Hydraulic Ram Pumping in Rural Community Development - Rijswijk University

1. HYDRAULIC RAM PUMPING IN RURAL COMMUNITY DEVELOPMENT
F. Zoller, J. Woudstra and M. van der Wiel
Rijswijk University of Professional Technical Education, the Netherlands and Biogas Technology Africa CC,
Durban, South Africa
ABSTRACT
The project started in August 2004 with the initiative of
Mrs. Fuphamia Ciliza, a member of a rural community
in Inchanga, KwaZulu Natal, to set up a vegetable
garden. Maintaining the vegetable garden was hard
work; especially carrying buckets of water from the
adjacent stream to the field. At that time Biogas
Technology Africa became involved via a local
development worker. David Alcock of Biogas
Technology Africa supplied the project with an
irrigation system based on a ram pump design he
developed in previous years. Maarten van der Wiel, at
that time student in his practical semester, working at
Biogas Technology Africa became involved in the ram
pump development. Because the pump design was still
in its development phase, Maarten set the goal of
improving the performance of the pump in terms of
delivery flow and efficiency. His research was focused
on specifying the characteristics of the Alcock
Hydraulic Ram Pump and on how to tune the pump to
changing site conditions. This paper presents the
outcome of his graduation assignment.
1. INTRODUCTION
Rijswijk University of Professional Technical Education
became involved in the project because of their activities
in the Inchanga region. They work in co-operation with
Kerk in Actie, a Dutch organisation that provides funding
for development projects. The main goal is to develop
sustainable energy applications in co-operation with local
industry and to support the implementation. The Inchanga
project showed promising results in terms of energy
conservation and social impact [1]. The graduation
research by Maarten van der Wiel can be seen as the final
step in the development of the Alcock Hydraulic Ram
Pump [2]. The next step is finding suitable ways for
copying this successful principle where needed, wherever
suitable conditions are available. Kerk in Actie has
promised financial support under the condition the request
for project funding comes from a local NGO that accepts
the responsibility for successful implementation.
2. DESCRIPTION OF RAM PUMP ASPECTS
General information about the ram pump has been adopted
from specified literature and the website of the Working
Group on Development Techniques [3]:
www.student.utwente.nl/~wot
“A ram pump is a water pumping device that is powered by
falling water. The pump works by using the energy of
water running down a drive pipe to the body of the ram
pump. Most of the water flows back to the stream via a
waste valve, a small amount of water runs to a much
greater height. In this way, water from a stream in a valley
can be pumped to an irrigation scheme on the hillside.
Wherever a fall of water of at least 1,0 m can be obtained,
the ram pump can be used as a comparatively cheap,
simple and reliable means of raising water to considerable
height”.
A ram pump installation consists of a dam in a stream, a
drive pipe that carries the water to a waste valve, a non-
return delivery valve, an air vessel and a delivery pipe.
Figure 1: Diagram of the ram pump
Ram pumps have a cyclic pumping action that produces a
characteristic beat during operation. Due to the cyclic
action the delivery flow is pulsating. The air vessel acts as a
shock absorber.
The cycle can be divided into three phases: Acceleration,
Delivery and Recoil.
2.1 DESCRIPTION OF THE RAM PUMP CYCLE
Acceleration
When the waste valve is open, water accelerates down the
drive pipe and discharges through the open valve. The
friction of the water flowing past the valve disc causes a
Drive pipe
Delivery pipe
Air vessel
Non-return
valve
Waste valve

2. force on the valve disc acting to close it. As the flow
increases it reaches a speed where the drag force is
sufficient to start closing the valve. Once it has begun to
move, the valve close very quickly.
Figure 2: Diagram of the ram pump in acceleration phase
Delivery
As the waste valve slams shut, it stops the flow of water
through it. The water that has been flowing in the drive
pipe has considerable momentum which has to be
dissipated. For a fraction of a second the water in the body
of the pump is compressed, causing a large surge in
pressure.
