Sunday 4 January 2015

Design of Sprinklers System on very high steep slope using Hammer Pressure Theory in State of Himachal Pradesh



During the year of 2008-09 Department of Agriculture, Government of Himachal Pradesh, decided to launch an ambitious project namelyDiversification of Agriculture through Micro Irrigation and Related Infrastructurewhich is now a flag ship State Sponsored Scheme and is being implemented with name of Pandit Deen Dayal Kisan Bagwan Samriddhi Yojan Part II. The project was submitted to NABARD for consideration under Rural Infrastructure Development Fund (RIDF) – XIV.
During the appraisal it was found that proposed project was based on very preliminary and tentative estimate. One of the serious flaws in the proposal was lack of design of sprinklers systems which are to be implemented in varying topography of Himachal Pradesh. There are large variations in topography especially slope parameters in Outer- sub Himalayan Zone (Siwaliks), Lower Himalayan Zone, Higher Himalayan Zone and Tibetian or Tethys Himalayan Zone. Hence, Hydraulic and Structural Design had to be devised for different topographic conditions.
A technical team in a personnel capacity and on voluntarily basis was associated comprising following resource persons :

Late Er. Y. P. Thakur
Executive Engineer,
Division Shimla
Agriculture Department, Government of HP
Chairman

Er. Rajesh Yadav
Manager, NABARD
Himachal Regional office, Shimla
Mission Leader
Er. Aswani Bhardwaj
Assistant Engineer,
Division Shimla, Agriculture Department, Government of HP
Member
Er. Sunil Kumar Kesary
Area Manager
HARVEL Irrigations Private Limited
Himachal Preadesh
Member

About the Project

Sprinkler Irrigation System :  15 Models of the systems were developed which are based on topography of three irrigation systems situated in district Kangra and Shimla for 5 field categories of 0.5 ha, 1 Ha, 2 Ha, 3 Ha and 4 Ha.. In the Kangra district two irrigation systems situated in Dehra and Baijnath Tehsil are representing plain and mid hill area while third one has been taken from Rohru Tehsil of Shimla district representing high hill area of the State. It is assumed that the water source would be either made available though tank irrigation and operating head would be met out from gravitational head of higher contour level or by providing booster pumps of maximum operating head of 35 m. Further in some areas where shallow wells, shallow tubewells, deep tubewells would be feasible, same would be utilised as source of water and water would be lifted by suitable capacity of the pumping machineries. For the systems situated at higher elevation than the available surface water, the low and medium lift systems would be installed as source augmentation structures. However, the first priority would be given to gravitational operation systems. Total area to be covered was 19987 Ha with a project cost of Rs.7,941.40 lakh. The main components proposed under sprinkler irrigation systems are as under :

Main Pipe : All pipes taken in the DPR are HDPE pipes of different diameters conforming to IS 4984. The grade of the pipe taken is of PE-63 up to 4 Kg/sqcm pressure class and PE-80 for pressure class of 6, 8, 10 Kg/sqcm. The main pipeline carries water from the tanks/pumping unit to the various parts of the field and supply water to the portable lateral through hydrants. Main line pipes are proposed to be buried so that they do not come in way of other agricultural operations.

Lateral Pipe : Lateral lines carry water from the main line to sprinklers or nozzles. Lateral lines proposed of HDPE pipes with quick couplings conforming to IS 14151-I Marked) to withstand pressure up to 3.2 Kg/sqcm. It is proposed to be portable. Length lateral pipes are taken in 3 m and 6 m. Each length has quick couplings. All couplings are provided rubber gaskets in female portion, which tightens the coupling and makes it, leak proof.

Sprinkler heads/Nozzles : Rotating head sprinkler nozzle having discharge capacity of 0.48 liters per second at a operating head of 1.76 Kg/sqcm has been taken in the DPR. The through range of the sprinkler is 12 m. The nozzle size of the sprinkler is 5.159 mm. The utilization rate of the sprinkler head is 2.4 cm/hr and 1.2 cm/hr at spacing of 6 x 12m and 12 x 12 m, respectively.

Riser Pipe : The riser pipe connects the rotating sprinkler head to the lateral. The pipe diameter is taken 20 mm with standard pipe threads and height 75 cm.

Hydrant : Brick masonry structure of size 0.45 x 0.45 x 0.375 m is proposed at 40 to 50 interval on main line. 50 mm hydrant including GI riser pipe, 63 mm PP ball valve, 63 mm connecting nipple, plain concrete grouting GI tee, connecting riser pipe with sub main including complete set of fitting etc. 

