Thinking about risk through methods

Risk management is  a topic with a large number of methods. Within the process industries, semi-quantitative methods are popular, in particular for determining required SIL for safety instrumented functions (automatic shutdowns, etc.). Two common approaches are known as LOPA, which is short for “layers of protection analysis” and Riskgraph. These methods are sometimes treated as “holy” by practicioners, but truth is that they are merely coginitive aids in sorting through our thinking about risks.


Riskgraph #sliderule – methods are formalisms. See picture on Instagram


In short, our risk assessment process consists of a series of steps here:

  • Identify risk scenarios
  • Find out what can reduce the risk that you have in place, like design features and procedures
  • Determine what the potential consequences of the scenario at hand is, e.g. worker fatalities or a major environmental disaster
  • Make an estimate of how likely or credible you think it is that the risk scenario should occur
  • Consider how much you trust the existing barriers to do the job
  • Determine how trustworthy your new barrier must be for the situation to be acceptable

Several of these bullet points can be very difficult tasks alone, and putting together a risk picture that allows you to make sane decisions is hard work. That’s why we lean on methods, to help us make sense of the mess that discussions about risk typically lead to.

Consequences can be hard to gauge, and one bad situation may lead to a set of different outcomes. Think about the risk of “falling asleep while driving a car”. Both of these are valid consequences that may occur:

  • You drive off the road and crash in the ditch – moderate to serious injuries
  • You steer the car into the wrong lane and crash head-on with a truck – instant death

Should you think about both, or pick one of them, or another consequence not on this list? In many “barrier design” cases the designer chooses to design for the worst-case credible consequence. It may be difficult to judge what is really credible, and what is truly the worst-case. And is this approach sound if the worst-case is credible but still quite unlikeley, while at the same time you have relatively likely scenarios with less serious outcomes? If you use a method like LOPA or RiskGraph, you may very well have a statement in your method description to always use the worst-case consequence. A bit of judgment and common sense is still a good idea.

Another difficult topic is probability, or credibility. How likely is it that an initiating event should occur, and what is the initating event in the first place? If you are the driver of the car, is “falling asleep behind the wheel” the initating event? Let’s say it is. You can definitely find statistics on how often people fall asleep behind the wheel. The key question is, is this applicable to the situation at hand? Are data from other countries applicable? Maybe not, if they have different road standards, different requirements for getting a driver’s license, etc. Personal or local factors can also influence the probability. In the case of the driver falling asleep, the probabilities would be influenced by his or her health, stress levels, maintenance of the car, etc. Bottom line is, also the estimate of probability will be a judgment call in most cases. If you are lucky enough to have statistical data to lean on, make sure you validate that the data are representative for your situation.Good method descriptions should also give guidance on how to do these judgment calls.

Most risks you identify already have some risk reducing barrier elements. These can be things like alarms and operating procedures, and other means to reduce the likelihood or consequence of escalation of the scenario. Determining how much you are willing to rely on these other barriers is key to setting a requirement on your safety function of interest – typically a SIL rating. Standards limit how much you can trust certain types of safeguards, but also here there will be some judgment involved. Key questions are:

  • Are multiple safeguards really independent, such that the same type of failure cannot know out multiple defenses at once?
  • How much trust can you put in each safeguard?
  • Are there situations where the safeguards are less trustworthy, e.g. if there are only summer interns available to handle a serious situation that requires experience and leadership?

Risk assessmen methods are helpful but don’t forget that you make a lot of assumptions when you use them. Don’t forget to question your assumptions even if you use a recognized method, especially not if somebody’s life will depend on your decision.

Why functional safety audits are useful

Functional safety work usually involves a lot of people, and multiple organizations. One key success factor for design and operation of safety instrumented systems is the competence of the people involved in the safety lifecycle. In practice, when activities have been omitted, or the quality of the work is not acceptable, this is discovered in the functional safety assessment towards the end of the project, or worse, it is not discovered at all. The result of too low quality is lower integrity of the SIS as a barrier, and thus higher risk to people, assets and environment – without the asset owner being aware of this! Obviously a bad situation.

Knowing how to do your job is important in all phases of the safety lifecycle. Functional safety audits can be an important tool for verification – and for motivating organization’s to maintain good competence mangement systems for all relevant roles.

Competence management is a key part of functional safety management. In spite of this, many companies have less than desirable track records in this field. This may be due to ignorance, or maybe because some organizations view a «SIL» as a marketing designation rather than a real risk reduction measure. Either way – such a situation is unacceptable. One key tool for ensuring everybody involved understands what their responsibilities are, and makes an effort to learn what they need to know to actually secure the necessary system level integrity, is the use of functional safety audits. An auditing program should be available in all functional safety projects, with at least the following aspects:

  • A procedure for functional safety audits should exist
  • An internal auditing program should exist within each company involved in the safety lifecycle
  • Vendor auditing should be used to make sure suppliers are complying with functional safety requirements
  • All auditing programs should include aspects related to document control, management of change and competence management

Constructive auditing can be an invaluable part of building a positive organizational culture – where quality becomes as important to every function involved in the value chain – from the sales rep to the R&D engineer.

