Mechanical Seals

Question 1

What are the objectives of a mechanical seal?

Answer 1

A. Control leakage along to pump drive shaft.

B. Prevent leakage of air into the pump under suction lift conditions.

Question 2

Compare compression packing and mechanical seals.

Answer 2

• mechanical seals reduce the need for seal water.
• mechanical seals are much more expensive
• you need an experienced a millwright to maintain and install a mechanical seal.
• mechanical seals have much longer operational life

Question 3

What two elements make up a mechanical seal?

Answer 3

• rotating element

- stationary element

Question 4

On a mechanical seal, primary sealing duty happens where?

Answer 4

Primary sealing duty is carried out between the seal’s rotating and stationary elements. No wear n tear takes place on the Pump’s equipment.

Question 5

What is the static seal point of rotating unit to shift?

Answer 5

The interface between the o-ring and the shaft in a mechanical seal

Question 6

What is an external mechanical seal?

Answer 6

Sealing surface is outside the stuffing box. It’s advantage is that the seal can be adjusted after installation.

Question 7

What is a lantern ring connected to?

Answer 7

The Seal water supply line.

Question 8

Water that comes through the lantern ring is used for work purposes?

Answer 8

Cooling and lubrication.

Question 9

What are the two main types of compression packing?

Answer 9

Automatic and compression packing.

Question 10

Name two common types of automatic packing.

Answer 10

U-cup and V pressure ring.

Question 11

What is the main advantage of compression type packing?

Answer 11

It uses thin contact clips to reduce heat generated by friction.

Question 12

Why is automatic packing called automatic?

Answer 12

The sealing action of the packing depends upon the pressure it is subjected to.

Question 13

Packing generally has the following characteristics:

Answer 13

• rectangular cross-section
• flexible so that it can be compressed
• corrosion resistant
• tough so that it can withstand rubbing against the shaft without self-destruction
• soft so that it does not score of the shaft
• good conductor of heat, so that it can transmit heat away from the contact surfaces

Question 14

What is a stuffing box?

Answer 14

The stuffing box is used to house the packing material, it forms the boundary between the wet side and the dry side of the pump.

Question 15

What is packing?

Answer 15

The packing consists of a series of rings constructed with a suitable packing material.

Question 16

What is a Lantern ring?

Answer 16

A ring that facilitates injection of cooling water into an intermediate point in the packing ring assembly through circumferential holes.

Question 17

What is the water inlet port?

Answer 17

A port that allows cooling water to flow into the stuffing box. This water provide cooling and lubrication.

Question 18

What is the gland?

Answer 18

A circular metallic element that is used to compress the packing and hold it in place. Tightening too much can bind the shaft, as the tighter it is compressed the harder it presses against the shaft.

Question 19

What are your gland stud bolts and nuts?

Answer 19

Nuts and bolts used to compress the packing elements. Properly compressed packing results in a slight leakage around the shaft. The leakage is necessary to ensure lubrication and cooking. Tightening too much will result in Shaft binding and loss of lubrication.

Question 20

What is the gland follower?

Answer 20

The portion of the gland that is inside the stuffing box.

Question 21

How can you tell when packing is worn out?

Answer 21

Leakage through the stuffing box increases. To improve the seal operators tightening the gland nuts. There is a limit to how much you can keep tightening gland nuts.