SWDM40 OPERATION & MAINTENANCE MANUAL
7.1.8 Simple Repair Technology for Kelly
Purpose: make sure there’s repair value ad corresponding repair technology for Kelly
according to criteria.
Range：This guideline specifies the repair value and corresponding repair technology.
Preparation：Assemble the second-hand Kelly to wash it with clean water. If it’s stuck, please
check any sand or foreign objects for clogging and Kelly locking.
1. Silt clogging: wash with clean water, and take out after it’s soften.
2. Impurity jamming: find out the jamming position, make a gas-cut tetragon at the pipe wall
position, and take out. If it’s hard to find, create a gas-cut ring at drive sleeve and inspect.
3. Kelly locking: check steel pipe outer wall for deformation, do a gas-cutting at the
deformation position.
4. Wash each section of Kelly to ensure its surface can be seen clearly for easy analysis.
Criteria Judgment for Kelly Repair Value
Discard Criteria
1. Whole Kelly twist and deformation.
2. Too much spline crack on the whole Kelly, the length of new steel pipe is also as the same as
the original size.
3. The use time is too long, the value of parts required to be changed, is almost 80% of the new
manufacturing ones.
Repairable Criteria:
Each section of Kelly can be repaired at one or two positions at most to ensure the use. The
repair cost is less than the sale value after remanufacturing.
Methods of Repair Technology
Square-head repair:
1.Connect 1.5m steel pipe at square head for gas cutting, cut spline at surplus place for
180mm-250mm to make every it form 45 bevel edge, mutually staggered, not damaging the
steel pipe, polish that after gas-cutting.
2. Determine whether the square head can be used repeatedly, if OK, gouge square head and
steel pipe welding groove, and polish to shine.
3. Cover the square head on the spring seat to connect 1.5m new steel pipe, open grooves on
two end of new pipe to guarantee the same axial less than 1.5mm, do that according to the heat
preservation requirements for preheating and welding.
4. Install spring-stiffened arc plate and do that according to the heat preservation requirements
for preheating and welding.
5. Measure the length of key bar which required to be arranged, weld that completely,
remembering that welding should be done one step by one step. After welding, polish the
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