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Always execute the following seal installation best practice guidelines for component and cartridge mechanical seals to achieve maximum pump mechanical seal MTBFs:
It is recommended that this best practice be incorporated into the plant maintenance procedure manual for mechanical seal installation.
Component mechanical seal installation
Primary seal face flatness will have been confirmed by the seal manufacturer and should be within 1-2 helium light bands. For this reason, the primary seal faces must be free of fingerprints, oil and/or grease.
Inspect the rotating head assembly as follows:
Secondary ‘O’ ring in pusher seal – inspect for discontinuities, confirm proper material and durometer. (Note: Do not lubricate ‘O’ ring.)
Typical installation errors:
Contaminated faces – can affect face flatness, resulting in excessive leakage. In addition, certain oils can set-up like adhesives and pull material out of the carbon primary ring faces after start-up, resulting in pre-mature seal failures.
Applying lubricant to secondary seals which can enter primary seal face areas – the same results apply as above.
Not setting proper spring compression: excessive compression – more seal wear. Low compression – will not provide sufficient face contact during start-up and standby conditions allowing excessive leakage.
Improper installation of mating ring into the gland resulting in excessive leakage due to improper face contact. Note that if back of mating ring is visibly ‘not flat’, the same result can apply. Stuffing box face TIR should be checked with dial indicator on shaft. Seal chamber face flatness should be no more than 0.005’ TIR.
Installation of gland to stuffing box not using equal and opposite tightening technique. Failure to tighten the nuts/capscrews properly can cock the mating ring, which will not allow for proper contact between the faces and result in excessive leakage between the seal faces.
Sleeve ‘O’ ring cut during installation, resulting in excessive leakage between shaft and sleeve.
Cartridge mechanical seal installation
Failure to have and implement a required mechanical seal installation procedure has been a principal cause of low mechanical seal MTBFs (lower than 12 months).
FAI has used this best practice since the 1990s to ensure that plant mechanical seal installation procedures are in complete accordance with mechanical seal vendors’ recommendations and to ensure optimum installed seal safety and reliability.