Yes, worn pin holes in a telescopic boom can often be repaired on-site, without removing the boom from the crane. The feasibility depends on the extent of the wear, the grade of steel involved, and whether the site conditions allow for controlled welding work. This article walks through the most common questions operators and fleet managers have about pin hole wear and what repair options are available.
What causes pin holes in a telescopic boom to wear out?
Pin holes in a telescopic boom wear out primarily due to repeated mechanical loading, friction, and micro-movement between the pin and its bore during crane operation. Over time, this continuous contact erodes the material around the hole, causing the bore to become oval, oversized, or structurally compromised. The rate of wear accelerates when lubrication is insufficient or when the crane operates under high-cycle loads.
Several factors contribute to pin hole degradation:
- Inadequate lubrication: Pins that are not regularly greased generate metal-on-metal friction that removes material from the bore wall with every movement.
- High-cycle operation: Cranes that extend and retract their booms frequently place constant stress on the pin connections, which accelerates wear compared to low-cycle applications.
- Overloading or shock loading: Operating a crane near or beyond its rated capacity places peak stress on pin connections, compressing and deforming the bore over time.
- Corrosion: Offshore environments and outdoor storage expose pin holes to moisture and salt, which weakens the surrounding steel and speeds up material loss.
- Misalignment: If boom sections are not perfectly aligned during operation, lateral forces concentrate on one side of the pin hole, causing uneven and accelerated wear.
Left unaddressed, worn pin holes alter the load path through the boom structure. What begins as minor slop in a pin connection can eventually lead to cracking in the surrounding material, particularly in high-strength steels where stress concentrations are more critical.
Can worn pin holes be repaired without removing the boom?
In many cases, yes. Worn pin holes in a telescopic boom can be repaired on-site without removing the boom from the crane, provided the damage is limited to the bore area and the surrounding base material is structurally sound. The key requirement is that welding conditions on-site can be controlled sufficiently to meet the material specifications of the boom steel.
On-site repair is most viable when:
- The wear is confined to the pin hole bore and has not caused cracking in the parent material
- The boom is made from standard or medium-grade steel, where welding procedures are less restrictive
- The site provides adequate shelter, temperature control, and access for qualified welders and inspection equipment
- A Welding Procedure Specification (WPS) appropriate to the material grade is available and followed
High-grade steel booms, particularly those manufactured from 960 or 1100 N/mm² steel, present a greater challenge. These materials are sensitive to heat input and require highly controlled welding procedures to avoid introducing new defects. On-site repair of pin holes in these steels is technically possible but demands specialist expertise and pre-qualified welding procedures. Not all repair contractors have the qualifications or experience to work safely on ultra-high-strength crane booms.
What does the on-site pin hole repair process involve?
An on-site pin hole repair follows a structured process that begins with assessment and ends with certified inspection of the completed weld. The core steps involve removing worn material, rebuilding the bore with weld metal, machining the hole back to its original dimension, and verifying the repair through non-destructive testing.
A typical on-site repair sequence includes:
- Initial inspection and measurement: The bore is measured to determine how much material has been lost and whether the surrounding steel shows any cracking or deformation. Magnetic Particle Inspection (MPI) is commonly used at this stage to detect subsurface cracks.
- Material verification: The steel grade is confirmed so the correct filler material and preheat temperature can be selected. This step is critical for high-strength steels.
- WPS preparation: A Welding Procedure Specification is prepared or referenced, defining the exact parameters the welder must follow, including heat input, interpass temperature, and filler material.
- Bore preparation: The worn surface is cleaned and prepared to ensure proper fusion of the weld metal. Any loose or damaged material is removed.
- Weld build-up: The bore is built back up using approved filler material, applied in controlled passes to manage heat input and avoid distortion.
- Machining: The rebuilt bore is machined to the original pin hole diameter and tolerance, restoring the correct fit for the pin.
