Emergency Stops

Mark Lewandowski -Corporate Engineering Machine Controls

Learning Objectives

After this section, the students will be able to:• Describe the Emergency Stop Function and

requirements• Describe the three Stop Categories• List two common E-Stop devices and describe

their requirements

Emergency Stop Function

Covered in NFPA 79, EN 60204-1, and EN 13850

• Shall override all other functions

• Stop machine as quickly as possible without creating other hazards

• Reset shall not initiate restart

• Not a substitute for other safeguarding

Stop Categories

• Category 0– Remove power immediately.

• Category 1– Ramp machine to zero speed then remove power– Typical P&G E-Stop for servo machines– Need time delay safety relay (or safety PLC)

• Category 2– Ramp line to zero speed leave power on

• Every machine must have a cat. 0 stop– May be done by E-stop or Machine Main Disconnect

E-stop Devices

• Common types include:

– Push-buttons

– Pull-cord switches• Devices shall be positive opening• E-Stop actuators shall be colored Red with a Yellow

background

Safety E-Stop Device Requirements

Safety rated Emergency Stop Pushbuttons:

– shall have normally closed, positive- opening contact(s) (I.e. 1 for single channel with monitoring, 2 for control reliable) .

– for control reliable applications with removable contact blocks, shall have the two contacts on separate contact blocks.

– shall be red mushroom, 40 mm minimum diameter, with detent, requiring manual reset after actuation. Yellow Background

E-Stop Protection Devices

• Must be continuously operable and readily accessible by all operators– No covers are allowed

• Located at each operator control station, as well as at other locations as determined by the risk assessment

• Measures against inadvertent actuation should not impair its accessibility

If Button Protection is Needed

• Re-orient or relocate is best option• If needed, a protective device around the

button can be installed:– Must maintain a 120mm diameter clear area

around button– Cannot extend above the plane defined by the pressed button– P&G preference is 2 small bars above and below

E-Stop Pull Cord Device

• Pull Cord Switches

In order to meet Category 3, Pull Switches MUST be of the taut-line style.

Other versions cannot detect broken or cut cables.

Emergency Stops

End of Section

For questions contact:• Your local HS&E resource• Your local PC&IS resource• Mark Lewandowski – CET Machine Controls