This is a multispring externally mounted, balanced seal with "O" ring as secondary sealing member. This seal can be used for corrosive services as the metallic components i.e retainer, spring, thrust ring do not come in contact with liquid to be sealed.
Dry running seals do not require any external media for lubricating the faces. Thus these seals are used in food products and pharmaceutical industries where external liquids can contaminate the product & affect its quality.
Also the seal accommodates the shaft movement, vibrations and deflection.