Zenith Pumps manual Operation, Installation

Operation

Polymer enters the PEP-II pump on the suction side where shaft rotation exposes gear tooth volumes between the gear teeth. Polymer fills these spaces and is transported to the discharge side where the gear teeth mesh together, decreasing the gear tooth volumes and displacing the polymer. Due to the precision tolerances and close clearances within the rotating spaces, very high pressures can be achieved at the pump discharge with extremely high volumetric efficiencies.

As PEP-II pumps rely on the metered polymer for lubrication of internal bearing surfaces, the operating speed is designed to be from 10 to 90 rpm on most extrusion processes depending on process parame- ters. Do not allow the pump to run dry or attempt to pump poor lubricating

fluids such as water or solvent. When high-viscosity fluids are used, more time is required to fill the tooth volumes. As a result, the inlet pressure must be increased or the gears must rotate at a slower speed to ensure complete volume filling. Proper speed and inlet pressure must always be maintained to prevent cavitation and to ensure proper lubrication.

Slip can occur across the sides

of the gears from the high-pressure side to the low-pressure side. The amount of slip depends on four factors: polymer viscosity, speed, differential pressure and pump clearances. Under reasonably stable operating conditions, slip is repeat- able and predictable, and pump operation can be adjusted to compensate.

Installation

Pumps should be carefully unpacked to make sure that the shipment is complete. If any items are missing or damaged, the freight carrier and Zenith should be noti- fied immediately.

To prepare the pump for use:

1)Where required, install the heat plates as follows. Zenith-supplied heat plates are machined to tolerances that eliminate the need for heat transfer cement. All bolts used should be lubricated with high-temperature thread lubricant such as DAG Dispersion 154, Felpro C-100 or equivalent.

2)Place the top heat plate on the pump, then place the insulation jacket on top of the heat plate. Install and tighten the bolts, taking care not to crack the insulation block.

3)Repeat for the bottom plate, noting that bottom heat plate mounting bolts are typically used to mount the pump to its mounting block.

4)Place the supplied metal O-rings into the counterbores in the pump ports, and attach the inlet and discharge porting flanges with lubricated screws. Replace the O-rings after each use. Torque down the screws in a crisscross pattern, taking them first to 1/4 the recommended torque value, then to 1/2, to 3/4 and finally to their full recommended torque value as shown on the table on page 10. If the flanges are not supplied by Zenith, make

certain that their mating faces are flat, with no pilots that protrude into the pump. Check that the pump rotates freely by turning the shaft with your hand.

5)The pump drive shaft should be connected to the motor drive assembly with a flexible coupling, a double universal joint shaft or an appropriate Zenith SJMC coupling. Side loading on the pump shaft is to be avoided at all costs.

6)If water is used for sealing, connect either 1/8-27 or 1/4-18 NPT fittings to the Rheoseal and turn on the water. Be sure to avoid excessive cooling, or damage to the pump may occur.

7)Turn on the pump heaters. A 250° F temperature rise per hour is recommended for cold starts. No attempt should be made to start the pump until the entire pump is at operating temperature. Cold starts are the most common cause of pump failure.

On start-up, a small amount of molten polymer should be introduced into the pump by slowly rotating (less than 5 rpm) the pump by hand to ensure that the pump is free turning and well lubricated. With sufficient inlet pressure, the pump can then be started at a very slow speed, with discharge pressure low enough to maintain low loading. When operating satisfactorily, the pump and system may now be gradually brought up to normal process speeds and pressures.

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