Pilz PZE 9 safety relay

Input circuit ground fault: If Y1 or Y2 is short circuited to ground, the internal monitoring circuit of PZE 9 will cause the output relay to lose power and the safety contacts to open (the manual clearly states: "Earth fault in the input circuit: The output relays de energy and the safety contacts open.").

Feedback loop grounding fault: Detection depends on the capability of the base unit.

These designs enable PZE 9 to safely expand contacts without compromising the original safety circuit level.

Safety feature data and lifespan chart

5.1 Safety level parameters

The security level that PZE 9 can achieve depends on the connected base unit. But the data of the module itself is as follows (from the safety feature data diagram in the manual, please refer to the original figure values). According to a typical Pilz contact extension module, the B10d value (median number of dangerous failure cycles) of PZE 9 is usually high, and the PFH (probability of dangerous failure per hour) is generally at the 1.0E-8 level. The safety related characteristic values stated under safety related characteristic data can only be achieved if the base unit also exhibits these safety characteristic values

Suggest using PAScal software to calculate the overall security function results. Common applications:

Combined with PNOZ X, it can achieve SIL CL 3, PL e (highest level).

Combined with PNOZmulti, it can also achieve SIL CL 3 and PL e.

5.2 Contact Life Curve (Service Life Chart)

The manual provides a Service Life graph, with the x-axis representing the number of switching cycles and the y-axis representing the contact current (A). The curves correspond to different load types (AC15/DC13). For example, under AC15 (230V) load, the contact life is about 4 million times when the current is 0.2A. In practical applications, if the expected total number of switches is lower than this value, the PFH value given in the manual can be used for calculation; If it exceeds, mechanical wear and tear should be considered.

Measures to extend the lifespan of contacts:

Install suppression circuits (RC, varistor, freewheeling diode) on inductive loads.

Avoid overcurrent (exceeding the rated value).

For DC inductive loads, freewheeling diodes can increase the contact life by several times.

Common on-site troubleshooting

6.1 Fault phenomenon: PZE 9 is powered on but the safety contacts do not engage after the input is closed

Possible reasons:

The input circuit is not truly conducting (there is no voltage difference between Y1-Y2).

The basic unit has not output a safety signal.

Feedback loop wiring error or open circuit.

Internal relay malfunction.

Troubleshooting steps:

Measure the voltage between Y1 and Y2: In the closed state, it should be 24V DC (or AC power supply voltage, for AC models). If it is 0V, check if the safety output of the basic unit is normal.

Check feedback loop Y3-Y4: Measure at the feedback input of the base unit to ensure that the loop is connected. When using a multimeter to measure Y3-Y4 of PZE 9 in the resistance range (after power failure), it should be a short circuit (when the relay is not excited? In fact, Y3-Y4 may be an open circuit when it is not excited? Please refer to the internal circuit diagram. The manual does not provide a detailed internal circuit, but the feedback loop is usually composed of auxiliary contacts and safety contacts. Insurance practice: Check if the feedback loop indicator light on the basic unit is on.

If all the above are normal, replace the PZE 9 module.

6.2 Fault phenomenon: After the input circuit is disconnected, the safety contact cannot be opened (critical situation)

Phenomenon: After resetting the emergency stop button, the device can still start (i.e. the touch point is stuck).

Reason: Welding of safety contacts due to overcurrent or frequent switching.

handle:

Immediately cut off the main power supply.

Measure the resistance of each safety contact with a multimeter (in power-off state), which should normally be infinite. If the resistance of a pair of contacts is close to 0 Ω, it indicates that they have been welded.

Replace the entire PZE 9 module (contact repairs are not allowed).

Check if the load current and suppression circuit are correct. If necessary, install a lower speed fuse or increase the contact rating.

6.3 Fault phenomenon: The basic unit cannot be reset (startup prohibited)

Reason: The feedback loop of the basic unit detected that the internal contacts of PZE 9 did not open properly (possibly due to previous welding or mechanical jamming causing the feedback loop to remain conductive after the input loop was disconnected).

troubleshoot

Close the input circuit of PZE 9 (leaving Y1-Y2 open) and observe whether the CH.1 and CH.2 LEDs are turned off. If the LED is still on, it may be an input circuit ground fault or an internal module fault.

Measure the resistance of Y3-Y4: normally it should be an open circuit (because the relay is not excited). If there is a short circuit, it indicates that the safety contact or internal feedback contact is stuck.

Replace PZE 9 and check the external wiring.

6.4 Fault phenomenon: The status of CH.1 and CH.2 indicator lights is inconsistent (one on and one off)