This type of pressure rise is known as water hammer. As
the pressure rises higher than the backpressure in the
delivery pipe, it forces water through the delivery valve (a
non-return valve). The delivery valve stays open until the
water in the drive pipe has almost completely slowed down
and the pressure in the pump body drops below the delivery
pressure.
The delivery valve then closes, stopping any backflow from
the air vessel into the pump and drive pipe.
Figure 3: Diagram of the ram pump in the delivery phase
Recoil
Due to the water hammer, the water in the drive pipe will
compress from the waste valve further upstream, locally
decelerating the water and increasing the pressure. The
front of this pressure rise travels upstream through the drive
pipe and reaches the supply source. The expansion changes
the pressure rise in an equal but opposite pressure. This
pressure surge will travel back downstream through the
delivery pipe. The propagation of the pressure surges up
and down the drive pipe, locally decelerating the velocity
of the water step-wise each time they pass by, will continue
until the velocity and kinetic energy of the water is
exhausted. At this moment the pressure is low enough for
the waste valve to reopen, water begins to accelerate down
the drive pipe and out through the open waste valve,
starting the cycle again.
2.2 EFFICIENCY AND POWER
The power required to raise water is proportional to the
water’s flow rate multiplied by the height through which it
is lifted (in a ram pump qdelivery⋅hdelivery). Similarly, the
power available from falling water is proportional to its
flow rate multiplied by the distance dropped (Qwaste⋅Hsupply).
A ram pump works by transferring the power of a falling
drive flow to a rising delivery flow.
Water running down drive pipe
Water is forced
through the
open delivery
valve
Water is discharged
to the storage tank
via the delivery pipe
Water accelerates down drive pipe
Water discharge via
open waste valve

3. Ram pump manufacturers usually define the efficiency of
the pump as:
plysupwaste
deliverydelivery
ersmanufactur
HQ
hq
⋅
⋅
=η
However, this equation does not give a good representation
of the efficiency of the ram pump, as it does not have a
datum level. A better representation is given by Rankine
[4], which defines the efficiency of the ram pump
installation as a whole and takes the water level in the
supply source as the datum:
plysupwaste
plysupdeliverydelivery
Rankine
HQ
)Hh(q
⋅
−⋅
=η
Any reference to efficiency in this paper is to the Rankine
efficiency. It is useful to know the efficiency because we
can use it to predict the delivery flow of a system and to
compare two different pumps. To obtain a good delivery
flow, the efficiency of the pump should be high, there
should be a large drive flow, and the delivery head should
not be too many times the drive head. The value of Rankine
efficiency depends upon many factors including the design
of the pump and the system being used.
2.3 SUITABLE AREAS
Although all watercourses slope downwards to some
degree, the gradient of many is so small that many
kilometres of feed pipe or canal would be needed to obtain
a fall of water large enough to power a ram pump. The best
geographical area for ram pumps is one which is hilly, with
rapidly dropping watercourses, as can be found in the
Valley of a Thousand Hills.
2.4 LIFE AND REALIBILITY
Ram pumps operated at fairly low throughput have proved
extremely reliable. Some have run without stopping for
many years in systems supplied with clean water from a
reservoir. Failures in ram pump systems often occur outside
the pump itself – blockage of filter screens, damage to
pipes, sedimentation of pipes and tanks etc.
2.5 TUNING TO SITE CONDITIONS
Any particular ram pump is normally capable of running
under quite a wide range of conditions. Most manufacturers
quote operating ranges of drive head, drive flow and
delivery head for each pump size. When there is a limited
amount of drive water available, the waste valve has to be
tuned to make the most efficient use of that water to
produce the best possible output. At many sites there is a
seasonal variation in the drive flow available.
2.6 ECONOMIC FACTORS
One of the greatest benefits of ram pump systems is that
they have extremely low running costs. There is no input of
expensive petroleum fuels or electricity, making the
systems very inexpensive to operate. The purchase cost of a
pump, however, is usually only a fraction of the capital cost
of a system: drive and delivery pipe work and storage tank
are usually the most expensive parts.
