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.
(2) 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 dirt.
(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
Check 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.
(1) 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

(1) 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:

(2) 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.
(4) Subtract 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 stuffing box.
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.
(2) Slide 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.
(5) Compress 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 a bind.

AFTER INSTALLING

1. Push rotary unit by hands after installing and ensure the rotary unit to move freely and have flexibility.
2. 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.
3. Before 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.