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Are Single Mechanical Seals Necessary?

2019-04-10

    Mechanical seals are an integral part of the pumping system. In a manufacturing system that involves pumping out products through pipes, prevention of leakage is important. The invention of the mechanical seal presents an opportunity for sealing the leakage points. In this case, these points are the rotating parts and stationary parts. If you are looking to make the shift from packing to mechanicals seals, note that the benefits will overwhelm you. Among which includes; ease of maintenance, low costs, and high efficiency.

At the onset of the evolution of magnetically coupled systems, industrial technicians would drive the pumps directly with a motor shaft attached to the pump shaft. This kind of coupling required a seal. Traditional pump seals consisted of packed rings that would be squeezed and fitted around the shaft on the pump housing. The packed rings were designed from a number of fibrous materials so as to prevent industrial liquids from leaking out of the pumping pipes. The possibility of the liquid leaking was very high given the rising amount of pressure exerted into the pump. Introduction of air into the pump due to negative pressure could also have been one of the causes for leaking. Negative pressure could be caused by having the pump running while open. An additional problem associated with traditional pumping systems was crystallization or the event of air being pumped into the pipes. To counter this challenge, material engineers introduced the addition of water inside the lanterns rings which were situated between the packed rings. Unfortunately, the renovations failed to counter all the challenges present in the packed rings. The persisting problems remained to a high amount of skill for installing and the attention to detail required for the very installation of the packing rings into the pumping system.

Also, take note that mechanical seals will usually leak liquid vapor from high-pressure zones to low-pressure zones. Simultaneously, a highly viscous liquid lubricates the faces of the mechanical seal and absorbs heat resulting from the generated friction. The fluid continuous out of the seal faces with the absorbed heat and dissipates it into the atmosphere as liquid vapor. To understand more about this working, an easy background into the framework of the single mechanical seal is unavoidable. The surface of the single seal consists of two flat faces sealed and slide into each other through a spring. Inside the two flat faces, a fluid flame settles that is generated by the pumped product. The main objective of the fluid film is to prevent both the stationary and mechanical seals from touching each other. The absence of the film fluid is known as dry running the pump and is known to cause excessive friction, and finally wearing out of the mechanical seal. Therefore, the main advantage of a single mechanical sealing is to prevent exposure of hazardous chemical liquid into the environment. The practice of single mechanical seals usage is hence important if you want to seal a pump or machine that is risky to the environment.

The disadvantages of the traditional packing rings opened room for mechanical seals. The ease of installation and the fact that the mechanical seals could run for a long time with no servicing made them an adaptable component of the modern-day pumping system. When the mechanical seals are fitted into the pumping cavity, the need for adjustment is not a priority. During assembly of the mechanical seals, an impeller is fitted against the spring assembly and in turn, sets the definite spacing between the two mating surfaces. The distance ensures that lubrication by the liquid is constant. Two main types of mechanical seals came into existence. They are the single mechanical seal and the double mechanical seal. Each of them is available in various configurations and designs that are meant to meet the needs of a variety of sealing application.

The single mechanical seal is mostly preferred for machines because it is optimally leakage resistance. However, a protective mechanism should be put in place to prevent entry of abrasive particles within the two services. Abrasive particles are likely to cause oozing of the liquid which is subjected to extreme pressures, which would end up the pumping system dripping.

The event of cavitation is also a major challenge with the single mechanical seal. Cavitation causes vibration which is a possible cause for leakage. Additionally, the likelihood of the seal getting chemical attacks and becoming roughened is high. Such roughening would cause abrasion, and eventually, wear out the seal. Thereby, shortening the mechanical seal’s lifespan and resulting in premature liquid leakage. The final problem is having the seal situated inside the pump chamber. Therefore, results in the exposure of the components of the mechanical seal to often attacks from the pumped fluid. The components of the mechanical seal are often times made from metal.

The design of thermoplastic pumps that implement nonmetallic solutions is therefore important to solve the challenge. However, an additional requirement is unavoidable that calls for the relocation of the mechanical seal’s components at the exterior of the pump housing and beneath the support plate. The make of this design, therefore, considers a stationary ceramic face that usually comes into contact with the lubricating liquid and a contact cup on the other side. Having the single mechanical seal situated in this position is therefore strategic in preventing the metal from coming into contact with the liquid. Another factor that contributes to the seal’s no contact components are having the contact spring located at the external.

Single mechanical seals are highly valuable if you care about the lifespan of the pump machinery. Investing in this seal will make sure that the maintenance cost of your pumping system is low. Given that the installation process is also simple, the seal is meant to save you a lot of time.

The rapid reduction of liquid leakage is the main benefit of the mechanical seal. Durability coupled with efficiency, makes the mechanical seal to be the most preferable leakage protection. Single mechanical seals are quite necessary with the advent of pump systems that contain dangerous chemicals.


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