A. BOREHOLE CASING- PERMANENT PIPING – PUMP CHAMBER
The “blind” casing and the perforated casing (screens) of borehole will be of suitable diameter to fit the submersible pumping unit that will finally be installed. The plate thickness of the casing is 4-6mm, are straight, made of steel plate of quality St 37-2. They will be autogenous welding, in straight line and without added metal, by the method Electric Resistance Welded with High Frequency (ERW / HF), according to DIN 1626/2458. Casing and screens will not have a transverse seam. The openings of the screen section are of bridge type (bridge slot) according to DIN 4922. The tubes can be protected with hot or electrolytic galvanizing, after your choice. We recommend hot-dip galvanizing.
The connectors (sockets) of the casing pipes and the screens, are made according to DIN 4922 of the same quality material as the casing and the screens. They have length of at least 100mm and thickness of 12 mm. The joints are threaded with a semicircular thread with two (2) coils per inch and at a depth of at least 70mm from the ends, according to European standards. They are welded to the ends of the pipes with a continuous seam outside and inside and are perfectly concentric with respect to the axis of the pipe.
The upper part of the casing column will be protected with a suitable screw cap and padlock. The lower part of the casing can end in a conical pipe (cone). The cone can be replaced with gravel of suitable volume that will be thrown properly before the gravel and after cleaning the inside of the casing, to create the desired block at the bottom, which does not allow mud and gravel filter to enter.
Particular care must be taken in the way the gravel is thrown, so that it does not clog and damage the drilling. If a cone is installed, it should be made of such a material (not steel) that it can be drilled, if trapped, without damaging the casing.
In case, the pulp is mud, before laying the casing, the hole pulp will be circulated and diluted. The dilution should be such that, in order not to endanger the walls of the borehole. Also by using diluted mud, it is possible to achieve good cleaning and development of the borehole, in order to properly handle the aquifer.
If the casing is done without proper dilution and the gravel is placed in high density mud, there is a case of not achieving the growth and “opening” of the aquifers, leading to a much smaller supply than the capacity of the aquifers.
The borehole casing will be accompanied by a legal certificate of the manufacturer.
B. HEAVY TYPE PVC PIPES
The plastic casing are type PVC-U (rigid PVC), they are heavy type of 10-12 atm. They have strong resistance against chemicals, sunlight and oxidation by water. Non-toxic and suitable for drinking water. They are more durable than plain PVC and with greater tensile and compressive strengths.
The connection is made with connectors (sockets) that are made according to DIN 4925 of the same quality material as the pipes. The screen (filter tubes) are made by a special machine in the manufacturing plant. The length of casing and screen pipes is 3 meters.
C. PIEZOMETRIC PIPES
Piezometric pipes, iron pipes, diameter 1”, heavy type , with sockets, galvanized, will be placed outside the permanent steel pipes of the drilling. The piezometric pipes will be placed between the outer walls of the casing (pump chamber) and the borehole walls. The piezometric pipes are intended to monitor the groundwater level in the drilling.
The piezometric tube will communicate at the bottom with the inside of the casing and at a depth that will be determined by the supervision. It will not have slits, so that the level is measured inside the permanent piping and not outside it. The support of the piezometric pipe will not be done by electric welding in the casing, but with galvanized wire that will be tied in a suitable way. Welding destroys the galvanizing.
The piezometric tube will have a cap and a security lock at the top. When cleaning the borehole after casing installed, the piezometer must be closed with the safety cap to prevent the mud from circulating through it, with the risk of clogging and disuse.
In UPVC plastic pipes the piezometric pipe will be placed together with the submersible pipe inside the “pump chamber”.