RP-01638

original diameter) x 1001(original diameter).
The angular position of the hole was defined
as 0 = 0° for the diameter in the plane of the
lever and 0 = 90° for the diameter perpendicular
to it. Wear in the bore of the wooden
bushing was plotted against calendar time
and against total work output (Fig. 10). As
expected, the wear was more dependent on
the total work output than on calendar time.
The magnitude of the wear also varied from
handpump to handpump depending not only
on the total work output but also on the
dampness of the wooden bushing and the
slack in the lever system. It was also not
surprising that the wear in the plane of the
lever (0 = 0°) was greater than that perpendicular
to it (0 = 90°).
Wear of the high
Wear of piston rings
density polyethylene piston rings was calculated
as a percentage from: (original thickness
- measured thickness) x 100/(original thickness).
Wear of the piston rings was also
plotted against calendar time and against total
work output. Again, the wear is more a
function of total work output than calendar
time. The average total wear of the piston
rings over the 8.5-month period was of the
order of 4%.
Wear of the
cylinder
pumping section of the handpump
At the end of the field test, the
PVC pump cylinder was replaced by a new
cylinder. The original pump cylinder was cut
into two halves along its cylindrical axis and
the wall thickness measured in the laboratory.
Figure 11 shows the variation of wall thickness
of the pumping section of the PVC
cylinder of a handpump that had been in use
in the field for approximately 2 years. Wear
was very significant and had extended, in this
case, to about two-thirds of the original wall
thickness of the handpump cylinder. In the
present design, high density polyethylene
piston rings were used and the above results
show that the PVC cylinder wears more than
the polyethylene piston rings. This shows
that the original choice of materials is not
satisfactory. Because it is easier and more
economical to replace the piston rings than
the pumping cylinder, it is more desirable to
have a combination where the piston rings
wear while the pumping cylinder is more
resistent to wear.
A member of the present project team, in a
current experimental investigation, has shown
that low density polyethylene wears about 10
times faster than high density polyethylene
when rubbing against PVC material in clear
water. However, until further tests are
carried out to determine whether piston rings
made from low density polyethylene or some
other material can reduce wear in the PVC
cylinder significantly in a field environment, a
temporary solution to the cylinder wear
problem is to raise the piston to a new,
unworn, section of the pumping cylinder
after every 2 years of use.
Conclusions
After approximately 2 years of use in the
field, except for severe wear of the PVC
pumping cylinder, the handpump of the present
design appears to have withstood the
wear and tear of everyday use and required
only minor maintenance and repair. Routine
maintenance is required after every 2 years
either to replace the worn section of the
cylinder or to raise the piston to an unworn
section of the cylinder.
Because the major components of the
present handpump are made from plastics,
the use of injection moulding techniques
offers great promise for cost reduction when
the handpump is produced in large numbers.
Acknowledgment This project was funded by a
grant from the International Development Research
Centre. This is gratefully acknowledged. The
author would like to thank the local Ministry of
Health personnel in Ipoh, Seremban, and Kuala
Pilah for their cooperation in getting the handpumps
installed and monitored during the field test.
Last, but not least, our appreciation goes to the
village users of our present handpumps for their
patience and tolerance during the field tests.
Re ferences
Goh, S.Y. 1980. The performance characteristics of
a reciprocating piston water lift pump. Ottawa,
Ont., Canada: International Development Research
Centre. Interim progress report, Water pumping
technology - Global project.
Sternberg, Y. 1978. Testing of wood bearings for
handpumps. Washington, DC, USA: International
Bank for Reconstruction and Development.
Research Working Paper Series, P.U. Report No.
RES 13.
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