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 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


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


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 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


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


K2K1

K3

To Voltage Converter

+24VDC

0 VDC

Fuse OK

Relay Reset

To K2K1

To K1


Page 6 of 22


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



Reset

DC INDC OUT


Circuit Below

CH1 INCH1

START (RESET)

K1

K2

K3

K3

K1

CH2 IN K3

K2CH2



K2K1To K1

CH2


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



Reset

DC INDC OUT


Circuit Below

CH1 INCH1

START (RESET)

K1

K2

K3

K3

K1

CH2 IN K3

K2CH2



K2K1

CH2


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



Reset

DC INDC OUT


Circuit Below

CH1 INCH1

START (RESET)

K1

K2

K3

K3

K1

CH2 IN K3

K2CH2



K2K1

CH2


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



Reset

DC INDC OUT


Circuit Below

CH1 INCH1

START (RESET)

K1

K2

K3

K3

K1

CH2 IN K3

K2CH2



K2K1

CH2


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



Reset

DC INDC OUT


Circuit Below

CH1 INCH1

START (RESET)

K1

K2

K3

K3

K1

CH2 IN K3

K2CH2



K2K1

K3

To Voltage Converter

+24VDC

0 VDC

Fuse OK

Relay Reset

To K2CH2


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


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


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


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



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


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


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


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


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


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


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


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


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


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



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


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



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


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

Documents

Safety Relay Training