Interlock Systems

What is the purpose of an interlock?

• To lock a dangerous machine so it cannot be used
• To prevent incorrect or dangerous command selections
• To ensure that only authorised people use a machine
• To ensure that safety systems do not stop a machine working

What happens if the safety guard is in the 'up' position?

• The machine operates normally
• The machine speeds up
• The machine refuses to operate
• The machine reduces speed

What does an interlock do with conflicting commands?

• It ignores them
• It executes both commands
• It prioritises the selection of commands
• It stops the machine

Which switch is used to disable the control circuit for the other direction in a motor?

• Normally-open (NO) switch
• Normally-closed (NC) switch
• Both NO and NC switches
• None of these

What would happen without interlocks in a forward and reverse motor system?

• Motor would stop
• Motor would run smoothly
• Forward and reverse could be selected simultaneously
• Nothing would happen

What is the purpose of a position limit switch?

• To start the machine
• To control the speed of the machine
• To inform the control system that a moving part has reached a specified position
• To turn off the machine

What happens when a limit switch breaks in a gate system?

• The gate continues moving
• The gate stops immediately
• The relevant contactor is de-energised and unlatched
• The gate changes direction

What colour should emergency stop buttons always be?

• Blue
• Green
• Red
• Yellow

What is the most important aspect in the design of an emergency stop button system?

• It is always better to use a normally-open (NO) stop button
• The stop button should always be coloured yellow
• The machine should always stop immediately
• The machine should not re-start as soon as the button is released

What type of switch is used in a 'break before make' system?

• Normally-open (NO) switch
• Normally-closed (NC) switch
• Both NO and NC switches with a delay
• None of these