Preliminary Hazard Analysis (PHA) Packet

This packet is intended for use in the fourth year mechanical engineering design sequence. The material in this packet should help design teams perform a Preliminary Hazard Analysis (PHA) on their design projects. A PHA is a design tool that helps engineers identify and deal with hazards in the earliest stages of design. By performing a PHA, the students will be more likely to recognize and correct the hazards associated with their designs.

Time for presentation is approximately 30 minutes.

Objectives:

1. To develop an understanding of the procedure used to perform a PHA.
2. To understand the benefits of using a PHA.
3. Increase awareness of safety issues.
4. To help students identify and correct hazards in their design projects.

This packet includes the following items:

· Lecture material for the instructor
· Overheads to be used during the lecture
· Example problem for use in class (integrated in the overheads)
· Assignment description and student handouts
· Assignment grade sheet

Download the Preliminary Hazard Analysis Module in printable Adobe Acrobat Format (pdf). This includes overheads in a ready to use format.

Homework problem solutions, exam problems, and exam solutions are available to qualified recipients. Send an email with request information to Dr. Donald Bloswick.

Preliminary Hazard Analysis (PHA) Lecture Outline

I. Introduction to Preliminary Hazard Analysis (PHA)

1.      (Overhead #1) Overview

a)      A Preliminary Hazard Analysis is used to identify hazards associated with a design while the design is still in its earliest stages.

b)     Appropriate measures may then be incorporated into the design to deal with the hazards.

c)      Subsequent hazard analyses should then be performed as the design progresses to deal with new hazards as they are identified and to assess the ability of the design to minimize the harmful effects of the expected hazards. Failure Modes and Effects Analyses (FMEA), Failure Modes, Effects and Criticality Analyses (FMECA), and Fault Tree Analyses (FTA) are also commonly used to assess and minimize the hazards of a design.

2.      (Overhead #2) Benefits of PHA

a)      The final product must be “safe”. A PHA helps designers to identify and deal with hazards.

b)     Modifications that are made in the earlier design stages are less costly and easier to implement than modifications that are made in the later design stages.

c)      A PHA helps the designer to anticipate hazards, thereby reducing the number of surprises that occur during the design process. In many cases, taking the time to perform a PHA may actually speed up the design process.

II. (Overhead #3) Break down of steps in PHA

1.      Identify known hazards.

a)      (Overhead #4) Preliminary hazards matrix.

                                             i.       A preliminary hazard matrix divides hazards into generic groups.

                                           ii.       The preliminary hazard matrix is used to associate potential failures with these generic hazards groups.

b)     (Overhead #5) Hazards checklist.

                                             i.       A hazards checklist may be used to identify specific hazards.

                                           ii.       No hazards checklist should be considered complete since hazards that are not included on the hazards checklist may exist or arise during the design process.

c)      The following sources may also be useful in identifying hazards:

                                             i.       Equipment descriptions

                                           ii.       Accident/incident report data

                                          iii.       Past operational history of similar tasks

                                         iv.       Review of other historical records

(Adapted from Vincoli, Jeffrey W., Basic Guide to System Safety, Van Nostrand Reinhold, New York, New York, 1993, p. 68.)

2. (Overhead #6) Determine the cause(s) of these conditions.

a)      The possible causes for a particular hazard are often numerous. The PHA should attempt to identify all possible causes.

b)     The causes of hazardous conditions will often become more apparent as the details of the design are better defined.

3.      Determine the potential effect of these conditions on personnel, equipment, facilities, and operations.

a)      The failure of one part of a system may cause the failure of other parts of the system. The PHA should estimate the overall effects of a hazard or failure.

b)     (Overhead #7) The severity of the effects of a hazard or failure may be categorized as follows:

i. Catastrophic (May cause multiple injuries, fatalities, or loss of a facility)

ii. Critical (May cause severe injury, severe occupational illness, or major property damage)

iii. Marginal (May cause minor injury, minor occupational illness resulting in lost workdays, or minor property damage)

iv. Negligible (Probably would not affect the safety or health of personnel, but is still in violation of a safety or health standard)

Bloswick, Donald S., Systems Safety Analysis, NIOSH P.O. #939341

4. (Overhead #8) Determine the probability that an accident will be caused by the hazard.

a) Generally, estimates of the probability of an accident in the early design stages are very subjective.

b) (Overhead #9) Accident probabilities may be loosely categorized as follows:

i. Probable (Likely to occur immediately or within a short period of time)

ii. Reasonably Probable (Probably will occur in time)

iii. Remote (Possible to occur in time)

iv. Extremely Remote (Unlikely to occur)

Bloswick, Donald S., Systems Safety Analysis, NIOSH P.O. #939341

5. (Overhead #10) Establish initial design and procedural requirements to eliminate or control these hazards.

