Polarstar Kythera SA Metering Screws

These metering screws are used to adjust the speed of the nozzle as it returns forward. There is a precision orifice through the screw that limits flow into the dump chamber. The smaller the orifice, the slower the nozzle moves.

Size Selection:

As of serial number 4581, Kythera SA systems ship with the 0.024" screw installed. To reduce nozzle speed, select a screw with a smaller orifice size. The majority of installs operate fine with the stock screw. If it is already feeding reliably, there isn't much to gain by reducing nozzle speed.

The 0.015" screw is an extreme reduction in flow and will significantly impact nozzle speed and maximum rate of fire. We do not recommend this size except in special cases.

Orifice Size vs Input Pressure:

Since the metering screw limits recharge rate and nozzle speed, the maximum rate of fire will be reduced if a smaller orifice is used at the same input pressure as a larger orifice. The smaller screws are generally used at higher pressures where the nozzle speed has increased due to additional force/flow, so in most cases max rate of fire has already increased and the smaller orifice is only reducing back down to where it was originally.

NOTE: The metering screws have a 1.5mm hex drive. Be very careful when installing or removing them as to not strip the drive. There is no need to torque them so FINGER TIGHT ONLY.