Dear Martin: Yes indeed; it's very good to have enough head over de penstock top surface for get away the possibility of vortex and air bubbles entry. You can see at pages 120 -121 of 'Microhydropower Sourcebook', by Allen R. Inversin, a graph, correlations and equations for that. Check the 3 m head with the water velocity and diameter in the penstock......
Regards, Carlos ------------------------------------------------------ ----- Original Message ----- From: Martin.Leahy To: '[EMAIL PROTECTED]' Sent: Wednesday, September 29, 2004 6:18 AM Subject: RE: [microhydro] trash rack Thanks Carlos, Do you think the think the fact that the penstock is under >3m of water most of the time helps? There is an overflow (600 mm) pipe directly (3 m) overhead and I would hope that some of the trash will take this route... Regards, Martin -----Original Message----- From: Carlos Bonifetti [mailto:[EMAIL PROTECTED] Sent: 29 September 2004 01:06 To: [EMAIL PROTECTED] Subject: Re: [microhydro] trash rack Hi Martin: I think that 2 x 2 m trashrack is too small for 1.5 cu m /s. The size must be at least 3 times that area thus giving more time for trash and leafs collection between cleaning task. Industrial galvanized 'cat walks' are good and cheap. We are using it succesfully. If some boys needs less space than 25 mm for more retaining security, they can put extra bars at the middle of spaces. Regards, Carlos -------------------------------- ----- Original Message ----- From: millstreamhydro To: [EMAIL PROTECTED] Sent: Monday, September 27, 2004 8:07 AM Subject: [microhydro] trash rack I have posted a sketch of a trash rack in the files section (trash rack.doc)for a turbine we are installing. The rack itself will be 2m x 2m made from the stuff they use for industrial 'cat walks'. Essentially this consists of several 25mm x 5mm bars spaced 25mm apart with distance ferrules at 125 mm. The turbine is an old Gilkes series 'c' 18". one part of the runner has 35 mm gaps and these taper off but I assume 25mm trash and leaves will pass. It is designed for open flume operation but it suited my site to pipe the water (1.5 m3/s) to it via 1m diameter pipe. The chamber is therefore covered. The rack will be mounted on two H beams 11m long and driven into the mud floor of the lake (which has a water volume of 55,000 m3. Water level above the pipe inlet center (and trash rack) will vary from 0 to 4m. The rack will be hauled up tipped over and returned using a geared winder with 8mm rope (capable of pulling one tonne). Any comments? Regards, Martin Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! 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