Bloswick, Donald S., Systems Safety Analysis, NIOSH P.O. #939341

III. Example (pressure cooker)

1. The five critical components of a PHA are often assembled in a tabular form.

2. (Overheads #11 and #12) Follow the example through the five steps of PHA for several hazards. (The students have a copy of the example PHA in their assignment handouts.)

IV. (Overhead #13) Post-PHA design

1. Procedures must be established to ensure that hazard elimination or control measures are effectively incorporated into the design.

2. (Overhead #14) A hazard report may be created for each new hazard as it is identified during the design process. The hazard report is used to track a hazard through the design process to make sure that appropriate measures are incorporated into the design to eliminate or to adequately control the hazard. (Hammer, 355).

3. (Overhead #15) The ability of the design to eliminate or at least control every identified hazard must be verified by test results.

4. A hazard report may be signed off only after the design has proven effective in eliminating or adequately controlling the hazard.

V. (Overhead #16) Limitations of PHA

1. PHA will only be as effective as the design team’s ability to recognize hazards. If a hazard is not recognized, the PHA will be of little help in minimizing the hazard.

2. A PHA does not effectively account for interactions between hazards.

VI. Lecture Summary

1. Designers may use PHA to assist in controlling and/or eliminating the hazards associated with a design.

2. Some additional time must be spent early in the design process to perform a PHA. However, the safety and economic benefits of using a PHA will provide a significant return on the invested time for the PHA.

Overhead 1

Preliminary Hazard Analysis (PHA)

Qualitative analysis performed in the earliest stages of design:

1. Helps to identify potential hazards.

2. Helps to formulate appropriate measures to deal with hazards.

Overhead 2

Benefits of PHA

1. Helps ensure the product is safe.

2. Modifications are less expensive and easier to implement in the earlier stages of design.

3. Decreases design time by reducing the number of surprises.

Overhead 3

PHA Steps

1. Identify known hazards.

2. Determine the cause(s) of the hazards.

3. Determine the effects of the hazards.

4. Determine the probability that an accident will be caused by a hazard.

5. Establish initial design and procedural requirements to eliminate or control hazards.

Overhead 4

Preliminary Hazard Matrix

System/Operation ____________________________

Evaluator ___________________________________

Date ______________

HAZARD GROUP	POTENTIAL AREAS FOR FAILURE
	Structural	Electrical	Pressure	Leakage/Spill	Mechanical	Procedural
Collision/Mechanical Damage
Loss of Habitable Atmosphere
Corrosion
Contamination
Electric Shock
Fire
Pathological
Psychological
Temperature extremes
Radiation
Explosion

(Adapted from Vincoli, Jeffrey W., Basic Guide to System Safety, Van Nostrand Reinhold, New York, New York, 1993, p. 68.)

Overhead 5

Hazards Checklist (Page 1 of 4)

System/Operation ____________________________
Evaluator ___________________________________
Date ______________

Electrical
___ Shock
___ Burns
___ Overheating
___ Ignition of Combustibles
___ Inadvertent Activation
___ Power Outage
___ Distribution Feedback
___ Unsafe Failure to Operate
___ Explosion/Electrical (Electrostatic)
___ Explosion/Electrical (Arc)

Mechanical
___ Sharp Edges/Points
___ Rotating Equipment
___ Reciprocating Equipment
___ Pinch Points
___ Lifting Weights
___ Stability/Topping Potential
___ Ejected Parts/Fragments
___ Crushing Surfaces

Pneumatic/Hydraulic Pressure
___ Overpressurization
___ Pipe/Vessel/Duct Rupture
___ Implosion
___ Mislocated Relief Device
___ Dynamic Pressure Loading
___ Relief Pressure Improperly Set
___ Backflow
___ Crossflow
___ Hydraulic Ram
___ Inadvertent Release
___ Miscalibrated Relief Device
___ Blown Objects
___ Pipe/Hose Whip
___ Blast

Acceleration/Deceleration/Gravity
___ Inadvertent Motion
___ Loose Object Translation
___ Impacts
___ Falling Objects
___ Fragments/Missiles
___ Sloshing Liquids
___ Slip/Trip
___ Falls

