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Crane Use in Arboriculture:
Risk, Justification, Skills & Compliance
By Tim Walsh, CTSP
As a profession, we are becoming increasingly aware of the risks that we face, as well as how to reduce these risks. Dr. John Ball deserves much of the credit for his work with, and the sharing of, information about accident and fatality statistics. This article is going to take a look at one area where we can reduce risk and increase productivity, by properly using cranes.
Using cranes does not eliminate risks; it reduces many but also can introduce others, especially if not done correctly. This article will take a brief look at risk in tree care focusing on those risks that can be reduced by the use of cranes. It will also address some key justifications for using cranes, some of the skills required to climb off of a crane, and regulations that allow our use of cranes.
A quick review of the fatality statistics from 2006 shows that 95 percent of our fatalities are in the "Big Four" categories (Courtesy of Dr. John Ball):
- Transportation related 28 percent
- Falls 27 percent
- Struck-by's 23 percent
- Electrocution 17 percent
The falls are from a variety of situations, but include aerial-lift boom failures, unsecured falls from aerial lifts, unsecured falls while climbing, cutting of single tie-in point while climbing, tree failure, and miscellaneous falls. Some of the last classification comes from OSHA fatality reports where there weren't witnesses and the compliance officer could not figure out the cause.
The struck-by's include a variety of types of incidents as well, everything from being hit by a falling tree to a chipper hood, chain saw or other piece of equipment. Most of these fatalities are during removal or rigging operations. Either someone walked into a drop zone or part of the tree failed during rigging
A quick review of the fatalities listed by OSHA found the following crane-related fatalities:
- 1984 - Moving logs with crane, log stuck on stump, worker tried to free it, log swung into him
- 1993 - Moving/transplanting tree from truck, crane boom broke from pedestal landing on employee
- 1991 - Load line contacted 7,600-volt line while worker on the ground was holding the ball
- 1999 - Two employees electrocuted when load line contacts 25 kV line
- 2001 - Transplanting 90-foot tall tree, repositioned four times, fell on crane operator
Non-fatal crane related accidents from OSHA:
- 1998 - Worker using ladder to access canopy to secure load line, ladder fell, shattered wrist, two broken ribs, leg laceration
- 1998 - Worker being hoisted from load line fell 35 feet due to improper tying of knot, fractured neck, jaw and big toe
- 1999 - Climber fell 45 feet while being hoisted, improperly secured
In September of 2006, The National Institute for Occupational Safety and Health (NIOSH) published an ALERT, "Preventing Worker Injuries and Deaths from Mobile Crane Tip-Over, Boom Collapse, and Uncontrolled Hoisted Loads." The publication lists the fatalities where a crane was either the primary or secondary source of a fatal injury for all industries, not arboriculture. There were 719 fatalities from 1992-2002. The three biggest groupings of fatal incident are as follows:
- Struck by an object, such as an uncontrolled load or part(s) of a mobile crane, accounted 40.3 percent of these fatalities.
- Electrocution fatalities due to cranes contacting overhead power lines accounted for 24.1 percent.
- Falls from crane structure or cab, including workers who were killed while in man baskets, accounted for 12.2percent.
Justification for using cranes
The primary argument that OSHA has against our use of cranes in tree care deals with the fact that we hoist workers on the load line (please see "Crane Best Practices in Tree Removal: Hoisting a Qualified Arborist," by Mark Adams, March 2007 TCI, for details on tie-in procedures). OSHA says that it isn't safe; the crane manufacturers do not allow it, but they would allow us to hoist personnel in a man basket.
The fatality statistics do not support the OSHA argument that hoisting workers on the load line, as we do in arboriculture, is not safe. The few fatalities and accidents in tree care are not related specifically to being hoisted by a crane. The two falls from the load line were from not being properly secured and could have happened while climbing in the tree.
The NIOSH crane-related fatalities do not indicate an increased risk either. Especially as some of the falls were while the worker was in a man basket. The man basket argument is not even logical as it would be impossible to work from one in most trees. Also, if we did use the man basket to secure the load line to the tree we would still have to descend out of the basket to get to the tree to make the cut. I have not worked with man baskets before but I do not think that you are supposed to leave them on the load line while you are lifting a load.
Almost 50 percent of tree care related fatalities come from falls and struck-by's. The use of cranes would not eliminate all of these fatalities but would definitely reduce many. Probably the biggest area of risk for us is when we are aloft. The use of cranes reduces this risk and others, listed below. (Courtesy, in part, of TCIA's Peter Gerstenberger)
- Reduces time aloft
- Reduces the number of cuts, can take larger pieces
- Reduces energy demands, fatigue issues
- A crane is an engineered, rated, predictable support structure. The tree is not.
- Several people die each year when the tree they are in fails. Nobody has ever been killed through the practice of being hoisted. Ever.