- Post-repair inspection: A 100% visual inspection and MPI are performed on all new welds to confirm there are no cracks, inclusions, or incomplete fusion. Where required, ultrasonic testing may also be carried out.
Documentation is produced throughout the process, including photographs of the damage, the WPS used, and the inspection results. This paperwork supports the crane’s certification record and is essential for compliance purposes.
Does repairing pin holes affect CE certification or the crane’s load rating?
A correctly executed pin hole repair does not affect the crane’s CE certification or its rated load capacity, provided the repair is carried out according to an approved Welding Procedure Specification and verified through the required non-destructive testing. The repaired boom section must be restored to its original dimensions and structural integrity for the existing certification to remain valid.
The critical factor is that the repair process is documented and traceable. CE certification for a mobile crane is tied to the structural integrity of its components. A repair that is performed without a qualified WPS, without proper inspection, or by personnel who are not certified for the relevant steel grade creates a gap in the crane’s compliance record. In practice, this means:
- The repair must be performed by qualified welders holding the appropriate certifications for the material and welding position
- All non-destructive testing must be completed and documented before the crane returns to service
- Where a notified body is required, third-party inspection must be arranged and the results added to the crane’s documentation
- The repair does not require the crane to be re-certified from scratch, but the repair record must be retained as part of the crane’s ongoing compliance file
This is one of the reasons why crane boom repair work on high-grade steel requires specialist contractors rather than general welding firms. The technical quality of the weld and the completeness of the documentation are both essential to maintaining the crane’s legal operating status.
When should a telescopic boom go to a workshop instead?
A telescopic boom should be sent to a workshop when the damage around the pin holes is too extensive for reliable on-site repair, when the steel grade requires conditions that cannot be replicated in the field, or when additional structural damage is found during inspection. Workshop repair offers controlled temperature, specialist tooling, and the ability to perform more complex machining and testing.
Specific situations that typically require workshop repair include:
- Cracking in the parent material: If MPI reveals cracks radiating from the pin hole into the boom wall, the repair scope extends beyond the bore itself and requires a more controlled environment.
- Severe material loss: Bores that are significantly oversized may require insert sleeves or structural reinforcement that is impractical to carry out on-site.
- Ultra-high-strength steel: Booms manufactured from 960 or 1100 N/mm² steel require strict preheat and post-weld heat treatment conditions that are difficult to guarantee on an open job site.
- Multiple repair locations: When a boom requires simultaneous repairs at several points, workshop conditions allow for better sequencing, consistent quality control, and more efficient inspection.
- Third-party certification requirements: Some insurers or clients require that structural repairs be performed under workshop conditions with full third-party oversight.
The decision between on-site and workshop repair is ultimately a technical one based on material grade, damage severity, site conditions, and the documentation requirements of the crane owner. When in doubt, a preliminary inspection by a qualified crane repair specialist will determine which route is appropriate before any work begins.
How Rusch Cranes handles telescopic boom pin hole repair
Rusch Cranes provides specialist repair services for telescopic boom pin holes, combining qualified welding expertise, documented procedures, and full inspection capability. Their team works on mobile crane booms made from steel grades up to 1100 N/mm², making them one of the few contractors in Europe equipped to handle the most demanding repair scenarios.
Key aspects of Rusch’s approach to pin hole and boom repair include:
- Preparation of a Welding Procedure Specification and Repair Plan before any work begins
- Material strength checks and precise measurements taken at the outset of every repair
- 100% visual inspection and 100% Magnetic Particle Inspection on all new welds upon completion
- Third-party notified body involvement for ultrasonic or X-ray testing where required
- A one-year guarantee on all completed repairs, with CE testing remaining valid after repair
- Global deployment capability, with technicians available to travel to job sites worldwide, including the Netherlands, the Middle East, and beyond
If your crane has a worn pin hole or you are unsure whether on-site repair is viable, contact Rusch Cranes directly to arrange an assessment and receive a clear recommendation based on your boom’s steel grade and the extent of the damage.
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