24.06.2010

Tower crane spigot alert

Manitowoc/Potain has issued a service bulletin and warning regarding a batch of substandard tower spigots on its K600 and K800 tower sections. The bulletin has also been referenced by a UK HSE warning notice.

The warning follows two catastrophic spigot failures, one in Chicago in February 2009 and one in London this April. The failure, which starts as a small crack, is thought to be due to inadequate heat treatment.

Whilst investigations continue all spigots manufactured between 1st November 2006 and 28th February 2007 are suspected of being substandard and subject to replacement.
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Fi 1:A spigot with its number clearly seen

Manitowoc Crane care says that the K600 and K800 series mast sections are only used on its MD, MDT and MR series cranes. Each tower section has a unique PIN /identification number. The numbers for mast sections produced in this time period are between 80323 - 103784.

The potentially affected spigots are in the ranges 3086* to 3496* and 0037* to 0577* - the letter on the end of the reference number is irrelevant for identification.

The action required is easy. For stored sections they simply need to be checked to see if they are within range and then the spigots changed, or at least checked.

For cranes in service the sections need to be checked to see if any of them are included in the list of potential affected sections. If a potentially bad section is identified, it must be pulled out of service immediately and then the spigots checked to see if any of them are potentially substandard.

If it is not possible to dismantle a crane that has a potentially bad section within tts tower, Manitowoc crane care can help you add some factory approved re-enforcements intended to last until the end of the job or until a break in the work load. If in doubt at all contact Steve Bradby at Manitowoc cranes UK in Gawcott, Buckinghamshire.

The HSE Bulletin reads as follows:

"We are aware of two crane mast failures in which faulty mast section spigots were implicated."

"The first of these incidents was in Chicago in February 2009. The most recent incident involved a crane in London in April 2010. Metallurgical tests undertaken on the London crane showed that the spigot failed catastrophically in brittle fracture from a small fatigue crack. The tests have shown that the failed spigot did not meet the performance characteristics specified for the component. It is believed that there was a flaw in the heat treatment process during the manufacture of the spigot. Whilst investigations continue to isolate the cause of the problem, as a precaution all spigots manufactured between 1 November 2006 and 28 Feb 2007 are suspected of being substandard and subject to the remedial action outlined in this document"

Background:

If a tower crane mast fails and collapses there is potential for multiple fatalities. Tower crane masts or towers are constructed from a number of individual sections which are located one on top of another to achieve the required height. For the type of cranes covered by this safety notice, spigots provide a means of connecting individual mast sections together. Their condition is crucial to the integrity of the mast. Each mast section has four spigots. They locate within female housings on the mast section fitted above. Once assembled the batch numbers of the spigots are hidden by the female housing and cannot be read. There is no non-destructive testing which can be undertaken to check the current condition of the spigots.

The only effective means of preventing mast collapse is to identify and remove all potentially affected spigots from service or weld additional reinforcement in accordance with the specification provided by Manitowoc Cranes.

Specific details of affected cranes, sections and spigots:

We have been informed by Manitowoc Cranes that the K600 and K800 series mast sections are only used on MD, MDT and MR series cranes. K600 and K800 series mast sections manufactured between 1 November 2006 and June 2007 (when spigot stocks were exhausted) are in scope. Each mast section has a unique identification number known as a PIN number. See figure 2 for details of where to find the number. The numbers for mast sections produced in this time period are in the range 80323 - 103784.

Figure 1 gives an example of the spigot number. The potentially affected spigots are in the ranges 3086* to 3496* and 0037* to 0577* - the letter on the end of the reference number is irrelevant for identification.

Action required:
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Fi 1:A spigot with its number clearly seen

Stored Mast Sections
• Identify and record mast PIN numbers and full spigot numbers (including the letter at the end) for all K600 or K800 series mast sections. Any with spigot numbers in the range specified should be withdrawn from stock immediately and quarantined.


In use Mast Sections
• All erected Potain tower cranes should be scrutinised to identify any mast sections with PIN numbers in the specified range.

• Any erected cranes with the relevant mast sections should be taken out of use immediately and arrangements should be made to:

- Either dismantle the crane sufficiently to view spigot numbers on all relevant mast sections. Record all spigot serial numbers and, where they are in the potentially affected range, take the mast section out of service and quarantine.

- Or weld additional sections in accordance with the specification provided by Manitowoc Cranes. This work will need to be undertaken following a safe system of work and to an assured quality standard. Welds must be inspected and non- destructively tested on completion. Arrangements must be made for documented competent person weekly inspection of the welds and at least monthly non destructive testing for the entire time the crane remains erected.

Manitowoc Cranes can advise.
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Fig 2: how to spot the section numbers

•Whichever option is selected, the work must be managed rigorously to ensure the safety of anyone who might be affected. Safe systems of work, safe access and competence are key elements.

•Please retain mast sections for further possible investigation by HSE. We will not be able to complete investigations if we do not have further supplies of spigots to test.

Recommendations

•It is recommended that you identify both mast section serial numbers and spigot batch numbers for your entire inventory of mast sections for Potain MD, MDT and MR Tower Cranes. As investigations into the defect progress, we may need to ask for more cranes to be removed from service. It will be easier to take proportionate action if you can identify where potentially defective spigots have been used.

•It is recommended that you retain photographic evidence of the checks you undertake.

Relevant legal documents:
•Health and Safety at Work etc Act 1974, Sections 2 and 3
•Lifting Operations and Lifting Equipment Regulations 1998, Regulation 4
•Work at Height Regulations 2005, Regulation 6

References:
•Manitowoc Crane Care Service Bulletin T10-019a dated 11 June 2010
For general advice on tower cranes work see
•Strategic Forum for Construction Plant Safety Group - guidance on tower cranes [3]
•Construction Plant-hire Association Tower Cranes Technical Information Notes [4]
Further information:

Email: [email protected]
Post: Manitowoc Crane Group (UK) Ltd
Manitowoc House, Network 421,
Radclive Road, Gawcott, Buckingham. MK18 4FD.