Temperature Extremes
___ Heat Source/Sink
___ Hot/Cold Surface Burns
___ Pressure Evaluation
___ Confined Gas/Liquid
___ Elevated Flammability
___ Elevated Volatility
___ Elevated Reactivity
___ Freezing
___ Humidity/Moisture
___ Reduce Reliability
___ Altered Structural Properties(
e.g., Embrittlement)

Radiation (Ionizing)
___ Alpha
___ Beta
___ Neutron
___ Gamma
___ X-Ray

Radiation (Nonionizing)
___ Laser
___ Infrared
___ Microwave
___ Ultraviolet

Notes:
1. Neither this nor any other hazards checklist should be considered complete. This list should be enlarged as experience dictates. This list contains intentional redundant entries.
2. This checklist was adapted from "Preliminary Hazard Analysis (Lecture Presentation)," R.R. Mohr, Sverdup Technology, Inc., June 1993 (Fourth Edition).

Overhead 6

PHA Steps

1. Identify known hazards.2. Determine the cause(s) of the hazards.

3. Determine the effects of the hazards.

4. Determine the probability that an accident will be caused by a hazard.

5. Establish initial design and procedural requirements to eliminate or control hazards.

Overhead 7

Hazard Severity Classifications

Catastrophic - Causes multiple injuries, fatalities, or loss of a facility.

Critical - May cause severe injury, severe occupational illness, or major property damage.

Marginal - May cause minor injury, minor occupational illness resulting in lost workdays, or minor property damage.

Negligible - Probably would not affect the safety or health of personnel, but is still in violation of a safety or health standard.

Overhead 8

PHA Steps

1. Identify known hazards.

2. Determine the cause(s) of the hazards.

3. Determine the effects of the hazards.

4. Determine the probability that an accident will be caused by a hazard.

5. Establish initial design and procedural requirements to eliminate or control hazards.

Overhead 9

Accident Probability Classifications

Probable - Likely to occur immediately or within a short period of time.

Reasonably Probable - Probably will occur in time.

Remote - Possible to occur in time.

Extremely Remote - Unlikely to occur.

Overhead 10

PHA Steps

1. Identify known hazards.

2. Determine the cause(s) of the hazards.

3. Determine the effects of the hazards.

4. Determine the probability that an accident will be caused by a hazard.

5. Establish initial design and procedural requirements to eliminate or control hazards.

Overhead 11

Pressure Cooker Safety Features

1. Safety valve relieves pressure before it reaches dangerous levels.

2. Thermostat opens circuit through heating coil when the temperature rises above 250° C.

3. Pressure gage is divided into green and red sections. "Danger" is indicated when the pointer is in the red section.

Overhead 12

Preliminary Hazard Analysis (Pressure Cooker)

Hazard	Cause	Effect	Probability of Accident due to Hazard	Corrective or Preventive Measures
Shock	Faulty wire insulation creates circuit to ground through operator when operator touches cord.	Mild shock to electrocution depending on the overall resistance to current flow through the person's body. The overall resistance would depend on factors such as the resistance of the person's shoes, whether or not his or her fingers were wet, and the condition of the insulation.	Remote	Use insulation that is very resistant to deterioration. Use a grounded cord (3-prong plug). Only plug the pressure cooker into outlets that are equipped with a ground-fault circuit interrupter.
Fire	Sparks are generated near a flammable material when current passes from the cord to another object at a point where the insulation is faulty.	Significant damage to system and surroundings.	Extremely remote (A fault must be present in the insulation, sparks must be generated, and a flammable material must be located very close to the cord. The probability that all of these conditions will exist simultaneously is very low.)	Same three used for shock. Keep flammable materials away from system.
Burn	Person touches hot pressure cooker surface or hot materials inside pressure cooker. Steam from safety valve burns person.	First or second degree burns depending on how long the person's skin is in contact with the hot surface or material.	Reasonably probable	Use hot pads if the pressure cooker must be touched. Keep pressure cooker out of the reach of children. Put a cover on the safety valve to spread the steam out so that it is not concentrated enough to burn the skin
Explosion	Thermostat and safety valve fail, and no one notices that the pressure gage indicates "danger."	Sever injuries or fatalities. Loss of system. Damage to surroundings.	Remote	Use only high quality thermostats and safety valves. Use more redundancies. (Example: Two safety valves)

Overhead 13

Post-PHA Design

1. Establish procedures to ensure that hazard elimination or control measures are effectively incorporated into the design.

