Nov 12, 2018

Safety Lockout System - SLS

An alternative isolation method for LOTO

Typical existing equipment used to isolate motive power from industrial machines and processes are not designed to handle the frequency of access required for modern machinery. Historically, a manual disconnect device has been used to remove the hazards related to motive energy sources.

Challenges of manual disconnects:

  • "Frequent use" rating which yields only 1.3 on/off cycles per day for an AC23A rated manual disconnect swith
  • Disconnects can fail to an unsafe condition
  • 36" clearance in front of the disconnect enclsoure is required
  • Arc flash hazards to the disconnect operator may be present
  • Possible 'false zero' voltage verification
  • ...and many more

A contactor system is optimal for high cycle rates, but is NOT a disconnect isolating device unless AC23A rated as a unit.

The solution?
The Pilz SLS Safety Lockout System is the first Safety Isolation Control System to be certified as an Isolation System to the new ANSI/UL6420 standard for “Equipment used for system isolation and rated as a unit”.

The Safety Lockout System (SLS) from Pilz allows remote operation of the power Isolating switching device from Remote Lockout Stations (RLS) mounted by each access point to safely isolate the main electrical, hydraulic and pneumatic circuits of a machine or plant. Unlike other Remote Lockout Systems which are used for unexpected startup only, the Pilz Safety Lockout System is the first to be ANSI/UL 6420 Listed as an Energy Isolation Device for electrical power.

Shutdown can be initiated from any given location of the machine or plant and in most cases only requires applying one personal lock. The safe condition is tested and displayed by a “System Isolated” light. This system provides automatic zero energy verification in order to protect personnel and comply with industry standards for Energy Isolation and prevention of unexpected start up.

The SLS system uses redundant contactors mounted remote from the machine by the power equipment supplying the machine, usually an MCC or other power distribution system. Power contactors have typical mechanical life ratings of 1,000,000 to10,000,000 cycles.

Contactors can be controlled remotely by using Remote Lockout Stations (RLS). Multiple switches can be placed anywhere on the machine. They operate on 24VDC low current and are small, so they do not require a 36-42 inch space in front of the panel.


  • Operates remotely, keeping the operator safe from arc flash hazards
  • Energy isolated light indicates safe status, no need for proper PPE to measure voltage for verification
  • Rated in millions of LOTO cycles instead of thousands, extending the life of the system compared to alternatives
  • Simplified LOTO procedure for complicated machinery and processes, saving time and money
  • Single point lockout of multiple energy sources for immediate safety
  • Small 24VDC Remote Lockout Stations easily mount next to multiple access points to promote following proper procedures and negate requirement for 36” to 42” clearance in front of the switch
  • Uses cost-effective cables for local disconnects


  • Two control systems - The first system is based on the PNOZmulti controller for single zone isolation.  This system can be installed, commissioned, and maintained by the customer. The second system is available with the Pilz PSSuniversal safety control system for multiple zone control of energy isolation and also for imbedding into a machine that currently utilizes a Pilz processor. This version requires Pilz integration services assistance.
  • Third-party Lab tested and UL certified to ANSI/UL 6420 as a “system” including Common Cause Failures of a dual channel safety contactor system such as mechanical and electrical ruggedness, Type 2 SCCR, EMC, Temp Rise and safety  functionality
  • Tested and rated as a unit AC23A — a Disconnect for electrical energy Isolation
  • CAT4/PL e design per ISO 13849 and tamper proof sealed
  • As many as 64 remote lockout switches may be used to request isolation
  • The RLS box has an “Energy Isolated” verification light indicating a safe status
  • Optional modules for pneumatic and hydraulic power isolation
  • Hardwired interface to any machine Safety Related Control System for E-stop, zero speed and valve independent control
  • Optional diagnostic display or Ethernet interface

Further information

Pilz SLS White Paper
Pilz SLS Brochure

Pliz SLS Presentation


Pilz Remote Lockout System

Pilz Automation Safety L.P.
7150 Commerce Boulevard
Canton, MI 48187

Telephone: +1 734 354-0272

Technical Support

Telephone: +1 877 745-9872

Press contact

Telephone: 734-392-0211

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