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ADVANCED SEALING TECHNOLOGY 
INSTALLATION INSTRUCTIONS 
 

AST 40 BEARING ISOLATOR

 

 

 

PREPARATION

 

 
1.  Disassemble the equipment so that the seal can be 

installed over the end of the shaft.  Clean the seal 
cavity. 

 
2.  Remove all sharp edges and burrs from the shaft 

especially where the O-ring will slide.  Cover threads 
and keyway slots with thin tape to prevent cutting the 
O-ring. 

 
3.  The shaft finish must be smooth, free from nicks and 

grooves.  It should feel smooth when you run your 
fingernail along the shaft (32-63 microinch Ra). 

 
4.  The shaft diameter must be .001/-.003 inch of 

the nominal shaft size. 

 
5.  The shaft must run true in the area where the seal is 

installed.  No more than .001 inch of runout per inch 
of shaft diameter is acceptable.  Use a dial indicator 
to measure runout. 

 
6.  Bearing end play must not exceed .010".  Excessive 

end play or shaft runout will shorten seal life.  Check 
with a dial indicator. 

 

INSTALLATION

 

 
1.  The bearing isolator has three parts:  the seal case, 

the magnet, and the insulator (Figure 1).  The seal 
case is the rotating part of the seal, including the 
carbon, and has an O-ring on its inside diameter.  
The magnet has one lapped face and one unlapped 
face.  The insulator adapts the magnet to fit the 
equipment housing bore and acts as a magnetic 
insulator between the magnet and the housing. 

 
2.  Disassemble the seal by pulling the seal case straight 

back from the magnet.  Sliding the seal case across 
the magnet will damage the carbon. 

 

 
 
3.  If the magnet is separate from the insulator, lubricate 

 the magnet O-ring and the outside diameter of the 
magnet with the fluid provided.  Install the magnet O-
ring into the insulator.  Cover the highly polished 
lapped surface of the magnet with a lint-free wiper 
and press the magnet into the insulator by hand until 
the magnet is squarely seated.  

Hammering the 

magnet will break it. 

 
4.  Press the insulator into the equipment housing using 

an installer made of aluminum, brass, wood, or plastic 
(Figure 2).  Press on the insulator only, not the 
magnet.  Use a dial indicator to check squareness of 
the insulator to the shaft. 

 
5.  Without touching the carbon face, remove the O-ring 

from the seal case and lubricate it with the fluid 
supplied with the seal.  Reinstall the O-ring. 

 
6.  Completely lubricate the shaft where the O-ring will 

slide with a small amount of the same fluid. 

 
7.  Slide the seal case along the shaft and into contact 

with the magnet (Figure 3).  Push the O-ring which 
contacts the shaft toward the carbon using an 
installer (Figure 4) or thin plastic shim.   

 
 

NOTE

 

 
The seal installer should be familiar with the installation 
of mechanical seals and with the plant safety 
requirements.  If you are in doubt about any phase of 
installing this mechanical seal, stop the installation and 
get assistance.  The decision to use any AST mechanical 
seal in a particular service is the customer's 
responsibility.

 

7/12/05

 

 

 

ADVANCED SEALING TECHNOLOGY, 250 North Street A-11, Danvers MA  01923 USA  (978) 750-8001  Fax:  (978) 750-6980

 

 

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