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UPGRADING MACHINE SAFETY
DEVICES AND INTERLOCKS
By Paul Malburg
Facility Engineer / Controls Manager
Madico, Inc.
SAFETY CONTROL DEVICES ON OLDER
EQUIPMENT (UPGRADING)
• Introduction
• OSHA Requirements
• Risk Assessment
• Safety Components Options
• Risk Category versus Electrical Rating Category
• Summary & Questions
INTRODUCTIONS
How our company got started doing Risk
Assessments
How safe was our equipment and what is the
meaning of “Control Reliable” circuits
The working relationship between Manufacturer
(End User) and Equipment Vendors
OSHA TERM
“GENERAL DUTY CLAUSE”
Employer shall furnish a place of employment which are free from recognized hazards
Employer will comply with all occupational safety and health standards
Employees shall comply with occupational safety and health standards and all rules, regulations
LAMINATING AND COATING INDUSTRY ARE
COVERED UNDER THE FOLLOWING
STANDARDS, (BUT NOT LIMITED TO)
ANSI B11.19, "Performance Criteria for Safeguarding“
ANSI/ RIA R15.06, "Safety Requirements for Industrial Robots and Systems”
ANSI/ASSE Z244.1, "Control of Hazardous Energy”
NFPA79, “Electrical Standard for Industrial Machinery”
OSHA TERM
“BEST PRACTICE”
The best practices guide is not a standard or
regulation
Safety practices in a manufacturing facility begin
with a Hazard Analysis or Risk Assessment
Three ways to improve safety -- engineering
controls, administrative controls and the use of
personal protective equipment (PPE)
TYPES OF CONTROLS
Physical changes and improvements
made to a machine or workstation.
These include electrical control circuits,
machine guards, isolation devices, and
hazard isolation.
Include, but are not limited to written
procedures and training. Training is the
main tool that ties all safety practices
together.
This is equipment which protects
employees from harm. In terms of
hazard control methods, usage of
personal protective equipment is the
last hazard control.
Personal
Protective
Equipment
Administrative
Engineering
BEST
PRACTICE
HAZARD ANALYSIS / RISK ASSESSMENT
It identifies risks through
observations of the interaction
between the worker, job,
environment and tools. Once
hazards are identified,
management puts controls in place
to prevent, reduce or eliminate them. The benefits of a comprehensive
hazard analysis are improved safety, lower costs and
increased productivity.
RISK REDUCTION CATEGORY
RISK REDUCTION
CATEGORY
SAFEGUARD PERFORMANCE CIRCUIT PERFORMANCE
R1 Hazard elimination or hazard substitution Control reliable
R2A Engineering controls preventing access to
the hazard, or stopping the hazard
interlocked barrier guards, light curtains,
safety mats, or other presence sensing
devices
Control reliable
R2B Single channel with
monitoring
R2C Single channel
R3A Non-interlocked barriers, clearance,
procedures and equipment
Single channel
R3B Simple
R4 Awareness means Simple
ELECTRICAL RATINGS BY CATEGORY
SUMMARY OF REQUIREMENTS BY CATEGORY SYSTEM BEHAVIOUR Notes
CATEGORY B When a fault occurs it can lead to a
loss of the safety function. Category B in itself has
no special measures for
safety CATEGORY 1
As described for category B but with
higher safety related reliability of the
safety related function.
CATEGORY 2
The loss of safety function is
detected and periodically checked
by the machine control system
CATEGORY 3 When the single fault occurs the
safety function is always performed. Multiple faults caused by
a common cause or as
inevitable consequences
of the first fault shall be
counted as a single
fault.
CATEGORY 4
When the faults occurs the safety
function is always performed. The
faults will be detected in time to
prevent the loss of safety functions.
SAFETY COMPONENTS
• Guards Fixed in Place
• E-Stops and Cable pulls
• Tongue Interlock Switches
• Pressure –sensitive safety edges
• E-Stop Safety Relay
• Programmable Safety Controllers
• Safety Programmable Logic Controllers (Safety PLC)
• Pressure Sensitive Safety Mats
• Area Scanners
• Light Curtains
RISK ASSESSMENT
TURRET WINDER SECTION
SEVERITY OF
INJURY
EMPLOYEE
EXPOSURE
AVOIDANCE TO
HAZARD
RISK
REDUCTION
CATEGORY
Serious Injury
More than
First-Aid
Frequent Not Likely R1
Likely R2A
Infrequent Not Likely
R2B Likely
Slight Injury
Less than
First-Aid
Frequent Not Likely R2C
Likely R3A
Infrequent Not Likely R3B
Likely R4
Serious Injury
More than
First-Aid
Frequent Likely R2A
RISK REDUCTION
CATEGORY
SAFEGUARD PERFORMANCE CIRCUIT
TYPE
R1 Hazard elimination or hazard
substitution Control Reliable
R2A
Engineering controls preventing
access to the hazard, or
stopping the hazard
R2B
Single channel
with
monitoring
Single channel R2C
R3A Non-Interlocked barriers,
clearance, procedures and equip. R3B Simple
R4 Awareness means
R2A
Engineering controls preventing
access to the hazard, or
stopping the hazard
Control Reliable
OPTIONS FOR ADDING SAFETY DEVICES TO TURRET WINDER
R2A
Engineering Controls
Control Reliable
Risk Reduction
Dpf Safe Distance (Ds) Ds
DS = [K * (TS + TC + TR)] + DPF
SUMMARY & QUESTIONS