Performance Evaluation of Perfo Spray Irrigation System

Transcription

1 Performance Evaluation of Perfo Spray Irrigation System K. L. Bidkar 1, K. T. Phalak 2, P. D. Jadhao 3 kisan_bidkar@rediffmail.com 1, phalak_kt@rediffmail.com 2, jpradip11@rediffmail.com 3 1, 2, 3. Civil Engineering Department Sandip Institute of Engineering and Management, Nasik, India 1, 2 K. K. Wagh Institute of Engineering Education and Research Centre, Nasik, India 3 Abstract In India both surface and ground water, are scare and its proper utilization is must. All flow irrigation system gives about 40 to 45% efficiency. Search for, a most efficient irrigation method for private users was studied and solution to this is, pressurized irrigation methods. Perfo Spray System has effective use of Water, Irrigation of steep and rolling topography without producing runoff and erosion, Proper irrigation of shallow soils, Frequent watering whenever needed for germination crop is possible Labor saving, Leaching of salts from saline soils, Keeps crop free from insects and diseases. This system operates with low pressures (5 to 15m), This system has high application rate hence irrigation time is less and hence more are can be irrigates by moving lateral in short time with careful handling Useful for vegetable fields, nursery and orchards. Keywords Perfo Spray, Uniformity Coefficient, Wetted Width I. INTRODUCTION Use of sprinkler system being in the early part of this century. The earliest type used was lawn sprinklers. Before 1920 sprinklers were used only for orchards, nurseries and intensive vegetable production. After 1930, Light weight sprinklers. In 1950, Aluminum pipe and efficient pumping sets, better sprinklers, further increased the use of sprinklers. After 1960, successful efforts were made to increase efficiency of sprinklers, to reduce labor cost this lead to wide use of sprinkler system. Type of Sprinklers: Sprinkler systems are divided into two basic parts. 1. 'Set System' that operates with the sprinkler set in a fixed position. 2. 'Continuous Move System' that operates while the sprinkler is moving the field. 'Set system' is further divided into periodic move system and fix system. Periodic move system include hand move, and tow & side roll laterals, side move laterals with or without trail lines and gun and boom sprinklers. Fix system includes small or big gun sprinklers mounted at stationary positions, orchard sprinkler, perfo spray, hosefed sprinkler grid. Continuous move system includes travelling sprinklers, centre pivot, linear move lateral. The detail classification is given below: (A) Periodic Move System a)hand Move b) Toe c)side Roll d)gun Boom (I)Set System Sprinkler (Types) (B) Fix System (II )Continuous System (A) (B) Travelling Centre Pivot A. PERFOSPRAY PIPE SYSTEM Perfo spray pipe system spray water from small holes drilled at uniform distance along the top and sides of the lateral pipe. The holes are sized and spaced so as to apply water reasonable uniform between adjacent lines of perforated pipe. Each hole emits a jet of water which in rising and falling breaks up into small drops that are sprayed by air turbulence over the irrigated area. Components of Perfo Spray System: [1] Pattern and Performance Arrangement: In perfo spray irrigation laterals, the holes are drilled in a standard pattern and the pattern sequence is repeated at precise interval along the length of the line. In this particular system, in a pattern sequence seven holes are provided and this pattern sequence is repeated at every 26 inches. This pattern decides the distribution of water application. IJETT ISSN: April 2015 Volume 2 Issue 1 266

2 [2] System Layout: The layout consists of i) 'Water source (S) ii) Pumping unit (P) ii1) Filter unit (F) iv) Main line (M) There may different layouts of main pipe and lateral, Fig. 2 Perforated Portable Line v) Laterals. Fig.1 Layout of Perfo Spray Irrigation System Also following parameters to be considered: 1. Number of holes, their arrangement and diameter combine to fix the characteristics of particular perforated pipe. Wetted width depends on above factor. 2. Distribution pattern to be Rectangular. 3. Limiting wind speed = For better performance, lateral should be moved closed to field boundary from which wind is blowing. The above points should be kept in mind while preparing layout of the system. Water is pumped from water source and it passes the filter, then through main pipe it is supplied to laterals, which applies water through perfo spray. Fig. 3 Nozzle Line II. DESIGN PROCEDURE AND OPERATION CHARACTRESICS 1) Deciding application rate according to soil type and soil characteristics. 2) As per field size find out optimum lateral spacing length of lateral. 3) Then for above factors find out dia. of lateral with standard whole pattern and lateral inlet pressure and lateral discharge. IJETT ISSN: April 2015 Volume 2 Issue 1 267

