Director,
T.E.(Terry)
Manning,
Schoener 50,
1771 ED Wieringerwerf,
The Netherlands.
Tel:
0031-227-604128
Homepage:
http://www.flowman.nl
E-mail: (nameatendofline)@xs4all.nl : bakensverzet
Incorporating
innovative social, financial, economic, local administrative and productive
structures, numerous renewable energy applications, with an important role for
women in poverty alleviation in rural and poor urban environments.
"Money is not
the key that opens the gates of the market but the bolt that bars them"
Gesell, Silvio The
Natural Economic Order
Revised English
edition, Peter Owen, London 1958, page 228
The
European developed and built Village Life spring rebound inertia or water oscillation
hand-pumps for boreholes in developing countries were first formally presented
during the International Water Resources Association's world congress held in
Brussels from 9th-15th of June, 1985. They represent a major technological
break-through which might, but for political factors and vested interest, have
had a profound influence on the International Drinking Water Supply and
Sanitation Decade 1981-1990 and thereafter. They were one of the very few
genuine technological advances to have come out of the International Drinking
Water Decade and undoubtedly present the most fascinating development in
hand-pumping this century. Spring rebound inertia pumping allows for extreme
simplicity of pump construction, the total elimination of all organs of
transmission and parts in relative movement below ground level, extreme
facility of installation and maintenance, particularly wide possibilities of
application, maximum security of water supply including the use of multiple
independent unit installations and excellent resistance to sand, adaptability
to local social and cultural structures, universal use especially by children,
low global long-term costs of operation, village level operation and
maintenance (although Village Life pumps were already post-VLOM at their
conception) and real perspectives for local manufacture of pumps and/or spare
parts. They are particularly suited to use in development aid projects because
they have a global long-term cost per litre of water pumped which is only a
fraction of that of other types of hand-pump currently available on the market,
and therefore yield a very low recurrent maintenance cost onus for beneficiary
communities.
They
eliminate at origin the insurmountable technical problems inherent in pumps
traditionally used for the supply of safe drinking water to poorer communities
throughout the world.
The difference between spring rebound inertia (water oscillation) pumps and
traditional pumps is that spring rebound inertia pumps, exploiting the
characteristics of the oscillatory cycles of the water column in the feed pipe
to obtain their pumping effect, use a principle of physics for their operation,
whereas rod-type pumps, for instance, use a mechanical device. This fundamental
innovation carries with it a number of consequences such as to revolutionise
hand-pumping in developing countries. The following are some of them.
It
is a pump comprising first a lever system attached to an upper pump body
containing an above-ground piston or plunger, secondly a lower chamber closed
at the bottom by a no-return valve and containing a series of elastic balls or
elements called ovoids (the same pump can be used at all depths by varying the
number of these balls or ovoids), and thirdly a single 1 1/4" flexible
16PN polyethylene pipe joining the upper pump to the lower chamber by means of
rapid couplings. The lever and the upper pump form a first oscillating group,
while the balls or ovoids in the lower chamber together with the water in the
feed pipe comprise a second oscillating system. The two oscillating groups have
to be put into resonance with one another for the pumping action to take place.
After
installation once-only initial priming is needed to fill the system with water.
The lever system is then moved downwards and upwards more or less as with other
types of lever pump. On the downwards stroke, the energy applied is transmitted
from the lever system to the above-ground piston (or plunger) and thence to the
mass of water present in the column. The water in turn transfers the energy to
the special elastic elements in the lower chamber. These, contracting, store
the energy in the form of potential elastic energy. At the lower dead point or
close of the (variable - the stroke can finish at any point) downwards stroke,
the elastic elements spring back to their original volume, returning the energy
stored to the column of water in the feed pipe. The kinetic energy of the water
is such that, as it tends by inertia to continue its upwards movement in the
feed pipe, if the piston frees itself from its seal, a quantity of water simply
spills out of the pipe at the top, while at the same time a small vacuum is
created at the bottom of the feed pipe so that the foot valve opens and the
same quantity of water is sucked into the lower chamber, thus concluding the
pumping cycle. The actual pumping is thus done by the water itself as it
oscillates in the feed pipe.
As
spring rebound inertia pumps are dynamic machines, the number of parameters
which can be applied is too numerous to map out in graph form. The following
drawings are based on an average for one operator, average capacity with two
operators, and maximum capacity with one or two operators. Although these pumps
are hydraulic units with a double passage of water along the feed pipe, their
efficiency has been independently measured as being up to 50%. While this may
be slightly lower than that of some other hand-pumps operating within a narrow
application band and often for a limited period of time (wear and tear of parts
makes the efficiency of traditional pumps unstable), efficiency is, as the
notes set out below convincingly demonstrate, only one aspect of professional
hand-pumping and by no means the most important one. Each user can operate the
pump according to his own desires, provided he adopts the correct RHYTHM
of pumping for the installation in question, which is designed to be about 80
strokes per minute, which in turn is the rate of the human heart-beat.
