Page 528 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Pump Mechanical Seal Flush Best Practices Best Practice 8 .13

Best Practice 8.13Practice 8.13
Best

Always execute the following seal installation best practice It is recommended that this best practice be incorporated into the
guidelines for component and cartridge mechanical seals plant maintenance procedure manual for mechanical seal installation.
to achieve maximum pump mechanical seal MTBFs:
Lessons Learned
Component seal faces must be cleaned with clean cloth and
rubbing alcohol (or alcohol wipe) just before installation. Proper care Failure to have and implement a required mechanical seal
must be taken to not touch the faces after cleaning. installation procedure has been a principle cause of low
Limited grease should be used on seal gland ‘O’ ring as it can mechanical seal MTBFs (lower than 12 months).
migrate to the seal faces and cause damage. Proper practice is to
sparingly apply grease to ‘O’ ring groove then install it in the gland. Benchmarks
This will ensure ‘O’ ring will stay in the groove when installing the
FAI has used this best practice since the 1990s to ensure that plant
seal.
mechanical seal installation procedures are in complete accordance
Use liquid soap sparingly on sleeve ‘O’ ring to assist in installation. with mechanical seal vendors’ recommendations and to ensure opti-
mum installed seal safety and reliability.

B.P. 8.13. Supporting Material casing and mark (with bluing pen) the point on shaft or sleeve
directly below the seal chamber face. Remove shaft and
bearing bracket from casing and mark the dimension where
Component and cartridge mechanical seal the back of the retainer sits when assembled.
installation guidelines - Attach seal head to shaft/sleeve and ensure that set screws
are installed on clean and undamaged shaft areas. If this is not
Component mechanical seal installation possible, carefully de-burr with a file and smooth out with
emery cloth.
- Refer to the vendor instruction book and obtain all required - Note: If sleeve ‘O’ ring is installed, confirm proper material,
mechanical seal components. size and durometer and apply a small amount of ‘Krytox’ or
- Have a clean area available for the components and ensure equal lubrication and install. Assure shaft surface is clean and
that there are no finger prints, oil or grease on the primary free of any burrs and carefully install sleeve being sure ‘O’
seal faces. Wipe with alcohol using a lint free cloth if ring is not damaged.
necessary. - Install the stationary seal face into gland evenly to ensure face
- Primary seal face flatness will have been confirmed by the is not cocked. Assure that any finger prints are removed with
seal manufacturer and should be within 1e2 helium light alcohol and lint free towel.
bands. For this reason, the primary seal faces must be free of - Stationary ‘O’ ring checks e confirm proper material,
fingerprints, oil and/or grease. durometer and inspect for discontinuities.
- Inspect the rotating head assembly as follows: - Install gland to stuffing box using opposite and even
- Secondary ‘O’ ring in pusher seal e inspect for tightening technique. Prior to doing so, a sweep of the seal
discontinuities, confirm proper material and durometer. chamber face is required to ensure proper sealing between
Note: do not lubricate ‘O’ ring. gasket/‘O’ ring on seal gland and seal chamber. A dial
- Ensure that all springs (if a pusher seal) are sitting upright and indicator should be attached to the shaft and the shaft will be
have not been dislodged from their counter-bores. rotated to cover a complete sweep of the seal chamber face.
- Confirm that shaft or shaft sleeve surface finish, where TIR should be no more than 0.005’.
secondary ‘O’ ring or Teflon wedge will ride, is maximum of - After seal is completely installed, conduct a static pressure
32 rms, using a comparator. check. Consult the seal vendor for the proper pressure if
- Clean and de-burr the shaft area and seal chamber area as static limit is not indicated on seal drawing. If any leaks are
required using a solvent that will be compatible with the observed, consult seal vendor immediately.
process fluid. Note: assure all piping/tubing is isolated from - Typical installation errors:
flush/quench ports. Plastic plugs need to be installed in all - Contaminated faces e Can affect face flatness, resulting in
flush/quench after isolation of piping/tubing up to the point excessive leakage. In addition, certain oils can set-up like
of the piping/tubing reinstallation. adhesives and pull material out of the carbon primary ring
- Install the seal head carefully being sure not to damage the faces after start-up, resulting in premature seal failures.
secondary ‘O’ ring, or the ID of the primary ring on the shaft/ - Applying lubricant to secondary seals which can enter
sleeve. primary seal face areas e the same results apply as above.
- Proper spring compression check (‘working height’) e obtain - Not setting proper spring compression: excessive
dimension from seal drawing which shows the distance compression e more seal wear. Low compression e will not
between the back of the seal retainer and the seal chamber provide sufficient face contact during start-up and stand by
face. Then fit the bearing bracket and shaft up against the conditions allowing excessive leakage.

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