I have the problem of frost protecting our berry crop with irrigation sprinklers and the process works well if I could only figure out a way to keep the sprinklers from icing up while they are working.Ice accumulates on the flipper arm and the sprinkler stops turning.Also, ice accumulates on the spring that works the flipper. The spring is metal and the body of the sprinkler is plastic. I've tried spraying the sprinklers with white lithium grease and that didn't work.Also WD 40 failed. Any suggestions PLEASE!!!
Normally water supplies are installed underground in a frost proof fashion, so they don't ice up even when there is no flow. This means that the water out of the tap should have a temperature a few degree above 0 Celsius, even in winter. I assume this applies to your water supply too.
My concern is the connection from your tap to the sprinkler on the field. If this is installed above ground or is just a free running garden hose, the water may well cool down enough that it is close to freezing at the nozzle of your sprinkler.
My suggestion would be to apply some form of insulation to any such supply line. Raking loose soil or leave mould onto any pipe directly on the ground would be a good and cheap first attempt to prove the case and might make already enough of a difference to reduce or even stop the icing altogether. The sprinkling against frost damage is not feasible at very low temperatures anyway.
If you got a lot of uninsulated pipe that is not on the ground, par example vertical lines to overhead sprinklers, you could use bubble wrap to add some further insulation.
I also agree with the other answers on protecting the spring with some form of cover, as has been done with this sprinkler head, that is specifically build for frost sprinkling.
I will try to give a direction since I do not know the exact details (exact construction of the sprinkles, temperature ranges and availability of power)
In short, try heating up the parts of the sprinkles the freeze. Try putting a thermal lining thing (that e.g. a cooling bag is made of) around them to form a bag/box around the parts you want to protect but so that it can still operate/rotate and condensate flow out of it. Now depending on temperatures you need a source of heat. I found that an old good 15W light bulb was enough in a similar application (a thermo box to store vegetables outside during winter). You may be lucky to be able to power it off a solar panel if it produces enough energy to keep it independent of main power. One may be able to generate some power off flowing water under pressure but it will likely be not be enough. Otherwise running low voltage wires along with the pipes may be an option.
Ordinarily I'd suggest using resistance heating wire. That would work for the spring, but IIRC the flipper is a moving part that hits the water stream, so it'd be difficult to wire that up. Maybe you can heat up the stationary part that the flipper sits on.
You could try wrapping a thin plastic sheet around the spring. Tape the plastic to both ends of the spring so the plastic will move around as the spring contracts and expands. The plastic prevents water from getting in between the spring windings at least, and perhaps the plastic will move around enough for accumulated ice to break off before it can clog up the spring.