The Procedure for Potential Consequences:
Consequences:
•
• Begin with a Failure Mode (referred to as FM-1), and a list of all its potentialBegin with a Failure Mode (referred to as FM-1), and a list of all its potential consequences.
consequences.
•
•
Separate the consequences that can be assumed to result whenever the Separate the consequences that can be assumed to result whenever the Failure Mode FM-1 occurs. Identify these as Effects of FM-1.
Failure Mode FM-1 occurs. Identify these as Effects of FM-1.
•
•
Write additional Failure Modes
Write additional Failure Modes for the remaining consequencesfor the remaining consequences (consequences which could result when FM-1 occurs, depending on the (consequences which could result when FM-1 occurs, depending on the circumstances under which FM-1 occurred).
circumstances under which FM-1 occurred).
The new Failure Modes imply that unlikely consequences
The new Failure Modes imply that unlikely consequences will will result by result by including the circumstances under which they occur.
including the circumstances under which they occur.
•
• Separate the consequences that can be assumed to result whenever theSeparate the consequences that can be assumed to result whenever the additional Failure Modes and their special circumstances occur. Identify these additional Failure Modes and their special circumstances occur. Identify these consequences as Effects of the additional Failure Modes.
consequences as Effects of the additional Failure Modes.
Consider this example, which illustrates the Procedure for Potential Consider this example, which illustrates the Procedure for Potential Consequences. During the Effects brainstorm, the team may tend to Consequences. During the Effects brainstorm, the team may tend to identify very severe consequences and the unlikely circumstances under identify very severe consequences and the unlikely circumstances under which they occur. When analyzing the penlight bulb, a team member which they occur. When analyzing the penlight bulb, a team member
may observe that the bulb could prematurely burn out when being used may observe that the bulb could prematurely burn out when being used as a flashlight, the resulting darkness causing the user to trip, fall, and as a flashlight, the resulting darkness causing the user to trip, fall, and be injured. Another member may observe
be injured. Another member may observe that atmospheric pressurethat atmospheric pressure variation could cause the bulb to explode while
variation could cause the bulb to explode while being used for an eyebeing used for an eye examination, resulting in injury. Such extraneous predicaments are examination, resulting in injury. Such extraneous predicaments are typical of a brainstorm and can be
typical of a brainstorm and can be expected. But rather than write aexpected. But rather than write a new Failure Mode for every bizarre situation recorded by the team, t new Failure Mode for every bizarre situation recorded by the team, thehe events should be grouped into a broad Effect category, such as "
events should be grouped into a broad Effect category, such as "injuryinjury or death
or death". Ultimately, Effects are categorized into one of ten groups,". Ultimately, Effects are categorized into one of ten groups, according to
according to Severity. Severity. It is advantagIt is advantageous to write eous to write Failure Modes Failure Modes thatthat encompass all the Effects in a Severity grouping, such as "
encompass all the Effects in a Severity grouping, such as "Fails toFails to provide 3 ± .5 candela of light under critical
provide 3 ± .5 candela of light under critical conditions
conditions". All product failures that lead to ". All product failures that lead to injury or death areinjury or death are automatically included; there is no need to attempt to
automatically included; there is no need to attempt to identify all theidentify all the circumstances under
circumstances under which injury or which injury or death could redeath could result. sult. The tradeoff The tradeoff for this convenience is that the likelihood of failure under
for this convenience is that the likelihood of failure under anyany criticalcritical
The first step in analyzing risk is to quantify the Severity of the The first step in analyzing risk is to quantify the Severity of the Effects. Effects are rated on a scale of 1 to 10, 10 being the most Effects. Effects are rated on a scale of 1 to 10, 10 being the most
severe. The team should agree on consistent evaluation criteria and severe. The team should agree on consistent evaluation criteria and a sensible ranking system. The design and process ranking systems a sensible ranking system. The design and process ranking systems presented in
presented in Table 1Table 1 andand Table 2Table 2 are based on AIAG standards.are based on AIAG standards.
Effects are evaluated as a group when assessing risk, even though Effects are evaluated as a group when assessing risk, even though they are assigned Severity values individually. It is assumed that all they are assigned Severity values individually. It is assumed that all Effects will result if the Failure Mode occurs. Therefore, the most Effects will result if the Failure Mode occurs. Therefore, the most serious Effect takes precedence when evaluating risk potential. This serious Effect takes precedence when evaluating risk potential. This model accounts for Causes that have multiple Effects. Issuing
model accounts for Causes that have multiple Effects. Issuing design and process changes can reduce Severity ratings.
design and process changes can reduce Severity ratings.
Notes of interest:
Notes of interest: