Pd pump Systems neslab p/N 000878 Rev. 08/15/96 Service Manual

Coupling Types
1. BRONZE COUPLING
The bronze coupling is a sacrificial coupling. It is a softer metal
than either the steel pump bearing race or the steel motor shaft.
The coupling will wear to avoid wearing these more critical
components. The coupling is also intended to shear in two in
the event the pump stops unexpectedly due to foreign matter in
the pump, or seizure. This protects the motor by unloading it
and allowing it to continue turning.
A new coupling is supplied with replacement PD pumps. It is
temporarily held in place with a soft foam strip. This strip should be
removed and discarded.
The coupling is slightly asymmetrical. The wide tab fits in the
motor, and the narrow tab fits in the pump.
NESLAB adds a lubrication cup to the motor shaft on PD pumps
using bronze couplings. This has been found to extend the useful
life of the coupling. See COUPLING LUBRICATION.
Figure 13

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Coupling Types (continued)
2. NYLON COUPLING
Some PD pumps use a straight nylon coupling. This coupling is
slightly tapered. The wide end fits in the motor, and the narrow end
fits in the pump. It does not require the lubrication cup used with
the bronze coupling.
The bronze and nylon couplings are interchangeable. There is
no particular advantage to using one or the other.
 3. CAPTIVE COUPLING
Older PD-1 pumps have a captive tab emerging from the pump
which is actually the end of the rotor shaft. This tab mates directly
with the motor slot. There is no removable coupling on these
pumps.
The current PD-1 pumps have the same removable coupling
(bronze or nylon) which is used on the PD-2 pumps.
The captive coupling pumps are no longer available and may be
directly replaced by the removable coupling style pumps.

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