Tham khảo tài liệu 'handbook of lubrication episode 2 part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Volume II 605 FIGURE 18. Typical pomp stuffing box with compression packing. 1 Shaft finish to pm 10 to 20 pin. CLA shaft hardness Rockwell C-50 shaft runout should not exceed mm in. TIR. 2 Bore finish 1 to pm 40 to 60 pin. CLA. 3 Rings nearest gland are deformed most approximately 70 of wear under first 30 of packing. 4 Harder end rings are sometimes used at gland and at throat. 5 Packing length D. 6 Packing radial thickness to D. 7 Throat clearance 0 2 to mm to in mm maximum. 8 Gland-to-bore clearance to mm to in. . 9 Gland-to-shaft clearance to mm to in. . 10 Tap locations for lantern gland inlet. 11 Lantern ring. have better high temperature wear resistance with a sacrifice in low temperature flexibility. PTFE a thermoplastic rather than an elastomer has a wide temperature range and is resistant to almost all fluids. It is difficult to process and is usually employed as assembled seals. Butyl epichlorhydrin an ethylene-propylene terpolymer EPDM are used in special purpose seals. Packing Seals Mechanical shaft packings include compression packing automatic or lip packing and squeeze packing. Compression packings are a pliable material compressed between the throat and gland of a stuffing box for reciprocating oscillating and rotating applications. Leakage in dynamic applications is usually on the order of 50 to 500 m hr but may be essentially zero in semistatic valve stem applications. Automatic packings utilize a flexible lip energized by the contained fluid pressure. Employed primarily for reciprocating applications heat dissipation problems restrict rare rotating applications to speeds below 1 m sec 200 ft min . Squeeze packings utilize precision-molded elastomer rings such as the O-ring installed in precisely machined grooves glands on cylinders pistons or rods in hydraulic or pneumatic 26 Squeeze packings are most frequently used in reciprocating
