Understanding the Components of a Dry Gas Seal System

Understanding the Components of a Dry Gas Seal System

When it comes to gas compressors, dry gas seals play a crucial role in their efficient operation. Dry gas seals are designed to prevent leakage of the gas being compressed, which can consume energy and reduce the efficiency of the compressor. In this article, we will break down the key components of a dry gas seal system and how they work together to ensure the effective operation of a gas compressor.

Introduction to Dry Gas Seal Systems

A dry gas seal system is made up of two tightly fitting seal rings that separate the process gas, usually a hydrocarbon, from the atmosphere. The seal rings are mounted on a stationary ring and rotating ring that forms the compressor shaft. Together, they work to maintain a seal that prevents any leakage of process gas.

Seal Rings

The seal rings are perhaps the most important component of a dry gas seal system. They are made from a variety of materials, including carbon, silicon carbide, and tungsten carbide. These materials are chosen for their resistance to wear and chemical degradation.

The two seal rings are separated by a small gap that is around one hundredth of a millimeter wide. This gap allows for a thin layer of gas to form between the two rings, enabling them to glide past each other without any physical contact. This process is called the hydrodynamic effect, and it is what allows the seal to function without any lubrication.

Labyrinth Seal

The labyrinth seal is a component that helps to keep the process gas from leaking. It is a series of concentric rings that are machined into the shaft. The rings form a maze-like structure that the gas must navigate in order to pass through.

As the gas moves through the labyrinth seal, its speed decreases, and the pressure increases. This pressure differential pushes the gas into the hydrodynamic gap between the two seal rings, where it is then trapped. The labyrinth seal also creates a barrier that prevents the gas from escaping back into the atmosphere.

Gas Circulation System

The gas circulation system is another essential component of a dry gas seal system. Its main purpose is to provide a constant flow of clean gas into the seal cavity. The gas must be filtered to remove any contaminants that could damage the seal rings.

The gas is typically supplied from a compressor's upstream process line. It is cooled and filtered before being introduced into the seal cavity. The gas circulation system also includes a series of control valves that help regulate the pressure of the gas within the cavity.

Barrier Fluid System

The barrier fluid system is used to keep the seals lubricated, which prevents any damage to the seal rings. The system consists of a reservoir of oil that is circulated around the seals at a controlled temperature and pressure.

The oil used in the barrier fluid system is typically a synthetic lubricant that is resistant to the hydrocarbon gas being compressed. The oil is cooled to a temperature slightly below that of the process gas to prevent any vaporization. This ensures that the seal cavity remains full of oil, which helps to protect the seal rings from damage.

Seal Housing

The seal housing is the enclosure that houses the dry gas seal system. It is usually located between the compressor and the gas being compressed. The housing is designed to provide a high degree of protection for the seals, as well as the optimal seal environment.

The seal housing is typically made of stainless steel or other corrosion-resistant materials. It must be designed to withstand the high pressures and temperatures that are present in the compressor.

Conclusion

Dry gas seal systems are an essential component of gas compressors. They are designed to maintain a tight seal that prevents any leakage of the process gas being compressed. The key components of a dry gas seal system include the seal rings, labyrinth seal, gas circulation system, barrier fluid system, and seal housing. Each of these components plays a crucial role in ensuring the efficient operation of a gas compressor. By understanding how these components work together, operators can ensure the reliable operation of their compressors and avoid any unplanned downtime.