investigation report worker fatally injured when …...2017/06/06 · f-ohs-123116-9a1a8 alberta...

Report No-F-OHS-123116-9A1A8 January 2019 of 11

Investigation Report

Worker fatally injured when struck by chain

June 6, 2017

F-OHS-123116-9A1A8 Alberta

Final Report

Labour Occupational Health and Safety

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The contents of this report This document reports Occupational Health and Safety’s (OHS) investigation of a worker who was fatally injured in June 2017. It begins with a short summary of what happened. The rest of the report covers this same information in greater detail. Incident summary Four workers were troubleshooting the lifting device on a lumber stacker. The workers were underneath the equipment, manually operating the hoist cylinder, unknowingly overriding the hoist limit switches. The hoist knees travelled the knee columns until they reached the metal plates that had been welded on the top of the knee columns. The hoist kept lifting against these metal plates until one of the hoist chains failed at the anchor bolt, striking a worker in the neck and upper chest, fatally injuring the worker. Background information West Fraser Mills Ltd. operating as Manning Diversified Forest Products Ltd., Employer West Fraser Mills Ltd. (West Fraser) is a diversified wood products company producing lumber, laminated veneer lumber (LVL), medium-density fibreboard (MDF), plywood, pulp, newsprint, wood chips and energy with facilities in western Canada and the southern United States. West Fraser acquired Manning Diversified Forest Products Ltd. (Manning Diversified) in 2015. Manning Diversified has been in operation since 1993 and has approximately 150 employees. US Natural Resources, Stacker Manufacturer US Natural Resources (USNR) is a supplier of equipment and technologies for the wood processing industry. USNR supplies systems, service and support for plants around the globe. USNR is the manufacturer of the lumber stacker involved in this incident. The lead hand had been employed at the mill since it opened in 1993 and had held many positions throughout their career. At the time of the incident, the lead hand was the maintenance supervisor/lead and a journeyman millwright.


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Equipment and materials The machine involved in the incident was a Newnes Stacker Stick/Lathe Placer. A lumber stacker was used to stack dimensional lumber, and typically consisted of the following components:

Unscrambler Transfer table Stick placer Hoist system Outfeed chains, rollcase Control console

The stacker operated as follows: 1. Dimensional lumber entered the unscrambler where it was separated into single, evenly

spaced boards and sent to the transfer table. 2. Lumber accumulated at the transfer table to form a single layer. 3. The lumber was then transferred to the hoist knees where a layer of spacer sticks were

placed on top of the layer of lumber. 4. The hoist knees were then lowered allowing for an additional layer to be placed on top of

the sticks. 5. The lumber was loaded onto the outfeed chains/roll case and the hoist knees raised for the

next stack of lumber.

On the incident lumber stacker, raising and lowering of the hoist knees was achieved by the hoist system. The hoist system consisted of a hydraulic cylinder referred to as the hoist cylinder and a series of chains and drums which lifted the hoist knees when the hoist cylinder extended. The extension of the hoist cylinder was controlled by three limit switches.


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Figure 1. The underside of the stacker, and the access point to the hoist cylinder and hydraulics.


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Figure 2. The metal grates are the guards that were removed to access the hoist.


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Figure 3. Looking straight on at the hoist, the chains are on the left and right. The lead hand was standing in front of the chain on the right, the second worker was standing on the left manually operating the hoist cylinder.


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Figure 4. This is the right hoist chain; the arrow indicates the anchor bolt location where it failed. The bolt in this photo is a new bolt that had been installed.


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Figure 5. This is the outfeed of the stacker; the red arrows indicate the metal plates that had been welded to the knee hoist columns.


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Figure 6. The top photo is the anchor bolt that failed, the bottom bolt on the right is a new one.


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Sequence of events The stacker had been experiencing issues with the hydraulic cylinder, and the cause was suspected to be that the cylinder was leaking. The lead hand and three other maintenance workers were tasked to trouble shoot the cylinder and determine where exactly it was leaking from, and identify actions to repair the leak. The lead hand had reviewed the stacker manufacturer’s specifications and standard operating procedures (SOP’s) on the morning of the incident. The lead hand removed the guards and then accessed the area of the machine where the cylinder was located, and they began troubleshooting by manually operating the stacker hydraulics. This was done to determine the maximum travel distance of the piston, and the effectiveness of the limit switches. The lead hand then directed a second worker to manually action the hydraulics, and then increase the travel of the piston. As the second worker increased the travel on the piston for a second time, the chain on the stacker released at the anchor bolt, striking the lead hand in the chest. The lead hand was unconscious for a period of time and regained consciousness by the time Emergency Medical Services (EMS) arrived. The lead hand was transported via ambulance to the local hospital where they were assessed and observed until approximately 5:00 p.m. later that same day when they were transported by air ambulance to Grande Prairie Hospital. The lead hand died from their injuries shortly after arriving at the Grande Prairie Hospital. OHS arrived on site the following day to conduct the investigation. OHS brought in a mechanical engineer a few days later, and they worked with the manufacturer representative and the employer to determine the cause of the incident. The anchor bolts were seized as evidence, and materials testing was completed on both anchor bolts. The tests determined that there were no existing structural flaws found in the bolt that failed. The mechanical engineer reported that the incident occurred as a result of the worker manually operating the hoist cylinder, overriding the system limit switches. At some point, there had been metal plates welded at the top of the knee columns, inhibiting the upward movement of the hoist knees. The anchor bolt failed as a result of a single event structural overload. The overload was a result of high loading on the anchor bolts due to the restraint of the hoist knees by the metal plates welded to the top of the knee columns.


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Completion A review for enforcement action was completed on February 23, 2018, and it was determined that prosecution or an administrative penalty were not appropriate based on the circumstances surrounding this incident. This investigation was closed on February 24, 2018. Signatures

ORIGINAL REPORT SIGNED November 28, 2018

Lead Investigator Date

ORIGINAL REPORT SIGNED December 21, 2018

Manager Date

ORIGINAL REPORT SIGNED January 10, 2019

Director Date

investigation report worker fatally injured when …...2017/06/06 · f-ohs-123116-9a1a8 alberta...

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