HYDROSTATIC COIL PUMP – a possible pump design for 3rd
By Alex Weir firstname.lastname@example.org July 2001 and updated 2004 July
I wrote a very long (106 pages) and mathematical unpublished
report May 1979 while between jobs, based on work done by Kamil Vanek
(supervisor) and Mohamed Dibwe in 1978 when he was a 3rd year Bsc
Agric student at Sokoine University, Morogoro Tanzania (thank you Mohamed –
hope you get to read this sometime!).
That mathematical report tried to do by simulation what would have been
difficult or too lengthy or expensive using physical test rigs.
There was some stuff on this flying round the email systems
again year 2001 on some UN pump study, so I guessed I should extract the bare
bones and lay them out here.
The Dibwe project was very practical but unfortunately I do
not have access to the report since leaving Sokoine in 1978 (my fault – not
theirs!). My study and this short
report are a combination of my theoretical stuff plus what I remember of the practical
results. Hopefully the Dibwe report is
still on some shelf in the Library or Agric Eng Department at Morogoro….
ADVICE for feasibility study and/or design/construction:
pump works best with about 5 coils – less produces only small pumping heads
and more produces no advantage but loses efficiency. Use the pump with about 45-50% immersion.
More than 50% (i.e. pump axis centerline below water level) reduces maximum head.
Less than 45% increases maximum head but reduces flow rate.
bore are best at or above 42mm (1.5 inch) . 28mm bore (1 inch) is possible but 21mm (3/4 inch) results
in lowered maximum head and probably also efficiency. Out of interest we built the pump in a
converted domestic galvanized steel water tank like you find in a house
loft. 2 Wooden bearings held the
steel water pipe shaft on which the coil was mounted. The pump was hand driven by a crank
handle with no gearing. Larger bore is probably more cost
effective - lower unit cost per water output rate.
Up to 81
mm bore (3 inch) should be perfectly feasible. Maybe even much more.
speed of the pipe entrance nozzle can be 0 – 3 metres/second. From 3-6 metre/second then maximum head
reduces. Above 6 metre/second then
flow probably stops. 3 m/sec will maximise water flow rate for the chosen
coil diameter and pipe bore,
therefore giving better economics.
- A 1
metre diameter coil should produce 2 metre water column maximum left,
which should be equivalent to 4 metre maximum lift because the output
column is typically 50% water and 50% air (if the coil is 50% immersed in
the water, i.e. the water level is at or near the coil centerline). A 2 metre diameter coil should give 3-6
metre maximum lift. A 3 metre
diameter coil should give 4-8 metre maximum lift.
with our relatively primitive equipment, we never managed to measure pump
efficiency – sorry. But I would
guess 50% is realistic. Losses are
in compressing and expanding the air columns inside the pump, temperature
losses of that compressed air, friction between the water and the coils
about using this pump as an anchored paddle-driven machine floating in a
river (like the crude illustration above). Big rivers like you find in
DRC Congo or Brasil could be very interesting. I calculated that paddle driven HCP would be economically
feasible if the average stream velocity were 1 metre/second or greater.
is only really one critical part – the output seal from the rotating coil
to the non-rotating feed pipe – we used for this a standard pipe fitting
rotating seal (I think) – available off the shelf. But I know that Kamil Vanek made some
changes and/or modifications to make it work better. Out of interest,
immersing the pump say 55% - with the centerline just below the water level -
may be advantageous in that the rotating seal will be under water, and may perform
better. We didnt check that idea out at the time.
SUMMARY OF DIBWE/VANEK FINDINGS
- Pipe bore of 21 and 28 mm were
tested. Mean coil diameter 1.05
metre. Degrees of immersion from
25% to 45%. Inlet velocities 0-3
metres/second. Number of coils
1-6. With and without a reducing
coupling at the inlet end of the coils to try to boost flow rate.
lift increased with more coils and slower inlet velocity.
coefficient remained about 1.0 until max head or overvelocity was reached.
coil immersion produced higher maximum lifts, but of course the output
column had a higher proportion of air than water.
lift obtained was about 6 metres (must have been with 25% immersion - my comment year 2001).
SOURCES OF MORE INFO
- Anyone interested can have my 106 page
report in JPG format on CD at cost, or better still a photocopy plus
airmail charge (since I have not yet photographed or scanned the paper
report). Email me email@example.com
Ohlemutz in 1973 did his PhD at some unspecified USA University on “The
Spiral Version of the Hydrostatic Coil Pump”
Pickford in 1978 was doing some work at Loughborough Univ. Tech. Dept Civil
Engg, Water + Waste Engg for developing countries, UK
Kirkby in 1978 was doing some stuff at Univ. Dar es Salaam Faculty
Volunteer Agency (MS?) in 1978 was somehow involved – maybe thru Peder
Kirkby. (https://www.ms.dk ?).
Hedges from the BBC world service radio (https://www.bbc.co.uk)
did some radio programs about 1978
on this pump plus other related stuff.
Secretariat of London had a Rural Technology Meet in Arusha Tanzania 1978
at which we demonstrated this pump among other equipment we were
showing. They may have some photos
Research Institute (McGill University Canada) and/or IDRC (https://www.idrc.ca) have probably got some
report(s) and/or plans on the HCP.
- Do a
web search with https://www.google.com
or some similar good quality search engine(s).
the HDL CD’s (https://www.humaninfo.org)
or a search from their site if possible.
Acknowledgements and thanks
Vanek of DANIDA and Sokoine Univ (now
in Prague), Mohamed Dibwe (the man!), Bob Doyle formerly of ITDG, VITA (https://www.vita.org)
, ITDG of London, Peder Kirkby, John Pickford, Henrik Have (firstname.lastname@example.org) of DANIDA, Frank Inns of Cranfield
Silsoe College UK and UNFAO, Tanzania Government, Sokoine University Tanzania, DFID UK, and DANIDA Denmark.
Below is stuff from 2004 - Jonathen Thorpe from New Zealand
has developed a very exciting and working version of the HCP, paddle driven
From: JAM [mailto:email@example.com]
Sent: Friday, July 09, 2004 4:34 PM
To: alex weir; Dale Fritz
Cc: Corsont@aol.com; firstname.lastname@example.org
Subject: coil pump progress
Summer has been busy here in Osh Kg. We have completed the big pump, which delivers 16 l/min up to 25m ht. With paddle size 0.5 x 0.5m it takes quite some stopping in the 1.5m/s stream current.
Hopefully I can increase the delivery flow to 20 l/min, by placing a scoop on the inlet.... there still seems to be some spare power in the paddle.
See photo attached.
I will be wrapping up here in kg, and going back to NZ in August, but there is someone else who will be continuing the work when I am gone. Will keep in touch.