3 4) Find out how many laterals are to be operated at a time and then, accordingly find out discharge of main pipe and design main pipe. [3] Application Rate Perforated pipe is available only for few rates of application ranging from 19 to 25 mm/hr. This limitation is due to fact that relatively large perforation must be used to obtain uniform coverage and to avoid excessive clogging. This limit in application rates reduces flexibility in design. A lateral spacing of 12 m, less than the water spread is used to provide sufficient overlap between wetted patterns to prevent dry areas. Where winds are over 8, overlap of 1.5 to 2.0 m is recommended. The spread depends on the operating pressure, thus pressure can be adjusted to obtain wide range of lateral spacing. [4] Lateral Length The length should be such that the pressure variation along the line should be within prescribed limit (These are given in manufactures catalog.) High application rate also restrict length of lateral. [5] Lateral Design Since perforated pipe lateral have equally spaced outlet, the general principle applicable to the design of lateral with other sprinkler system also apply to perfo spray type. The manufacturer of perforated pipe have simplified the design of laterals by furnishing performance table for each combination of pipe size and application rate for given length of the line and desired spread; it is easy to read the operating head and lateral discharge. III. SYSTEM EVALUATION A. EQUIPMENT NEEDED For concluding elaborate evaluation of the perfo spray sprinkler system following equipments is required. 1. A tape, for checking hole spacing and wetted width, height of trajectory etc. 2. Catch can is to collect the applied water. 3. Pressure gauge to measure pressure at different point along lateral. 4. Stop watch or watch. 5. Buckets to collect discharge from selected jets. 6. Measuring Cylinder To measure discharge collected into catches and buckets. 7. Leveling staff and Dumpy level. B. INFORMATION TO BE COLLECTED 1. Catch can discharge to be collected in specific pressure to get application rate and distribution pattern. 2. Wetted width and height trajectory along the lateral, to decided optimum length. 3. Pressure along the lateral to see whether operating pressure difference is within acceptable limit. 4. Discharge the selected holes to find out discharge per unit length. 5. speed and direction. 6. Hole size and extent of clogging. Other information such as i) Type and make of pipe. ii) Hole patterned its sequence. iii) Type of soil etc. IV. ANALYSIS AND RESULTS A. OPERATION PRESSURE The system was evaluated at different condition (a) Lateral sloping downward with slope 3%. (b) With lateral zero slope. The pressures are observed at different points and they are tabulated in table No. I, it can be seen that for a) For sloping lateral, the variation in pressure in initial portion and end position of lateral is nil i.e., friction head loss is compensated by downward slope. This is case for all operating pressure i.e., 1.0 kg/cm 2, 1.5 kg/cm 2 and 2.0 kg/cm 2. b) For horizontal lateral, the observed operation pressure were from 1.4 kg/cm 2 to 1.0 kg/cm 2 along lateral from initial to end of lateral. B. THE WETTED WIDTH The wetted widths observed for different pressures are tabulated in table. No. V and VI for pressure 1.0 kg/cm 2,1.5kg/cm 2,2.0 kg/cm 2 with different wind direction of speed. The readings are taken for different wind directions and wind speeds and from the table we see that, a) When operating pressure is increased; the wetted width increases. b) The wetted width on wind down side is more than the other side. c) As the wind speed across the lateral increases; wetted width increases, due to earring water along with wind. d) When wind is blowing parallel to lateral it has less effect on wetted width. C. JET CHARACTERISTICS The trajectory observed was very uniform along the length of lateral. For all pressures, from table VII, it can be seen that, average trajectory for observed rate of 1.0 kg/cm 2 = 3.70 m, for 1.5 kg/cm 2 = 4.35 m, and for 2.0 kg/cm 2 = 5.25 m It is approximately 1/3 rd of the width of coverage which is typical for perforated pipe. The alignment and uniformity pattern sequence were very good. D. FLOW RATES Several holes are checked at different pressures. The pipe is turned and one jet is taken in the bucket for 60 sec. Then IJETT ISSN: April 2015 Volume 2 Issue 1 268

