Performance Comparison Between Tandem Dry Gas Seals and Tandem Mechanical Seals

Performance Comparison Between Tandem Dry Gas Seals and Tandem Mechanical Seals
	Tandem Mechanical Seal	Tandem Dry Gas Seal
API682 Standard	Plan11+52	Plan11+72+76 or 75
Auxiliary system configuration cost	Three pressure switches + seal oil tank (pressure vessel)	Two pressure switches and selected valves and piping fittings
Conclusion: The auxiliary system cost of Plan 11 + 52 is higher than that of Plan 11 + 72 + 76, and the current total cost is higher than that of dry gas seals.
Operating cost	It consumes more seal oil and desalinated water, with relatively higher power consumption.	It consumes only a minimal amount of nitrogen, and its power consumption is approximately 5% of that of mechanical seals.
	Conclusion: Dry gas seals have lower overall consumption.
Routine maintenance	Manual inspection and manual topping up of seal oil	Automatic nitrogen supply from the pipeline, maintenance-free.
	Conclusion: The routine maintenance workload of tandem mechanical seals is greater than that of dry gas seals.
Maintenance and overhaul	Seal failure may cause oil contamination, necessitating oil replacement or replenishment, which increases maintenance workload and leads to poor on-site environmental conditions.	By shutting off the gas supply, the seal can be easily dismantled and replaced. The operation is simple and does not cause contamination to the site environment.
	Conclusion: The replacement procedure for tandem mechanical seals is more complex than that for dry gas seals, and the on-site environment conditions are relatively poorer.
On-site environment	Seal oil can permeate through the sealing faces to the outside, resulting in poor environmental conditions.	Only a small amount of nitrogen leaks directly into the atmosphere, resulting in negligible impact on the on-site environment.
	Conclusion: Equipment using dry gas seals remains clean and free of oil contamination, and no routine cleaning is required.
Safe and reliable	In the event of primary seal failure, the secondary seal can operate for over 8 hours without sustaining damage.	In the event of primary seal failure, the secondary seal can operate for over 8 hours without sustaining damage, while nitrogen protection provides enhanced safety.
	Conclusion: Both systems provide high safety and reliability, with seal leakage monitored via remote and on-site monitoring systems.
Service life	To achieve a service life of 25,000 hours, higher-grade sealing materials are required, which increases the cost.		Standard materials can also achieve a service life of 25,000 hours.