Functional description

Dieses Thema enthält die folgenden Abschnitte:

The safety-related SF_Guard function block monitors a guard (e.g., door) with two-stage interlocking ‣ Verriegelungen gemäß DIN EN ISO 14119/14120
×‣ Interlocking in Accordance with DIN EN ISO 14119/14120
× according to DIN EN ISO 14120. The function block executes stop category 0 at its output.

S_StartReset and S_AutoReset can be used to specify a start-up inhibit and a restart inhibit.

Opening and closing the safety equipment

If the safety equipment (door) connected to the function block is opened, the function block sets its S_GuardOut output to SAFEFALSE. This defined safe state is maintained until the door is closed correctly and the restart inhibit (if active) is removed.
When the safety equipment is being closed, a SAFETRUE signal at inputs S_GuardSwitch1 and S_GuardSwitch2 reports that the closing operation has been performed correctly. The switching intervals of the position switches connected to inputs S_GuardSwitch1 and S_GuardSwitch2 are only monitored during the closing operation using the time set at DiscrepancyTime.

Hinweis
If only one signal reports the status of the door (one position switch only), this must be connected in parallel to both inputs S_GuardSwitch1 and S_GuardSwitch2. In this case, a time of 0 seconds must be set at DiscrepancyTime.

Start-up inhibit (S_StartReset)

S_StartReset is used to specify the start-up inhibit after activating the function block and/or starting the Sicherheitssteuerung.

S_StartReset = SAFEFALSE After the Sicherheitssteuerung has been started up and/or the function block has been activated at the Activate input, the start-up inhibit is active. The start-up inhibit is only removed if there is a positive signal edge at the Reset input.
Refer to the warning below this table.

S_StartReset = SAFETRUE After the Sicherheitssteuerung has been started up and/or the function block has been activated at the Activate input, no start-up inhibit is active.
Refer to the section "Warning when using ...".

Removing the start-up inhibit by means of a positive signal edge at the Reset input can cause the S_GuardOut output to switch to SAFETRUE immediately (depending on the status of the other inputs).

WARNUNG

Unintended start-up

Verify the impact of removing the start-up inhibit by means of a positive signal edge at the Reset input.

Make certain that appropriate procedures and measures (according to applicable sector standards) have been taken to help avoid hazardous situations when removing the start-up inhibit.

Do not enter the zone of operation when removing the start-up inhibit.

Ensure that no other persons can access the zone of operation when removing the start-up inhibit.

Use appropriate safety interlocks where personnel and/or equipment hazards exist.

Restart inhibit (S_AutoReset)

S_AutoReset is used to specify the restart inhibit after closing the safety equipment.

S_AutoReset = SAFEFALSE The restart inhibit is active after the safety equipment has been closed. The restart inhibit is only removed if there is a positive signal edge at the Reset input.
Refer to the warning below this table.

S_AutoReset = SAFETRUE The restart inhibit is not specified. As soon as the door is closed and SAFETRUE is present again at inputs S_GuardSwitch1 and S_GuardSwitch2 within the time set at DiscrepancyTime, the S_GuardOut output automatically switches to SAFETRUE.
Refer to the section "Warning when using ...".

After the restart inhibit has been removed, the status at the S_GuardOut output can switch from SAFEFALSE to SAFETRUE.

WARNUNG

Unintended start-up

Verify the impact of removing the restart inhibit by means of a positive signal edge at the Reset input.

Make certain that appropriate procedures and measures (according to applicable sector standards) have been taken to help avoid hazardous situations when removing the restart inhibit.

Do not enter the zone of operation when removing the restart inhibit.

Ensure that no other persons can access the zone of operation when removing the restart inhibit.

Use appropriate safety interlocks where personnel and/or equipment hazards exist.

Warning when using S_AutoReset = SAFETRUE and/or S_StartReset = SAFETRUE

The start-up inhibit and/or restart inhibit must only be deactivated if it is certain that starting up/restarting the machine/system will not lead to a hazardous situation or that a suitable start-up/restart inhibit is in place at another location or using other means.

WARNUNG

Non-conformance to safety function requirements

Verify the impact of a deactivated start-up inhibit (S_StartReset = SAFETRUE) and/or restart inhibit (S_AutoReset = SAFETRUE) on your machine or process prior to implementation.

Observe the regulations given by relevant sector standards regarding the start-up/restart inhibit.