Accessories : P/F of PP ball valve of different diameter, air release valve of 1 and 2” size, coupled bend, duly coupled tee, duly coupled end cap, sprinkler attachments, Foot batten assembly etc., have been incorporated in the estimate.

Drip irrigation Systems : Items of development under drip system are PVC pipe (63 and 75 mm) and 4 kg/sqcm, 12 mm lateral of LLDPE, flow control valve 75 mm, flush valve PP 63 mm, screen filter having capacity 10 cum/hr, by pass assembly (1.5” x 1.5”), Ventury (1.5’’) with manifold alonwith fittings and accessories. 50 Drip irrigation systems are proposed on pilot basis. The unit area of the field is taken 0.4 ha and spacing of the crop is taken 1 x 1 m. The estimated cost of this model is Rs.42300/- and per ha cost is Rs.106,000/-. Total coverage of this system was 20 Ha only with project cost of Rs.21.20 lakh.

Ponds/ Water Harvesting Structures : 15 models of the 6510 ponds/water storage structures have been proposed. 3 models of Kuchha pond, 3 models of Ponds lined with UV stabilised multilayered core laminated sheet of 200 GSM, 3 models of ponds with poly and brick lining and 6 models of RCC have been proposed. The capacity of the pond vary from 50000 liters to 600,000 liters with estimated cost of Rs.26,000 to Rs.490,000. The Unit costs of the pond/tanks vary from Rs.0.18 to Rs.3.60 per liters with average cost of Rs.0.86 per liter. Total cost of tanks/ponds was Rs.4711.20 lakh.

Low and Medium Lift Irrigation System : 500 small and 500 medium lift irrigation systems are proposed without distribution system. The water would be lifted from the perennial stream through rising main with the help of pumping machinery. Other previsions taken are pump house (medium lift), delivery tank, SOP and LS provision of source management. The estimated cost of low lift and medium lift is Rs.1.25 lakh and Rs.3.40 lakh, respectively. The design discharges have been taken 3 lps and 5 lps, against the total head of 35.85 m and 63.28 m, respectively. Total cost of low lift system was Rs.625.00 lakh  Similarly total cost of medium lift system was Rs.1700.00 lakh.  

Shallow and Deep Tubewells : 490 shallow tubewells (STW) and 10 deep tubewells (DTW) have been proposed as source augmentation structures. Shallow Tubewells are proposed with depth of 35 m and deep tubewells with 70 m depth having single assembly size of 150 mm and 200 mm, respectively. The estimated cost of STW and DTW is Rs.2.0 lakh and Rs.8.0 lakh which is only for drilling and development of tubewell. Total cost of shallow tubewell was Rs.980.00 lakh.

Shallow open wells : 500 shallow well of 2.45 internal diameter and 8 m depth made of RR masonry (0.35 thickness) are proposed as source augmentation structures where sufficient ground water would be available. The estimated cost of the borewell is Rs.1.10 lakh. Total cost of shallow open wells was Rs.550.00 lakh.
 
Pumping Machinery : 7510 number of pumping machinery has been proposed for different models and capacities ranging from 1.0 HP to 15 HP. The per HP cost of different models varies from Rs.5920 to Rs28040 including cost of accessories with average cost of Rs.4430. Total cost of pumping machineries was Rs.999.06 lakh.
Technical parameters

A) General Design : Parameters for the systems requirements for the 5 models  are as under:
    
S.    No.
Particular

Unit
Quantity/ Design Parameter

Model 1
Model 2
Model 3
Model 4
Model 5
1
Total CCA
Ha
0.50
1
2
3
4
2
Sprinkler Nozzle discharge at presure of
lps
0.48
0.48
0.48
0.48
0.48
3
Total No. sprinkler nozzles that will operate at a time from each Hydrant
Nos.
2
4
4
5
7
4
No. of Hydrants that will operate from each sub Main line
Nos.
1
1
2
2
2
5
No. of sub main lines that will operate in each tapping point
Nos.
1
1
1
1
1
6
No. of the tapping points that will operate at a time
Nos.
1
1
1
1
1
7
Sprinkler spacing
 m x m
12 x 12
12 x 12
12 x 12
12 x 12
12 x 12
8
Effective area covered by each sprinkler nozzle
sqm
144.00
144.00
144.00
144.00
144.00
9
Total discharge required to operate the system
lps
0.96
1.92
3.84
4.80
6.72
10
Total No. of sprinkler nozzles that will operate at a time in whole system
Nos.
2
4
8
10
14
11
Total area covered by sprinkler system at a time
Ha
0.0288
0.06
0.12
0.14
0.2016
12
Total number of the shifts required in whole system
Nos.
18.00
18
18
21
20
13
Duration of each shift
min
30.00
30
30
30
30
14
Total operating time
hour
9.00
9
9
10.5
10
15
Taking 10 hours of operation a day
day
1
1
1
1
1
16
Frequency of irrigation
day
3
3
3
3
3
17
Consumptive use
mm/day
4
4
4
4
4