One day statements like “please take the chapter on competence out of the management plan, we don’t want any difficult questions about systems we do not have” may seem like an impossible absurdity.

How independent should your FSA leader be?

Functional safety assessment is a mandatory 3rd party review/audit for functional safety work, and is required by most reliability standards. In line with good auditing practice, the FSA leader should be independent of the project development. Exactly what does this mean? Practice varies from company to company, from sector to sector and even from project to project. It seems reasonable to require a greater degree of independence for projects where the risks managed through the SIS are more serious. IEC 61511 requires (Clause that functional safety assessments are conducted with “at least one senior competent person not involved in the project design team”. In a note to this clause the standard remarks that the planner should consider the independence of the assessment team (among other things). This is hardly conclusive.

If we go to the mother standard IEC 61508, requirements are slightly more explicit, as given by Clause 8.2.15 of IEC 61508-1:2010, which states that the level of independence shall be linked to perceived consequence class and required SILs. For major accident hazards, two categories are used in IEC 61508:

  • Class C: death to several people
  • Class D: very many people killed

For class C the standard accepts the use of an FSA team from “independent department”, whereas for class D only an “independent organization” is acceptable. Further, also for class C, an independent organization should be used if the degree of complexity is high, the design is novel or the design organization is lacking experience with this particular type of design. There are also requirements based on systematic capability in terms of SIL but those are normally less stringent in the context of industrial processes than the consequence based requirements to FSA team independence. The standard also specifies that compliance to sector specific standards, such as IEC 61511, would make a different basis for consideration of independence acceptable.

In this context, the definitions of “independent department” and “independent department” are given in Part 4 of the standard. An independent department is separate from and distinct from departments responsible for activities which take place during the specified phase of the overall system or software lifecycle subject to the validation activity. This means also, that the line managers of those departments should not be the same person. An independent organization is separate by management and other resources from the organizations responsible for activities that take place during the lifecycle phase. This means, in practice, that the organization leading a HAZOP or LOPA should not perform the FSA for the same project if there are potential major accident hazards within the scope, and preferably also not if there are any significant fatal accident risks in the project. Considering the requirement of separate management and resource access, it is not a non-conformity if two different legal entities within the same corporate structure perform the different activities, provided they have separate budgets and leadership teams.

If we consider another sector specific standard, EN 50129 for RAMS management in the European railway sector, we see that similar independence requirements exist for third-party validation activities. Figure 6 in that standard seemingly allows the assessor to be a part of the same organization as an organization involved in SIS development, but further requires for this situation that the assessor has an authorization from the national safety authority, is completely independent form the project team and shall report directly to the safety authorities. In practice the independent assessor is in most cases from an independent organization.

It is thus highly recommended to have an FSA team from a separate organization for all major SIS developments intended to handle serious risks to personnel; this is in line with common auditing practice in other fields.

Why is this important? Because we are all humans. If we feel ownership to a certain process, product or affiliation with an organization, it will inevitably be more difficult for us to point out what is not so good. We do not want to hurt people we work with by stating that their work is not good enough – even if we know that inferior quality in a safety instrumented system may actually lead to workers getting killed at work later. If we look to another field with the same type of challenges but potentially more guidance on independence, we can refer to the Sarbanes-Oxley act of 2002 from the United States. The SEC has issued guidelines about auditor independence and what should be assessed. Specifically they include:

  1. Will a relationship with the auditor create a mutual or conflicting interest with their audit client?
  2. Will the relationship place the auditor in the position of auditing his/her own work?
  3. Will the relationship result in the auditor acting as management or an employee of the audit client?
  4. Will the relationship result in the auditor being put in a position where he/she will act as an advocate for the audit client?

It would be prudent to consider at least these questions if considering using an organization that is already involved in the lifecycle phase subject to the FSA.

New security requirements to safety instrumented systems in IEC 61511

IEC 61511 is undergoing revision and one of the more welcome changes is inclusion of cyber security clauses. According to a presentation held by functional safety expert Dr. Angela Summers at the Mary Kay Instrument Symposium in January 2015, the following clauses are now included in the new draft – the standard is planned issued in 2016:

  • Clause 8.2.4: Description of identified [security] threats for determination of requirements for additional risk reduction. There shall also be a description of measures taken to reduce or remove the hazards.
  • Clause 11.2.12: The SIS design shall provide the necessary resilience against the identified security risks

What does this mean for asset owners? It obviously makes it a requirement to perform a cyber security risk assessment for the safety instrumented systems (SIS). Such information asset risk assessments should, of course, be performed in any case for automation and safety systems. This, however, makes it necessary to keep security under control to obtain compliance with IEC 61511 – something that is often overlooked today, as described in this previous post. Further, when performing a security study, it is important that also human factors and organizational factors are taken into account – a good technical perimeter defense does not help if the users are not up to the task and have sufficient awareness of the security problem.

In the respect of organizational context, the new Clause 11.2.12 is particularly interesting as it will require security awareness and organizational resilience planning to be integrated into the functional safety management planning. As noted by many others, we have seen a sharp rise in attacks on SCADA systems over the past few years – these security requirements will bring the reliability and security fields together and ensure better overall risk management for important industrial assets. These benefits, however, will only be achieved if practitioners take the full weight of the new requirements on board.