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Safety Relay Training
Safety Relay Training
What You Will Learn:
After completing this lesson, you will be able to:
• Review the basic safety relay principles
• Understand the operation of the MSR 131 used with the Nachi robot
• Understand the 3 operational modes of the Safely Relays, Dual Channel +1- Mode, Automatic/Manual Reset, Manual Monitored Reset
• Understand troubleshooting the Safety relays using the LED indicators and logical troubleshooting techniques.
• Understand the common Safety relay circuit configurations -
• Component removal and replacement
Why Safety Relays?•
Before You Begin:
Per ANSI B11.19, Section 2.12, Definitions: Control Reliability is defined as a method of ensuring the integrity of the performance of guards, devices, or control systems
Per ANSI B11.19, Section 5.5.1, Control Reliability: When required by the performance requirements of the safeguarding, the device, system, or interface shall be designed, constructed, and installed such that a single component failure within the device, interface or system shall prevent a successive machine cycle. This requirement does not apply to those components whose function does not affect safe operation of the machine tool.
Requirements for a Control Reliable System
The use of redundant components (e.g. redundant safety contacts, output devices, safety relays etc.)
Capability of monitoring failures (e.g. safety relays, safety PLC, routine maintenance. etc.) Mere redundancy in not sufficient. Multiple failures may have unpredictable effects, therefore, monitoring and response to a single failure is essential. (ANSI Eli 20 section E6.13)
Monitoring Relays: require the use of positive guided relay contacts.
Control Reliability
The control system shall be constructed so that:
A single failure within the system does not prevent the normal stopping action.
Does prevent initiation of a successive cycle or stroke until the failure is coxTected.
Failure shall be detectable by a simple test, or indicated by the control system.
Page 1 of 22
Safety Relay Training
Safety Relay Basics
A safety relay circuit contains a pair of multipole positive-guided contacts used for switching power to the load. If one of the contacts is welded, the other contact can safely switch off the load. Each relay contains a N/C contact in the restart circuit which is used for self-checking. This N/C contact remains open in the event of a weld and prevents the safety circuit from restarting.
Conventional multipole relays cannot be used for safety purposes. After a conventional N/O relay contact welds, and the relay dc-energizes, the N/C contact is allowed to return to the closed position and the we)ded contact stays closed.
Standard Relay
Force Guided Relay
Page 2 of 22
NC NO NO
NC NO NO
Safety Relay Training
During operation of a relay the coil is energized pulling in the contacts. Contacts that were closed open and those that were open close.
The safety circuit with conventional contacts has no way of “knowing” that a contact weld has occurred and the machine is allowed to restart.
Page 3 of 22
NC NO NO
NC NO NO
Welded Contact
Safety Relay Training
Positive-guided contacts, also called captive or force-guided contacts, are designed so that all sets of contacts move in unison, using a mechanical linkage. A contact weld holds all contacts in place. This ensures that the N/C contact stays open after a N/U contact welds shut. Once one of the N/U contacts welds, the safety relay cannot be restarted. This feature is required by ANSI
Page 4 of 22
NC NO NO
Welded Contact
Held Closed
Held Open
Safety Relay Training
Safety Relay operation:
The following diagrams show the concept of safety relay operation. The diagrams do not represent the actual circuitry in the relay but does show their operational characteristics. There are other possible wiring configurations for safety relays. An E-Stop application is used in this example.
