10.11.2009

Crane tip warning

A mobile crane tipped over at a petrochemical plant in Singapore in late October with a similar set of circumstances to several other tip overs in the past six months.

In this case a four axle 100 tonne Tadano Faun All Terrain crane was set up and levelled on its outriggers when the crane needed to relocate for a new lift.
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The toppled crane

Having slewed the boom over the front, but left the boom at a 70 degree angle the crane operator climbed down from the cab and fully retracted the outriggers from each side of the chassis.

The crane, now on its wheels was no longer level, as the ground had a five percent grade with the paved ground sloping away to the side of the crane towards a storm drain...

As the operator climbed back into the crane’s superstructure cab, the crane’s 45 tonne counterweight began to pull/slew the superstructure towards the lower side of the chassis. The operator said that he tried to counteract the involuntary slewing but failed.
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The crane went over backwards and landed on its counterweight

Within two to three seconds the counterweight was fully over the ‘downhill’ side of chassis. The boom at a high angle also contributed to the lack of rearward stability, the crane then toppled over backwards and ended up resting on its counterweight with the rear of the chassis over two metres off the ground

Fortunately no one was injured and the damage to the structure it had been working on was relatively minor.
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Fortunately there was little material damage

A report issued this week by the plant’s operators, Exxon Mobil, highlighted the following facts which it hopes will be used to alert others to the errors and their causes:

- The incident resulted from several errors by the crane operator during preparation for moving the crane including:

- The crane’s boom was not stowed but left in the air at an angle greater than 70 degrees.

- The superstructure’s hydraulic slew brake was not set and not “pin locked” to the chassis.

- Counterweights were not stowed.

- Failure to recognise that the five percent slope could cause the crane to become unstable in the above configuration

The report added that the lifting supervisor recognised that the crane was becoming unstable and advised the crane operator. The crane operator acknowledged that he had heard the lifting supervisor, but took no action to change the situation. The lifting supervisor then took no further action, even though he recognised the danger.

The crane operator had been on site for three months operating different cranes, but had only been operating this unit for six days.

Incident Root Causes:

1. Improper attempt to save time & effort by the crane operator - The crane operator failed to adhere to manufacturer’s prescribed operating practices and did not understand the potential consequences of his actions.

2. Breakdown of effective teamwork, in particular between lifting supervisor and crane operator caused by ineffective communication in a multi-cultural setting compounded by poorly defined responsibilities
- The crane operator (Chinese Singaporean National) did not accept the lift supervisor’s instructions. The lift supervisor (Indian National) was unsuccessful in stopping the unsafe operation that he had recognised.

3. Lack of an effective controls process to ensure safe field practices for all crane activities - Insufficient monitoring / auditing of the actual setting up / de-mobilising of cranes for relocation. Ineffective verification of crane operator’s qualifications, competency and experience in the crane assigned to the operator.

Lessons Learned:

1. Lack of effective controls (i.e. system verification) will allow personnel with less than adequate qualifications, competencies, and
experience on to the job site with risk potential of unsafe acts that may lead to incidents

2. Communication styles in a multi-cultural setting can impact the effectiveness of team interaction and intervention processes that will
ensure safe work execution

3. Sharing of responsibilities and acknowledged authorities for all stages of work execution must be defined and understood by all
involved personnel

Vertikal Comment

This is very similar to an accident that occurred barely four weeks earlier with a similar sized Terex Demag All Terrain crane at a petrochemical plant in Qatar.

In both cases operator error caused by a lack of familiarity with the crane was largely to blame. Surely it is time that such plants insist on operators that are fully trained in the particular crane and that do not flit from crane to crane.

While this operator yo-yoing might work for simpler Rough Terrain cranes it is simply inadequate for the more sophisticated road-going All Terrain cranes.

To see the article on the Qatar accident click here