KANBrief 4/21

Everything in view: measurement of the field of view on self-propelled forestry machinery

EN ISO 11850, Forestry machinery – General safety requirements, describes basic requirements for the field of view on self-propelled forestry machinery, without specifying these requirements in a verifiable measurement procedure. A new standard is intended to close this gap.

Forestry machines are used for work deep in forests, between trees and bushes, on slopes and in uneven terrain. They are used for example to fell and delimb trees and to cut up tree trunks. Their use leads to hazards significantly different to those presented by other mobile machines such as earth-moving machinery. For this reason, experts are currently preparing a standard specifically governing measurement and assessment of the field of view on self-propelled forestry machinery.

International standard ISO 5006:2017, Earth-moving machinery – Operator’s field of view – Test method and performance criteria, can be referred to for measurements of the field of view on earth-moving machinery. The working group at DIN responsible for forestry machinery wishes to use this measurement method as a guideline for its work. It is based on a near-field measurement and a measurement on a visibility test circle at a radius of 12 m from the machine. How the method works can be described in simple terms as follows. For the purpose of measurement, two point light sources are mounted at eye height of a person sitting on the operator’s seat. A tester uses a mirror to determine whether the light source can be detected on the defined lines around the machine. Wherever the tester is not able to detect the light sources, the area is considered an obstruction in the field of view. The standard specifies what obstructions in the field of view are permissible for what type of machinery.

As an alternative to manual measurement, the planned standard is to describe a measurement method employing a standardized, electronic measurement system. This method simulates the visibility test circle virtually. It therefore requires significantly less space than the manual method, and the susceptibility to errors is reduced. The use of software also supports documentation of the measurement.

In addition, provision is made for a measurement method for assessing the horizontal view from the machine operator’s position (horizon view). To test the horizon view and possible requirements, series of tests are to be performed on forestry machinery with use of a prototype measurement setup. The background to this test is to define requirements for visibility beyond the 12 m radius in order to test the long-range view, which is important for the forestry sector. In addition to the measurement method, the new standard is also to describe requirements concerning the field of view that are adapted to the working conditions associated with forestry machinery. Depending on what requirements are satisfied by a forestry machine in a field of view measurement, different categories may be attained: green (good to very good field of view), yellow (satisfactory field of view) or red (sufficient, still tolerable field of view). Labelling of the category attained is to be affixed in the cab, thereby enabling the operator to determine the quality of the machinery’s field of view immediately.

The scope of the new standard is limited to field of view requirements for forestry work; requirements concerning visibility in road traffic lie outside its scope and are subject to the respective national regulations.

The work item will be launched formally as soon as the tests of the test methods and other preparatory work have been completed.

Katharina von Rymon Lipinski