Difference between Single and Double mechanical seal

Globe Star Engineers (India) Pvt. Ltd.

Mechanical seal

Difference between Single and Double mechanical seal

Mechanical seals are devices that seal machines between rotating parts (shafts) and stationary parts (pump housing) and are an integral part to the pump. Their main jobs are to prevent the pumped product from leaking into the environment and are manufactured as single or double seals. What's the difference between the two Mechanical seal?

 WHAT IS A SINGLE MECHANICAL SEAL?

                                                                                                     

A single mechanical seal consists of two very flat surfaces that are pressed together by a spring and slide against each other. Between these two surfaces is a fluid film generated by the pumped product. This fluid film prevents the mechanical seal from touching the stationary ring.

WHAT IS A DOUBLE MECHANICAL SEAL?

A double mechanical seal consists of two seals arranged in a series. The inboard, or “primary seal” keeps the product contained within the pump housing. The outboard, or “secondary seal” prevents the flush liquid from leaking into the atmosphere.

Double mechanical seals are offered in two arrangements:

• Back to back
• Two rotating seal rings are arranged facing away from each other. The lubricating film is generated by the barrier fluid. This arrangement is commonly found in the chemical industry. In case of leakage, the barrier liquid penetrates the product.
  
  
• Face to face
• The spring loaded rotary seal faces are arranged face to face and slide from the opposite direction to one or two stationary seal parts. This is a popular choice for the food industry, particularly for products which tend to stick. In case of leakage, the barrier liquid penetrates the product. If the product is considered “hot”, the barrier liquid acts as a cooling agent for the mechanical seal.