SUBJECT: IMPROVED MP5031 PRESS PLUMBING



Gentlemen:

Starting with presses manufactured on or after 8 March 89 (MILDATE 89411) we have improved the press plumbing by adding a check valve in the volume pump discharge as shown in the accompanying drawing.

CAUTION: In this design, when the check valve is installed, there must be a small bypass line around the volume pump so the pump always circulates a small quantity of water to lubricate its' seal and dissipate heat.

HERE'S HOW THE VOLUME PUMP DISCHARGE CHECK VALVE WORKS:

At the onset of the pressure cycle, both volume and pressure pumps are turning. While this provides the maximum water flow rate to refill the bell the quickest, the maximum pressure is limited to what the volume pump can deliver.

Moreover, polycotton and 100% polyester goods will naturally come to pressure quickly because there is less water to press out - thus favoring a shorter volume pump time. But 100% cotton contains much more water, so these goods require more time to reach the volume pump's maximum pressure - thus favoring a longer volume pump time.

The new check valve lets the volume pump contribute to the water flowing into the bell only as long as the back pressure exerted by the goods is less than the maximum the volume pump can exert. Providing the pressure pump alone can flow water into the bell fast enough to keep the pressure rising, the check valve will automatically close once the back pressure equals the maximum the volume pump can deliver. this prevents water from the pressure pump "backing up" through the volume pump - thus automatically shifting from "low" to "high" pressure at the absolutely most optimum time. This optimized the extraction effect by optimizing the time on maximum pressure.

CAUTION: The check valve is located where shown on the attached sketch for a special reason. The check valve cannot simply be installed on the outlet side of the volume pump but rather must be installed on the discharge or bell side of the volume pump valve because the hoses between the volume pump and the volume pump valve cannot withstand the high pressure. This requires certain different piping parts which are retrofittable on those earlier presses with horizontally mounted valves.

Very truly yours,
PELLERIN MILNOR CORPORATION



Norvin L. Pellerin
Director of Engineering