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Home › Publications › OHS Regulation › WCB Standards

WCB Standards

WCB Standard: G606 Boom Boat Operator Protective Structures, March 1990

© Workers' Compensation Board of British Columbia. All rights reserved. No part of this document may be copied, reproduced, or distributed for profit or other commercial enterprise, nor may any part be incorporated into any other publication, without written permission of the Workers' Compensation Board of B.C.

1. General

1.1. Scope
This standard pertains to any vessel used to push or pull logs, booms, bundles or bags in booming ground operation where the operator may be exposed to collision with water-borne logs. Examples of such vessels are dozers, side winders, boom scooters and tugs.

1.2. Purpose
This standard is intended to describe the minimum requirements for the design and selection of window guards, plates, framework and supports for a cab which will form and provide a protective structure for the operator occupying same.

2. Design Principles and Assumptions

The following points are stated to clarify the underlying principles and assumptions of this standard.

2.1.
The stiffness of the vessel is assumed to be in direct proportion to W x GM x SIN q were W is the weight of vessel, GM is the metacentric height, and q is the angle of heel.

2.2.
The stiffness of the operator protective structure is assumed to be very much higher than the vessel's heeling resistance. Hence the stiffness of the entire system is approximately equal to the heeling resistance of the vessel.

2.3.
It is assumed that the elements of the operator protective structure would be arranged in such a way to elastically deflect the projectile rather than arresting its motion.

2.4.
The derivation of the peak collision force is based on linear elastic collisions.

2.5.
It is a minimum requirement for the protective structure to have a "crush protection design capability" to withstand the force exerted on it by a hypothetical blunt log 1 m x 12 m (3 feet x 40 feet) striking end-on at a velocity of 1.5 m/s (5 fps).

Furthermore, there is an impact or strength requirement which is intended to ensure that all members of the cab will have adequate resistance to brittle fracture under cold temperatures.

2.6.
Finally, there is a visibility requirement which is to ensure that the operator's vision will not be seriously obstructed.

2.7.
The operator protective structure can be an integral part of a cab or it can be a "cage" outside an existing structure.

3. Design Loads

3.1.

      Imperial Units

3.2.

     Metric Units

W = weight of vessel, lbs. or N.

CM = distance from metacentric to hypothetic point of impact, ft. or meters, CM must not be less than 2.1 m (7 ft.).

F = dynamic design load, lbs. or N, less than or equal to the capsizing force.

4. Design Requirements

4.1. Frame
All frame members of the cab protective structure shall be designed to resist the applied load in accordance with clause 3.0 or with some other design criteria acceptable to the Board.

4.2. Cab Skin
All exposed unguarded sides of the cab shall be protected with metal plates or other suitable material. They shall be designed to resist the force as defined in clause 3.0.

4.3. Supports
The cab protective structure shall be secured to the structural parts of the vessel. Such structural parts shall be adequately reinforced to resist the loads imposed on them by the cab protective structure.

4.4. Fastenings
If bolts and nuts are used in the fabrication of the guard, they shall conform to or exceed the ASTM designation A325 requirements.

4.5. Visibility Requirements
The cab shall be equipped with adequate view areas. All such view areas shall be guarded by vertical members spaced at intervals of not more than 6 inches. These vertical members shall be designed to assist the force as defined in clause 3.1.

If flat bars are used as vertical elements, they should be in a radiating pattern to minimize interference with the operator's line of sight.

4.6. Impact Strength Requirement
All members of the half-door shall be fabricated of material with good impact absorbing properties. The following guideline may be used:

• low carbon content - maximum .28%
• high manganese - carbon ratio
• low phosphorous content
• fine grain size
• heat treated
• high ultimate energy resistance (Note: tough steel possessing acceptable impact properties)

Examples of steel meeting or exceeding the above requirements:

• ASTM A36 or CSA G40.21 - 38W for bars, angles and plate
• CSA G40.21 42W, 55W for HSS (Hollow Structural Sections) (CSA G40.16 and G40.17)

4.7. Weldment
Weldments shall conform to the applicable sections of general specifications for welding of steel structures, CSA W59.1-1970(or latest revision thereof) and shall be performed by licensed welders only.

4.8. Alternate Exit
The operator protective structure shall be provided with an alternate exit. Such exit shall have a minimum clear opening of 60 cm (24 inch) diameter.

4.9. Glazing (optional)
Only safety glass or other suitable material with similar shatter-resistant characteristics shall be used for window areas and such glazing materials shall be positioned at least 20 cm (4 inches) away from the window guard.

5. Minimum Sizes

The following recommended sizes and dimensions may be used in lieu of the design load criteria, clause 3.0.

5.1.
Minimum grid element size shall be 3/4" diameter steel rods or equivalent where a 1 1/4 x 1 1/4 x 0.10 HSS intermediate stiffener is used.

5.2.
Grid element size shall be proportionately increased as the dimension of the guard increases.

5.3.
Minimum column size shall be 3 x 3 x 0.125 HSS depending on the slope and length of the columns. 3 x 3 x 0.25 HSS is strongly recommended.

5.4.
Minimum roof beam size shall be 3 x 3 x 0.125 HSS.

5.5.
Minimum "cab skin" plate size shall be 11 ga to 16 ga depending on the size of intermediate stiffeners used.

5.6.
Gusset plates shall be incorporated where necessary.

5.7.
Materials with equal or better properties may be used in place of those stipulated in this Standard.

G606A BOOMBOAT O.P.S.

G606B TOWBIT GUARD

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