PVC Well Casing / Screen Pipes

 

Kawsar Casing & Screen pipes ensure that the water well remains a perennial source of clean water. Some Year ago the choice was only was metal pipe and Screens. The disadvantages were corrosion of casing pipes, determination of screens and formation of bacteria, resulting in abandonment of wells and, even worse contamination of the water source.

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Pvc well casing and screen is widely used because it is light strong, easy to install durable corrosion resistance and relatively inexpensive . The choice of any material depend upon its strength and weakness in relation to the particular intended use .Condition at a water well drilling site and within a borehole or generally aggressive. PVC casing and screens is easily able to with stand most condition but it is important for a driller engineer or hydro geologist to be aware of conditions or circumstances that might prejudice the integrity of PVC and consequently the bore hole.

The aim is to provide a basis for the correct selection and handling of PVC casing and screen.

PVC is a plastic. it has a low compressive and tensile strength related to steel. It can be a softened by heat, deform by sudden or gradual stress and shattered by strong impact. Generally PVC casing is stronger than PVC screen, and thick wall Pvc casing is stronger than thin walled casing.

PVC is much more flexible than steel, therefore it should be supported both on the ground and in the boreholes. It strength can be reduced by prolonged exposure to strong sunlight. It is attacked by solvent such as vinyl chloride. Volatile organic chemicals can pass through PVC by a process that is not fully understood. Today the modern technologies have enabled us to makes use of plastic pipes for this application.

ADVANTAGES

 

RESISTANCE TO EXTERNAL &INTERNAL PRESSURE:

Maximum hydraulic loading on casing pipes occurs during installation, grave packing, back filling and development of water wells. Hydrostatic pressure is caused by the column of drilling fluid of water present in the borehole . Rapid installation of a gravel pack or back fill increases the pressure on casing and screens pipes .Bridging and later collapse of gravel or backfill into the borehole can further subject casing pipes and screens pipes to shock loads. Poor mud control during water well development can also subject the casing to hydrostatic of differential pressure loading.

Kawsar screens pipes have the capacity to withstand hydraulic pressure. It is vital that the user makes a thorough assessment of each site requirement and only then select from our range of PVC casing and screen pipe.

All Kawsar PVC pipes are resistance to corrosion. As PVC is inherently more resistance than conventional steel products to clogging and encrustation, at a fraction of the cost. Kawsar PVC screen pipes are generally unaffected by substances encountered in well: hence no deteriotion in slots takes place. The raw material used for manufacturing fully complies with drinking water regulation and does not affect the quality of water.

Well rehabilitation cost are minimized, as PVC screens are inherently more resistance than conventional steel products to clogging and encrustation. PVC also outperforms stainless steel in highly corrosive environments, at a fraction of the cost .All screens are manufactured from PVC casing Pipes.

UNDER DRAIN

Slotted PVC pipe is ideal pipe for under drain pipe system.

Application includes, but not limited to

  1. Leachatecollection system for solid waste landfills.
  2. Drainage and Dewatering application.
  3. Mining heap leach products.

PVC under drain pipe is supplied with precious machine slots which provide greater intake capacity and continues, clog resistance, drainage of fluid, as compared to standards round hole as perforated pipe. Slotted under drain reduce entrance velocity into the pipe ,therebyreducing the possibility that solid will carried into the system. Slots row can generally be positioned symmetrically or asymmetrically around the pipe circumference , depending upon the application outside diameter are generally the same. For PVC or Non Corrugated polyethylene HDPE pipe. However the HDPE must be extruded with a thicker wall (and therefore a reduced cross sectional flow area) to obtain a comparable stiffness rating.

Types of Screen Design

 

Kawsar Slotted screens are obtained by making cuts all over the PVC pipe in order to exploit the screen collecting capability to maximum level. Slots are horizontal to pipes generatricles. Data show that horizontal opening are very hydraulically efficient and provide high collapse resistance thanks to the arc shapes of the material around them.

PVC slotted screens are usually used in fine soils to build up artesian wells, for drainage etc.

