Farmers Review Africa July/Aug 2017 Farmers Review Africa July/Aug 2017 | Page 65

Borehole casing & screens Africa and are the leading suppliers to all Drilling 2. Roscoe Moss Company Supplement screen (steel and PVC) must able to withstand Contractors, Consulting Engineers, Mines, Only a very small percentage of high-yielding various forces that are directly related to depth. Municipalities and other interested parties. water wells are constructed of blank and For example, assume that a new municipal well is WTPI's parent company SOTICI is based in Cote perforated casing manufactured from materials to be 150 feet deep. Its design might consist of 100 d' Ivoire, one of the largest PVC and Polyethylene other than steel. feet of blank casing connected to 50 feet of ISO 9003. Nevertheless, it is common for well designers to interval of the aquifer(s). With over 20 years' experience in the water most oen PVC, in an effort to reduce the Surface protection would typically consist of a supply eld, it puts the organisation among the construction cost of a new well. For some cement grout seal around the blank casing and privileged few who regularly supply the ongoing applications, PVC is a viable choice. manufacturers in W est Africa accredited with perforated casing that is installed within the depth consider alternative casing and screen materials, needs of companies who use PVC pipes. ese include construction companies, borehole However, one should understand and be willing drilling companies, water supply companies and to accept the inherent limitations of PVC, corporations. extending to a minimum depth of 50 feet. Finally, a lter pack (i.e., select gravel) would envelope the well screen. particularly if it is being considered to construct is seemingly simple PVC casing and screen well large-diameter water well. could fail structurally unless it has sufficient engineers alike, problem solving and advising Given that PVC pipes are available in 10-inch ID withstand depth-related forces such as: 1) the when the need arises. e company involves sizes, one might naturally assume that PVC is an hanging weight of the string of casing and screen; WTPI lends its expertise to contractors and tensile strength and collapse strength to itself in the putting together of complete "Drill acceptable choice. However, well diameter is and 2) the collapse forces generated from the Rig Packages" with competent staff to assist in the only one well design parameter; others have weight of cement grout used for the sanitary seal. training of local personnel throughout the greater importance. African Continent. For low yield wells and/or monitoring wells, Well depth is important because casing and longitudinal slots might be acceptable to some. [email protected] www.wtpi.co.za www.farmersreviewafrica.com [65] FARMERS REVIEW AFRICA July - August 2017