COMMON SPRAY SYSTEMS IN KENYA

COMMON  SPRAY SYSTEMS IN KENYA

CENTRAL SPRAY UNIT AND PUMPS

1. On CSUs the pressure should never normally need to exceed 25 bar. Most farms use a pressure in the range 20 -25 bar. This is perfectly adequate with small (size 8/10) nozzles for general pesticide application.
2. On CSU pumps the oil should ALWAYS be at a level BETWEEN the Max and Min indicator marks on the resorvoir. This level should be checked with the pump off. Never let oil be above Max or below Min. too much oil will cause pressure build up and will lead to leaking seals and diaphragms. Too little oil will result in insufficient lubrication,leading to parts wear and permanent to the pump. This also applies to pumps on tractor mounted hose reel sprayers.
3. Check and clean suction and agitation filters on C.S.U Tanks DAILY.If this is not done the filters can get blocked. Again, this will lead to excess pressure build up in the system and failure of seals, diaphragms and valves.
4. Check fan belts on motor/ pump pulleys regularly for wear, and replace when they show any signs of cracking / splitting. Do not run your pump with less than the required number of fan belts. This will strain the pulley.
5. The oil used in the pumps should be petrol oil 20 w 40. this normally will not need frequent topping up and only needs a to be changed when pump under goes 500 hour service or major repairs. Change oil much more frequently for smaller output pumps,say between 70 to 200 hours.
6. Please ensure that C.S.U operator does not EVER close off the agitation valve during operation in order to build up pressure. If this valve is closed and the pump is running then pressure will build up in the system and damage to seals and valves will occur.
7. Please ensure that when the spraying operation is completed the pressure regulating valve is turned off so that pressure is released from the system. This is essential in order that, when the machine is switched on again, there is no pressure remaining in the system. Once the machine is started the pressure regulating valve should be turned gradually to increase pressure to the desired level. If this is not done then there will be excess pressure in the system which will damage your pump.
8. If a pump develops a problem at any time when spraying then the unit should be stopped AT ONCE and one of your technicians should be called to inspect it and repair if necessary.
9. Ensure that any repairs are ONLY carried out by those technicians who have the necessary skills and competence.
10. Always keep a stock of spare parts on the farm so that you can carry out repairs in a timely fashion.
11. How to work out pump capacity / no . Of lances: for example, a pump with an output capacity of 106 litres per minute at max, pressure of 50bar . If you have eight lances , with two nozzles each, spraying simultaneously, that will be a total of 16 nozzles at a pressure of 25 bar (you should not need to go higher than this pressure ever), that will be an output of 1.07litres per minute per nozzle; x 16 nozzles = 17.12 litres per minute. The pump can handle 106 litres per minute, but there is some pressure loss due to friction in the pipework , although this is not normally significant.
12. General information: if the oil resorvoir on any pump is overfilled, this can cause the seals inside the pump to give way due to too much pressure. The oil should ONLY be between the Max and Min marks on the reservoir. The control unit can also have problems. The pressure gauge needs to be checked regularly. Without a working pressure gauge there is no way that you can ever calibrate your sprayer effectively; poor / no calibration is a very sure way to lose lots of money very quickly on the farm. The lances / nozzles are precision items of equipment and should be treated accordingly. They should be dismantled and cleaned DAILY after spraying,checking all nozzles, swirl plates, o-rings and filters are present and intact. They should NEVER be rested on the ground / in the mud. The filters will not get blocked by Wettable powder chemicals if the agitation in the tank is working properly, and the correct dose of chemical is used. If these requirements are not met then the powders will not dissolve properly, and the filters will of course clog up.

PETROL DRIVEN WHEELBURROW/PORTABLE AND TROLLEY SPRAYERS

You should regulary,before starting the engine, check and top up oil,if necessary. Check also the spark plug. The plug should be changed every 200 hours of use. The oil needs to be changed every 25 hours with 20w 40/50. you should also clean the air filter element regularly with compressed air and replace it every 100 hours (or 50 hours if used in very dusty conditions). Fuel can be of any octane rating but be sure the appropriate oil is used. You should keep a log book with the machine, recording accurately hours used, so that you can adhere to the above mentioned service intervals.

MOTORISED KNAPSACK SPRAYERS

Make sure you mix petrol and 2-stroke oil in a ratio of 25:1 as a standard rule.failure to which the engine perfomance is compromised with too much smoke or knocks and ceases if petrol is used without

mixing with oil or wrong oil is used.Apart from lubrication oil lowers the octane rating of the petrol used and improves its combustion.After every 20 minutes of work,rest the sprayer for7-10 minutes

to enhance better cooling. Avoid full throttle all the time for better maintainance.Avoid interfering with the fuel/air mixture set up as set by manufacturer.Only replace spark plug or adjust the gap as per the specification.Tighten loose bolts and nuts after every day of use .Remember to use chock button effectively and only when required;ie when the engine is cold.

