When is a safety system design with an assessment module necessary? Is it a requirement for all machines?
The parts of control systems assigned to perform safety functions in machines are called Control Parts Relating to Safety, o SRP, and can have material (hardware) and, on occasion, software support.
That one SRP whether it is suitable or not for performing machine safety functions depends on the so-called PL, o Benefit Level that it is assigned to it.
The Benefit Level, or PL, has five levels, from A to E, and they are defined according to the probability of dangerous failure per hour of the machine under study.
Said probability of dangerous failure per hour It depends on various factors:
MTTF: Mean time to dangerous failure, depends on the reliability of the components the machine has been manufactured with.
DC Diagnostic coverage, measures the internal machine system's ability to detect a fault.
The Cardiomyopathy The function of common cause machine failures.
We must also take into account other factors, such as usage procedures, environmental conditions, or the design processes themselves. The evaluation of Benefit Level It is not straightforward and is based on categorisation, according to certain design criteria and certain machine behaviours, in the event of a failure.
These Categories, as in the PL, they are also five: B, 1, 2, 3 and 4.
In summary, what is being evaluated is the design of the machine, how dangerous it is, and how much harm it can cause, whether it is used correctly or is deliberately misused.
The results that this study yields Benefit Level, a minimum safety category will be established. These will be the ones that define the safety control systems that must be installed.
Some examples would be two-hand control devices, interlocking devices, logic blocks (safety modules), or relays, valves, etc.
One Practical example what we're talking about would be this real case. It's required to determine the Benefit Level y category for a drill. Once obtained the Polish, it will need to be checked if it meets the required PL.
Determination of the required performance level (PLr)
The required performance level is determined by evaluating amount of risk reduction which are already provided, by themselves, by the safety-related parts of the machine's control system. The less they reduce the risk, the higher the PLr will be.
A risk assessment must be carried out which will be defined by a series of parameters that will be determined based on the severity of the injury (S1 and S2), frequency and/or duration of exposure to said hazard (F1 and F2), and the possibility of avoiding it (P1 and P2).
Category Determination
Category B is the basic one. If a defect occurs, it can lead to the loss of the safety function.
In category 1, improved defect resistance is achieved, primarily through the selection and application of components.
In categories 2, 3 and 4, better performance is achieved with respect to the specified safety function.
Category 2: It is periodically checked that the specified safety function is fulfilled.
Categories 3 and 4: The function of Category 2 is performed, and additionally, it is performed with a guarantee that a single defect does not lead to loss of safety.
Although they may seem somewhat complex, with these studies and actions, we will already be able to know whether or not a security system with an evaluation module is necessary, and what type of machinery requires its subsequent installation. Tice Group, We have a highly qualified team of technicians ready to help your company with all its Machine Safety needs. Don't hesitate to get in touch.
