ANSI/ISA standard affects existing SISs

It is important to recognize that the “grandfather clause” only addresses the SIS devices that were installed and commissioned prior to the issuance of S84.01-2004. It does not cover the management system aspects of the standard. The following requirements are applicable to all SIS whether existing, modified, or new:

• Documentation (e.g., the safety requirements specification)
• Procedures (e.g., operation, maintenance, bypassing, and testing)
• Training
• Failure tracking (e.g., process demands and dangerous failures)
• Management of change
• Auditing

Changes that potentially impact the SIS requirements should be evaluated through a management of change process. The need to make changes in the process, its control system, its non-SIS protection layers, and its SIS often defines when the “grandfather clause” is no longer applicable.

A second notable item in the OSHA citation is Item 8d, which made specific reference to determining “the required safety integrity levels, as per ANSI/ISA 84.01) of its PLCs and DCS, critical control and safety-instrumented systems.” The new standard includes specific requirements for the assessment of the instrumented systems used to mitigate process risk. A work process provides the key steps in defining the required functionality and risk reduction for the safety functions allocated to the safety instrumented system. The risk reduction requirements are compared to order of magnitude ranges provided in tables in S84.01-2004 to assign the safety integrity level (SIL) to the safety instrumented system.

The third citation related to this paper is Item 24, which concerned the company’s management of change process. The company was cited for not implementing a process “to address the technical impact, as well as the safety and health impact of … (b) Changes made in the staffing level of the plant in 2002 and 2003 to the maintenance staff as it impacted the ability to perform necessary inspections and tests to meet the requirements of the company’s mechanical integrity program.” S84.01-2004 includes a management system that requires, among other things, the identification of the resources responsible for carrying out each lifecycle phase, such as operation, testing, and maintenance.

Draft ISA TR84.00.04
According to draft ISA TR84.04 (expected to be released formally this year), there are two essential steps to determine the applicability of the grandfather clause:

• Confirm that a hazard and risk analysis has been done to determine qualitatively or quantitatively the level of risk reduction needed for each SIF in the SIS.
• Confirm that an assessment of the existing SIF has been performed to determine that it delivers the needed level of risk reduction.

TR84.04 states that, if the above activities have not been done, they should be scheduled for review at the next appropriate opportunity. The evaluation of the SIF should take into account various factors, such as device failure rates and associated design, operation, maintenance, testing, inspection and change management practices. TR84.04 Annex A provides examples of eight grandfather clause methods submitted by SP84 committee members.

Getting Started
The first step in addressing the grandfather clause is the development of a method for “determining and documenting” the applicability of the grandfather status of the SIS. Local regulations, applicable codes and insurance practices sometimes require that specific industrial standards be followed. In all cases, it is the owner/operator who is ultimately responsible for establishing the policies that support safe operation, including the evaluation of existing infrastructure against good engineering practices, such as S84.01-2004.

It is important that the method integrate with the existing process safety management (PSM) program. Management of change and process hazards analysis revalidations drive the re-evaluation of process risk and could challenge the appropriateness of a grandfather claim. Various study findings will require prioritization and actions plans. Work processes and procedures developed for PSM should be leveraged.

When deciding the priority of evaluations or the aggressiveness by which a facility is reviewed, it is important to consider, among other factors, the risk potential and anticipated gaps with the new standard. Those who complied with the intent of the 1996 version of the standard or with other recognized industrial standards should find very few gaps. Those who have not kept pace with their industrial peers may find significant gaps.

Once an owner/operator determines that the existing SIS does not meet the intent of the grandfather clause (i.e., “…the equipment is designed, maintained, inspected, tested, and operating in a safe manner”), there should be a defined decision making process to address the identified deviations. The resolution to the identified deviations should be directed at maintaining process safety. When there is a negative gap between the requirements and reality, these gaps must be addressed. Gaps are often managed based on the size of the gap and the nature of process risk (e.g., frequency and consequence) associated with the potential event. Many companies use a risk-ranking matrix to rank process hazards analysis recommendations. Similar work processes can be used to develop actions plans for closing the gaps.

The Challenge
The challenge facing many owner/operators is that they have not previously classified their automatically initiated shutdowns, so they do not know which ones fall under the umbrella of the standard and which ones do not. At many facilities, shutdowns are grouped under categories, such as emergency shutdown systems, interlocks, critical instruments, etc. No distinction is made between safety, environmental, asset, or business interruption risks.