BS 7901:2002 pdf download – Specification for recovery vehicles and vehicle recovery equipment
4.1 General The recovery vehicle shall be stable when casualty vehicle loads are imposed upon it in accordance with 4.2.1 and 4.2.2.
4.2 Static stability (stationary recovery vehicle)
4.2.1 Non-slewing booms Under all configurations of the recovery vehicle, as stated by the manufacturer in the rated capacity chart, the tipping moment calculated for a load corresponding to the rated capacity of the recovery equipment shall not exceed 75 % of the value of the recovery vehicle righting moment.
4.2.2 Partially slewing booms and fully slewing booms Under all configurations of the recovery vehicle, as stated by the manufacturer in the rated capacity chart, the tipping moment calculated for a load corresponding to the rated capacity of the recovery equipment shall not exceed 60 % of the value of the recovery vehicle righting moment.
NOTE Partially or fully slewing booms that are lockable in the position as defined for non-slewing booms may be considered as a non-slewing boom when so locked. The tipping line that moments used in the calculations are taken from shall be clearly identified. In the case of partially and fully slewing booms, the various tipping lines affecting stability as the boom slews within its full range of movement shall be clearly identified. Where tipping moment for the recovery vehicle is variable, e.g. free on wheels or stiff legs deployed, the stability requirements shall be calculated for all configurations. These calculations shall form part of the vehicle test certificate (see 21.1). For stability calculations the mass of the recovery vehicle shall be taken as its operational mass without any additional mass e.g. that of a casualty vehicle or ancillary equipment used for a lifting operation. All stability calculations shall assume firm level ground. This shall be stated on the test certificate (see 21.1).
4.3 Dynamic stability (moving recovery vehicles, lift and tow condition)
NOTE The speed limitation is an operational matter but manufacturers of recovery equipment should take this into account. The resultant front axle mass calculated for the application of a casualty vehicle load corresponding to the rated capacity of the recovery equipment shall be not less than 40 % of the plated mass of that axle. The recovery vehicle speed used for the calculations shall be either:
a) a value, s, in km/h given by the following equation: where x is the rear axle mass divided by front axle mass; or
b) 80 km/h; whichever is the lesser.
5 Mechanical components
5.1 General All exposed components shall be made of corrosion resistant material or have a corrosion resistant finish e.g. paint or plating. Components that could be affected by road dirt e.g. bearings, controls and cylinder rods shall be sealed. Components that are intended to be handled during recovery operations or are accessible to the operator shall not have sharp edges or rough surfaces.
NOTE Components which are intended to be fitted to other components during a recovery operation should be easy to assemble under adverse working conditions.
5.2 Rotating shafts, housings and slideways
Any rotating, or partially rotating shafts, housings and slideways shall either:
a) be of a non-lubrication material or self-lubricating material; or
b) be provided with a means of lubrication.
Any lubrication nipples shall be of a similar size and type and shall be readily accessible.
5.3 Containment of motion The motion of the recovery equipment shall be contained within its design limits by means of limiters conforming to BS EN 12077-2. Manually extending booms shall be fitted with a pull out limit stop and mechanical locking means for their retracted and incremental positions.
5.4 Partially slewing booms and fully slewing booms
NOTE In the case of proprietary slewing rings, it is particularly important that the manufacturer is consulted and given details of the rated loads to be applied so that the correct components can be selected. Provision shall be made to enable the boom to be mechanically locked to prevent inadvertent movement. A slewing check device shall be fitted to prevent booms slewing uncontrollably whilst in use.
5.5 Lift and tow equipment Lift and tow equipment shall incorporate a means to prevent accidental disconnection of the casualty vehicle during use. NOTE Lift and tow equipment should allow safe and easy connection to and disconnection from the casualty vehicle under adverse working conditions.