The diagram shows: Each B-Stop push button has two sets of contacts One set on the hot side of the circuit the other on the return side Manual reset push button to reset the relay Safety output contacts at the bottom Output monitors Y32 relay reset, Y35 Power applied
Page 5 of 22
A1
S33
S11
S11
S12
A2
S21
S52
S34
S22
Y1
Y1
Y2
S37
Y31
Y35
Y32
Y30
13
23
33
14
24
34
41
51
42
52K2
K1K1 K2 K3
K1 K2 K3
K1 K2 K3
E-Stop 1E-Stop 2E-Stop 3
E-Stop 1E-Stop 2E-Stop 3
Reset
DC INDC OUT
DC + DC -To Digitial
Circuit Below
CH1 INCH1
START (RESET)
K1
K2
K3
K3
K1
CH2 IN K3
K2CH2
To Digitial Circuit Below
To Digitial Circuit Below
K2K1
K3
To Voltage Converter
+24VDC
0 VDC
Fuse OK
Relay Reset
To K2K1
To K1
Safety Relay Training
Page 6 of 22
Safety Relay Training
Input Channel Open
Estop Circuit Input Open
POWER
CH 1 IN
CH 2 IN
START/RUN
CHI
CH2
E-Stop 1 open
No continuity to K1 or K2
Relay not ready to be reset
Only power LED on
Page 7 of 22
A1
S33
S11
S11
S12
A2
S21
S52
S34
S22
Y1
Y1
Y2
E-Stop 1E-Stop 2E-Stop 3
E-Stop 1E-Stop 2E-Stop 3
Reset
DC INDC OUT
DC + DC -To Digitial
Circuit Below
CH1 INCH1
START (RESET)
K1
K2
K3
K3
K1
CH2 IN K3
K2CH2
To Digitial Circuit Below
To Digitial Circuit Below
K2K1To K1
CH2
Safety Relay Training
Input Channels Closed
Estop Circuit all inputs closed
POWER
CH 1 IN
CH 2 IN
START/RUN
CHI
CH2
E-Stop string closed
Continuity across Cl-I I in and CH 2 in LED
CH 1 lin and CH 2 in LED’s On
Relay ready to be reset
Page 8 of 22
A1
S33
S11
S11
S12
A2
S21
S52
S34
S22
Y1
Y1
Y2
E-Stop 1E-Stop 2E-Stop 3
E-Stop 1E-Stop 2E-Stop 3
Reset
DC INDC OUT
DC + DC -To Digitial
Circuit Below
CH1 INCH1
START (RESET)
K1
K2
K3
K3
K1
CH2 IN K3
K2CH2
To Digitial Circuit Below
To Digitial Circuit Below
K2K1
CH2
Safety Relay Training
Reset Input Depressed
Estop Circuit Reset Closed
POWER
CH 1 IN
CH 2 IN
START/RUN
CHI
CH2
Manual reset closed
K3 coil on via NC contacts from K1 K2
K3 on closes K3 contacts on K1 and K2
K1 and K2 now have a complete current path and energize
CH1, CH2 and start LED’s on
Page 9 of 22
A1
S33
S11
S11
S12
A2
S21
S52
S34
S22
Y1
Y1
Y2
E-Stop 1E-Stop 2E-Stop 3
E-Stop 1E-Stop 2E-Stop 3
Reset
DC INDC OUT
DC + DC -To Digitial
Circuit Below
CH1 INCH1
START (RESET)
K1
K2
K3
K3
K1
CH2 IN K3
K2CH2
To Digitial Circuit Below
To Digitial Circuit Below
K2K1
CH2
Safety Relay Training
Relay Reset
Estop Circuit Reset ClosedK1 and K2 On
POWER
CH 1 IN
CH 2 IN
START/RUN
CHI
CH2
K1 and K2 on Seal contacts keep K1 and K2 on K1 and K2 contacts open in K3 circuit K3 turns off Relay is reset CH1, CH2 in and CH1, CH2 LED’s on start LED off
Page 10 of 22
A1
S33
S11
S11
S12
A2
S21
S52
S34
S22
Y1
Y2
E-Stop 1E-Stop 2E-Stop 3
E-Stop 1E-Stop 2E-Stop 3
Reset
DC INDC OUT
DC + DC -To Digitial
Circuit Below
CH1 INCH1
START (RESET)
K1
K2
K3
K3
K1
CH2 IN K3
K2CH2
To Digitial Circuit Below
To Digitial Circuit Below
K2K1
CH2
Safety Relay Training
Relay Reset
MSR 131 Circuit Diagram
POWER
CH 1 IN
CH 2 IN
START/RUN
CHI
CH2
Relay Reset Safety Contacts at 13, 14, 23, 24, 33, 34 closed NC contacts 41,42, 51, 52 open
Page 11 of 22
A1
S33
S11
S11
S12
A2
S21
S52
S34
S22
Y1
Y1
Y2
S37
Y31
Y35
Y32
Y30
13
23
33
14
24
34
41
51
42
52K2
K1K1 K2 K3
K1 K2 K3
K1 K2 K3
E-Stop 1E-Stop 2E-Stop 3
E-Stop 1E-Stop 2E-Stop 3
Reset
DC INDC OUT
DC + DC -To Digitial
Circuit Below
CH1 INCH1
START (RESET)
K1
K2
K3
K3
K1
CH2 IN K3
K2CH2
To Digitial Circuit Below
To Digitial Circuit Below
K2K1
K3
To Voltage Converter
+24VDC
0 VDC
Fuse OK
Relay Reset
To K2CH2
Safety Relay Training
GuardMaster MSR Safety Relays:
Safety Relay Selections
MSR131 Cat # 440R-C23137 (Safety Relay) MSR138 Cat # 440R-M23080 (Time Delay Safety Relay) MSRI22 Cat # 440R-E23 157 (Expansion Module)
