June 27, 2012 - 1 Comment
One of FESA’s key stakeholder groups is its Mechanised Harvesting Working Group, which includes contractors and equipment suppliers, and provides a platform for members to get together, discuss and commission work aimed at advancing the efficiency, safety and cost effectiveness of mechanised harvesting.
Chain link snapping and being flung off the cutter bar.
by Glynn Hogg, FESA Researcher and Programme Coordinator
Current work being undertaken by the group as requested by the stakeholders includes the following:
- Safety requirements and structures for operator protection when excavator-based machines are used in mechanical harvesting operations.
- Certification requirements for trainers to assist with continuous assessment and training of operators in mechanical harvesting operations within a single or group of contractor operations.
- Traceability of sawtimber in mechanical harvesting operations after processing.
The projects mentioned above are still underway, with preliminary results being compiled. This article focuses on some of the preliminary findings of the safety requirements for excavators used in harvesting operations.
Since the introduction of mechanised harvesting in South Africa, the use of ‘hybrid’ machines has been a factor. In the case of converted excavators, a machine that is designed and spec’d for the mining and construction industries, is being modified and introduced into forestry applications. These machines are now spread throughout the country in a variety of configurations, applications and conditions. It is a concern that legislation regarding their configurations in terms of operator protection is limited in South Africa. The OHS Act is the primary reference point in terms of legal compliance, but its brushstrokes seem too broad for any real standardisation. It basically requires that equipment is safe and well-maintained and without risks as far as is reasonably practicable, and operators who are trained and informed in all aspects of their job. Many companies and organisations have developed their own standards, but even these are not consistent with one another.
FESA does not in any way dictate statutory standards to the industry, but represents an independent research and development body alongside the ICFR which aims, with its stakeholders, to keep South Africa at the forefront of safety, innovation and development. The issues discussed in this article represent preliminary findings as a result of consultation with contractors and equipment suppliers, as well as from sourcing international literature.
It is clear that a ‘one size fits all’ approach to excavator safety standards in forest operations may not be the best approach. A modified windscreen, for example, which can withstand chain shot (a piece of chain link snapping off and shooting off the cutting bar) may not be necessary or may require different specification for a machine which does not have a bar and chain on the processing head (such as a machine which only debarks). Another example could be the requirement of a reinforced cab top – this may be necessary if the machine is felling trees or loading logs, but possibly not if the machine only processes on roadside, a safe distance from the felling and loading operations. FESA therefore recommends that the following considerations be taken into account before the safety requirements of these machines are defined:
- What function/s will the excavator be used for?
- Requirements may be different based on what the machine does (e.g. fell, debark, crosscut, load) and what it’s corresponding configuration is.
- Where will the excavator work?
- Will it be on roadside or infield?
- How close will it be to potential falling objects such as trees being felled or logs falling while being loaded?
- What are the conditions in which it will operate?
- What is the maximum slope it will need to negotiate?
- What is the ground roughness?
- Are obstacles present?
- How close will this machine be to other machines or activities?
Points to be considered when defining safety regulations for machines
- Roll Over Protective Structures (ROPS) – An international standard to ensure that if a machine rolls over, the cab is not damaged and the cab occupant is not injured. Compliance for this is generally similar to the construction and mining industries and thus does not need much modification.
- Tip Over Protective Structures (TOPS) – An international standard to ensure that if a machine tips over, the cab occupant is anchored within the cab and not injured. This deals with safety accessories such as seat belts and their fastening elements (anchorages) necessary to restrain an operator or rider within the cab. Compliance for this is generally similar to the construction and mining industries and thus does not need much modification.
- Operator Protective Structures (OPS) – An international standard to ensure that machine operators are adequately protected by stopping foreign objects from penetrating the cab. Compliance for this can differ significantly from the construction and mining industries.
- Falling Object Protective Structures (FOPS) – An international standard to ensure that falling objects do not deform the cab and cause injury to the cab occupant. Compliance for this can differ significantly from the construction and mining industries.
Some excavator-based harvesting safety considerations
Once the dangers specific to the excavator in question have been identified based on its work requirements, conditions and its configuration, one can begin to consider the following safety features which may apply to the excavator:
- Seatbelts and their anchorages should be legally compliant.
