[attachment=3064]

Safety Rules For Different Zones in Industrial Automation

INTRODUCTION



Safety is a situation, whereby the risk is not
greater than the limit risk.

Risk is a combination of the probability and the
degree of the possible injury or damage to health
in a hazardous situation.

Safety is relative.

There is no such thing as 100% safety.



DIFFERENT SAFETY STANDARDS


ANSI:- American National Standards Institute.
IEC:- International Electrotechnical Commission.
DIN:- Deutsches Institute of Normung
OSHA:- Occupational Safety and Health Administration
EU:- European economic Union (EN-standards)



Risk analysis:
Determination of the Limits of Machinery
All phases of machinery life
The limits of machinery including the intended use
The full range of foreseeable uses of the machinery
The anticipated level of training, experience, and ability of the user
Exposure of other persons to the hazards of the machinery
Hazard Identification
Risk Estimation



Risk Evaluation and Reduction
Safe machinery design

Protection measures for the risks that canâ„¢t be eliminated

Inform users of the residual risks

Information, instruction, training and supervision

Use of Personal Protection Equipment




Area Guarding
Switch off power when a person enters the hazard area
Prevent switching on power when a person is in the hazard area.





Choice of Protective Measures
1. Preventing access during dangerous motion
Fixed Guards
Movable Guards
Two-Hand Controls
Preventing dangerous motion during access.
Photoelectric Light Curtains
Pressure Sensitive Safety Mats
Pressure Sensitive Edges





Muting
The muting conditions defined in IEC 61508:
a. Muting is only permitted to be activated during the time span of the working cycle
b. Muting must be performed automatically.
c. Muting must not depend on a single electrical signal.
d. Muting must not depend completely on software signals.
e. The muting signals, if they occur as part of an invalid combination, must not permit any muting state.
f. The muting state is removed immediately after the pallet has passed through





The safety distance
OSHA Formula:
Ds = 63 X TS where Ds= Safety Distance
63 = Recommended hand speed in in/sec
TS = Total stop time in Sec
ANSI Formula:
Ds = K x (Ts + Tc + Tr + Tbm) + Dpf
Ds = The minimum safe distance
K = 63 (hand speed in in/sec)
Ts = Stopping time of machine, in seconds
Tc = Control circuit response time in seconds
Tr = Light curtain response time
Tbm = Response time of a brake monitor
Dpf = Depth penetration factor
S = (K x T) + C K = 1600mm/sec assumed operator speed
T = The overall stopping time of the system
C = Depth of penetration
S = Safety distance



CONCLUSION
High efficiency is required
High accuracy is required
Complexity increases
Terrorism increases
Safety is required