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Know and Understand Centrifugal Pumps Episode 11

Tham khảo tài liệu 'know and understand centrifugal pumps episode 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Know and Understand Centrifugal Pumps Figure 13-3 The mechanical seal The mechanical seal is a device that forms a barrier between rotary and stationary parts in the pump. The seal must block leakage at three points Figure 13-4 Between the faces rotary and stationary of the seal. Between the stationary element and the seal chamber housing of the pump. Between the rotary clement and the shaft or sleeve of the pump. These basic components and functions are common to all seals. The form style and design vary depending on the service and the manufacturer. The basic theory of its function and purpose nevertheless remains the same. The set screw that transmits the torque from the shaft is connected to the rotary face through the spring. It also provides for the positive and correct positioning of all rotary parts. BETWEEN SHAFT AND SEAL Figure 13-4 BETWEEN SEAL AND HOUSING BETWEEN ROTARY AND STATIONARY FACES I 184 I Mechanical Seals As the faces wear the spring extends maintaining the rotary face in contact with the stationary face. The shaft o-ring should be free to move axially on the shaft within the operational tolerances of the bearings. This is called axial play. The liquid s pressure in the seal chamber holds the faces together and also provides a thin film oflubrication between the faces. This lubricant is the pumped product. The faces selected for their low frictional characteristics are the only parts of the seal in relative motion. Other parts would be in relative motion if the equipment is misaligned or with loose tolerance in the bearings. The single unbalanced inside mounted mechanical seal This type of seal mounts onto the shaft or sleeve inside the seal chamber and pump. The pumped liquid comes into contact with all parts of the seal and approaches the outside diameter of the internally mounted faces keeping them lubricated. The environment outside the pump approaches the ID of the seal faces. The pressure inside the pump acts upon the faces to keep them