes and all the air bubbles have been removed from the drive pipe, the pump is ready to start. If air bubbles remain in the drive pipe, the impulse valves will not function. The impulse valves open and close automatically. (As described above, water runs down through the drive pipe, going faster and faster until it forces the overflow impulse or clack valve to close suddenly. The weight of the moving water suddenly stopped creates a very high pressure and forces some of water past a non-return or delivery valve into an air chamber, compressing the air more and more until the energy of the moving water is spent. This compressed air acts as a spring and forces the water in a steady stream up the delivery pipe into the storage tank.)

The pump has been developed with the intention that it should run for one year without replacement of any parts. The parts that generally need replacement are the rubber seals in the two valves and the rubber ring gaskets in the flanges of each pump. The rubber seal ring is the rubber piece which seals the overflow impulse and the delivery impulse valves. No special tools are required for the ordinary operation of the pump; the tools required for periodic pump repair are two ring spanners, two open spanners and two pipe wrenches. In actual practice, the system is prone to malfunction due to the failure of the pump and, consequently, the villagers have to rely on other small-scale water systems, although these alternate systems are quite often inadequate. The main cause of system malfunction is wear and tear on the rubber seals and gaskets, and the valve rods.

A good system is adopted to control the distribution of water from the taps. An operator from each ward, identified by the Village Water User's Committee, distributes water starting at 05:00. Each household gets about 45 litres. To minimize waste, a small pond is usually created in the area of the tapstands to collect water spilled at the tapstands and the rainwater. The water collected in the pond is used for washing utensils, bathing and watering cattle.

Level of Involvement

The technology was introduced by the United Mission to Nepal (UMN) with technical assistance provided by the Butwal Technical Institute, Nepal. An high level of community participation has been involved in implementing the technology. The success of the project has been due to the initiatives of the Village Water User's Committee, which has collected funds for, and promptly carried out, necessary repair works when failures occurred. (Unfortunately, there appeared to be no regularity in the collection of maintenance funds which limits the ability of the Committee to engage in preventive maintenance.)

Costs

The total cost of the project is $20 000. Maintenance and repair costs are somewhat in excess of $80.

Effectiveness of the Technology

The system supplies water to 14 households (about 100 people), and has been effective in reducing the time and effort formerly devoted to fetching water from the river. Suitability The technology can be introduced in areas where there is an abundance of water located at a source some distance below the settlement. It can be used in situations where there is no electricity to operate electrically-driven pumps. Depending on the source, the water can be used for drinking as well as irrigation purposes

Advantages

The advantage of this technology is its simplicity and lack of energy costs involved in pumping water.

Disadvantages

The disadvantage of this system is its irregularity, which is due to the lack of availability of spare parts and skilled manpower, rather than technical problems.

Further Development of the Technology

There are plans to implement further water supply projects in other districts of the eastern part of Nepal based upon this technology, which may be considered to be fully developed. However, for such systems to be successful, the local people must be trained to operate maintain the mechanism of the ram pump.

Information Sources

Friesen, R.M., J.F. Rollins, and Govinda Devkota. s.d. Hydraulic Ram Pump Hand Book. Butwal Technical Institute, Butwal, Nepal.

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