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January 5
Mechanical Seal Types Explained: Which One Does Your Pump Need?
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The main types of mechanical seals
According to Pump Industry journal, selecting the correct mechanical seal for your pump is essential to long and efficient operation.
Here is a breakdown of the main types of mechanical seals we have IN STOCK at Rural Pumps:
Type 6 mechanical seal
Type 6 seals (also known as Type 16 or Type B04) are very common seal for small house pressure pumps. They are a non-pusher type seal as they seal against the shaft at the back of the mechanism and use a bellows to seal in the pressure. The rotary face is commonly carbon graphite based but can also be available in silicone carbide and tungsten carbide. The stationary face is normally ceramic but can also come in silicone or tungsten carbide. To make them economical though they use a spring to assist the bellows. This makes them ideal for dirty and abrasive water conditions. They are also pressure rated to a maximum of 1000kpa.
Type 6 seals are only available in imperial sizes, we have Type 6 seals IN STOCK HERE in our webshop.
Type 6A mechanical seal
Type 6A seals (also known as Type 68 or Type B03) are generally used for lower pressure water transfer pumps and some irrigation pumps. They are a slightly different type of pusher seal. The main differences with a Type 6A seal is that it doesn’t use an o-ring seal around the pump shaft to hold in the water pressure. The stationary section actually holds both the wear face (normally carbon graphite but can be silicone carbide) and the spring base. This sat in a moulded rubber seal base in the pump housing. The rotary section is actually made from ceramic (and sometimes silicone carbide) and sat in a moulded rubber base which is set into a normally brass recess at the back of the impellor. While they can handle dirty and contaminated water the main downside to a Type 6A seal is that its only rated for 300kpa.
Type 6A seals are available in limited imperial sizes and also a small range of metric sizes, we have Type 6A seals IN STOCK HERE in our webshop.
Type 21 mechanical seal
Type 21 seals are generally widely used for larger high pressure water transfer pumps and irrigation pumps, particularly ISO and DIN type centrifugal pumps. They are a pusher type seal that uses a rubber type ring seal built into the rotary seal face. A spring and base then pushes against the back of the impellor to hold this against the stationary which is set into the pump back plate. The rotary face is commonly carbon graphite based but can also be available in silicone carbide and tungsten carbide. The stationary face is normally ceramic but can also come in silicone or tungsten carbide. They are generally not suited for dealing with dirty or contaminated water but can handle high dissolved salts and minerals, if the seal surfaces are silicone or tungsten carbide. They are also able to handle operating pressures up to 1000kpa (10 Bar)
Type 21 seals are stocked by Rural Pumps in metric (DIN) sizes for most common pumps and Imperial and uncommon DIN sizes as an order in item. We have a wide range of Type 21 seals IN STOCK HERE in our webshop.
Type 55 mechanical seal
Type 55 seals (also known as Burgmann B01 or BT-AR) are widely used generally for smaller domestic pumps and for water transfer pumps. They are a non-pusher type seal that uses an integrated bellows and shaft seal that seals in the pressure at the impellor end of the mechanism. A short spring assists the bellows in tensioning the seal face against the stationary but they don’t have very much flex in this mechanism so are limited to both application and operating pressure. The rotary face is commonly carbon graphite based but can also be available in silicone carbide and tungsten carbide. The stationary face is normally ceramic but can also come in silicone or tungsten carbide. They can handle dirty or contaminated water due to the use of a bellows. They are also able to handle operating pressures up to 600kpa (6 Bar)
Type 55 seals are stocked by Rural Pumps in only a couple of common small metric sizes but can be ordered in up to 70mm, we have Type 55 seals IN STOCK HERE in our webshop.