2. Prepare a hazard report for each hazard.

3. Verify that the design eliminates or adequately controls the hazard.

4. Sign off on the hazard report.

Overhead 14

HAZARD REPORT

IDENTIFICATION/TITLE ___________________________ REPORT NO. ________________

DATE INITIATED: ___________

EQUIPMENT/SYSTEM/SYSTEM _____________________ DATE THIS REPORT: _________

SIGNATURE: ________________

__________________________________________________

CLOSEOUT DATE: ___________

PERSON INITIATING REPORT: ______________________

DESCRIPTION OF HAZARD AND ACCIDENT WHICH MIGHT RESULT:

EVENTS AND CONDITIONS WHICH MIGHT CONTRIBUTE TO THE HAZARD OR ACCIDENT:

POSSIBLE MEANS TO ELIMINATE OR CONTROL HAZARD OR ACCIDENT EFFECTS:

ESIMATED PROBABILITY OF ACCIDENT OCCURRENCE:

CURRENT CONDITION WITH CONTROL

FREQUENT _____________________ _______________

REASONABLY PROBABLE _____________________ _______________

OCCASIONAL _____________________ _______________

REMOTE _____________________ _______________

EXTREMELY IMPROBABLE _____________________ _______________

MEANS OF VERIFYING ADEQUACY OF CONTROL/APPLICABLE SAFETY REQUIREMENTS:

ORGANIZATION/PERSON TO TAKE ACTION:

STATUS OF ACTION TO BE OR HAVE BEEN TAKEN:

(Adapted from Hammer, W., Occupational Safety Management and Engineering, 4^th ed., Prentice Hall, Englewood Cliffs, New Jersey, 1989, p. 555)

Overhead 15

Post-PHA Design

1. Establish procedures to ensure that hazard elimination or control measures are effectively incorporated into the design.

2. Prepare a hazard report for each hazard.

3. Verify that the design eliminates or adequately controls the hazard.

4. Sign off on the hazard report.

Overhead 16

Limitations of PHA

1. Hazards must be foreseen by the designers.

2. The effects of interactions between hazards are not easily recognized.

Preliminary Hazard Analysis (PHA) Assignment

A Preliminary Hazard Analysis (PHA) is commonly performed to help designers assess the effects of hazardous conditions in the earliest stages of a design. As part of the PHA, designers propose solutions that may be used to eliminate or control the hazards. By implementing design features to deal with these hazards early in the design process, the overall safety of the design may be improved, and the number of costly redesigns may be reduced.

A Preliminary Hazard Analysis involves the assessment of a design using the following five steps:

1. Identify known hazardous conditions and potential failures.
2. Determine the cause(s) of these conditions and potential failures.
3. Determine the potential effect of these conditions and potential failures on personnel, equipment, facilities, and operations.
The severity of the potential effects of a hazard or failure may be categorized as follows:

I. Catastrophic (May cause multiple injuries, fatalities, or loss of a facility)
II. Critical (May cause severe injury, severe occupational illness, or major property damage)
III. Marginal (May cause minor injury or minor occupational illness resulting in lost workdays, or minor property damage)
IV. Negligible (Probably would not affect the safety or health of personnel, but is still in violation of a safety or health standard)

4. Determine the probability that the hazard will cause an accident.
Probabilities of accidents may be loosely categorized as follows:

I. Probable (Likely to occur immediately or within a short period of time)
II. Reasonably Probable (Probably will occur in time)
III. Remote (Possible to occur in time)
IV. Extremely Remote (Unlikely to occur)

5. Establish initial design and procedural requirements to eliminate or control these hazardous conditions and potential failures.

For this assignment, perform a Preliminary Hazard Analysis on your design project. The PHA should be presented in a tabular form. Any additional information or considerations relating to the safety of your product that is not easily presented in a tabular form should be discussed in the memo accompanying the PHA. A preliminary hazard matrix form, a hazards checklist, and an example PHA for a pressure cooker are included in this handout to help you with your assignment.

Attachments

· Preliminary Hazard Matrix Form
· Hazards Checklist
· PHA of a Pressure Cooker
· Grade sheet

These attachements are available in the downloadable pdf file.

Bibliography

Bloswick, Donald S., Systems Safety Analysis, NIOSH P.O. #939341

Goldberg, B.E., et al., System Engineering "Toolbox" for Design-Oriented Engineers, NASA Reference Publication 1358, Marshall Space Flight Center, Alabama, 1994.

Hammer, W., Occupational Safety Management and Engineering, Fourth Edition, Prentice Hall, Englewood Cliffs, New Jersey, 1989.

Vincoli, Jeffrey W., Basic Guide to System Safety, Van Nostrand Reinhold, New York, New York, 1993, p. 68.)