The mechanical seal is used in a pump, mixer and other mechanical engineering scenarios to contain the fluid within a vessel where a shaft rotates through a stationary (or rotating) housing.

Why is mechanical seal important in this situation? It is because the rotating shaft has to move in a wet environment, but there should not be the leakage of pressurized fluid. Hence, the role of a seal is quite critical.

Does it mean the seal stops the leakage completely? Well, on the practical grounds yes because there is no ‘visible leakage’.

There is a little leakage as the fluid vapors get released into the atmosphere from the faces of the seal, though. Since the quantity is hardly quantifiable, the seals are considered leak proof.Seals and gaskets are sometimes custom-made to service unique applications, but we can group most seals that prevent leakage at the interface of a moving part and a stationary part into eight main types of component mechanical seals.

1. Wave Spring Mechanical Seals: Principally used for liquids of high viscosity, wave spring mechanical seals are popular for pharmaceutical, dairy, brewery and food processing applications. They are often fitted to the shaft with grub screws and in the case of high viscosity media would also have stationaries with anti-rotation pins. Some designs are specially constructed to work in shallow, confined seal housings.

2. Water Pump Seals: Because water is such a poor lubricant of seal faces, it is critical that water pump seals use excellent materials for applications such as shower pumps, irrigation, heating systems, swimming pools and spas.

3. Bellows Mechanical Seals: Compact, versatile, extremely reliable seals suitable for a wide range of applications. Available with either O Ring Mounted or Boot mounted Stationaries in DIN and Non-Din sizes. Recommended for media containing solids and are widely used in Pumps, mixers, compressors etc.Double (or dual) mechanical seals are designed to ensure maximum sealing safety. These seals virtually eliminate leakage of the fluid or gas being handled in pumps or mixers.

   • Double seals provide a level of safety/zero emissions compliance not possible with single seals. This is essential when pumping or mixing a dangerous or toxic substance.

   • Double seals are a must-have for certain applications in many countriesDouble (or dual) mechanical seals are designed to ensure maximum sealing safety. These seals virtually eliminate leakage of the fluid or gas being handled in pumps or mixers.

     • Double seals provide a level of safety/zero emissions compliance not possible with single seals. This is essential when pumping or mixing a dangerous or toxic substance.

     • Double seals are a must-have for certain applications in many countries

     • These seals are increasingly used by companies to meet specific environmental goals or emissions requirements.

     A properly installed double seal also allows for near complete control over the seal operating environment and fluid film over the seal faces. This factor alone can greatly maximize seal life.

     A double mechanical seal has two primary seals with a barrier or buffer fluid area in between. Each primary seal typically consists of a softer, narrower stationary face accompanied by a harder, wider rotating face. This arrangement enables the softer seal to wear while maintaining the integrity of the harder faced seal during service.

     Pump and seal manufacturers recommend double seals for a variety of reasons:

     • Prevent a hazardous product from reaching the atmosphere/polluting the environment

     • Avoid leakage of an expensive process fluid product

     • Maximize seal life by controlling the type of fluid film on the seal faces

     • Isolate the mechanical seal from atmospheric conditions

     • Provide an alternative when the process fluid will not provide stable and reliable lubrication of the seal faces (such as gaseous media, viscous fluids, non-settling slurries, or fluids liable to harden)

     • Establish a backup seal in the event of an inboard seal failure or planned equipment repair (or to identify seal failure during operation)

     • Avoid contamination of the process media should one seal fail

     Mechanical Seal Questions

     Q: What is a mechanical seal?

     A: An end-face mechanical seal is a device used on a rotating shaft to seal fluids. It consists of two flat faces that are installed perpendicular to the shaft. One of the faces is mounted stationary to the seal chamber or housing. The other face rotates with the shaft to provide the primary seal. Axial mechanical force and fluid pressure maintain the contact between the wearable seal face materials.

     Q: What is a cartridge seal?

     A: A cartridge-mounted, end-face mechanical seal (cartridge seal) is a completely self-contained unit that consists of the sealing components, a gland, sleeve, and hardware that allows the unit to be pre-assembled and preset. This feature eases installation and maintenance on rotating equipment on which axial adjustments are required.

     Q: What is a component seal?

     A: Component, end-face mechanical seals (a component seal) consist of a separate rotating member and stationary seat that mount in a gland or housing. Since they are not preset, installation and maintenance are generally more difficult requiring experienced technicians to properly install and adjust them.

     Q: What is an air seal?

     A: Air seals are non-contacting, pneumatic devices engineered for sealing rotating shafts. They protect against product loss, emissions, and contamination by using small amounts of air or inert gas that is throttled to create positive pressure and an effective seal.

     Metal Bellows

     A metal bellows is a precision-engineered, flexible metal component that acts as a leak-tight seal– effectively separating two environments from one another. These versatile parts can convert changes in pressure, temperature, and position into linear motion and be used for rotary transmission that maintains flexible mechanical and electrical connections.