Hazard Analysis

What is a safe machine?

Dangerous – the result of scientific method (example: automobiles, knives, ladders, vaccines, hot coffee, etc. can be dangerous without necessarily being defective)

Defective – a legal conclusion

Foreseeability – correctly anticipating the danger, risk, and usage

Negligence – irresponsible conduct (example: failure to anticipate, design, test, or warn)

Safe – a situation that has an acceptable risk, as defined by the law.

Tort – compensation to make someone “whole” again

Warranty – a financial reserve for anticipated returns

A machine is presumed to be safe if the machine is:

  1. Build according to a “model” code, and
  2. Certified by a competent “third party”

If there is an accident, generally speaking, a “safe” machine is the difference between a worker compensation insurance payment and a lawsuit for negligence.

But what if there is no model code book for the situation?

Hazard analysis introduction

The US Department of Defense originated the study of system safety in MIL-STD-882 primarily driven by the space rocket program. The goal is to apply engineering technique for the protection of personnel, equipment, facility, and the environment. MIL-STD-882 has evolved into numerous analysis techniques. Some are better known than others, with the most popular being:

  • Preliminary Hazard Analysis (PHA)
  • Fault Tree Analysis (FTA)
  • Failure Mode and Effects Analysis (FMEA)
  • What if? Analysis

In commercial industry, especially in semiconductor and solar cell factories using flammable, explosive, and toxic chemistry, the fire department and the insurance carrier often request a hazard analysis by a third party. Their goal is to maximize safety and minimize the financial risk.

CE Mark and SEMI S2 also serve a purpose of hazard analysis, but with more emphasis on conformance of the machinery.

CE is an abbreviation for ‘Conformité Européenne’, French for ‘European Conformity’. The CE Mark for machinery is the manufacturer’s guarantee that the machine meets the safety requirements for the European Union. The safety requirements are expressed in numerous “Directives” that have the force of law in Europe. Evidence that the Directive requirements can be satisfied either through either a direct assessment of the EH&S Annex (Environmental Health and Safety), or by using appropriate normalized standards (European norms).

Semiconductor Equipment and Materials International (SEMI®) is a trade organization whose members volunteer their time to develop consensus standards for equipment that is specific to the manufacturing of semiconductors. The standards are managed under the direction of ANSI to make sure there is no favoritism. The SEMI standards amount to hundreds of pages and cover all aspects of the machine including design, construction, installation, operation, maintenance, and decommissioning. The “S” standards apply to safe construction. The most popular SEMI standard is the SEMI S2-0706 for Environmental, Health and Safety Guidelines for Semiconductor Manufacturing Equipment.

What is the difference between a code check and a hazard analysis?

Code Check Vs. Hazardous Analysis Chart

Describe the hazard analysis techniques

Analysis techniques can be thought of as using either an inductive (bottom up) or deductive (top down) logical method. Deductive reasoning is where the future behavior is drawn from a set of premises, either true of false. Inductive reasoning is where the future behavior is based on hypothetical experience. The conclusion is more than the sum of the observations.

Preliminary Hazard Analysis (PHA) – PHA is the favorite technique for identifying hazards, causal factors, probability, severity, and mitigating safeguards. PHA is first choice in situations where the hazards are primarily electrical, mechanical, and fire.

Fault Tree Analysis (FTA) – FTA is a deductive approach that postulates an undesired “top event” and then takes it down through the numerous chains of events that would logically have to occur.

Failure Mode and Effects Analysis (FMEA) – FMEA is an inductive approach that postulates the effects of various sub-system failures. Classic reliability budgeting is based on component failure rates and redundancy modeling, etc. This kind of analysis could predict, for example, that there is a 1% chance of a space shuttle mission failure.

Markov Analysis – Markov is another inductive approach for modeling the probability of complex system performance over time. The result would be a prediction of system performance attributes including availability (up time and down time), lead time, queuing, reliability, safety, maintenance, etc.

What if? Analysis – This inductive method of analysis is based on the book “Guidelines for Hazard Evaluation Procedures” by the Center for Chemical Process Safety, American Institute for Chemical Engineers. This book is currently in the third edition, published 2008. The analysis is used to postulate and analyze how certain deviations (human error, mechanical failure, etc) can lead to an increase of risk. The analysis is a review of the most likely hazards, and what safeguards are in place (or should be in place) to prevent the hazard from becoming an accident. What if? Analysis is first choice in situations where the hazards are primarily flammable, explosive, and toxic chemistry.



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