MSRI3I Features:
Light curtain, Safety mat, Safety Contact inputs Positive guided safety. contacts Auxiliary contacts 2 Solid State Outputs, Inputs Closed and Relay Reset Cross fault monitoring Monitored or Automatic reset Removable terminals
Page 12 of 22
A1 S33 S34 S52
PWR
START
CH1 IN
CH2 IN
CH1
13 23 33 41 51
14 24 34 42 52
MSR131RTP
X3 S11 S12 S21S11 13 23 33
S22 41 51 51
X4 Y30 Y31 Y32A2 Y1 Y2 X1
Y35 42 52 52X2 14 24 34
CH2
CH2
Safety Relay Training
MSRI3 Cat # 440R-C23137 Specifications
Standards IEC/EN60204-1, ISOTR 2100, 1 (EN 954-1)Safety Category Cat. 4 per EN 954-1Approvals CE marked for all applicable directives, cULus and
BGPower Supply 24V AC/Dc, i IOV AC or 230V AC
0.8 to 1.1 x rated voltage, 50/60HzPower Consumption 4WFuses for Safety Output (External Recommended)
6A slow blow or IOA quick blow
Safety Inputs I N.C., 2 N.C., Light Curtain or Safety matMaximum Allowable Input Resistance
70 ohms
Reset Monitored manual or Automatic/manualOutputs 3 N.O. safety
2 N.C. auxiliary1 S.S. Inputs closed1 S.S. outputs active
Safety and Aux B300, AC-15, 5A/250V AC P300, DC-13, 3A/24V DC
Solid State 30mA short circuit protectedPower On Delay 1sResponse Time 15msRecovery Time 100msIndication LEDs Green = Power
Green = StartGreen = CH1 Input closedGreen = CH2 Input ClosedGreen = CH1 Output ActiveGreen = CH2 Output Active
Page 13 of 22
Safety Relay Training
Input Wiring Configurations:
N.C. Safety Input Contacts Cascaded Relay Contacts MSR1 31 checks for cross fault across inputs. Cascaded Control Relays
MSR13I’s output monitoring can accommodate:
Automatic, resets on power up if E-Stop and Yl, Y2 closed Manual reset, requires a low to high transition after the E-Stop circuit is closed Monitored Manual reset, requires closed contacts in the Yl, Y2 loop. Used to check externally
controlled relays Two solid state outputs can be monitored by a PLC to determine relay input conditions and reset
status
MSRI3 2 F Monitored Reset
Input 1 and 2 Closed Reset closed on S33 and S34 Ki and K2 contacts closed in Yl and Y2 monitor loop Y 1, Y2 loop open prevents a successful reset KI orK2 with welded contacts will open Yl, Y2 loop
Page 14 of 22
A2 X1 X2 X3 X4 Y30 Y32 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Safety Relay Training
MSR 2 N.C. Automatic Reset
Jumpers at S33, S34, S52, S11, Xl, 3 X3, X4 Relay no longer requires an external reset command Relay attempts auto reset on power up and continues until input I and 2 closed KI or K2 weld will prevent a successful reset
Page 15 of 22
A2 X1 X2 X3 X4 Y30 Y32 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Safety Relay Training
Troubleshooting MSRI3
CasePower LED
Start LED
CH1 IN LED
CH2 IN LED
CH1 LED
CH2 LED
S.S. Y35
S.S. Y32
Gate Output Check
1On
Reset On
On On Off OffOn Off Closed Off
When pressing the reset button, the Start LED turns ON, butoutputs do not turn ON. Check the monitoring loop between Y1 and Y2; it should be a closed circuit.
Page 16 of 22
A2 X1 X2 X3 X4 Y30 Y32 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Check Here
A1 S33 S34 S52
PWR
START
CH1 IN
CH2 IN
CH1
13 23 33 41 51
14 24 34 42 52
MSR131RTP
X3 S11 S12 S21S11 13 23 33
S22 41 51 51
X4 Y30 Y31 Y32A2 Y1 Y2 X1
Y35 42 52 52X2 14 24 34
CH2
Safety Relay Training
Troubleshooting MSRI 31
CasePower LED
Start LED
CH1 IN LED
CH2 IN LED
CH1 LED
CH2 LED
S.S. Y35
S.S. Y32
Gate Output Check
2On Off On Off On Off
Off Off Closed Off
1) Check the gate switch going to S21 and S22; it should he a closed circuit.2) Check the circuit between S11 and S52 it should be a jumper. If the gate is opened, the CH1 IN LED and CH1 LED will turn off, If gate is re-closed again, CH1 IN LED will turn on.
