Borewell casing: HDPE v/s PVC - Secundarabad
Submitted by ushbab on July 9, 2010 - 13:14
I am working with a construction company and one my client wants a borewell with 165 mm diameter and put 180mm HDPE pipe casing for it.
Few borewell contractors I approached told me that HDPE pipe cannot be put as casing and only PVC pipe can be put.
Kindly confirm whether it is true.
Comments
1. HDPE v/s PVC
Dear Sir,
In a way it is correct, due to technical reasons, the wall thinckness of HDPE pipe is much more than that of a normal PVC pipe.
The problem that arises when one tries to install HDPE casing instead of a PVC is that the standard combination of drill bits that are there on a normal drilling rig are suitable for driling 115 mm diameter, 152mm and 205 mm , and in this case when one drills a 4.5( 115mm) borewell the casing is used is 127mm ( 5inch inner diameter and 5.5 inch outer diameter) for this a 152 mm drill bit is suitable, If a HDPE pipe is used to get an clear ID of 125 mm the OD of the pipe is nearly 150 mm and does not allow an easy installaion in the well. Same is the case with the larger diameter pie suitable for 6 inch borewells (7 inch casing). Higher pressure rating will mean a thicker wall thickness as compared to a PVC pipe.
HDPE casings can be installed in areas where the drilling is completed with a temporary casing and on completion of the drilling operation a slightly smaller diameter casing is installed but it is risky especially where drilling fluid is normally air or water and no mud is used. The borewell may collapse and one may have to subject the borewell to flushing but without a hammer.
If you can find a drilling rig which drills both 4.5 inch and 6 inch borewells, they will manage to drill an 8 inch hole and then install a 6 inche (OD) HDPE csing and further drilling could be done with a 4.5 inch hammer.
Most probably you will have to arrange for the casing pipe.
Best of luck !!!!
2. HDPE V/s. PVC Casing.
Dear Ushbab,
I may add one more point which was not mentioned in the previous comment posted by wellwaterworks.
PVC casing pipes normally comes as self- coupled pipes while HDPE Pipes are plain on both ends. It is hard to make sockets manually while using HDPE as borewell casing pipes. This is another reason for the hesitation by borewell contracotrs. HDPE can be used as casing if the OB thickness comes below 6m.
Neeradhan
Geologist
Trivandrum.
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