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Project: Bio Sand Water Filter Project - Metal Mold Construction (DRAFT)
February 2014 – Present
- Kono District- Eastern Province - Sierra Leone
Working with local metal artisans in Koidu; Using the CAWST manual, technically trained and closely supervised construction of metal mold for CAWST bio sand water filter, mold completed April 2014.
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Challenges: A major constraint was local artisans were unsused to making high precision measurements, angles and cutting, and welding, had to teach basic technical drawing, accurate drawing out on sheet metal. Artisans used a process of overcutting then grinding down metal to avoid undercutting. Some of the higher thicknesses were too expensive to purchase in large quantities for the small amounts that were needed. It was necessary to scavenge waste offcuts instead. Close supervision was only possible on weekend visits from Kayima to Koidu, artisans were not confident to work in my absence, this delayed construction, extending work over a number of weeks. However provided the metalworkers with time to digest and upskill new techniques and standards.
The video above shows an innovation I'm looking forward to trying
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Lessons Learned:
Do not assume angles correct despite assurances, have set squares, metal markers and engineering rulers handy for accurate measurements (they used simple tape measure), check all measurements and angles thrice and weld once.
Actions: Next phase; construction of concrete filters and community training, due to commence August 2014, suspended due to Ebola crisis. Target for aggregate sourcing (remote control) Jan 2015. Target for Concrete filter construction training March 2015.
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| Mr Sesay Metalworkers at Gunpoint Koidu |
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| In the final stages the metal workers solved extractor problem with minimal supervision |
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| In the final stages the metal workers solved extractor problem with minimal supervision |
Biosand Filtration sand for water treatment are used to remove pathogens and suspended solids from water using biological and physical processes that take place in a sand column covered with a biofilm.
ReplyDeleteI am very interested in starting training in the Bo area. Can you help me with finding welders and supply sources?
ReplyDeleteIf its the metal mold you want to make, your best bet would probably be to use the welder I used in Koidu town, Kono District. It took a lot of very close supervision to get the accuracy and quality I needed, but now they've gone through the process you're more likely to get a decent mold from them, provided the same workers work on it, to the same standard - I can identify them for you and I may be able to help with remote supervision, though it would be better if I was there.
ReplyDeleteInterviewing the young man and his supervisors who did the job and getting a blow by blow account would be most useful for you especially if you intend to use fresh metalworkers in Bo. If you are, I would have someone take you round to visit a few first to see how they're set up and look at some examples of their work. Don't go for the first you see.
I can arrange a viewing of our mold in Koidu if that would help.
Regarding mold supplies, most of the metal was available either from local building suppliers or salvaged from scrap iron locally. Metal workers should have their own equipment but will charge you for consumables like grinding disks, welding electrodes etc. all locally available.
Regarding supplies for the concrete filters and contents, cement is readily available anywhere, rough sand can be dug up for you (river sand and saltwater sand are not suitable) gravel of various grades can be easily brought to you by locals, sourcing clean water for final washing of the gravel and sand may be a problem though most of the washing can be done with clean well water (avoid water that contains pathogens). I'm not sure whether you can get the vibrator gadget in Sierra Leone (see blog video) but I would highly recommend it having done some building work last year. Getting the bubbles out of poured cement is a pain (although this can be done by beating the mold all around with wood for 30 minutes while poking the wet cement with a rod). You may want to import the vibrator(s). The small rubber hose for the filter is also readily available locally from auto accessory shops, they had several grades in Koidu, some reinforced so as not to collapse.
How many filters are you looking to make and how soon? This will decide how many molds you will need.
Sorry if I've waffled on a bit but I've been chomping at the bit to get back to this project. I'm happy to assist in any way I can. My email is sahrfas@yahoo.co.uk
looking forward to seeing the mold and starting the construction of filters
ReplyDeleteGreat presentation
ReplyDelete