Page 17 of 22
A2 X1 X2 X3 X4 Y30 Y32 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Check Here
A1 S33 S34 S52
PWR
START
CH1 IN
CH2 IN
CH1
13 23 33 41 51
14 24 34 42 52
MSR131RTP
X3 S11 S12 S21S11 13 23 33
S22 41 51 51
X4 Y30 Y31 Y32A2 Y1 Y2 X1
Y35 42 52 52X2 14 24 34
CH2
Safety Relay Training
Troubleshooting MSRI3
CasePower LED
Start LED
CH1 IN LED
CH2 IN LED
CH1 LED
CH2 LED
S.S. Y35
S.S. Y32
Gate Output Check
3On Off Off On Off On
Off Off Closed Off
1) Check the gate switch circuit going to S11, S12 and S52. The circuit may have opened while the gate was closed. If the gate is opened, the CH2 IN LED and CH2 LED will turn off. If the gate is re-closed again, CH2 IN LED will turn on.
Page 18 of 22
A2 X1 X2 X3 X4 Y30 Y32 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Check Here
A1 S33 S34 S52
PWR
START
CH1 IN
CH2 IN
CH1
13 23 33 41 51
14 24 34 42 52
MSR131RTP
X3 S11 S12 S21S11 13 23 33
S22 41 51 51
X4 Y30 Y31 Y32A2 Y1 Y2 X1
Y35 42 52 52X2 14 24 34
CH2
Safety Relay Training
Troubleshooting MSR
CasePower LED
Start LED
CH1 IN LED
CH2 IN LED
CH1 LED
CH2 LED
S.S. Y35
S.S. Y32
Gate Output Check
4Blinking Off Off Off Off Off
Off Off Closed OffCheck for short circuit across the inputs: S11 to S2I, S11 to S22, S12 to S22
Page 19 of 22
A2 X1 X2 X3 X4 Y30 Y32 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Check Here
A1 S33 S34 S52
PWR
START
CH1 IN
CH2 IN
CH1
13 23 33 41 51
14 24 34 42 52
MSR131RTP
X3 S11 S12 S21S11 13 23 33
S22 41 51 51
X4 Y30 Y31 Y32A2 Y1 Y2 X1
Y35 42 52 52X2 14 24 34
CH2
Safety Relay Training
Troubleshooting MSR131
CasePower LED
Start LED
CH1 IN LED
CH2 IN LED
CH1 LED
CH2 LED
S.S. Y35
S.S. Y32
Gate Output Check
5On On On On Off Off
On Off Closed OffCheck the Reset button; it may be shorted or held in the closed position.
Page 20 of 22
A2 X1 X2 X3 X4 Y30 Y32 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Check Here
A1 S33 S34 S52
PWR
START
CH1 IN
CH2 IN
CH1
13 23 33 41 51
14 24 34 42 52
MSR131RTP
X3 S11 S12 S21S11 13 23 33
S22 41 51 51
X4 Y30 Y31 Y32A2 Y1 Y2 X1
Y35 42 52 52X2 14 24 34
CH2
Safety Relay Training
Troubleshooting MSR131
CasePower LED
Start LED
CH1 IN LED
CH2 IN LED
CH1 LED
CH2 LED
S.S. Y35
S.S. Y32
Gate Output Check
6Off Off Off Off Off Off
Off Off Closed Off Check power applied to A1 and A2.
Page 21 of 22
A2 X1 X2 X3 X4 Y30 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Check Here
A1 S33 S34 S52
PWR
START
CH1 IN
CH2 IN
CH1
13 23 33 41 51
14 24 34 42 52
MSR131RTP
X3 S11 S12 S21S11 13 23 33
S22 41 51 51
X4 Y30 Y31 Y32A2 Y1 Y2 X1
Y35 42 52 52X2 14 24 34
CH2
Safety Relay Training
Troubleshooting MSR131
CasePower LED
Start LED
CH1 IN LED
CH2 IN LED
CH1 LED
CH2 LED
S.S. Y35
S.S. Y32
Gate Output Check
7On On On On On On
On On Closed Off
1) Check for power at terminals 13, 14, 23 and 24.2) An internal component failure may have occurred in the MSR131 if power is present at 13 and 23.
Page 22 of 22
A2 X1 X2 X3 X4 Y30 Y35 Y1 Y2 14 24 34 42 52
A1 S11 S12 S21 S22 S52 S11 Y31 S33 S34 13 23 33 41 51L1 L2L3
K1
L2(Ground)
Reset
K2
MK1 K2
Safety Inputs
L1(120 vAC)
CH1 IN CH2 IN
MSR131
Relay InputsReset Closed
Check Here
A1 S33 S34 S52
PWR
START
CH1 IN
CH2 IN
CH1
13 23 33 41 51
14 24 34 42 52
MSR131RTP
X3 S11 S12 S21S11 13 23 33
S22 41 51 51
X4 Y30 Y31 Y32A2 Y1 Y2 X1
Y35 42 52 52X2 14 24 34
CH2
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