- Polycarbonate safety glass should be used to protect the operator from chain shot and can also be used as protection against intruding obstacles (e.g. logs). Polycarbonate has a wide range of applications and quality specs, from food containers to police riot gear and even the cockpit canopy of the F-22 Raptor Stealth fighter jet. In the application for excavator operator protection, it serves the purpose of what is commonly known as ‘bullet proof glass’. It is also recommended that this polycarbonate not be completely flat with the operator, but rather be angled and curved so as to deflect intruding obstacles, rather than try to stop them. The more perpendicularly an obstacle hits the polycarbonate, the more likely it is to penetrate and vice-versa.
- Install a chain catcher designed to minimise chain shot if the harvesting head uses a chain and bar but does not have a suitable catcher installed.
- If guards in front of the cab are used, they should be close enough together so as to not allow logs to enter in-between them, but also not so close as to hamper the operator’s vision of the work area, as this would result in increased fatigue and thus a higher likelihood of unsafe work. These guards should aim to deflect intruding objects (such as a tree length which is being debarked) away from the cab, rather than certain grill designs which deflect objects into the cab. Some engineers place these guards on the inside of the polycarbonate safety glass. The idea behind this is that the guards are only used as a last line of defence to stop intrusions which penetrate the polycarbonate.
- No drilling holes in the frames of the excavator unless it is done by an approved organisation, to ensure it does not compromise the cab integrity and adheres to legal requirements.
- Undercarriage modifications can be made to lower the machine’s centre of gravity for improved slope handling.
- Raising the cab: the higher a cab is raised, the more potentially unstable the machine becomes due to the higher centre of gravity.
A few practical working techniques and principles which can help to further increase the safety of these operations include, among many others:
- Never use the saw when the saw bar is directly in line with the cab or other persons.
- Do not re-use riveted connecting components when making repairs to chains.
- Follow recommended practices for maintenance and use of the chain, bar and sprocket.
- Keep a safe working distance between machines.
- Adhere to safe working distances from ground workers and other people.
Some of the requirements enforced in British Columbia relating to excavators in forest operations include the following (www.worksafebc.com):
- Polycarbonate should be at least 1/2 inch (i.e. 1.3 cm) thick and adequately supported from behind along the perimeter with at least a one inch (i.e. 2.5 cm) overlap and by members in one direction not more than 10 inches (i.e. 25.4 cm) apart.
- Window guards can be used instead of polycarbonate. They should be made up of mild steel bars or rods with a maximum opening of 64 square inches (i.e. 413 square centimetres), on the front, sides (where permitted by boom clearance), and back of the cab (if there is a hazard of intruding or flying objects, such as another machine working nearby).
- Heavy duty roof structures (designed to absorb 8 500 foot – pounds of energy) are required.
- The cab structure should be designed to resist a force of at least 11 500 pounds (i.e. 5 216 kg). This simulates a 2 000 pound blunt log impacting the cab at approximately four miles per hour.
- An alternate exit meeting up to legal requirements in case of the primary exit being blocked, is required.
- Where boom clearance does not permit a side window guard meeting WCB Standard G603, a window guard meeting WCB Standard G604, Standard for Light-Duty Screen Guards for Off-Highway Equipment may be used. An adequate substitute for WCB Standard G604 is polycarbonate where it is at least 1/4 inch thick and supported from behind with at least a one inch overlap along the perimeter. Section 16.11(4) of the OHS Regulation requires each polycarbonate window on mobile equipment manufactured after February 1, 2002, or otherwise installed on mobile equipment after that date, to be marked to show the thickness and grade of the material.
- Do not drill holes in polycarbonate windows to mount the window on the machine, or for the installation of accessories such as windshield wipers. Consult with the Board’s Engineering Section for further assistance on window guards made using polycarbonate.
Additional standards can be found on the International Organization for Standardization (ISO) website (www.iso.org). Recommended ISO standards regarding safety requirements for excavator machines in forest operations include the following:
- ROPS = ISO 8082:2003
- TOPS = ISO 6683:2005
- OPS = ISO 8084:2003
- FOPS = ISO 8083:1989.
The FESA Mechanised Harvesting Working Group is open to FESA stakeholders.
Please email Glynn Hogg at email@example.com should you require more details or wish to keep abreast with the findings of this or any other of the current projects.
Published in April 2012