3. NUMERICAL MODEL
A large number of researchers have analysed the ram
pump’s performance by formulating equations derived
from their perception of the operation of the ram pump.
However, from the earliest research, to more recent
research that use complex differential equations and
computerised modelling to describe the unsteady flow in
the pump [5], little investigation has been made into the
influence of the characteristics of the valves on the
performance of the ram pump. Therefore this research
focuses on an analysis of the valves. It was chosen to base
the numerical analysis on rigid column theory. This
simplification makes it possible to calculate the
acceleration and speed the rigid column of water through
Newton’s second law. In this analysis the water in the drive
pipe will be represented by water flowing through a control
volume. The water in this control volume is considered to
be a rigid column. The velocity of the water flowing
through the control volume can be determined by
integrating the acceleration of the water. The acceleration
of water flowing through the control volume can be worked
out with Newton’s second law: the sum of the forces equals
its mass times its acceleration. Therefore the acceleration
can be worked out by dividing the sum of the forces on the
water column by its mass.
The sum of forces depends on the position of the valves.
When the waste valve is open the resultant force is the
gravitational force on the water, minus the friction losses in
the drive pipe and drag force on the valve disc. When the
delivery valve is open the friction losses of the waste valve
disc are replaced by the friction losses of the delivery valve
and the force created by the backpressure from the water in
the delivery pipe has to be subtracted from the equation.
As can be concluded from the analysis of the operation of
the ram pump, the position and motion of the valves
determine the period of the cycle. In a way similar to that
of the description of the acceleration and speed of the water
and the forces acting on the water column, the acceleration,
speed and velocity of the waste valve disc can be worked
out.
This model does not include the pressure rise and drops
caused by the water hammer as the model is based on rigid
column theory. Therefore a logical function is included in
the model to keep the waste valve closed while the pressure
is high. The logical function can be formulated as setting
the resultant force on the valve to zero when the valve disc
is in it top position until the velocity of the water is zero.

4. The valve will start to open when the pressure drops, which
is at the instant the velocity of water drops below zero.
To establish the motion of the delivery valve equations
similar to those for the waste valve could be formulated,
however the motion of this valve it completely governed by
water hammer. Another logical function is included: the
delivery valve opens instantly (and completely) when the
waste valve closes and the delivery valve closes instantly
when the waste valve starts to open.
Evaluation of the numerical model
The numerical model has been evaluated by comparing the
results with a model based on unsteady flow theory by
Tacke [4]. The comparison is made by applying both
models on experiments by Take on the Blake Hydram. The
comparison shows that the results derived from the model
based on rigid column theory and the results of the model
based on the unsteady flow theory are the same for delivery
heads below 10 m. Verification of the model with own
experimental testing (see chapter 5) did not show good
agreement between calculated results of the model in
absolute numbers and measurements. However, both
results show a similar influence of the input variables on
the output variables. We came to the conclusion the model
can be used to give a qualitative explanation on the
influence of different input variables to the ram pump
performance.
4. NUMERICAL MODEL TESTING; TUNING
TO SITE CONDITIONS
The characteristic of the ram pump system can be changed
by adjusting the waste valve. During the research a new
type of waste valve has been developed in which the
weight and the stroke of the valve disc can be adjusted. The
numerical model has been used to find optimum weight
and stroke for various site conditions. The variable of the
amount of water available is not part of the numerical
model, it is one of the constrains in the practical
application. Tests results of this numerical model lead to
the following conclusions:
• The Rankine efficiency will decrease non-
proportionally with an increase in valve weight;
• The Rankine efficiency will decrease with an
increase in stroke length;
• The delivery flow will first increase with an
increase in weight, but will eventually decrease
again when more weight is added (the delivery
flow will have an optimum at a specific weight);
• The delivery flow will increase with an increase in
stroke length (up to a maximum when the
increased cycle time will exceed the benefit of a
larger delivery flow per cycle).
