Our Case Studies

Excavator Mainframe

In this example of an excavator mainframe you can see highlighted in green, cracking that has developed from the defects of a poor repair root run, with the root run exhibiting poor profile, missed non fused edges, excessive penetration and even unmelted wire in the weld pool. These defects have created stress concentrations that have developed multiple cracks. 

In this particular case the cracks were found a week after the initial repair was made resulting in needing further repairs at the next service day. 

The next available planned service day was three weeks from that point in time, so it was decided to wait until then because 1: It had only just been repaired. 2: The small cracks where considered low priority and predicted to not grow.

One the day of the service the area was re-inspected and the cracks where noted to have grown to over 550mm in total combined length in three different directions making the second repair much more complex. This also resulted in an extra 11 hrs required to complete the repair, beyond the 12 hrs that was planned. 

Poor quality root runs in single sided weld repairs can often mask crack like features when ultrasonic inspection is conducted, making it difficult to determine if the repair is actually cracked or just poor root profile. In this case, it was lucky that this particular section of the structure had limited access to the inside of the mainframe so that the weld root could be visually inspected, Most other box section structures are typically fully enclosed, making crack detection from root defects difficult. The result of this is that the crack typically is only detected once it has reached full section thickness so it is visible, at which time the visible crack is only the tip of the iceberg with the cracking internally often four times longer.

The Cost Of Poor Quality:  12 hrs of machine down time equates to approximately $40,000. 

23 hrs of welder labour & equipment may cost $8,000. That’s $48,000 in unnecessary costs all because of a substandard repair.

It is easy to see how issues with poor quality weld repairs across a fleet of equipment would add up to a massive cost. For example, in a fleet of 5 Excavators, if similar repair issues were to occur 3 times per year for each unit, then the total annual cost could easily be more than $750,000. This is assuming that the repairs can be scheduled, and in a full unplanned breakdown scenario the cost would be significantly more.

Haul Trucks

Axle Box

This example is of a haul truck axle box and is a perfect example of how a weld repair should not be completed.¶
The attempted repair has cracked straight through the center of the weld and continued cracking at both ends. This suggests the crack was not entirely removed prior to welding but also suggests the cracking could be emanating from an internal support member.

At the very least a single side repair could have been conducted to remove all identified cracking and at a later time in the near future a confined space set up for a back gouge to be completed to improve the repairs fatigue resistance and also address other weldments in the area with poor weld toe profiles where cracking may be propagating from.

Another important repair fatigue life improver is the finished weld cap profile, the awful profile of this repair has dramatically reduced the fatigue life and has more than likely contributed to recracking.

Chassis Cracking

Just about every chassis in its life has developed cracking. In this extreme case the extent of cracking was so severe imminent structural failure was highly probable if the truck continued under its normal operating conditions, a closer inspection revealed that in fact 80% of the chassis had cracked full thickness.

The truck was stood down for immediate repairs but had to unfortunately wait until next shift due to no welding labour available, the entire repair took just under two shifts to complete.
Due to the severity of the repair it was recommended that the chassis have windows cut out to repair internally and investigate how the crack developed, the truck was planned to have this work completed at its next overhaul that was only a couple of months away.

On further investigation once a window had been cut from the chassis it was apparent there had been multiple unrecorded previous repair attempts in this area. The crack initiation sites were observed to be located on the weld toe of an internal stiffener and backing bar before emanating full thickness to the underside of the chassis then traveling up the sidewalls. This example highlights the importance of finish requirements of a weld and the correct fitment of backing bar.

Example 3

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Problem

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Solution

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Problem

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Crack Repair Solutions

 

Providing solutions for chronic and/or severe cracking issues in all equipment. We provide the technical detail and support, and work with your preferred welding supplier to ensure you get the best repair outcome.

Don’t throw critical components such as steering arms and wheel motor frames away because they have cracks in them. We can repair them and ensure that they are safe and fit for extended service.

In order to get the job done right, sometimes it is necessary to have an expert welding supervisor on hand in order to advise on the repair and monitor the work done by the welding crew. And if you have no procedures and no welder competency tests, then sometimes your welding supervisor is all you can rely on.

Want to know the current state of your business in terms of how weld repairs are handled? We can provide an audit process so that you have a clear understanding of where your business is now, and what can be done to get you to the next level. WQMS can also audit your welding contractors to ensure that they are delivering the service you require.

Want to know the current state of your business in terms of how weld repairs are handled? We can provide an audit process so that you have a clear understanding of where your business is now, and what can be done to get you to the next level. WQMS can also audit your welding contractors to ensure that they are delivering the service you require.

WQMS provide a range of training and coaching services. Our half day welding awareness training will take your staff to the next level. We can also provide focussed training for your welders, teach them new techniques and upskill, and enable them to pass their welder competency test piece.

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