MECHANICAL SEAL INSTALLATION INSTRUCTIONS
CAUTION: Never put hands on the lapped seal faces or put lapped seal faces down on the workbench.
PREPARATION BEFORE INSTALLING
1.Clean and check pump parts.
(1) Check if installed mechanical seal`s type and size are correct.
Clean mechanical seal parts, shaft surface and stuffing box etc. Keep
clean during installing, especially seal face of rotary ring and
stationary ring and secondary seal surface should not be no impurity or
(3) Should smear machine oil or lubricant grease onto the
surface of shaft or shaft sleeve and mating faces between gland and seal
rings to assemble conveniently. Should also smear machine oil or
lubricant grease onto the surface of rotary ring and stationary ring to
avoid damaging seal face because of dry friction.
2.Check secondary seal elements
if dimensions of secondary seal are correct, mainly including elastomer
O rings, Teflon wedges (Teflon rings), Graphite foils etc. Replace
shaft or shaft sleeve and gland if worn in secondary seals.
Compression value of O ring between rotary ring and stationary ring
should be properly.Sealing performance will be poor if compression value
is too small, but if it is too big,installation will be
difficult,friction resistance will become big and also float-ability
will be poor.Commonly compression value adopts 6%-10% of section
diameter and interference to shaft adopts 1%-3%.
(2) PTFE wedges
belongs self-tightening style sealing, medium pressure is higher,
sealing performance is better. ID of PTFE wedge is 4-5mm smaller than
shaft diameter. OD is 0.3-0.4mm bigger than installation dimension.
Especially note that opening direction of PTFE wedges should face to
medium when installing.
(3) Check if surfaces of rotary ring and
stationary ring are smooth and flat, meanwhile check if scratch, rack
and distortion are on the surfaces. Very easy method can test if seal
face is qualified. Make both surfaces of rotary ring and stationary ring
stick together. If they can only produce relative sliding and can not
be divided by hands, this shows that seal faces are qualified.
3.Check if the pump can be good starting.
Remove all burrs which would cut O rings or cause misalignment. Pay attention to set screw marks.
4.Check shaft radial run out and shaft axial movement
Permitted value of shaft run out will be different according to shaft
diameter. For example with sing stage centrifugal pump, permitted value
of run out is as following:
|Measured Diameter||Permitted Value of Run Out|
Permitted Shaft axial movement will be different according to equipment
type. Theoretically, axial movement is more smaller, more benefit to
install the seal, normally not exceed 0.10mm.
INSTALLING MECHANICAL SEAL
1.Bolt stuffing box back plate to the pump frame.
2.Install shaft sleeve.
3.Screw on impeller to hold shaft sleeve in proper position on the shaft securely.
4.Scribe a line on the shaft sleeve at the face of stuffing box.
5.Remove stuffing box plate.
6.Determine operating length of mechanical seal.
(1) Place gland on clean area of workbench with stuffing box face up.
(2) Install stationary seal face with secondary seal in the gland.
(3) Place gland gasket in proper position.
(4) Place rotary unit, lapped face down, against the lapped stationary seal Face.
(5) Measure the distance from gland gasket to the top of seal under rotary unit at free height.
7.Determine compression value on the seal.
(1) Multi-spring with less than 2” in diameter require 1/8 ”compression.
(2) Multi-spring with over 2” in diameter require 3/16” compression.
(3) Single spring mechanical seal compression is fixed and usually is 1/2 of free length of single spring.
the proper compression from the length of the seal determined in step
6(5). This will be the working height of the seal from the face of
8.Scribe a second line the exact distance from the first line as determined in step 7(4).
9.Install mechanical seal in the pump.
(1) Place gland with stationary seal face and gasket on the pump shaft.
rotary unit on the shaft sleeve and set the back of the rotary unit on
the second scribe line as determined in step 8. Set screw of rotary unit
to the shaft sleeve.
(3) Bolt stuffing box back plate to the pump frame.
(4) Install impeller using new impeller gasket.
gland against stuffing box plate. Double check seal compression by the
gap between gland gasket and stuffing box plate (Same as step 7).
Tighten gland studs evenly. Rotate shaft to ensure the seal not to be in
1. Push rotary unit by hands after installing and ensure the rotary unit to move freely and have flexibility.
Set up rotating shaft by hands to ensure the shaft to be even and
light. If feeling very heavy, check if the shaft touched the stationary
ring and if mechanical seal touched stuffing box.
operating, medium must be filled in the equipment to prevent dry
friction which can cause seal failure. After static testing through
importing medium, if leakage is less than 5.6g per hour (5-6 drops per
min), this seal installation is accordance with requirement and can set
up the pump.
4. Must adopt flushing, filtrating and cooling for
some mediums like crystallizing easily, containing solid and temperature
exceeding 80 oC.