DARLEY ZSP, Nstallation, Operation, Maintenance, Repair And Troubleshooting Instructions

Page: 114 / 155

Prepared by: DWS Rev.: A
Approved by: MCR
1
Date:09/25/2001
Revised by: RJG 1200583.doc
Revision Date: 02/07/12
Mechanical Shaft Seal
This pump assembly incorporates high quality mechanical shaft seal(s) separating the pump housing
components from atmosphere. Depending on the pump design, there may be one or two seals on each
impeller shaft.
The seal size, design type, component materials, and housing configuration have been specifically
designed for this pump application and rated operating parameters.
Mechanical Seal Basics
A mechanical seal is a device that houses two highly polished components (known as faces). One face
rotates, the other is stationary. A secondary elastomer bellows seals the primary ring to the shaft. An o-
ring or cup seal seals the mating ring in the housing. The polished seal faces of the primary and mating
rings are pressed together by a spring mechanism to provide adequate force to affect a seal. The force
acting between the seal faces increases in direct proportion to product pressure.
The elastomer bellows seal utilized in this pump has the following design features:
•
Mechanical drive of the primary seal ring. The drive band’s notch design eliminates
overstressing the elastomer sealing bellows.
•
Bellows design provides automatic compensation for shaft endplay, run out, and primary ring
wear.
•
Seal face contact pressure is controlled by a single, non-clogging coil spring. This coil spring
has been custom welded per Darley specifications to eliminate high-speed spring distortion.
The seal housing is designed and ported to provide optimal water flow and pressure assuring proper
cooling and flushing of the seal components.
MATING RING
WITH O-RING
SEAL
PRIMARY RING
WITH BELLOWS
SEAL
SEAL COIL
SPRING
WATER FLUSH
PORT
IMPELLER
SEAL
HOUSING