Risk = Likelihood * Severity - Can we mitigate the Severity?

[Ronen E]

In the offered example, the problem was that the mounting bolts apparently were not torqued during original installation and apparently were not checked during periodic maintenance, and progressively crept out under sustained load plus thermal cycling and vibration. All of the real-world-plausible mitigations for the GE design would have been to likelihood, not severity.

Back at original design time, severity could have been mitigated by designing the system so that the gamma camera was lateral to the patient, who would have been laying "on edge". Then the severity (of harm to the patient) of the camera falling off its mount would be minor. i.e. it would delay the medical imaging procedure or cause it to be re-located to another imaging suite. Such a camera configuration however would be medically inferior in regard to skeletal alignment and gravitational organ displacement. So instead, apparently, mitigation of likelihood was accepted as the better approach. The problem was that follow-through on that likelihood mitigation was not properly implemented.

If the point of this particular example was to argue that severity cannot be reduced, it's not a good example.

Once again, it comes down to how things are defined, and there are more than one "right" way to do it.

Then the severity (of harm to the patient) of the camera falling off its mount would be minor.

I disagree with this approach. "Camera falling off its mount" is not a harm IMO. Patient death (or injury) is a harm; Camera loss is a harm; Prevention of timely diagnosis is a harm.

The severity of patient death (as unlikely as it may be) in the hazardous situation of a camera falling off its mount right next to the patient is still top. The probability of this hazardous situation leading to this specific harm is the big risk difference between top mounting and lateral mounting.

Cheers,
Ronen.

 

[Ninja]

Lots of wordsmithing going on.

If a camera falls on a patient, the only thing that can limit severity is the weight and shape of the camera, and how far it fell.
If the camera weighs 8grams, the severity is low. If it weighs 300Kg, it is high. If it is 8grams falling from 200meters, it is high.
All of the rest of the design considerations and mounting bolt maintenance is addressing likelihood.

When looking at the severity if something happens, the concept that it HAS happened is presumed. Avoiding the occurrence or acting to avoid the occurrence does not address the severity, it addresses the likelihood.

Will it happen? = likelihood
It has happened already, what's the damage? = severity

 

[kgott]

I think the one think that has been missed in this thread and I should have addressed this in my earlier thread, is that when assessing likelihood and severity, it should be done using a consequence and likelihood matrix. This enables a criteria to used that will enable reasonably consistent assessments to be made by all users. It will also demonstrate that a process is in place for assessing and managing risk.

While I don't know, I suspect that this may have been where the OP was coming from with the original question. Within this context consequence remains the same and only the severity can change.

Using an unwanted event based on motor vehicle rollover example, when assessing risk the consequence remains the same but the severity reduces when a control such as wearing seat belts is introduced.

Similarly, the likelihood reduces further when, for example, a pre-start inspection of the vehicle is introduced as a control measure.

As further control measures are introduced the likelihood reduces again.

 

[fiona_young]

Severity level: 1= Little 2=minor 3=lost working hours 4=disable 5=fatal
likelihood 1= impossible 2=occasionally 3=sometimes 4=often 5= very often
Rt=R*L

Hazard description: Sparks during welding:
Hazard situation: Sparks splitting on operator?s body, burning skins or eyes.
Severity = 2, Likelihood= 5, so Rt= 2*5 = 10,
We implemented some protective measures. We ask operators to use PPE and add protective equipment around.

Actually, in your way of explaining, the measures we take mitigate the Likelihood of occurrence of hazard situation, Spark itself is not hazard. Only when it occurs with operator around will arouse danger.
As I comprehend, the likelihood refers to the hazard situation where people may get hurt, not the likelihood of sparks occurrence.

 

[sagai]

I have spent far to much time in this thread, that's my last here.

Really surprising and scarring to be honest to see the level of ambiguity, inconsistency and unconscious (or conscious) incompetence going on among dedicated professionals for the interpretation of such a fundamental concept like risk management.

It somehow goes back to me that regardless regulators and societies spending horrendous efforts and dedication to this subject, neither the suitability of the corresponding standards and guidances nor the training vehicles lined up behind this scope are actually transferring proper knowledge for public.

 

[Jim Wynne]

Really surprising and scarring to be honest to see the level of ambiguity, inconsistency and unconscious (or conscious) incompetence going on among dedicated professionals for the interpretation of such a fundamental concept like risk management.

I think you're conflating the container and the thing contained. Ambiguity in the mechanisms of FMEA, and there are many, doesn't mean that risk is not properly analyzed and mitigated. The object is risk identification and mitigation, not how the FMEA form gets filled out, or whether the animal that's eating you is a crocodile or an alligator. The problem of competence, if there is one, resides in the idea that the instrument used to record risk analysis activities is the risk analysis.

