SLOTTED PIPES, CASING PIPES AND SCREENS

Discharge in Liters/minute	Calculated Weight (Plain end)
	Minimum	Recommended
Up to 475	100	100
475-1125	150	150
1300-3000	200	250
3000-5250	250	300
5250-9500	300	350
9500-13300	350	400
13300-19000	400	450
19000-26500	450	500
26500-34000	500	550

Selection Off Screen Diameters
The designed yield of a tubewell is 150m²/h (1.5 Cusecs) and a screen having 20% open area is proposed to be used in a length of 20m to tap an acquifer of 25m thick. Diameter, of the screen is to be worked out.
As Q = A x V

Where Q = discharge in m²/s, A = effective open area of the screen
V = entrance velocity in m/s (to be ltd. to 0.03 m/s)

Therefore, A = 150/3600 x 1/0.03 = 1.39m²
Taking effective area as 50% of that provided, in order to taking into account the reduction of the effective area of the screen opening with time due to incrustation rearrangement of the acquifer particles around the screen and coverage by gravel, etc.

Grains size curves of a typical aquifer materials covering sand are shown in figure :

Very Fine Sand Fine Sand Medium Sand Coarse Sand Very Coarse Sand Gravel All Dimensions are in Millimeters

The required open area = 2 x 1.39 = 2.78m²
Open area of pipes = x d x l x open area
Where d = dia of pipe, l = length of pipe
Therfore, d = 2.78/ x 20 x 20 = 0.22m or 220mm

The required sceen dia works out 220mm.

Selection of Slot Size
Acquifer Material Classification - The acqifer material may be classified into various categories according to the following ranges of the particle size:

Fine Gravel	- above 2.0 mm
Coarse Sand	0.5 - 2.0 mm
Medium Sand	0.25 - 0.5 mm
Fine Sand	0.05 - 0.25 mm
Silt	0.002 - 0.06 mm
Clay	below 0.000 mm

Typical Slot Pattern

All Dimensions are in Millimeters Developed view of a typical well screen plan slotted type	All Dimensions are in Millimeters Slotting Arrangements

SOCKETED CASING PIPES

Nominal Bore of Pipe	Outside Diameter of Pipe	Thickness of Pipe	Mass of Plain Tube	Socket Outside Diameter	Overall length of Socket, min
100	114.3	5.4	14.5	130.0	114.3
125	141.3	5.4	18.1	157.0	120.6
		7.1	23.5
150	168.3	5.4	21.6	154.0	127.0
		7.1	28.2
175	193.7	6.4	29.6	211.6	152.4
		8.0	36.6
200	219.1	6.4	33.6	237.0	152.4
		8.0	41.6
225	244.5	7.1	41.6	262.5	165.1
		9.0	52.3
250	273.1	8.0	52.3	291.0	177.8
		10.0	64.9
300	323.9	8.0	62.3	346.0	177.8
		10.0	77.4

The values have been calculated on the basis of the formula:
W=0.024 66 x (D-t) t kg/metre. Where D = outside diameter in mm, and T= thickness in mm.

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PLAIN CASING PIPES

Nominal Bore of Pipe	Outside Diameter of Pipe	Thickness of Ppipe	Mass of Plain Tube
(mm)	(mm)	(mm)	(kg/m)
100	114.3	5.0	13.48
125	141.3	5.0	16.80
150	168.3	5.0	20.13
175	193.7	5.4	25.10
200	219.1	5.4	28.46
225	244.5	6.0	35.29
250	273.0	7.1	46.57
300	323.9	7.1	55.47
350	355.6	8.0	68.57
350	355.6	10.0	85.22
400	406.4	10.0	78.60
400	406.4	10.0	97.75
450	457.2	10.0	110.28

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