IntroductionIn late 2011 the Bureau of Safety and Environmental Enforcement (BSEE) introduced the “Revisions to SEMS Rule”, more commonly known as SEMS II. Public comments have been received but the rule itself is still in draft form.
Some safety management professionals feel that SEMS II is too prescriptive and should be modified before being released in its final form. The purpose of this short article is to contribute to the discussion by providing information and thoughts on prescriptive and non-prescriptive standards. The article is organized into the following sections:
A prescriptive approach can also be used for engineering design. For example, API RP 14C, which has been incorporated into SEMS, states the following with regard to safety systems.
The safety system should provide two levels of protection to prevent or minimize the effects of an equipment failure within the process. The two levels of protection should be independent of and in addition to the control devices used in normal process operation. In general, the two levels should be provided by functionally different types of safety devices for a wider spectrum of coverage.
Many experts believe that the RP 14C standard is out of date given the sophistication and reliability of modern instrumentation systems. And those experts may be right. But a design engineer has to follow the rule as written. If someone disagrees with the rule, then they have to work on revising that rule.
Prescriptive standards are sometimes criticized for being “just a checkbox”. But “checking the box” provides a foundation for other, more subjective types of risk analysis and measurement. For example the SEMS rule to do with operating procedures states, “(a)(6) You must develop and implement written procedures . . that address . . . Bypassing and flagging out-of-service equipment.” If an auditor or inspector goes on to a platform and finds that there are no procedures for safely bypassing equipment then he or she will certainly “check the box”, and rightly so.
With regard to the audits the prescriptive approach offers the following benefits:
It is up to the managers, technical experts and the operations/maintenance personnel to determine how this goal is to be achieved. This lack of detail explains why process safety standards, such as OSHA’s PSM or BSEE’s SEMS, are so short. These standards simply require that a program be in place, that it be followed and that it works, i.e., that it be effective in reducing the number of incidents. The program that they develop and implement is unique to that facility.
Non-prescriptive management programs have to be performance-based because the only measure of success is success. Hence the only true measure of success of the program is not to have incidents. But, from a theoretical point of view, such a goal is impossible to achieve. No matter how well run a facility may be accidents will occur; risk can never be zero. For this reason some PSM professionals chose not to use the terms “compliance” on the grounds that true compliance can never be achieved.
The example provided above to do with operating procedures is basically non-prescriptive. There must be a (prescriptive) procedure for bypassing out-of-service equipment, but the SEMS rule provides no guidance as to how that procedure should be written, how detailed it should be or how it should be communicated to the facility personnel. Each facility will do what it considers to be the best for its own operation, and a program developed in one location may not work elsewhere.
All Standards Fundamentally Non-PrescriptiveIt can be argued that, in the limit, all standards are non-prescriptive. Standards such as RP 14C are typically written by a committee. The committee consists of highly experienced experts in the field. They share their experiences and knowledge to come up with a prescriptive standard, but one that is — at root — subjective, i.e., it is still based on judgment.
Acceptable RiskIf it is decided to follow a non-prescriptive approach to the setting of standards then criteria are needed to decide what level of risk is acceptable. For example, if an engineering design team decides not to follow the requirements of RP 14C regarding the number and type of safety devices on a pressure vessel, then that team must justify whatever risk criteria it does choose. They can do this with the following approach.
As Low as Reasonably Practicable Risk - ALARPThe concept of ‘As Low as Reasonably Practical’ is sometimes used to determine acceptable risk. This term is usually abbreviated to ALARP (sometimes facetiously referred to ‘As Low as Regulators Permit’). The idea behind this term is that risk should be reduced to a level that is as low as possible without requiring ‘excessive’ investment.
One panel has developed the following guidance for giving a value to ALARP.
Use of Management ElementsMost discussions to do with performance-based standards, including what has been written so far in this article, tend to assume that success will be measured through a quantitative assessment of risk. However another approach is to develop standards around management elements. Most safety management systems are made up of a mix of technical and management elements, as can be seen in the following list which consists of the elements of SEMS.
The Regulator's Dilemma
If a regulator approves those programs then he or she has implicitly stated that the program is satisfactory and that the assumed level of risk is acceptable. If, later on, a deficiency is found with the program (either during an audit or an incident investigation) then the regulator must take some responsibility (and the owner/operator can deny all responsibility).
The UK HSE (2005) responded to this difficulty with the following statement,
. . . “acceptance” requires satisfaction with the duty holder’s approach to identifying and meeting health and safety needs. HSE “accepts” the validity of the described approach as being capable, if implemented as described, of achieving the necessary degree of risk control, but HSE does not confirm the outcomes of that approach.
Finally, regulatory agencies in particular will never place a numerical value on human life and suffering because any number that they develop would inevitably generate controversy. Hence they cannot develop quantitative, risk-based measurement criteria.
This paper started out by considering whether the proposed SEMS II rule could be considered prescriptive or non-prescriptive.
Each of these new sections are written in much the same way as elements of the original SEMS rule. They are of about the same length and contain about the same level of detail. However, the titles themselves suggest a broader management approach, and so one that is considerably less prescriptive than SEMS. This comment applies in particular to the third of the above elements: Employee Participation. This element contains five paragraphs, of which the first is key,
(a) Management must consult with their employees on the development and implementation of the company’s SEMS program.
Copyright © Sutton Technical Books 2007-2012. All rights reserved
PO Box 2217