B) Hydraulic and structural design of the lateral : Model wise hydraulic design of the lateral is based on the design discharge as per above general design table and frictional losses has been calculated on the basis of Modified Hazen William Formula and multiple outlet factor. The operating head is calculated on the basis of minimum operating pressure of 1.75 kg per sqcm for operating sprinkler, height of riser is taken 0.9 m and  frictional losses in the maximum length of the lateral pipe for given topography. Accordingly it is observed that the operating head required is varies from 19 m to 22 m, hence pressure class of the HDPE pipe is taken 3.2 kg per sqcm in all the cases. 
                                               
C) Hydraulic and structural design of the Main Pipes : Model wise hydraulic design of the main is based on the design discharge as per above general design table and frictional losses has been calculated on the basis of Modified Hazen William Formula. The minimum and maximum head is adjusted with operating head required for lateral pipe to be jointed at each hydrant points by manipulating diameter of main pipes keeping maximum velocity of 3.08 m/s. All the pressure such as maximum gravitational head at any interval of hydrants (i.e cumulative static pressure) due to change in altitude, hammer pressure due to stopping of hydrants during shifting operation and if the sufficient head is not available then the head developed by the booster pumps are considered while hydraulic designing of main pipes. Accordingly, pressure class of the pipe has been selected on the basis of maximum head possible between the hydrants i.e sum of the cumulative static head and hammer pressure. Hence, 4, 6, 8 and 10 Kg per sqcm having grade PE-63 and PE-80 and diameter vary from 40 mm to 110 mm has been incorporated in different models.

Sample Model Design            

Model Project Name :  Micro Irrigation Scheme at village Bhamnoli in GP Bhamnoli in Tehsil Rohru District Shimla (HP)

The maximum internal pressure likely to come under worst circumstances is taken equal to the sum of full static pressure and water hammer pressure

P = Ps + Ph

Where,

P   = Total internal maximum pressure,
Ps  = Static Pressure, and
Ph  = Water Hammer Pressure


Hoop Tension = P X d / ( 2 x t )



Where,

d = diameter of the pipe and
t  =  thickness of the pipe

Hoop tension should not exceed the Safe allowable tensile stress of the pipe material

Coefficient of Hydraulic Capacity for HDPE Pipe : 1.00  (AS PER MODIFIED HAZEN WILLIAM'S FORMULA)

Optimum Velocity Range      : 0.3 to 1.8 m/s but maximum 2.0 m/s

Operating Head of Nozzle     : 1.76 kg/sqcm (18.13 m of water)

Height of the riser pipe           : 0.90 m

Part I : Hydraulic Design of Main / Sub-Main and Lateral Pipe

S.     No.
Line

RDs

Length (m)
Required Discharge (lps)
Diameter (mm)
Velocity (m/s)
Frictional Losses (m)

From
To
From
To





1
2
3
4
5
6
7
8
9
10
1
Tank
A
0
50
50
6.72
67.2
1.89
2.57

Add 25 m head to be provided by the booster pump
2
A
B
50
100
50
6.72
56.5
2.68
5.91
3
B
C
100
150
50
6.72
53.5
2.99
7.68
4
C
D
150
200
50
6.72
53.5
2.99
7.68
5
D
E
200
250
50
6.72
52.9
3.06
8.11
6
E
F
250
320
70
6.72
52.9
3.06
11.35
7
F
G
320
370
50
6.72
50.6
3.34
10.04
8
G
H
370
420
50
6.72
50.6
3.34
10.04

S.     No.
Line

Hydraulic Level
(m)

Ground Level (m)
Residual Head (m)
Diff. Static Head (m)
Cum Static Head (m)
Pressure Break Provision

