One of our main areas of experience is around implementation and management of functional safety philosophies.For example we recently managed the assessment, design and implementation of safety systems and control system configuration for 2 major projects at GlaxoSmithKline, Montrose (Scotland).This work is summarised as follows:
Performing Safety Integrity Level assessments in accordance with IEC61508 and IEC61511 and providing the client with a Safety Requirements Report which detailed the areas and activities of greatest risk and the subsequent mitigating actions that were required to reduce that risk.This document is a key stone in functional safety lifecycle management and was used as the basis of design for interlock configuration and maintenance management.One of the projects was on a remote manual plant where trained operators and local operating procedures were previously used as independent layers of protection against asset damage, loss of production, minimising potential releases to the atmosphere etc.Leading industry failure rate databases such as FARADIP.THREE (FAilure RAte Data In Perspective) state that operator error is likely to occur once in every 100 operations.It is therefore important the manufacturers baseline their operation to see where their most hazardous activities are in terms of consequence to personnel, assets, business performance and environment and employ additional layers of protection such as Safety Instrumented Systems (instrument interlocks) to reduce the probability of the unwanted event occurring.The major benefits to the client were reduced lifecycle costs for plant interlocks, reduced risk from adverse events and the realisation that the implementation of a functional safety philosophy was not over engineered with safety interlock systems being installed on every identified hazard.Instead a measured approach was delivered which provided value added engineering.
Review of all new and existing alarms.Firstly, alarm priorities were defined for the client DeltaV process control systems, as initial surveys showed that 60% of all alarms were deemed “Critical”.There are examples throughout industry showing the importance of effective alarm management such as the 1994 explosion at the Texaco Milford Haven refinery which injured twenty-six people and caused damage of around £48 million.Following this, the HSE reported that there were too many alarms and they were poorly prioritised.Indeed in the last 11 minutes before the explosion the two operators had to recognise, acknowledge and act on 275 alarms.Using a policy in line with ISA-S18 JTEC critiqued each alarm for impact on safety, environment, quality etc. and ranked each alarm in line with the newly defined alarm categories.The review mechanism and resulting Alarm Schedule facilitated a reduction in overall configured alarms, detailed operator responses for all operational/system alarms and resulted in fewer alarms being deemed critical.The Alarm Philosophy schedule was the key design document for implementing the process Alarm Management Strategy.
Control system HAZOP (CHAZOP) assessments were performed on the DeltaV systems and newly configured software to validate the robustness of both the system architecture and software build.This was split into two parts; System CHAZOP and Functional CHAZOP.In the first part the DeltaV system was examined for potential consequences resulting from hardware failures, problems with human interfaces and system interfaces.In the Functional CHAZOP the design of critical control modules were challenged and the process HAZOP actions and associated SIL Reports were cross checked.This resulted in actions which prompted code re-design and included items such as critical spares procurement and development of maintenance and operating procedures.