The product is manufactured according to customers need: the slots length and the number depend on the requested open area, moreover, cuts can be made on one, two, three or four sides of the pipes whereas the slots width is related to soil granulometry.

 

VERTICLE SCREEN

 
 

HORIZENTAL SCREEN

 
 

PERFORATED SCREEN

 

 

 

SLOTTED PIPE

 

 

 

CALCULATION OF PERCENTAGE OF SLOTTED AREA

 

 

PVC SCREEN TRANSMITTING CAPACITY - SCHEDULES 40 & 80

 

 

Pvc Pressure And Strength Tables

Testing methods and procedures used are in compliance with ASTM F480 standards for thermoplastic pipe in all applicable areas.

Note

  1. Values noted with an asterisk (*) are based on minimum wall & include a 50% safety factor.
  2. Values noted with a double asterisk (**) are recommended dry hanging weight for threaded PVC schedules 40 & 80.

These values are calculated based on the minimum cross sectional areas of either the box or pin thread portion of the joint after machining. The resulting minimal area was multiplied by 7,000 psi tensile strength per ASTM D-1784 to yield the recommended dry hanging weight. even through these calculated values are lower than actual Johnson screens test data. Johnson recommends not to exceed the above values for well construction.

JOINTING TYPES

 

THREADED JOINTS

 

BELL END JOINTS

 

 

INSTALLATION & JOINTING PROCEDURE:

 

Arrange the pipe assembly on the ground.

 

  • Fix the centering guides the pipes once in every 15 meters (minimum), just below the neck of the socket, with the open end of the centering guides facing upwards while lowering . Always use a plain casing pipe (sand trap) for the first pipe to be lowered, with a conical end cap(Bull-nose) blanking the spigot end of the pipe. Fill this pipe with water or drilling fluid before lowering into the well.
  • Wash the remain borehole thoroughly with fresh drilling fluid (Bentonite Solution) for 40 – 45 minutes from the bottom , keeping the specific gravity of the drilling fluid to below 1.4 This will prevent heavy sedimentation at the bottom of the borehole and also easy lowering of the assembly.
  • To obtain better result, ensure that the reamed borehole is at least 15 to 20cms more than the outside diameter of the casing pipe.
  • The Sand trap is the lowest pipe in a tubewell and is the first to be selected. Fit this pipe with an end plug (cap) and centering guide.
  • Lower the sand trap into the borehole and hold with a split clamp with the socketed end facing upward.
  • The next pipe, which is either a screen pipe or a plain pipe(depending on lithology of well ) is fitted to sand trap by screwing them together.
  • Jointing pipe can be done either by strap wrench or with manila rope. Never used a chain range. Clean the threads to remove mud or burrs using wire brush. Soap solution maybe used to lubricate the joints Avoid grease or waste oil.
  • Fit the socked end of the next pipe (Which can be a screen /plain casing) with the fitting cap.
  • Connect the lifting cap securely with the wire rope of the drilling fram. Use winch of drilling machine to lift the threaded pipe string.
  • This pipe string is jointed to the pipe already lowered into the borehole.
  • Center the assembly pipe string and permit it to descend into the borehole by releasing the split clamp, Fill the pipe with water or mud solution to equalize pressure.
  • Repeat the operation till all the casing and screens are lowered according to the lithology of the well. The time needed to make each joint is less than 5 minutes.
  • Lowering time can be reduced by the casing and screens on the ground to make additional lengths. Do this correctly as per lithology of the well to avoid wrong placement of screens in the bore well.
  • Do not set the lowered pipe assembly at the bottom of the borehole. Ensure at least 10 feet of free bore below the sand trap. This help the lowered casing and screen pipes to remain hanging and achieve a vertical installation.
  • Centering guides should always be fixed at a minimum interval of 1.5 meter to ensure uniform gravel asking around the casing and screen pipes.

 

KAWSAR Well casing are made available up on orders within shortest possible time period in vertical & horizontal slots along the length, however customized screening pipes provided with pores can also be produced fulfilling all requirements while considering requisite technical parameters.