From
To
Upper End
Lower End





1
2
3
11
12
13
14
15
16
17
1
Tank
A
1000.06
997.49
975.06
22.43
25.00
25.00

2
A
B
997.49
991.59
964.98
26.61
10.08
35.08

3
B
C
991.59
983.90
954.90
29.00
10.08
45.16

4
C
D
983.90
976.22
947.30
28.92
7.60
52.76

5
D
E
976.22
968.11
939.70
28.41
7.60
60.36

6
E
F
968.11
956.76
929.06
27.70
10.64
71.00

7
F
G
956.76
946.71
921.46
25.25
7.60
78.60

8
G
H
946.71
936.67
913.86
22.81
7.60
86.20


S.     No.
Line

Dia of Lateral
No. of Sprinkler
Velocity
Multiple Outlet Factor
Losses
Operating Head Required
Pressure Class of the pipe

From
To







1
2
3
19
20
21
22
23
24
25
1
Tank
A
53.5
7
1.49
0.4304
1.58
20.61
3.2 Kg/sqcm
2
A
B
53.5
7
1.49
0.4304
1.58
20.61
3.2 Kg/sqcm
3
B
C
53.5
7
1.49
0.4304
1.58
20.61
3.2 Kg/sqcm
4
C
D
53.5
7
1.49
0.4304
1.58
20.61
3.2 Kg/sqcm
5
D
E
53.5
7
1.49
0.4304
1.58
20.61
3.2 Kg/sqcm
6
E
F
53.5
7
1.49
0.4304
1.58
20.61
3.2 Kg/sqcm
7
F
G
53.5
7
1.49
0.4304
1.58
20.61
3.2 Kg/sqcm
8
G
H
53.5
7
1.49
0.4304
1.58
20.61
3.2 Kg/sqcm

Part II : Structural Design of the Main and Sub-main (HDPE PIPE)


Max Hammer Pressure, Ph (max) = 1433 V/ SQRT ( 1 + ( Ew / Ep ) * ( d / t ))


Where,
V = Velocity of Water
Ew = Modulus of elasticity of water )                 : 2100000 KN/sqm ( KPa )
Ep = Modulus of elasticity of HDPE pipe )         : 667000 KN/sqm ( KPa )
d   = Diameter of pipe
t   = thickness of pipe

S.     No.
Line
Length (m)
Dia (mm)
Velocity (m/s)
Cum Static Head (m)
Water Hammer Pressure (m)
Field Test Pressure Which shall be greatest of

From
To





1.5 x Col. 28
Col. 28 &  Col 29
1
2
3
25
26
27
28
29
30
31
1
Tank
A
50
67.2
1.89
25.00
1.23
37.50
26.23
2
A
B
50
56.5
2.68
35.08
1.74
52.62
36.82
3
B
C
50
53.5
2.99
45.16
2.40
67.74
47.56
4
C
D
50
53.5
2.99
52.76
2.40
79.14
55.16
5
D
E
50
52.9
3.06
60.36
2.81
90.54
63.17
6
E
F
70
52.9
3.06
71.00
2.81
106.50
73.81
7
F
G
50
50.6
3.34
78.60
3.44
117.90
82.04
8
G
H
50
50.6
3.34
86.20
3.44
129.30
89.64

S.     No.
Line
Max FTP of Col 30 and 31
Pressure Class of the HDPE Pipe
Dia of the pipe (mm)
Cum Length (m) of pipe of particular dia and PR

From
To




1
2
3
32
33
34
35
1
Tank
A
37.50
4 Kg/sqcm
75.00
50.00
2
A
B
52.62
4 Kg/sqcm
63.00
50.00
3
B
C
67.74
6 Kg/sqcm
63.00
50.00
4
C
D
79.14
6 Kg/sqcm
63.00
100.00
5
D
E
90.54
8 Kg/sqcm
63.00
50.00
6
E
F
106.50
8 Kg/sqcm
63.00
120.00
7
F
G
117.90
10 Kg/sqcm
63.00
50.00
8
G
H
129.30
10 Kg/sqcm
63.00
100.00





Total
420.00

After incorporating all above technical and financial parameters and the detailed estimates, cost of the DPR increased from Rs.143.51 crore to Rs.198.08 crore. We are thankful to Officers and especially to then Hon’ble Chief Minister of Himachal Pradesh for according approval within a very – very short time i.e. within 2 days.

  
This project has now became "State Sponsored Scheme" of Himachal Pradesh's Government and we are so lucky for getting opportunity to formulate this flag-ship Project.