Mechanical Seals vs Gland Packings

The argument for Mechanical seals vs Packing glands has been lenghty since asbestos related packing glands fell out of favour in the mid 90's. Since then both have experienced favour in the industry but in reality they both have a place and time to be used. We have tried to sum this up into an easy to interpret table below.
 

Comparison	Packing	Mechanical Seal
Initial Cost	One Unit Cost	10 Unit Costs
Reliability	Ample warning of impending faulure with good possibilities of correction	Little or no warning of end of working life with the possibility of sudden failure
Installation	Very simple, little skill needed. Correct procedure to be followed by manufacturer	Skilled fitting and controlled environment needed for precise alignment
Running Maintenance	Extended service life is achieved by adjusting gland at maintenance intervals	None between seal refurbishment
Spares	Cut to lenght. Relatively low cost and readily available	Specific seal components can be tricky to get. Cost of holding stock can be substantial
Shaft Wear	Can be signifcant in highly abrasive slurries	None between seal refurbishment
Operating Costs	Friction losses sllightly higher with packing. Slight media leakeage needed for fluid film lubrication	Usually very low leakage of fluid media. Clean fluid is often needed at the seal faces for satisifactory performance
Absorb Eccentric Forces	Yes	No
Typical Operational Paramaters	Up to 25 Bar 25m/s	Up to 35 Bar 25m/s
Temperature Range	Typically More	Limited to spring & seal