National Crane 600H, Service Manual

Page: 19 / 232

NATIONAL CRANE
08-19-2022 Control # 092-13
1-7
600H SERVICE MANUAL INTRODUCTION
1
Fatigue Of Welded Structures
Highly stressed welded structures are subject to cracking
(fatigue) when repeatedly subjected to varying stresses
caused by twisting, shock, bending, and overloads. Inspect
equipment periodically for weld fatigue. The frequency of
inspections depends on the age of the equipment, the
severity of the application, and the experience of the
operators and the maintenance personnel. The following are
known high stress areas and should be inspected as part of
a preventive maintenance program:
• Hydraulic cylinder and boom pivot attaching points.
• Outrigger pads, beams, boxes and attachment
structures.
• On the frame in the area of doubler plates and
crossmembers.
• Turntable bearing connection (where bearing is welded
to the crane turret).
• Counterweight support structures (were applicable).
• Hydraulic cylinder end connections.
The above is provided only as a guide and your inspection
plan should not be limited to the areas listed. A visual
inspection of all weldments is good practice.
Loctite®
Always follow the directions on the Loctite® container, as not
all Loctite® types are suitable for all applications.Various
types of Loctite® are specified throughout the Service
Manual. The following types of Loctite® brand adhesives are
available from the Parts Department of the local National
Crane distributor.
Application of Medium Strength Loctite®
NOTE: The fastener may be re-used; the adhesive may be
re-applied over cured adhesive residue.
The following procedure covers the proper application and
curing method for medium strength Loctite® adhesive/
sealant (Loctite® #243).
NOTE: Ensure the threaded surface, both male and
female, is clean of contaminants and free of dirt
and oil.
1. Apply a bead perpendicular to the thread, several
threads wide, in the approximate area of threaded
engagement (see Figure 1-1).
2. In a blind hole application, a bead of several drops of
adhesive should be applied into the bottom of the hole to
be hydraulically forced up during engagement.
After application and engagement of mated threads, fixturing
will occur within five (5) minutes. Time required to achieve
full strength is 24 hours.
Fasteners and Torque Values
Use bolts of the correct length. A bolt which is too long may
bottom before the head is tight against the part it is to hold. If
a bolt is too short, there may not be enough threads engaged
to hold the part securely. Threads can be damaged. Inspect
them and replace fasteners, as necessary.
Torque values should correspond to the type bolts, studs,
and nuts being used.
The torque tables are provided by National Crane for
reference when performing maintenance.
Use of proper torque values is extremely important. Improper
torquing can seriously affect performance and reliability.
Identification of fastener grade is always necessary. When
marked as a high strength bolt (grade 5, 8, etc.), the
mechanic must be aware that he/she is working with a highly
stressed component and the fastener should be torqued
accordingly.
NOTE: Some special applications require variation from
standard torque values. Reference should always
be made to component overhaul procedures for
recommendations.
CAUTION
Skin and/or Eye Hazard!
Loctite® type adhesives contain chemicals that may be
harmful if misused. Read and follow the instructions on
the container.
!
4203
FIGURE 1-3
Bead Application
Bead Application
8213-1
8213-2
REFERENCE ONLY