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Quick hitch devices on excavators

Summary

This guidance describes what a quick hitch is, discusses common failure modes, in particular with semi-automatic hitches, and directs inspectors to take action in response to certain site scenarios.

Introduction

The purpose of this guidance is to address key issues that inspectors should wish to consider during relevant inspections and gives guidance on instances where enforcement may be appropriate.

A quick hitch (QH) on an excavator is a latching device that enables attachments to be connected to the dipper arm of the plant and interchanged quickly.  An excavator operator may change the bucket on his excavator up to 30 times a day in order to maximise the machine productivity.

A significant number of all accidents investigated on excavators are attributed to the bucket detaching from a QH and injuring a ground worker, most of which are fatal and major injuries.  However, there may be many more dangerous occurrences that occur that might not be reported when a bucket detaches unintentionally from the hitch, but without injury because no one is underneath at the time.

Action

Inspectors should ask the following questions when assessing the safe management of QH use:

If inspectors suspect that the QH is malfunctioning or has parts missing evidenced by:

Then inspectors should request involvement of their local SG mechanical specialist.

Advice to duty holders on good practice can be found in HSE’s safety alert to the industry on quick hitches of 17 December 2007.

Inspectors should establish whether the hitch is permanently attached to the excavator and ensure that the hitch is part of the thorough examination as part of the machine or as an accessory depending on the response given.

See Appendix 1 for recommended enforcement action and Appendix 2 for photographs of what to expect.

Background

Manufacturers

Typically, the QHs are not made by the excavator manufacturer, although some QHs are ‘badged’ with the excavator manufacturer's name and are supplied by them.  There are known to be 20 or more manufacturers on the market, most of whom have several different designs of QH.

A standard bucket is secured to the dipper arm with two pins.  QHs may pick up a standard bucket using the original pins, or the QH may have a dedicated attachment system that only fits buckets with matching engagement lugs.  The advantage of dedicated systems is that the original radius of bucket movement can be maintained by compensating for the thickness of the QH, thus keeping the same break out force as the manufacturer intended.  The disadvantage is less flexibility because only dedicated buckets can be used. In addition, a significant investment in dedicated buckets and attachments is required.  For this reason most systems are ‘pin’ type rather than dedicated type.

Quick hitch systems

The QH systems on the market can be manual or non-manual.  Non-manual systems are known as semi-automatic and automatic:

QH systems have become increasingly common and now many large excavators and some mini-excavators are fitted with QHs.  QHs need to be maintained and may well be replaced during the life of an excavator.  If they are replaced, then it is important that the controls are compatible with the new hitch, or are replaced at the same time.

Although incidents have occurred with automatic QHs, accident statistics suggest that the majority of incidents occur on semi-automatic systems where a manual safety pin should be inserted, but where the operator failed to do so.  See Appendix 3 for detailed reasons why this may be the case.

Thorough examinations

If the QH is used for lifting (many QH's have a lifting eye for this purpose), the weight of the QH has to be deducted from the SWL of the excavator.  QHs fitted with lifting points/attachments are subject to the requirements of Lifting Operations and Lifting Equipment Regulations (LOLER) 1998.  See Appendix 4 for details of QHs and thorough examinations.

Organisation

No special visits or other organisational requirements are involved.

Further References

Contacts

Construction Sector Safety Unit.

Appendix 1: Recommended enforcement action

No SSW: (Management are not aware whether safety pins are required, or do not carry out routine checks)

Consider IN (MHSW 5(1))

No SSW: Ground workers are required to work below excavator buckets fitted with QHs

PN and possible prosecution

No pin fitted when it should be

Consider PN (PUWER 5(1)).  If more than one instance on the same site consider prosecution

Evidence that operator does not know how to use hitch

PN (PUWER 7(2)) on hitch (work can continue if hitch is removed and bucket replaced directly on the dipper)

Evidence of poor maintenance

IN or PN (PUWER 5(1)) if hitch appears likely to cause bucket detachment.  Involve SG if necessary

No risk assessment covering bucket detachment

Letter or IN (MHSW 3(1) or 3(2))

Appendix 2: Photographs – what to expect

Photo 1: Semi-automatic type of QH (Safety pin about to be inserted)

Semi-automatic type of QH (Safety pin about to be inserted)

Photo 2: Automatic type (Closed position)

Automatic type (Closed position))

Appendix 3: Reasons why the majority of incidents occur on semi-automatic systems

This may be the case because:

There is a management issue in ensuring that the safety pin on semi-automatic hitches is always fitted.  In some cases, supervisors may not be aware of whether a pin is required or not, or how to check whether it is in the correct position.

In addition to precautions relating to the way the QH is operated, the basic precaution of ensuring ground workers are not required to work close to, or under the bucket (for example, within an excavation) should be strictly maintained.

Appendix 4: Quick hitches and thorough examinations

If the QH is permanently attached to the excavator, then it can be treated as though it is part of the machine and should be thoroughly examined at least every twelve months, unless either there is an examination scheme which determines otherwise, or a competent person has set a different period, for example, due to its condition, or to particularly harsh operation (e.g. use with a hammer).

If the QH is not permanently attached to the excavator, then it should be treated as a lifting accessory and have a thorough examination every six months, or in accordance with an examination scheme.

Since the implementation of the Supply of Machinery Regulations 2008, there has been discussion between HSE, manufacturers, suppliers and user trade associations regarding the reclassification of couplers.  This is an ongoing debate and further details will be provided, once a definitive legal position has been given via Europe.  In the interim however, HSE categorises new QHs in accordance with the Supply of Machinery Regulations 2008 as interchangeable equipment.

This means each hitch should be CE marked and provided with a Declaration of Conformity (D of C), and this declaration fulfils the requirement of a thorough examination for the 12 months following the date on the D of C.  After this date, thorough examination of the quick hitch is required if suitable for use in lifting operations.  For QHs supplied by the excavator manufacturer as part of the original equipment, the D of C for the excavator is sufficient.

Updated 2013-10-25