4 average volume caught/ho1e for particular is calculated. The results tabulated in table no. I E. UNIFORMITY APPLICATION Uniformity of the sprinkler pattern was estimated by catch can data. This data is given in table no. II, and III for operating pressures 2.0 kg./cm 2, 1.5 kg/cm 2,1.0 kg/cm 2 the top figures are actual caught and bracketed values are application rate mm/hr. The coefficient of uniformity is calculated for different pressures with different over lapping. The results are given in the table II and III. F. CLOGGING Clogging is main problem in using perforated pipe irrigation and much care is necessary in order to minimize the problem. All water taken from water supply should clean or must be passed through filter. The pipe can be clogged by debris picked up while pipe is being moved. The inspection showed that 10 % of the holes are clogged fully and 12 % partly. pipe has suffered more. V. RECOMMENDATIONS From the evaluation test following recommendations can be made, [1] From table II, III it can be seen that pressure 1.0 kg/cm 2, 1.5 kg/cm 2 gives better uniformity in application (81 % to 87% ). But at operating pressure 2.0 kg/cm 2 and above the uniformity in application is not achieved (33% to 75%) due to formation of very small droplets due to high pressure and these droplets are carried by wind and drift, hence uniformity is affected. Hence operating pressure should be less than 2.0 kg/ cm 2. It is as the recommendations of manufactures. [2] Lateral spacing calculated as per uniformity criteria are i) From table IV for l.5 kg/cm 2 = 10 m. ii) From table III for 1.0 kg/cm 2 = 8 m. [3] The present evaluation was carried out on soil which has basic infiltration rate equal to 15 mm/hr. The test showed more runoff, erosion on the field and from table VII, it can be seen that, application rates calculated from hole discharges (bracketed) are same for all three pressures. This is due to increase in wetted width with increases in operating pressure, resulting into almost same application rate. The application rates same were observed below: [4] The discharge calculated per unit length (from holes), generally tallies with the performance table with application rate as 25 mm/hr from table I. [5] From table I, it can be seen that for sloping lateral down ward 1 to 2.5 % there is no problem of pressure variation. But in case of leveled lateral the pressure variation at initial to end section is 24 %which is nearer to acceptable limit ( < 20%) and discharge variation 7.5 % from inlet to last pipe which is also with acceptable limit (i.e. 10%). This perforated lateral up to 60m can safely be used for zero slopes. [6] It is learnt that the system is recently purchased and installed, even then it was observed that there was 10 % of the holes were clogged fully and 12% partially clogged. (Ref. table VI). i) System should be operated with filter unit in future. ii) Handing of lateral should be careful to avoid earth or mud into the lateral. iii) Lateral should be flushed before each irrigation. [7] It can be seen from the catch can data, table II, and III, that uniformity of application is affected specially at the initial and end es of the lateral when wind direction is not perpendicular to lateral. Hence as per as possible, the layout should be such that the lateral is perpendicular to the wind direction. VI. SUGGESTIONS FOR FURTHER STUDIES 1. System should be evaluated for pressure below 1 kg/cm 2 (say 0.8 kg/cm 2, 0.6 kg/cm 2, 0.4 kg/cm 2 ). 2. Up slopes lateral alignment should be tried to find out maximum allowable lateral length. 3. System should be evaluated for actual field conditions. When crops are being grown. To find out water application efficiency, water requirement efficiency and coefficient of uniformity. 4. Evaluation studies may also be carried out using more than one lateral operating at a time, so as to suit the available pump capacity. i) 1.0 kg/cm 2 operating pressure = 26.5 mm/hr. (for 8 m spacing). ii) 1.5 kg/cm 2 operating pressure = 26.0 mm/hr (10 m spacing) Hence system should be used for these soils which has basic infiltration rate more than 25 mm/hr. To avoid runoff and erosion of soil and to have high water application efficiency. IJETT ISSN: April 2015 Volume 2 Issue 1 269