- Cranes reduce the hazards and strenuous nature of the work for the crew on the ground as well. Fewer chain saw cuts to make and fewer pieces to chip.
- Dramatically reduces the chance of a "struck-by" to the person aloft and on the ground, as compared to any other form of rigging. There is much more control
- Reduces manual materials handling and back injuries
Suggested minimum skills necessary to climb off of a crane
(courtesy, in part, of Mark Adams and Don Roppolo)
- Qualified line clearance arborist
- Proper chain saw techniques:
- proper notches and hinges
- bypass cuts
- understanding of pinching and how to avoid it
- understanding a rip cut and being able to use it on a slowly moving/twisting piece without getting pinched
- Advanced rigging skills
- working over obstacles with ropes to understand balance and how pieces react differently according to where and how they are tied
- ability to use multiple slings for balancing, lifting, etc.
- Risk assessment to be able to identify when climber positioning and/or actions increase climber risk and what to do to reduce that risk
- Tree risk assessment (able to thoroughly assess structural integrity and know low-impact rigging techniques to minimize force on the tree)
- Crane hand signals
- additional hand signals in addition to the standard crane hand signals (i.e. one sling, two slings, balancer, big saw, what's that weigh, etc.)
- Knowledge of how crane lifting capacity is affected by boom angle and length
- Ability to estimate wood weights of different tree species
- wood weights is important and includes not just trunk pieces, but branches, with and without foliage
- Understanding of crane limits (no side loading the boom to break pieces free)
- Understand how degree of line plum affects where the piece is going to go
- Understanding the importance of minimizing the shock load by how the pieces are cut.
- Understanding how to minimize swing. Understanding how to cut pieces so that there is minimal movement/swing after the piece is free.
- Knowledge of how to use the type of sling/choker to be used and where to cut in relation to the side on which the choker is placed.
- Knowledge of the hazard unstable ground poses (saturated soil, buried septic tanks/fields, cisterns, pipes, building foundations, etc.)
- Understanding of ANSI Z133 standard as it relates to crane use.
Precedence for allowing the use of cranes to hoist personnel
Federal OSHA
In 2006, a tree care company was cited for not having an operable anti-two block or load moment indicator. In the citation, it lists the following as a way to correct the hazard:
"b) Follow and utilize the ANSI/ISA Z133.1-2000 standard in crane inspection and safety measures prior to lifting employees by the crane."
http://www.osha.gov/pls/imis/establishment.violation_detail?id=309777308&citation_id=01001
Oregon OSHA
1999 interpretation letter, "…nothing (in the standards that apply to tree work) prohibits a crane from being used to hoist a worker into position as long as a proper attachment system and saddle (such as a boatswain's chair) is used."
http://www.cbs.state.or.us/osha/interps/1999/rogers.pdf
Washington OSHA
General industry crane regulations, specifically WAC 296-24-23533, "Cranes and derricks suspended personnel (work) platforms," provides for the use of a "boatswain's chair." The rule specifies: "The worker's lanyard shall be secured to the lift line above the headache ball or to the crane hook itself."
http://www.lni.wa.gov/wisha/rules/generalsafety/html/24_d2.htm#WAC296-24-23533
Washington OSHA also refers to the ANSI Z133.1 standard as the "applicable industry consensus code" for their compliance officers to use. (WISHA Regional Directive: 20.75
Tree & Shrub Trimming, Pruning, Removal, etc., Date Issued: September 18, 2006).
California OSHA
Title 8, Chapter 4, Section 3427: Allows for hoisting a worker on the load line using an approved arborist saddle.
The future of crane use in arboriculture
- ANSI Z133 revision scheduled to begin in October. Now is the time for people to get involved with the Crane Task Group.
- OSHA to pursue an arborist standard. This is an opportunity for all of us to insure that we get the standard that we deserve. Crane use is an important issue for us to work on together with OSHA instead of against each other as we had done in the past.
- Best Management Practices?????
- Collaborative Crane Workshops. The first crane use workshop done in partnership with the Department of Labor and a crane company took place at the end of May. (Details were not available at the time this article is being written).
Credits
ANSI Z.133.1-2006, American National Standard for Tree Care Operations–Safety Requirements, ISA.
"Z133.1 Safety Standard, 2006: Using Cranes Safely," by Steve Chisholm, H. Dennis P. Ryan and Peter Gerstenberger, Arborist News, volume 15, Number 4, August 2006.
"Crane Use and Safety in Tree Care," by David Rattigan, Tree Care Industry, July 2006.
"Crane Best Practices in Tree Removal: Hoisting a Qualified Arborist," Mark Adams. Tree Care Industry, March 2007.
NIOSH Alert: Preventing Worker Injuries and Deaths from Mobile Crane Tip-Over, Boom Collapse, and Uncontrolled Hoisted Loads. DHHS (NIOSH) Publication Number 2006–142 September 2006.
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