Safety sensor must be connected to a safety PLC - - programmable logic

'Safety equipment ( Such as stop, the security, security sensors, light curtains, grating, valve, etc. ) Why access security loop, can not only access to the common I/o points of the PLC controller? '

if you use the safety light curtain and so on safety input unit, and use normal using a logic control of PLC, the security level of the whole security system cannot achieve a higher security level. Chances of errors because ordinary PLC controller controller is much higher than the safety, so if you need a security system of the whole circuit to achieve a higher security level for security, the whole system circuits of all components need to achieve high level of security, including the input sensor, control unit and output actuators.

first of all, according to the safety of international standard ISO 13849 - machine 1 'security system design method of the control section ( SRP/CS) 'And the corresponding national standard GB/T 16855. The provisions of 1, 2008, first to evaluate machine all risk, assess a PLr ( The Performance Level required for the requirement of the whole security system security Level) , and then to the safety design, through the use of components of safety grade evaluation, to determine the ultimate security system level of PL, see whether it has reached the requirement of PLr finally.

safety circuit design: after assessing the PLr, according to different degree of danger and its danger to safety circuit design, including input elements ( Scram, hands button, safety light curtain, safety grating, security locks, etc. ) The control unit ( Controller, etc. ) And the output elements ( Relay, contactor, valve, etc. ) 。 Calculating total PL: according to different security function, calculated the safety loop total PL, see if the end result is greater than or equal to the PLr, if meet the requirements, is a suitable safety design. If does not meet the requirements, the need to make the system overall design or change some components PL is greater than or equal to the PLr.

if the components combined with a series of control system based on PL SRC/PS, is also able to calculate the total PL and considering the following: a) Using element minimum performance levels ( PL低) b) PL element and element = N low, namely the number of the whole system to achieve a PL value, each element of the whole system PL value should be greater than or equal to at least this value.

Sample: suppose that a system of , minimum performance level for a total of four elements, the entire system of PL value of PLb. If a system minimum performance level for PLd, a total of three components, the entire system of PL value for PLd. Suppose that a workstation with robots to take material, then access to the other location for other operations, people need to often in and out of the robot taking the place of the workpiece.

first assess PLr hit people seriously injured due to the robot, so choose the S2, due to the frequent operators need to enter the danger zone, so choosing F2, if a robot dozen come over, if the speed is slow, depending on the degree of skilled operators and reaction, can escape from the danger, select P1, eventually PLr = PLd.

so, PL simple estimate table, according to the total system security design need to use the input and control components requires at least PLd device. Because ordinary programmable controller level of PL is not more than, therefore, the security level of the whole system is can't meet the requirements of PLr = PLd, therefore is not conform to the design of the safety standards, must use PLd above the safety of the controller.

as for the individual components of operating performance grade PL, some can be found from the element parameters in the table, such as safety light curtain, security scanner, safety PLC controller, etc. And some of the elements is to get through calculation, the contactor, for example, safety relay module, etc. Among them, the subsystem of PL value can be calculated by SISTEMA software and assessment and generate the corresponding report.

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