Observation of installations in
Children,
on the other hand, who are typically the best users, will tend to use shorter
strokes and take, say, 30 seconds longer to fill the same container.
Refer to: CAPACITY for further information
Village
Life pumps can be installed vertically and/or horizontally even with bends in
the single length of feed pipe used, and they are accordingly entirely
insensitive to shoddily drilled holes and can be operated from any source of
water. Problems with the installation and maintenance of rod pumps which
require a perfectly vertical hole are too well known to call for analysis here.
Village
Life pumps have no parts in relative movement below ground level, and therefore
they are much less sensitive to sand than is the case with other pumps where
sand and impurities collect at the bottom of the lower cylinder and greatly
aggravate wear and tear on valves and seals etc calling for frequent removal of
the system from the bore-holes and the replacement of parts, with all of the
implications notoriously connected with traditional pumps in this respect.
Village
Life pumps use one single length of 1 1/4" 16PN flexible polyethylene feed
pipe with a nominal pressure rating of 16 bar for each pumping unit. These
pipes, fitted to the lower cylinder and to the upper pump by means of simple
rapid couplings, are normally continuous in length, so that the pumps can be
installed and/or pulled in the space of a few minutes, whereas traditional
pumps often present long, difficult, and heavy installation procedures because
of the need to assemble and dismantle rods and pipes, where this does not turn
out to be practically impossible. Repeated frequent assembly and dismantling of
rods and pipes tends in fact to ruin the threading and make removal for
maintenance highly problematic.
The
single feed pipe means that several Village Life pumps can where appropriate be
installed in the one 110mm ID (or larger) bore-hole, thereby better exploiting
the investment in the bore-hole and further increasing the security of water
supply. In larger communities, and provided the capacity of the bore-hole so
permits, this feature can substantially reduce the number of bore-holes which
have to be drilled, and therefore the global cost of rural water supply
projects to the point where the Village Life pumps may even have a negative
value where the value of the cost-savings in bore-holes is greater than the
cost of the pumps.
As
all other units (double, triple and even quadruple pump groups) fit on the same
foundation bolts as the single unit version, the fact that several pumps fit
down the same bore-hole means that the principle of progressive investment can
be applied where bore-hole capacities so permit. A village can receive a single
unit pump in a first phase, and thereafter substitute the single unit with a
double pump group (the original pump would be installed elsewhere) and so on to
adapt without further investment in bore-holes to population increases and to
increases in water requirements accompanying an improvement of the standard of
living of the community.
Installation
and maintenance times and costs increase with rod-type pumps with the length of
the rods and pipes, and therefore with the depth of the water level in the
bore-holes, while at the same time the weight, the inertia, and the attrition
of the rods increases, so that the work required to pump increases more then
proportionately with the depth of the installation. This means that the use of
rod-type pumps, theoretically utilisable at depths of more than 25m. is not in
such cases advisable in practice. While such conclusion may not have been
widely publicised, partly because of the considerable vested interests
involved, it is a fact that the search for alternative systems of hand pumping
was undertaken world-wide for this reason. Water oscillation or spring rebound
inertia pumps completely eliminate at origin these problems. They become progressively
ever more attractive with respect to traditional pumps the deeper the level of
water in the borehole (up to 45-50m!!, for deeper boreholes go solar - see Solar Spring pumps), the more isolated the location, the
more intensive the use, and the more aggressive the water. Installation and
withdrawal times do not vary with depth and there are no rods or riser pipes to
get rusty or move.
Due
to the automatic return of the column of water in the feed pipe of spring
rebound inertia pumps, their lever system returns to its upper dead point on
its own. This phenomenon has made it possible to adopt the world's first
combined foot and hand system for lever pumps and thereby to optimise the use
of the operator's energy and enable him to obtain good capacities even where
pumping continuously for extended periods. A traditional handle system enables
the user to exploit about 40% of his potential force without giving him the
possibility of alternating the muscles in play. The combined hand and foot
lever system used for Village Life pumps not only allows for the exploitation
of roughly 70% of the potential force available, but assures the possibility of
changing over from one leg to the other as well so as to obtain a "long
distance running effect". Furthermore, water oscillation pumps can thus be
operated either by hand and/or by foot. They can also be operated by two or
more persons together should this be considered advantageous by the users
involved.
Traditional
pumps are basically constant force pumps in the sense that a certain force is
required to be able to move the handle in a given situation to raise a constant
amount of water, and the same force is required to continue moving it, while
there is a certain direct relationship between a stroke and the volume of water
pumped so that the variability in the volume of water pumped tends to be
determined by the number of strokes made. Water oscillation pumps profoundly
modify hand pumping in this respect, as practically everything in a water
oscillation pump is variable, and above all, THE AMOUNT OF FORCE APPLIED,
and therefore the length of the stroke and the volume of water pumped with each
stroke. Water oscillation pumps are truly dynamic machines which can be used by
the very young, the very old, the fit, and the sick, according to their
physical capabilities, the time they have available, the amount of water they
have to pump, and their mood of the moment. The use of a water oscillation pump
is therefore in these respects similar to that of another excellent dynamic
machine : the bicycle. Rhythmic extremely light limited strokes will still
yield water. Naturally there is a relationship between the force applied on any
given stroke and the amount of water pumped, so that longer (not quicker)
strokes will normally produce more water. The dynamic nature of the Village
Life spring rebound inertia pumps makes them especially suitable for use by women
and children, who are the ones who usually have to do the pumping. Children can
use the pumps at any depth for which they are recommended, while current models
have been designed in such a way as to be more efficient with lower force
input.