5. EXPERIMENTAL TESTING
In order to establish the exact parameters of the Alcock
Hydraulic Ram Pump an experimental test set-up similar to
the system that is used in Inchanga (see chapter 6) has been
made. The parameters variable and constant:
Table 1: Parameters variable and constant for
experimental testing
Variable Value
Mass of the waste valve 60, 176, 211, 293 and 409
grams
Stroke of the waste valve 5 and 10 mm
Constant Value
Supply height 2,0 m
Delivery height 5,0 m
Length of drive pipe 8,8 m
Diameter of drive pipe 42 mm
Diameter of delivery pipe 20 mm
Diameter of waste valve 40 mm
Table 2 and 3 show the results of the measurements on the
Alcock Hydraulic Ram Pump in the experimental testing.
Each result is an average of at least 5 measurements.
Table 2: Results of experimental testing of the Alcock
Hydraulic Ram Pump with valve stroke 5 mm
Valve
weight
(grams)
Delivery
flow
(l/min)
Waste
flow
(l/min)
Rankine
Efficiency
(-)
Cycle
time
(s)
60 5,75 16,4 0,53 0,46
176 6,45 23,0 0,42 0,60
211 7,25 24,6 0,44 0,65
293 7,05 30,5 0,35 0,74
409 6,75 35,5 0,29 0,91
Table 3: Results of experimental testing of the Alcock
Hydraulic Ram Pump with valve stroke 10
mm
Valve
weight
(grams)
Delivery
flow
(l/min)
Waste
flow
(l/min)
Rankine
Efficiency
(-)
Cycle
time
(s)
60 5,85 23,3 0,38 0,56
176 6,55 30,4 0,32 0,72
211 7,30 33,5 0,33 0,80
293 8,35 40,2 0,31 0,94
409 6,20 39,6 0,24 1,01
6. THE INCHANGA PROJECT
Besides numerical model testing and experimental testing,
the ram pump system has been applied and evaluated in a
vegetable garden in Inchanga. Biogas Technology Africa
supplied this vegetable garden with a ram pump irrigation
system. In this project the drive head is 1,5 m with
delivery head in the storage tank up to 5,0 m. The
evaluation period was one year. During the wet season the
average delivery flow was determined at 6 l/min. During
the dry season the water level of the stream was extremely
low, causing the ram pump to work erratically. Adjusting
the waste valve, and thereby reducing the intake flow to the
lower amount of water, solved this problem. The reduced

5. delivery flow was sufficient in combination with an
efficient drip irrigation system. The local community took
care of the maintenance of the ram pump; they kept the
filter at the inlet of the drive pipe clean and the put the
pump system back in motion after stagnation. In case of
major malfunction they could contact Biogas Technology
Africa.
The Alcock Hydraulic Ram Pump is made in kit form,
including all the pipe work but excluding the storage tank
and it is priced between 1000 and 1800 SAR (prices are
highly dependent on site conditions). The Alcock
Hydraulic Ram Pump is designed to run with drive heads
of 1,0 to 3,0 m, with delivery heads of up to 25 m.
7. CONCLUSION
The Alcock Hydraulic Ram Pump proved to be a reliable
ram pump system in an irrigation system of a vegetable
garden in Inchanga. By adjusting the waste valve the
amount of intake water could be adjusted to the limited
amount of water during the dry season.
To suit site conditions the following rules for adjusting the
waste valve have been derived from numerical model
testing:
• When water is limited the weight and stroke
should be minimised;
• When water is abundantly available, the stroke
can be maximised and the weight can be chosen at
the optimum of the delivery curve.
For both situations experimental tests have been performed.
The results of experimental testing can be presented in
graphs of delivery flow and efficiency versus the valve
weight for the Alcock Hydraulic Ram Pump:
0,00
1,00
2,00
3,00
4,00
5,00
6,00
7,00
8,00
60 176 211 293 409
Valve weight (grams)
Deliveryflow(l/min)
0,00
0,10
0,20
0,30
0,40
0,50
0,60
Rankineefficiency(-)
flow
efficiency
Figure 4: Measured effects of Delivery flow and Rankine
efficiency versus valve weight for a stroke length of 5 mm.