5 Table I Volume Caught/hole/min for Different Pressure & Slope of Lateral Table II Catch Can Data for Pressure2.0 kg/cm 2 Pipe No Lateral 2.5% down 2.0 kg/ 1.5 kg/ 1.0 cm 2 cm 2 kg/ cm 2 Vol. Vol. Vol. Caught Caught Caught / / / Hole/ Hole/ Hole/ min min min (in lit) (in lit) (in lit) Zero Slope 1.4 kg/ cm 2 Vol. Caught/ Hole/ min (in lit) l l l Lateral Initail Dir. = 4.06 = 4.06 = 4.29 Catch Can caught (cm3/hr) (12) (27) 1320 (15) 1730 (17) (49) (33) (17) (2) (32) (30) (20) (5) (48) (29) (17) (7) 3130 (37) 3600 (39) 4750 (52) (0) ( 6) (12) (24) (38) ( (2) (14) 5) (50) (16) (30) (54) l l Mean = 4.29 = (36) (26) (10) (0) (46) 2360 (8) 4600 (26) (50) 3200 (10) (36) (6) (16) 660 (8) 2300 (26) (0) (2) (52) (2) (24) (12) 1680 (18) 540 (6) (2) 100 Bracketed no. are mm/hr IJETT ISSN: April 2015 Volume 2 Issue 1 270

6 Table III Uniformity Coefficient (CU) from Catch Can Data for Different Pressure & Lateral Direction =4.06 =4.29 =2.10 =3.1 =1.37 =5.16 =3.1 =2.29 =4.6 Cu for 12 m lateral spacing Cu for 10 m lateral spacing 75.11%, 83.59% 59.79% 73.43% 33.37% 75.97% 78.88% 74.64% 62.19% 86.96% 66.92% 81.29% 87.81% 53.21% For Pressure 2.0 kg/cm2 1.0 kg/cm2 1.5kg/cm2 Pres sure (kg/ cm 2 ) Table V Wetted Width for Different Pressure and Direction speed () Wette d Widt h speed () Wetted Width speed () Wette d Width Table VI Wetted Width for Different Directions for Operating Pressure 2.0 kg/cm 2 Pipe No at 2 kg/cm2 Trajectory height at1.5 kg/cm2 at 1.0 kg/cm2 Holes Clogged Full (No.) Holes Clogged Partially (No.) Pipe Table IV Wetted Width for Pressure 1.0 kg/cm 2 with Different wind Direction speed 3.1. speed 1.3. speed Left Right Total Left Righ Total Left Right t Total IJETT ISSN: April 2015 Volume 2 Issue 1 271

7 Table VII Average Depth Applied Pi pe No Opera ting Press ure (kg/ cm 2 ) Late ral Spac ing of Lateral Av. Depth Applied (mm/hr) wette d width From Hole Dischar ge rate (mm/hr) (24) (24) (24) (23) Bracketed figures are less values due to the effect of clogging. Remarks The application rate arrived by hole, discharge are higher than the application rates arrived by catch can data. This is due to some of the holes clogged and were hence sampled holes gives more discharge. REFERENCES [1] Merrrriam O, Keller O : Farm Irrigation System Evaluation.A guide for management. Utah State University, Lagan, 1978 [2] Finkel H: Hand Book for Irrigation Technology, Vol. I, CRC Press INC., Boca Raton, Florida. [3] Premier Irrigation: Irrigation Management System Design Training Notes Publication No. T60 issue No., [4] Premier Irrigation: Premier PerfoSpray Irrigation System for Forest Nursaries [5] Keller J.: Sprinkler and Drip Irrigation System notes Utah State University Lagon, Utah, [6] P.N. Modi :Irrigation, Water Resources & Water Power Engineering, [7] IrrigationTheory and PracticeA.M. Michael,Vikas Publishing House, Pvt Ltd. [8] R.S. Varsheny: Irrigation Engineering Theory & Design. IJETT ISSN: April 2015 Volume 2 Issue 1 272