The
installation and maintenance costs for Village Life pumps are such as to yield
a long term cost per litre of water pumped which is only a fraction of that of
other hand-pumps available on the market. Full and detailed costs projections
indicating a global long-term cost per litre of water have been published.
Excluding amortisation of the initial investment costs for purchase and
installation, amortisation of the costs of the bore-hole, and excluding
eventual associated health and sanitation costs, but including all costs to the
recurrent charge of the villages such as labour, spare parts, amortisation of
spare parts so as to bring the pump back to new working condition at the close
of each ten years' period, the projection comes to US$ 0.000045 per litre.
Assuming 8 hours' effective work per day (15-16 hours' use) and an average of
While
the initial purchase cost (investment input) of a European built stainless
steel water oscillation pump is higher than that of a traditional pump made,
say, in India, the global installed cost shows a lesser difference, while if
traditional rod-pumps have to be supplied with stainless steel rods and riser
pipes, the cost of the traditional pump installed may be considerably higher
than that of an installed water oscillation pump without bringing any marked
improvement in real terms to the overall maintenance costs which generally
finish up as a recurrent charge on the village, which cannot afford them. This
gives rise to a fundamental political consideration : the clear need for
operators (especially local governments) to seek the initial investment (pumps
plus spare parts networks) which will yield the lowest recurrent cost onus on
the beneficiary communities after installation, instead of choosing the pump
which APPEARS to be cheaper. The only true measure of evaluating a
hand-pump is how much it costs per litre of water effectively pumped over a
long period of time, say 10 or 20 years. The initial purchase price of the pump
has relatively little to do with such costs. There are hand-pumps on the market
which have cost more than their original purchase price every year for
maintenance, and some of these may even have to be replaced after just a few
years.
Yet
another revolutionary aspect of Village Life system spring rebound inertia
pumps, is that certain parts, typically subject to wear and tear over a long
period, can be re-utilised several times. For instance the two (upper and
lower) bronze piston guides and the brass lever guide plaques and the nylon
lever guides (which are the parts in contact respectively with the above-ground
piston and the lever group) can be rotated, then inverted, then interchanged
with one another and can therefore be re-utilised from four to six times.
In
theory, the most critical parts of a spring rebound inertia pump are the
free-floating elastic elements placed in a chamber at the bottom of the
bore-hole above a no-return valve. For this reason, the springs have been
pluralised. Village Life pumps are supplied as standard with eight elements. A
pump with eight elements can work with seven, six, five, four, or even with
just one element. The reduction in the number of working elements makes the
pumping stroke harder and shorter, but the pump continues to function. For this
reason, it is technically impossible for a spring rebound inertia pump to stop
operating between periodic preventive maintenance visits, so that loss of use
of the pumping system and of the borehole can be reduced to 0%.
Spring
rebound inertia pumps do not necessarily require skilled labour or particular
margins of tolerance for their manufacture. Traditional rod-type pumps are more
complex and delicate because of the presence of transmission organs. They
require more expert labour and, above all, closer quality control. While
European built spring rebound inertia pumps are built entirely from stainless
steel, there is wide potential for manufacture in other areas in accordance
with locally available materials and technology.
The
Village Life pumps have been designed in such a way that parts subject to wear
and tear over a long period can, in emergencies, be replaced at village level
using recovery materials such as used motor vehicle tyre tubes (foot valve
rubber) or local leather (above-ground piston seal). The only tool needed is a
knife or a pair of scissors. Water oscillation pumps require no lubrication or
systematic maintenance, and do not generally break down even when they need
attention. Their simplicity has enabled the developers to arrive at a level of
robustness and resistance as to be able to offer a serious guarantee against
breakdown due to wear and tear of any part for a period of 12 months from the
date of installation however intensive the use may be. In this sense, the
Village Life pumps were not only "post-VLOM" at their inception, but
also "post-plastic".
Village
Life system spring rebound inertia pumps entirely eliminated at origin at their
inception in the early 1980's all problems relating to the use of plastic
elements below ground, which have for the last fifteen years absorbed such a
large part of the attention of researchers in official spheres. The single
continuous length of flexible polyethylene feed pipe used with spring rebound
inertia pumps was introduced many years before official circles even started
trying to adapt plastic feed pipes for use with traditional rod type pumps, and
is the most practical solution since the single feed pipe can bend, does not
need vertical boreholes, and has no joints which have to be held firm.
