Risk reduction in MotoSuiveur-secured hoists, according to EN ISO 12100:2010: Safety of machinery — General principles for design — Risk assessment and risk reduction.
Object
The evaluation of risk reduction is conducted with the representation of risk reduction process as featured in ISO 12100:2010(E) on Figure 1 below. Numerous references to this document are made in what follows.
Process
Step 1
Siguren Technologies assumes that :
- the risk analysis is already internally done by the end user, or by the hoist provider.
- the identified risk is: “A load drop can lead to severe injuries or damage to health or death”.
Step 2
We assume that this risk is currently not adequately reduced and needs to be further reduced to an acceptable level.
Step 3
According to Clause 6.1, the mandatory Step 1 is risk reduction by inherently safe design measures*. They must be applied as close as possible to the load, i.e., at the rope drum.
The MotoSuiveur Unit (MS) is an inherently safe design measure against load drop.
It applies the principle of positive mechanical action (Clause 6.2.5) directly to the drum. Moreover, the MS achieves its protective measure without relying on any control system: Clause 6.2.11 (Applying inherently safe design measures to control systems) is not used, hence:
- ISO 13849-1 Safety-related parts of control systems (PL) not applicable.
- ISO 62061 Functional safety of safety-related control systems (SIL) not applicable.
*According to Clause 3.20 (inherently safe design measure) an inherently safe design measure is a protective measure which either eliminates hazards or reduces the risks associated with hazards by changing the design or operating characteristics of the machine without the use of guards or protective devices.
- The MS eliminates the risk of load drop in case of hoist failures (both mechanical and control)
- The MS eliminates the risk of load overspeed and uncontrolled movement
Indeed, when an MS Unit is attached to the drum, it becomes physically impossible to freewheel it or to run it at high speed. The MS Unit will inescapably and safely arrest the drum.
Step 4
This upgrade does not generate specific hazards during the normal use of the crane.
Main hazards during maintenance are covered at the design level.
Hazards during installation must be assessed separately.
Step 5
By implementing a MotoSuiveur unit attached to the drum flange, the risk is dramatically reduced.
Further risk reduction may not be necessary **.
We assume that the measures called by Clause 6.1 (General) are already in place:
- step 2: Safeguarding and/or complementary protective measures
- and step 3: Information for use
** An overload can also lead to a load drop, or even to the collapse of the whole crane. The Torque Limiter, specially designed as a part of the “MotoSuiveur Solution” is an inherently safe design measure against overload and can be easily implemented at the gearbox input.
Step 6
Finally, SIGUREN can assist the end user (or hoist provider) with the documentation that shall demonstrate the results and how the risk reduction has been achieved.
