Yaroslavl ???-236, Maintenance Manual

Page: 29 / 270

30
specified parameters with the help of comparison it is allowed to use the reference quality pattens
(quality standard) of the parts which should have corresponding marking and should be approved in
accordance with the established procedure.
2.7.13 Thread is controlled with the visible inspection of the critical parts with the
help of screw thread gauge. To provide the quality of assembly during the repair and reliability
of the threaded fasteners (provisions of the tightening force) thread-stripping and other defects
are not allowed.
2.7.14 Controlling the parts and assembly units such defects as breaks, cracks,
hollows, pockets and others are controlled with the help of visual inspection. It such defects are
not characteristic for such details these defects should not be mentioned in the technical
conditions. To decide whether to reject the detail or to recover it organization should consider its
technical capabilities and reason ability of the repair as to the economical efficiency.
2.7.15 It is allowed to re-use the open antifriction bearings if they comply with the
requirements of the simplicity of rotation and noise character in comparison with the approves
quality standard. Increase of the tip clearance in the bearings determined at the gauge should be less
than 1.5 times comparing with nominal values of the tip clearances.
2.7.16 Fasteners admitted to the re-use after the inspection should be applied in
accordance with their purpose and application in the assembly unit. For this purpose they should
be sorted during the engine disassembly according to their dimension-type as to the legends.
2.7.17 Bolts and nuts with the worn (rolled), rumpled ribs of the hexagon of bolt or screw
head is not allowed if their width across corners exceeded
the following values:
"Turn key"
dimension, S,
mm 10 12 13 14 17 19 22 24 27 30
Width across
corners, mm 10.5 12.7 14.0 14.8 18.3 20.6 24.0 26.0 29.4 32.5
It is not allowed to re-use the following threaded parts: bolts, screws, nuts and stud pins
having the following defects:
- stripping, crushes, dints, deformation, thread corrosion;
- crook, bending of the bolt, nut and stud pin bar;
- strain hardness and wear of the butt end;
- head breakage, break, extensions exceeding the norm of the rod;
- galling at the thread;
2.7.18 Parts and assembly units having the anti-corrosive coating are visually
inspected. Damaged coating should be recovered.