The MK-II Oscillamatic Controller from Williams Milton Roy is a fully pneumatic pulser/timer that drives Williams series metering pumps without any electrical power — making it inherently safe for hazardous-area chemical dosing in remote locations. It delivers timed pneumatic pulses to single-acting plunger, piston, or diaphragm pumps, then exhausts to allow the pump to reset, creating a continuous adjustable stroking cycle.

How does the MK-II operate without electricity?

The controller uses supply air or gas (25–65 psi) to power both its logic and its pump actuation. Inside the anodized aluminum body, a sliding spool with diaphragm seals separates upper and lower chambers. A capillary tube with an adjustable needle valve meters air from the lower to the upper chamber. When pressure builds sufficiently in the upper chamber, the spool shifts downward, the pilot plug closes the vent and routes supply pressure to the pump — causing it to stroke. After discharge, the spool resets, the pilot plug opens the vent, and the pump exhausts to refill. The cycle repeats automatically without any electrical signal or solenoid.

How is the stroke rate adjusted?

The stroke rate is set by turning the knob located under the red protective cap, which adjusts a needle valve controlling airflow through the capillary tube. Restricting flow lengthens the cycle time; opening it shortens it. The adjustment range spans approximately 1 to 45 strokes per minute, allowing precise matching of chemical feed rate to process demand without changing pump hardware.

What makes the diaphragm seal design different?

Unlike the MK-X which uses U-cup seals, the MK-II employs diaphragm seals on the sliding spool. Diaphragm seals are self-lubricating — they do not require oil or grease and are far less prone to sticking after periods of inactivity. This makes the MK-II more reliable in intermittent-duty applications and in environments where maintenance access is limited. Elastomer options include Neoprene as standard and Viton® for elevated temperatures or aggressive chemical atmospheres.