Show wood pipe for canals the following from the bureau of intimation U S dept of agriculture will be of interest i to a largo large number of in this new country where most of qu our r ditches are still to be built I 1 I 1 how long will it last is a question asked perhaps more than any other concerning the use of woodpile wood pipe for irrigation that the life wood pipe should be at least SO years if the pipes are fully expose exposed dand and supported free from all contact with the soil if the material is either fir or redwood and if the pipe has been properly maintained is the conclusion of a specialist of the U S department of agriculture in a professional paper on wood pipe for conveying water for irrigation bulletin no irrigation engineering and the owners of irrigation works will be particularly interested int ersted in this new pamphlet j which maybe may be had free of charge by applying to the tha department of agriculture washington ington D C 1 the length of life of wood pipe is dependent on the life of the 1 wood rather than on the bands altho contrary theories were were held SO 30 u geors ago only in in rare instances have the tha bands failed first corrosion of the bands being a chemical action requires the presence of moisture and oxygen it C usually occurs most rapidly where pipes are buried and the backfill is wet under conditions which as a rule aro are most favorable for the life of the wood corrosion is greatly accelerated by the presence of alkali in the soil the decay of wood pipe is due primarily to the growth of fungi though possibly certain forms of bacteria may assist in the final destruction of the wood cells the growth of fungi toan extent to the life of the wood requires a favorable combination of moisture air and heat the exalus exclusion I 1 on 0 of f a any ny one of these beyond certain limits inhibits their growth pipes fully exposed to the atmosphere mo sphere and free from contact with the soil will as a rule be too dry on the exterior to favor the development of fungus spores and so long as the outside of a pipe remains dry no appreciable preci able decay will occur even though the internal pressure Is very light decay of exposed pipes almost invariably starts at the ends of the staves as a result of I 1 leaky joints where water leaks out and runs down over the outside of the pipe favorable conditions are afforded for the growth of the algae which usually get a start then mosses may begin to grow in the soil that collects on such spots ind and decay spreads to adjo adjoining inin staves bruising th the e stav staves esin in handling or injuring by too tight cinching cin ching of bands renders them more susceptible of infection by the spores of wood destroying fungi thus hastening decay the life of exposed pipes may be prolonged by promptly stopping all leaks as they develop and b by y keeping the exterior dry the I 1 decay of buried pipes has also in some instance es been arrested by removing the covering and leaving them exposed the asphaltum or tar coating applied to machine banded pipe while intended primarily asa as a pro petion against corrosion of the bands doubtless helps also alio to some extent in preserving the wood until recently the practice has been to leave the ends of wooden sleeve couplings untreated these couplings almost invariably decay long before the main pipe this may indicate that infection by wood destroy ing organisms starts principally where the coating is absent though less perfect saturation of the wood in the sleeves may be more largely res responsible pons alc for the early decay as it may bo be noted also that decay occurs at summits of pipe lines where air accumulates much sooner that at depressions on exposed portions of new pipes the united states reclamation service has used a paint consisting of 6 pounds of red oxide mixed with I 1 gallon of boiled linseed oil one gallon of the paint was wag sufficient for two coats on square feet of pipe where exposed to the sun and where water from leaky joints runs down over it this paint does not last long much of it beino being gone in two years repainting while the pipe is in use is usually not practicable because oil paint will not adhere readily to wet m material t 1 aa the use of paint on exposed pipes under ordinary conditions probably adds very little to their life the new bulletin which consists of 37 pages contains a number of figures and tables of practical use to irrigation engineers continuous stave pipe and machine banded pipe are described in great detail and many specific instances are given to show how long on wood pipe may be expected to last under special conditions |