It somehow goes back to me that regardless regulators and societies spending horrendous efforts and dedication to this subject, neither the suitability of the corresponding standards and guidances nor the training vehicles lined up behind this scope are actually transferring proper knowledge for public.

It's all pretty simple: A risk or potential risk is identified, and a decision as to how to address it is made by cognizant individuals. If there's widespread confusion and consternation regarding how to fill out the form, it indeed means that the form and its underlying instructions are most likely defective, but that's not a good excuse for failing to actually do conscientious risk analysis.

 

[Ninja]

Severity level: 1= Little 2=minor 3=lost working hours 4=disable 5=fatal
likelihood 1= impossible 2=occasionally 3=sometimes 4=often 5= very often
Rt=R*L

Hazard description: Sparks during welding:
Hazard situation: Sparks splitting on operator?s body, burning skins or eyes.
Severity = 2, Likelihood= 5, so Rt= 2*5 = 10,
We implemented some protective measures. We ask operators to use PPE and add protective equipment around.

Actually, in your way of explaining, the measures we take mitigate the Likelihood of occurrence of hazard situation, Spark itself is not hazard. Only when it occurs with operator around will arouse danger.
As I comprehend, the likelihood refers to the hazard situation where people may get hurt, not the likelihood of sparks occurrence.

My opinion,

The hazard is a spark touching the operator.
Anything to prevent a spark from touching the operator is mitigating likelihood.
Anything to lessen the damage caused when a spark touches skin is mitigating severity (can't think of a single thing for this one).

The likelihood of a spark's occurrence factors into the frequency of a spark touching skin...but the spark existing is secondary. The "Failure" (FMEA) is a spark touching skin.

Just out of personal curiosity...did it take a "10" score on a piece of paper to do something about this?
Weren't the repeated shouted curses of the welders enough to do something about it?

 

[Ronen E]

I think you're conflating the container and the thing contained. Ambiguity in the mechanisms of FMEA, and there are many, doesn't mean that risk is not properly analyzed and mitigated. The object is risk identification and mitigation, not how the FMEA form gets filled out, or whether the animal that's eating you is a crocodile or an alligator. The problem of competence, if there is one, resides in the idea that the instrument used to record risk analysis activities is the risk analysis.


It's all pretty simple: A risk or potential risk is identified, and a decision as to how to address it is made by cognizant individuals. If there's widespread confusion and consternation regarding how to fill out the form, it indeed means that the form and its underlying instructions are most likely defective, but that's not a good excuse for failing to actually do conscientious risk analysis.

I don't know how it is in other industries, but the fact of the matter - in the medical devices industry - is that many times proper risk mitigation means that the whole thing becomes economically non-viable. On the other hand, no one wants to halt medical technology progress or to deprive the public of useful devices. So the net effect is, many times, companies going through the motion of "mitigating risk to an acceptable level" while in fact it is "mitigating risk to the budget boundaries", and just making an appearance that the total residual risk is acceptable. At that point complex matrices and calculations come in very handy (regardless of real added value).

This industry is lucky (or unlucky) to have an adverse event reporting system and strict recall regulations that actually demonstrate to whoever is interested, every other week, that risks are often not properly identified and mitigated to an acceptable level. It just seems that some companies can afford it.

 

[Ronen E]

If a camera falls on a patient, the only thing that can limit severity is the weight and shape of the camera, and how far it fell.
If the camera weighs 8grams, the severity is low. If it weighs 300Kg, it is high. If it is 8grams falling from 200meters, it is high.

Again, "a camera falls on a patient" is not a harm, therefore there's no point in assigning a severity ranking to it, and hence such ranking can't be reduced.

"A camera falls on a patient" is a hazardous situation, which can possibly result in the harms: patient death, severe injury, temporary patient inconvenience, or others (depending on the specifics). "The weight & shape of the camera", and "how far it fell", for example, affect which of the harms are likely to eventuate, thus they affect the probability of the hazardous situation leading to a specific harm (likelihood of occurrence).

Reduce the camera's weight from 2000Kg to 200g, and you have significantly reduced the probability of "camera falls on a patient" leading to "patient death" etc. etc. However, that has not reduced the severity of "patient death" at all.

If the post-mitigation probability is close enough to zero, maybe the specific harm can be effectively taken off the list of a certain hazardous situation's potential harms. If that harm was the most severe among them, it can be said, in a way, that this hazardous situation's severity has been reduced (if "hazardous situation's severity" has a meaning at all). However, such a reduction is only a result of actually mitigating probability (bringing it close enough to zero).

 

[sagai]

One more thing for the original poster.

Probably you can utilise the content of this website here:
http://www.hse.gov.uk/welding/index.htm

If you look into the resources section, the whole bunch of professional materials can be reached about welding safety.