Double Cartridge Mechanical Seals

Double cartridge mechanical seals are advanced, pre-assembled sealing solutions designed to provide the highest level of safety, reliability, and emissions containment in pumps, mixers, and other rotating equipment. They incorporate two sets of primary seals (inner and outer) into a single, easy-to-install unit, isolated by a barrier or buffer fluid system.
Key Features and Benefits
Maximum Safety and Reliability: The dual seal configuration provides a secondary line of defense. If the primary (inner) seal fails, the secondary (outer) seal continues to prevent fluid leakage and environmental contamination.
Emissions Control: They are specifically engineered to meet strict environmental regulations by preventing hazardous or volatile fluids from escaping into the atmosphere.
Ease of Installation: The entire assembly is pre-engineered and ready-to-fit, which minimizes installation errors, reduces downtime during maintenance, and ensures proper alignment of all components.
Versatility in Demanding Conditions: Suitable for handling highly corrosive, abrasive, high-temperature, or hazardous fluids that are challenging for single seals.
Lubrication Management: The barrier fluid circuit provides a controlled lubricating environment for the seal faces, which extends the service life, especially when handling non-lubricating process fluids or fluids that crystallize.
Common Types and Operation
Double cartridge seals operate with an external support system that circulates a barrier or buffer fluid between the two seals.
Double Seals (Pressurized Barrier Fluid):
Operation: The fluid circulated between the seals is at a pressure higher than the process fluid. This ensures that the barrier fluid leaks into the process stream (preventing contamination of the atmosphere), provides superior lubrication, and is ideal for hazardous or toxic media.
Tandem Seals (Unpressurized Buffer Fluid):
Operation: The fluid circulated between the seals is at a lower pressure than the process fluid. The primary seal handles the main pressure; if it fails, the secondary seal prevents environmental escape. A monitoring system detects the pressure increase between the seals, signaling primary seal failure. Ideal for volatile organic compounds (VOCs).
Metal Bellows Seals: The secondary seal uses a flexible metal bellows instead of traditional O-rings, enhancing durability in high-temperature applications where elastomers might degrade.
Applications
Double cartridge mechanical seals are used in critical applications across demanding industries:
Chemical and Petrochemical Processing: For sealing highly corrosive, toxic, or hazardous fluids in pumps and mixers where absolute containment is essential.
Oil and Gas: In refineries, pipelines, and offshore platforms for reliable sealing of various hydrocarbons and volatile process fluids.
Power Generation: Used in boiler feed pumps and other critical equipment operating under high temperature and pressure.
Pharmaceutical and Biotech: In processes requiring high purity and zero emissions to prevent product contamination and meet safety regulations.