RP-01638

Overview of Technical
Performance
Goh Sing Yau
After the Consumers' Association laboratory
tests, a proposed design of the pumping
element with a piston and a foot valve was
accepted by the International Development
Research Centre (IDRC) for testing in the
IDRC Asian network of handpump projects.
Development of the IDRC Design
The piston assembly consists essentially of
a polyvinyl chloride (PVC) piston with two
polyethylene rings (see Fig. 1A). Laboratory
tests were carried out in Thailand and
Malaysia to determine the critical values of:
(1) orificeipiston and orifice/foot valve area
ratios; (2) valve weight; (3) valve gap;
(4) stroke length; and (5) the stroke rate
needed to obtain optimum performance as
characterized by high volumetric and
mechanical efficiencies. The results of the
laboratory tests were incorporated into the
modified versions of the piston (see fig. 6 of
the Malaysian paper, page 45).
Initial laboratory and field tests of the foot
valve (see Fig. 1) in Thailand, Sri Lanka, and
the Philippines showed that the original polyethylene
cup seals did not provide an effective
water-tight seal and leakage was excessive.
To overcome this problem, a nonremovable
foot valve (see fig. 7 of the Thailand paper,
page 28) was used, with the foot valve solventwelded
or bolted to the pump cylinder. Later,
a double-lipped rubber seal was developed by
the Malaysian group to replace the polyethylene
cup seal for use in a removable foot valve
(see fig. 6 of the Malaysian paper, page 45).
The original IDRC design recommended a
PVC or polyethylene valve flap. The use of
these valve flaps caused excessive leakage
that was particularly noticeable in the foot
valve. The initial modification carried out by
Thailand was to use a rubber disc with a brass
backing-plate glued on to it. To prevent
accumulation of sand at the valve seat,
elevated lips were cut on the valve seat. The
seal could be further improved with a spring
to press the valve flap onto the seat. However,
laboratory tests in Malaysia indicated
that the spring-loaded valve flap increased
the work input substantially and hence
decreased the mechanical efficiency.
It was discovered after several months of
use that the glued-on brass backing-plate
detached itself from the rubber disc. A further
modification was subsequently successfully
introduced in Thailand by replacing the
previous valve flap design with a single
rubber disk 0.25 inch (0.64 cm) thick without
the backing plate or the spring. This modification
was also found to be successful in the
Malaysian project.
In Sri Lanka, where there was difficulty in
obtaining polyethylene rods, leather cup seals
were used in place of polyethylene rings and
cup seals.
Development of the Above-Ground
Components
Different configurations of the aboveground
components were used in the four
countries; these are summarized in Table 1.
The concrete pedestal adopted by the
Philippines appears to be a simple, cheap
alternative to the traditional pump stand.
Timber lever handles (used in Malaysia and
the Philippines) and timber/galvanized-iron
bearings (used in model L3 in Sri Lanka and
in Malaysia) have been found to be practical
and durable. When cheap timber is available,
timber components appear to be the obvious
choice. The use of timber components also
simplifies maintenance and repairs by handpump
users at the village level.
Field Tests
A mid-project review meeting attended by
investigators from each of the participating
countries was held in Kuala Lumpur from 26-
28 August 1980 to exchange experiences
gained in laboratory and field tests and also to
propose a common field-monitoring proce-
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