Double Mechanical Seal Barrier Fluids and How They Work

Author:Site Editor     Publish Time: 2021-02-22      Origin:Site

Dual mechanical seals are used in the process of electrical engineering. They are an essential component of any machine since the mechanical seal prevents the fluid from leaking from inside the machine, thus avoiding any external damage. 

 

Machines such as pumping equipment are commonly known to have double-acting mechanical seals. Since shaft leakage can result in an unsafe working condition for the workers, lessens the reliability of the company, and has negative environmental impacts, manufacturers are now becoming more concerned regarding the inclusion of mechanical seals in the machines. 


Dual mechanical seals


As the name suggests, a double mechanical seal allows the machine to have an outer layer or seal to ensure that the pumped fluid remains inside only. Between the two mechanical seals is a small cavity with a barrier or buffer fluid. This fluid acts as a barrier between the fluid inside the pumping machine and the external environment – not allowing it to pass through even if there is a leakage. 

 

mechanical seal application


The difference between the buffer and barrier mechanical fluids

 

In an unpressurized system or when there is no artificial pressure being induced inside the pumping machine to contain the primary fluid, there is a buffer fluid used in the mechanical seal. The reason behind this classification is that the buffer fluid acts as a ‘buffer’ or a safety interval between the primary fluid being pumped inside and the external atmosphere.

 

In a pressurized system where there is pressure inside the pumping machine to maintain a smooth flow of the fluid inside, a barrier fluid is used inside the mechanical seal. 

 

Both buffer and barrier fluids can be supplied and stored using a range of different methods. Depending upon the pressurized or unpressurized system of the pumping machine, the supply method can be chosen using a predetermined piping plan. In most machines, the piping plans are set according to the standard API 682 provided by the American Petroleum Institute.   

 

Type 1: unpressurized system


The system used to supply the buffer fluid in a mechanical seal is known as Plan 52. This plan is relatively simple since both the supply and return valves are directly connected to the mechanical seal. The entire circulation process of the buffer fluid is overlooked by the pumping ring that is placed inside the mechanical seal. 

 

Type 2: pressurized systems

 

Barrier fluids in a double cartridge mechanical seal are similar to the unpressurized system, but they include an additional method to keep the barrier fluid pressurized inside the mechanical seal. Following are the three most common types of supply plans used for mechanical seal barrier fluids:

 

1. Plan 53A: A pressure regulator is added in the cavity between the two mechanical seals to control the pressure created via Nitrogen. There is no additional seal attached between the barrier fluid and the Nitrogen gas. 

 

2. Plan 53B: Similar to 53A, this plan involved the use of a pressure bladder in which the pressurized nitrogen is contained. This prevents the interaction of the barrier fluid and the gas. 

 

3. Plan 53C: This is the most modern form of barrier fluid supply plan. It involved the use of a pressure amplifying piston that accumulates pressure from inside the mechanical seal chamber and balances it according to the area available on either side of the pressure piston. This allows for the barrier fluid to remain entirely secluded from the pressurized gas.

 

Do you need a mechanical seal barrier fluid?

 

To protect your mechanical seal and pumping system effectively, it is important to invest in either barrier fluid or buffer fluid. 

 

As explained earlier, the two different types of fluids are designed to be used under different circumstances. However, each of these fluids is able to protect the mechanical seal by providing lubrication to the pump, controlling any buildup of friction, and avoiding the instance of fluid leaks. 

 

double cartridge mechanical seal


How to choose a barrier fluid


There are various kinds of mechanical seal barrier fluids that you can choose from, but you must consider the characteristics of the fluid beforehand. Here are a few important considerations before choosing a barrier fluid for the double mechanical seal:

  • Safe and easy to handle

  • Does not have chemical interactions with the seal material

  • Is not an organic compound or hazardous air pollutant since that could damage the entire pumping system

  • Can continue flowing properly in extremely low temperatures

  • Remains liquid 

  • Nonflammable

 

Common types of barrier fluids

 

Most operators have now narrowed down their choice of barrier fluids into two main categories: water and oil. These liquids have important characteristics that allow them to be a suitable fit between the mechanical seals. Following are all of the common types of mechanical seal barrier fluids used in the industry: 

 

1. Water solutions

Water is a highly effective barrier fluid, especially since it is a thermal conductor, inexpensive, and extremely easy to handle. Water can be transported easily without worrying since it is nonflammable and is compatible with all kinds of mechanical seal materials. Using water as a barrier fluid will also prevent the problem of it interacting with the pumped fluid since water does not damage or change any solution.

 

2. Hydraulic and lubricating oils

Oils are the second-best option available to operators due to their flexibility in service temperatures and greater fluid stability. Unlike water, the oil will not change its form to solid if kept in temperatures below 0 degrees. Oil is also likely to be more stable than water as a mechanical seal barrier fluid since it doubles as a lubricant inside the seal. Due to the wide range of oils available in the market, it is easy to choose one that fits your requirements perfectly. Most operators tend to opt for oils that have the least additives in them. Oils that have a viscosity below ISO Grade 32 are generally the most popular option as mechanical seal barrier fluids. 

 

3. Other types of barrier fluids

Apart from water and oil, some operators tend to go a step further and opt for more complex barrier fluids. These include alcohol, synthetic oils, kerosene fuel, and even heat transfer fluid. 

 

WenDong is a professional mechanical seal manufacturer and mechanical seals distributor in China, providing high-quality and affordable double mechanical seals. If you have any needs, please contact us now!


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