Type 2100 mechanical seal
Type 2100 seals (also known as B05) are widely used in water transfer and industrial high pressure pumps. They are a hybrid pusher /non-pusher type seal that uses an integrated bellows and shaft seal that seals in the pressure at the seal face and at the impellor end of the mechanism. A spring assists the bellows in tensioning the seal face against the stationary. The rotary face is commonly carbon graphite based but can also be available in silicone carbide and tungsten carbide. The stationary face is normally ceramic but can also come in silicone or tungsten carbide. They can handle dirty or contaminated water due to the use of a bellows. They are also able to handle high operating pressures up to 1600kpa (16 Bar)
Type 2100 seals are stocked by Rural Pumps in only a couple of common metric sizes but can be ordered in up to 100mm, we have Type 2100 seals IN STOCK HERE in our webshop.
Type MG1 mechanical seal
Type MG1 seals are widely used in small domestic and industrial high pressure pumps, most commonly the horizontal multistage pumps from Davey, Franklin and others. They are a hybrid pusher /non-pusher type seal that uses an integrated bellows and shaft seal that seals in the pressure at the impellor end of the mechanism. A spring assists the bellows in tensioning the seal face against the stationary and this spring is very strong and has a short stroke. The rotary face is commonly carbon graphite based but can also be available in silicone carbide and tungsten carbide. The stationary face is normally ceramic but can also come in silicone or tungsten carbide. They can handle dirty or contaminated water due to the use of a bellows. They are also able to handle high operating pressures up to 1200kpa (12 Bar)
Type MG1 seals are stocked by Rural Pumps in only a couple of common metric sizes but can be ordered in up to 100mm, we have Type MG1 seals IN STOCK HERE in our webshop.
Type Uniten mechanical seal
Uniten type seals (also known as type 3 simplex or DIN) are widely used in water transfer and domestic pressure pumps. They are one of the most basic in design but reliable seals and are a simpler pusher design. The shaft seal uses a rubber O-ring shaft seal that seals in the pressure at the seal face end of the mechanism. A spring tensions the seal face against the stationary. The rotary face is commonly carbon graphite based but can also be available in silicone carbide and tungsten carbide. The stationary face is normally ceramic but can also come in silicone or tungsten carbide. They are generally only used for clean water due to the seal movement and using O-rings. They are also able to handle high operating pressures up to 1000kpa (10 Bar)
Uniten type seals are stocked by Rural Pumps in only a couple of common metric sizes but can be ordered in up to 40mm, we have Type Uniten or Type 3 seals IN STOCK HERE in our webshop.
Cartridge Seals (vertical multistage seals)
Cartridge type seals (also known as Grundfos seals or VM seals) are a particular type of integrated design widely used in vertical multistage industrial pumps, particularly the Grundfos CR/ CRE and similar like the Davey VM. They are designed as a one piece mechanism that can be removed and reinstalled from the outside of the pump housing without having to disassemble the pump. This is very important with vertical multistage pumps as they can have 10 or more impellors and a lot of associated parts and can be time consuming to correctly rebuild. The rotary and stationary are pressed together but still are able to rotate against each other. This cartridge has a thread or similar locking mechanism on its outside and this is used to lock it in place just inside the top of the pump housing, this has the stationary face built into it. The rotary mechanism has a long bellows with an O-Ring shaft seal that runs up its inside and also the inside of the stationary. This comes out the top of the stationary section and has a locking collar attached to it which is generally grub screwed onto the pump shaft to both tension it and set the pump height in the housing. The rotary face is commonly silicone carbide or tungsten carbide. The stationary face is normally silicone or tungsten carbide too. They are can be used for dirty water but solids generally block up a vertical multistage pump. They are rated to handle high operating pressures up to 1000kpa (10 Bar) but can generally run much higher.
Cartridge seals are available from Rural Pumps in only a 12mm, 16mm and 22mm sizes in both bolt in and thread in types, we have a range of Catridge type seals IN STOCK HERE in our webshop.
Please contact us if you are looking for something unusual or use our pump selector in our webshop to get a replacement seal for your pump.
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mechanical seal, pumps