Role and responsibilities of EPCs in the safety lifecycle of a project

An EPC’s perspective of executing SIL projects

This article indicates the importance of Safety Instrumented Systems (SIS), Role and responsibilities of EPCs in the safety lifecycle of a project as per IEC61511 edition 2. Includes a case study revealing the challenges faced by an EPC during SIL implementation.
 
^ Role and responsibilities of EPCs in the safety lifecycle of a project

Article by Iyer Chandramouli, Chief Engineer – Process Control and Automation, Tecnimont Private Limited
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Safety Instrumented Systems (SIS) are often regarded as having a very high initial and maintenance costs. However, as late Mr. Trevor Kletz stated “If you think safety is expensive, try an accident". Accidents cost a lot of money, which not only causes damage to plant and personal injury, but also leads to loss of company’s reputation & potential longterm revenue loss. Many research studies and analysis have shown that the benefit-to-cost ratio calculations for implementation of SIS are in its favor i.e. a properly designed, installed, tested, and maintained SIS reduces the likelihood of process risk & prevents the hazardous event from taking place and thereby achieving higher functional safety of the process plant.

Due to many disasters’/accidents which occurred in past like Seveso, Piper Alpha platforms, Chernobyl, Bhopal gas tragedy many standards were framed/designed to improve the inherent safety of the plant. International standards on functional safety for Process Industry are IEC61508 & IEC61511.

The role of EPC, End user, Licensor, SIS integrator for each phase of the IEC61511 safety lifecycle is indicated in Table 1.

Case study

The following case study is based on a project whose name cannot be disclosed due to confidentiality. The facility in question, a petrochemical plant, had the SIF designed for powder from degasser.

In case of very low Temperature in Degasser, safety logic shall close the outlet knife gate valve O-port. If the safety logic fails to close the Knife gate valve, then there is a chance that the powder can pass through the valve into the downstream equipment and if it comes in contact with the open atmosphere then there is a high possibility of leading it into a fire & explosion.

Problem Statement

Considering the criticality of the SIF, SIF was classified as SIL 2 by licensor in FEED SIL report.

Licensor recommended knife gate valve O-port make and model was not certified for SIL 2 application.

Options proposed by EPC contractor to Licensor & End User
  • Option A Licensor to accept recommended make and model of knife gate valve without SIL certificates based on their past Project applications & reliability data.
  • Option B Inclusion of new shut off valve which is certified for this application.
  • Option C Alternate make and model of Knife gate valve was proposed by EPC to licensor for approval.
Licensor response to EPC options
  • Option A Proven in use Concept to be used in absence of SIL certificates.
  • Option B Two valves in series was not acceptable due to Powder application.
  • Option C Matching performance & SIL certificates of Alternate make & model is EPC responsibility.
Problems posed by licensor’s response
  • Option A As per IEC61511 edition 2, Proven in use concept is replaced by Prior Use concept. Prior Use concept requires Operational & maintenance documentary evidence that the device has been used in similar project in similar environmental conditions (i.e. similar operating temperature, pressure, humidity etc.). Licensor/Recommended vendor/End User to provide necessary documentation required for prior use concept based on past operational data of a similar project with similar environmental conditions.
  • Option B Option ruled out based on process concern.
  • Option C Alternate make and model of Knife gate valve Techno-commercial evaluation by EPC Contractor. EPC Contractor had to get the approval from Licensor before ordering the valves.
Solution taken by EPC contractor
  • Option A was dropped due to lack of documentary evidence indicating operational data
  • Option B was dropped.
  • Option C was evaluated & adopted by EPC contractor.
Impact of Selected Option (i.e. Option C) for EPC Contractor
  • Cost Impact: Vendor of the Alternate make provided the SIL certificates but at an additional cost and actually got the knife gate valve model certified in the process under the EPC's cost.
  • Schedule Impact: Delay in Ordering of Knife gate valve due to Techno-commercial evaluation of new vendors
Conclusion of Case Study
  • During SIL classification study, there shall be awareness for the use of mandated vendor devices & their limitations related to availability of SIL certificates & safety manuals.
Key points to be taken into consideration during project engineering phase as per IEC61511 edition 2
  • Hazard and Operability study (HAZOP) makes the process robust by analysing Risk’s.
  • SIL study specifies the required reliability for each component of SIF.
  • Risks and Demand scenarios shall be properly defined during HAZOP/SIL so that all risks are properly covered & not exaggerated.
  • Hardware Fault tolerance (HFT=1) to be met for SIL 3 loops.
  • SIL certificates and safety manual to be collected during SIF verification for each component of the SIF.
  • Functional Safety Audit (FSA) to be included & carried out as per Safety lifecycle plan document during engineering & O&M phase.

Table 1: Roles of EPC, End user, Licensor, SIS integrator for each phase of the IEC61511 safety life cycle


IEC61511 Safety life cycle phase  Study/Work performed EPC roles and responsibility
Hazard & Risk assessment (Clause 8) PHA/HAZOP study (Process Hazard Analysis) Conducting PHA/HAZOP Study. Identify the Hazards & Hazardous events which can occur during normal Operation.
Allocation of safety functions to protection layers (Clause 9) SIL study Conducting SIL study. Assign SIL level to each SIF
SIS safety requirements specification (Clause 10) Safety Requirements Specification (SRS) Preparation of SRS based on SIL report.
SIS design and Engineering (Clause 11,12,13) Design of SIS hardware and application program Provides input documents to SIS integrators for Design of SIS hardware/software.
SIS Installation, commissioning and validation (Clause 14 & 15) Installation, commissioning and validation Performs SIS installation, commissioning, integrated testing and SIL validation.
Operation & Maintenance (O&M), Modification, Decommissioning (Clause 16,17,18) Operation & Maintenance, Modification, Decommissioning End User/Owner has to ensure that the O&M, Modification, Decommissioning are done to meet SRS requirements without degrading the SIL levels of each SIF during O&M.

 

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