MANUAL KNAPSACK SPRAYER(Read good qualities of a knapsack sprayer ,mantainance and calibration on good spraying practice concept.)

BOOM SPRAYERS(Reff spray systems)

LANCES / NOZZLES

Many sprays lances I have seen are in a terrible state, leaking chemicals all over the place. The big problem here concerns cleaning / maintenance . The spray lance and nozzles are precision items of euipment and must be treated as such in particular.

1. Never put lances /nozzles on the ground / in the mud. This will cause blockages and damages to the nozzles.
2. Never use pliers to tighten the nozzle caps. If something needs to be tightened then ONLY do it by hand. Pliers or a spanner should ONLY be used to loosen tight caps . If there is a leak, then dismantle the nozzle holder and check the 'o' rings are present and in good condition. Keep some spare 'o' rings , filters, swirl plates, nozzles and RG caps in stock. Nozzle filters and swil plates should ALWAYS be present. The filters prevent blockages, and the swirl plate is designed to help the nozzle spray properly. Without the swirl plate the nozzle will NOT work properly.
3. NEVER EVER unblook a blocked nozzle with a pin or wire. These ceramic nozzles are designed to last far much longer than metal nozzles when using high pressures and abrasive chemicals; but they are delicate and will be easily damaged by probing with a pin, needle or wire. If a nozzle ever gets blocked then it should be removed from the holder and cleaned in a bucket of clean water , using an old toothbrush . Also clean the filter and swirl plate at the same time. The spray team should ALWAYS carry a bucket of CLEAN water and a toothbrush in the field when spraying.
4. Ideally the nozzles / filters / swirl plates should be cleaned carefully AT LEAST once a week and preferably every day after spraying. Also check all 'o' rings are present and in good condition.
5. Whenever dismantling / reassembling nozzle holders please ensure that all the pieces are VERY CLEAN, especially the threads of the nozzle holders and caps. If they are replaced with dirt / soil in the threads then those threads will e stripped off and the whole thing will leak . Then you need to replace them. It is NO GOOD to use thread tape/sisal string etc to do these repairs. If it is leaking then open, check and clean if necessary-DO NOT use thread tape and DO NOT tighten with pliers. All of the nozzle holders and caps will need replacing on lances if they are worn out for this reason.
6. ALWAYS use water as clean and filtered as possible when filling the spray tank. If necessary use an even finer mesh sieve on top of the one in the tank opening. This will decrease the chances of blockages of filters / nozzles, increase the efficacy of the chemicals and decrease wear on the pump and its diaphragms and valves.
7. NOZZLES (example) I checked the flow rates of the four nozzles on a customer's lances. They were giving output as follows (in litres per minute) 1.35 / 1.48 / 1.05 / 0.80. this was at a pressure of 10bar. The size brown nozzle is designed to give 0.68 it/min at 10 bar. It is recommended to replace them when flow rate exceeds 10% from original flow (indicated on the attached chart). In this case 10% greater than 0.68 lt/min is 0.75 lt/min. These nozzles were effectively causing the customer to spend 50 / 56/35 /15% more on chemicals than they needed. If you add these percentages to the monthly chemical bill an multiply by 12 months in a year you can work out how much money can be literally poured down the drain by worn out nozzles. Worn out nozzles will also do a WORSE spray job by overdosing with heavy droplets that do not stick on the leaves, but run off onto the ground.
8. A good spraying pressure with size 10 (brown) nozzles in 20 – 25 bar. This does not need to be exceeded. It will give a good a good fine spray with good penetration for most insecticide / fungicide applications.
   Calibration jug with accurate litre measurements up to 2 litres
   stopwatch or watch with a secondhand.
   You set the pressure to 10bar or whatever pressure you want to test.
   You spray ONE nozzle into the jug at a time, timing for one minute
   you measure the output and compare it to the flow rate indicated on the chart
9. this takes 20 minutes maximum and well SAVE you a fortune. The cost of new nozzles can not compare to the cost of chemicals and you will see how important and cost effective it is to check these rates regularly. This exercise also enables you to check that your pressure gauge is accurate.
   If you observe all of the above requirements then you will achieve overall a better, safer,cheaper and more efficient spray job with your sprayer. The principles obviously apply to any sprayer on your farm.
   In the meantime please impress upon your spray team the importance of CLEANING AND MAINTENANCE as part of GOOD SPRAYING PRACTICE.