Verify that a suitable start-up inhibit is in place at another location or using other means.

Interlocking and guard locking according to DIN EN ISO 14120

The function block fully supports two-stage interlocking ‣ Verriegelungen gemäß DIN EN ISO 14119/14120
×‣ Interlocking in Accordance with DIN EN ISO 14119/14120
× in accordance with DIN EN ISO 14120.

Hinweis
The safety-related SF_Guard function block does not support the monitoring of a guard with guard locking.
For this reason, the overtravel and access times of the machines and system parts to be secured must be taken into account during the risk assessment process. If the overtravel time of the machine or system in the zone of operation is greater than the possible access time (the period within which a person can reach the zone of operation), interlocking devices with guard locking must be used. In such cases, the safety-related SF_GuardLocking 2 function block is to be used.

WARNUNG

Unintended machine operation

Perform an in-depth risk assessment that includes all items in the safety path, including access times to zones of operation, to determine the appropriate safety-related equipment for your specific application, based on all the applicable standards.

Safety equipment with two position switches

If two single-channel position switches are used in the safety equipment, their signals must be connected individually to the Sicherheitssteuerung. Connect one of the signals to input S_GuardSwitch1 of the function block and the other to the second input S_GuardSwitch2.

If two two-channel position switches are used in the safety equipment, the four signals must be connected individually to the Sicherheitssteuerung.

The two-channel evaluation of the signals for each position switch must be performed outside of the safety-related SF_Guard function block, either through respective parameterization of the input channels of the safety-related input device or by using the safety-related SF_Equivalent or SF_Antivalent function block upstream. This evaluation should result in one signal for each of the position switches. Connect one of the signals to input S_GuardSwitch1 of the function block and the other to the second input S_GuardSwitch2.

Hinweis
Cross-circuit monitoring is not performed by the function block. It is your responsibility to perform this monitoring function outside of this function block in the safety-related control system.

Safety equipment with one position switch

If one single-channel position switch is used in the safety equipment, you must connect its signal to both inputs S_GuardSwitch1 and S_GuardSwitch2 of the function block.

If one two-channel position switch is used in the safety equipment, its signals must be connected individually to the Sicherheitssteuerung.

Hinweis
The following applies to both scenarios (one and two position switches):
The S_GuardOut output of the function block is only switched to SAFETRUE if both inputs S_GuardSwitch1 and S_GuardSwitch2 are showing the SAFETRUE state and the rest of the signal combination is valid for such a scenario.

Number and design of supported position switches

The function block supports safety equipment with one or two mechanical or non-mechanical position switches.
Depending on the safety category (EN ISO 13849-1) or SIL (IEC 61508), single-channel or two-channel position switches with an equivalent or antivalent switch contact arrangement are required.

Monitoring of two-channel operation (cross-circuit detection) and the equivalence or antivalence of the signals must be performed outside of the SF_Guard function block, either through respective parameterization of the input channels of the safety-related input device or by using the safety-related SF_Equivalent or SF_Antivalent function block upstream.
SF_Guard processes one signal per position switch which, for two-channel position switches, results from the evaluation of two-channel functionality, either through respective parameterization of the input channels of the safety-related input device or by using the safety-related SF_Equivalent or SF_Antivalent function block upstream.

The position switches you are using must comply with the requirements of the DIN EN ISO 14120 standard.

S_StartReset = SAFEFALSE	After the Sicherheitssteuerung has been started up and/or the function block has been activated at the Activate input, the start-up inhibit is active. The start-up inhibit is only removed if there is a positive signal edge at the Reset input. Refer to the warning below this table.
S_StartReset = SAFETRUE	After the Sicherheitssteuerung has been started up and/or the function block has been activated at the Activate input, no start-up inhibit is active. Refer to the section "Warning when using ...".

S_AutoReset = SAFEFALSE	The restart inhibit is active after the safety equipment has been closed. The restart inhibit is only removed if there is a positive signal edge at the Reset input. Refer to the warning below this table.
S_AutoReset = SAFETRUE	The restart inhibit is not specified. As soon as the door is closed and SAFETRUE is present again at inputs S_GuardSwitch1 and S_GuardSwitch2 within the time set at DiscrepancyTime, the S_GuardOut output automatically switches to SAFETRUE. Refer to the section "Warning when using ...".