To help retain bearing lubrication and prevent contamination from the environment a seal (contact) or shield (non-contact) can be employed.
Often no seal (Open) is required when the bearing will be housed and externally lubricated or when operated in a vacuum.
‘Z’ Type Shield – The ‘Z’ type shield is a metal shield that typically is non-removable after installation as is it pressed in. There is a small gap about .005 inches between the shield and inner race. There is no contact so obtainable speeds and torque are not effected as in a contact type seal. Lubricant leakage can occur and contamination can enter through this gap. They have fair dust resistance and poor water resistance. Shields are good to around 350 F.
‘RS’ Type Seal – The ‘RS’ type seal is a rubber seal that makes contact with the inner race. Most commonly made of Buna-rubber. They are removable. They offer the best sealing against contamination and lubricant leakage. Generally the speed rating is reduced about 35% that of the ‘Z’ type or open and torque is increased. Temperature range is 15 F to 220 F.
‘V’ Type Seal – The ‘V” type seal is a non-contact type rubber seal that does not contact the inner race, but rides in groove machined in the inner races creating a labyrinth effect. Its performance falls between a metal shield and contact type rubber seal. Most commonly made of Buna-rubber. They are removable. They offer the good sealing against contamination and lubricant leakage. Generally the speed rating is not reduced and is comparable to that of the ‘Z’ type or open. There is no seal induced torque increase. Temperature range is 15 F to 220 F.
‘T’ Type Seal – The ‘T’ type seal is made of glass reinforced Teflon. This type of seal is removable and easily replaced. In most configurations the seal is held in place by a snap ring. The level of contact (sealing) can be adjusted to meet application requirements all the way from non-contact to heavy contact. Their best characteristic would be their high temperature capability of 500 F.
|METAL SHIELD||350 F||GOOD||LOW||COMMON|
|RUBBER (CONTACT)||220 F||LIMITED||HIGH||COMMON|
|RUBBER (NONCONTACT)||220 F||GOOD||LOW||COMMON|