The very mention of gas seals is likely to bring two thoughts to mind: complex and expensive. While this used to be a truism, technological advances now mean that a gas-lubricated option can have far-reaching positive effects on the quality and reliability of efficiency, as well as that of environmental impact within a variety of industries.
Dispelling the Myths Surrounding Gas-Lubricated Seals
Despite the advances that’ve led to a highly efficient sealing solution, there remains a common misconception that gas seals are only suitable for certain applications. This is certainly not the case and they can be used in virtually any equipment that has rotating shaft/s that need sealing.
In addition, gas-lubricated mechanical seals utilise inert gases, such as compressed air or nitrogen, to function. They don’t require the use of any hazardous gas to create a seal.
Advantages of Gas Seals
Gas seals offer unique advantages over those of wet seals.
- Longevity: Contacting wet seals have a short finite lifespan, and their failure is the number one cause of pump malfunction. Their average usable period is around three years. When this is compared to that of gas seals – with a typical lifespan of around 15 years (the life of the O-rings) – this alone makes a significant case for their use.
- Reliability: Several reasons make gas seals more reliable, including being non-contacting and therefore don’t wear. This results in higher consistency and reduced power consumption. They also generate very little torque and heat, and any gas leakage absorbs heat through gas expansion.
- Energy costs: Energy represents the largest factor of the expense of running pumps over their lifetime. Compared to that of a wet seal support system, those using gas seals have an energy consumption of less than 10%. In addition, no water treatment is necessary as there’s no need for water to flush the seals, removing the related costs from the equation.
- Maintenance: Repairs and maintenance are the second largest cost, taking into account the replacement of items and the man-hours to carry out the work. The no-contact running of gas seals negates wear and the need for replacement, dramatically reducing maintenance costs.
- Emissions and power consumption: The dual aspects of the use of inert gas or purified air, along with that of highly reduced power consumption, bring the process far closer to the goal of zero emissions. Gas seals fully comply with the latest emission requirements.
- Improved performance: Gas seals provide significant performance benefits, including negating the risk of buffer or barrier fluid entering the process. Quality seals improve the overall efficiency of the pumping system, reduce rotational losses and enhance motor efficiency.
Gas Seal Designs
Much of the reluctance to embrace the use of gas seals is down to the perception of expense, complexity and pump modifications. Also, instances of the sudden failure of associated equipment caused by a loss of barrier (LOB) gas situation has understandably caused further caution.
However, these obstacles are effectively overcome by the integration of various features into certain designs. These include:
- Incorporating a management system that autonomously regulates the gas flow and pressure. This dramatically reduces the risk of premature seal failure.
- Loss of barrier gas situations are recovered by the seal’s ability to convert to that of a traditional wet seal in such an event, and then converting back to a gas seal once the flow of gas is restored.
- Hybrid designs (hydrostatic and hydrodynamic lift-off mechanisms) mean the seal can lift-off at low speeds of 1.4m/s (<275 fpm). For applications that use frequent start-stop operations, this effectively reduces the frictional wear of the seal faces.
Gas seals offer many advantages over traditional liquid seals, including that of reliability, energy efficiency and the related environmental benefits. The key to an effective transition to gas-lubricated seals is that of selecting the designs that best suits the application.
Why choose Chesterton Mechanical Seals?
Our innovative, award-winning mechanical seals for pumps, agitators, mixers and other rotating equipment simplify installation, improve reliability, and extend the performance of fluid handling. Companies around the world turn to A.W. Chesterton Company for expertise in mechanical seals — in design, selection, installation, field service, and more.
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