0,00
1,00
2,00
3,00
4,00
5,00
6,00
7,00
8,00
9,00
60 176 211 293 409
Valve weight (grams)
Deliveryflow(l/min)
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
0,40
Rankineefficiency(-)
flow
efficiency
Figure 5: Measured effects of Delivery flow and Rankine
efficiency versus valve weight for a stroke length of 10
mm.
The results of experimental testing can be presented in the
following rules for adjusting the waste valve for the Alcock
Hydraulic Ram Pump:
When water is limited the weight and stroke should be
minimised: following figure 4 the parameters are: 5 mm
stroke and 60 grams weight. With a 2-m fall and a 5-m
delivery height; the delivery flow will be 5,75 l/min and the
Rankine efficiency will be 0,53.
When water is abundantly available, the stroke can be
maximised and the weight can be chosen at the optimum of
the delivery curve: following figure 5 the parameters are:
10 mm stroke and 293 grams weight. With a 2-m fall and a
5-m delivery height; the delivery flow will be 8,35 l/min
and the Rankine efficiency will be 0,31.
8. REFERENCES
[1] Wiel, M. van der: "The Inchanga Project Hydraulic
Ram Pumping in Rural Community Development"
Biogas Technology Africa CC/Technische
Hogeschool Rijswijk, October 2005.
[2] Wiel, M. van der: "Improving the performance of the
Alcock Hydraulic Ram Pump" Biogas Technology
Africa CC/Technische Hogeschool Rijswijk,
December 2005.
[3] Working Group on Development Techniques: “Ram
pumps” www.student.utwente.nl/~wot
University of Twente, Enschede, the Netherlands,
February 2006
[4] Take, J.H.P.M.: "Hydraulic Rams; a comparative
investigation. Communications on Hydraulic and
Geothermical Engineering" Report no. 88-1, Delft
University of Technology, Department of Civil
Engineering, Delft, the Netherlands, 1988.
[5] Najm, H.N., Azoury, P.H. and Piasecki, M.:
"Hydraulic Ram Analysis; a new look at an old
problem" Proceedings of the Institution of
Mechanical Engineers, Vol. 213 part A, 1999, pp.
127-141.

6. 9. ACKNOWLEDGEMENTS:
We would like to thank Gert de Gans and Bert Kling of
Kerk in Actie, Climate Plan, for their great support of our
projects in South Africa. And we would like to thank David
Alcock and Biogas Technology Africa for providing means
and time for experimental testing. Thank you!
CONTACT BIOGAS TECHNOLOGY AFRICA CC:
David Alcock, baekey@saol.com
+27(0)317645708 +27(0)828818108
10. AUTHORS:
Principal Author: Fred Zoller, B Eng, senior teacher at
Rijswijk University of Professional Technical Education,
department of Mechanical Engineering. Project manager of
the development of Sustainable Energy/Technology,
current projects in the Netherlands and Africa.
Email Fred Zoller: f.c.m.zoller@thrijswijk.nl
Co-authors: Johan Woudstra, MSc. Electrical Power
engineering, dean of the faculty of Electrical engineering at
Rijswijk University of Professional Technical Education.
Project manager of the development of Sustainable
Energy/Technology, current projects in the Netherlands and
Africa.
Email Johan Woudstra: j.b.woudstra@thrijswijk.nl
Rijswijk University of Professional Technical Education:
Lange Kleiweg 4, 2288 GK Rijswijk, the Netherlands
Maarten van der Wiel, B Eng, The research was carried out
by Maarten van der Wiel in the context of a graduation
assignment, which was successfully completed in January
2006. Email Maarten vd Wiel: Maartentof@hotmail.com
Tel: +31612684228
Presenter: The paper is presented by Fred Zoller.