Introduction
iFluids Engineering and Consultancy W.L.L. was awarded to perform SIL (Safety Integrity Level) Assessment for EPIC – Various facilities of Qatar Gas including:
- SIL Study for AKG Sales Gas Diversion to RL3 (LNG Trains 6 & 7)
- SIL Study for installing filters in LR1 AND LR2 (Refinery) condensate line in Medgulf Construction Company W.L.L
- SIL Assessment for Barzan Onshore Asset – Qatar Gas Operating Company Ltd
The primary objective of the Safety Integrity Level (SIL) study is to systematically evaluate the integrity of Safety Instrumented Systems (SIS) and ensure they meet the required safety performance standard within a process system. This involves assessing the Potential hazards associated with the process, Identifying the safety functions required to mitigate those hazards, and Evaluating the reliability of the SIS components.
Case Study 1 -SIL Study for AKG Sales Gas Diversion to RL3 (LNG Trains 6 & 7)
The AKG facility is designed for 2000 MMSCFD sales gas production, operating based on market demand. In AKG assets, natural gas from inlet facilities is routed to the Acid Gas Removal Unit (AGRU) to eliminate acid gases. This is followed by a Dehydration and Mercury Removal unit for addressing water, Mercaptans, and Mercury concerns, preventing freezing at low temperatures.
In the Dehydration unit, during drier regeneration, residue gas serves as regeneration gas and is later treated in the Regeneration Gas Treating unit (Selexol unit) to remove Mercaptans. The treated gas is water-saturated and meets sales gas specifications, being further re-injected into the sales gas stream by the excess gas compressor (EGC). However, the AKG asset experiences production curtailment during winter due to reduced sales gas demand, compounded by Barzan’s production initiation in 2020.
To optimize gas utilization, meet LNG production specifications, and enhance safety measures, it is necessary to recycle excess gas back to the Acid Gas Removal Unit (AGRU) via a bidirectional sales gas backup line. Additionally, the Spent Regen Gas Compressor, inactive for over five years, requires maintenance, including the replacement of instrument cables and other internal and external parts, as identified through a detailed inspection.
Two routes are proposed for excess gas from AKG-1 and AKG-2 to reach AGRUs. The primary objective of the SIL classification/assessment study was to evaluate the adequacy of Independent Protection Layers (IPLs) in place for mitigating major process hazards. This assessment quantifies risk reduction requirements in terms of SIL to ensure Safety Instrument Functions (SIFs) meet specified risk reduction levels.
- AKG-1 excess gas will be routed to AKG1 AGRU through AKG-1 EGC, followed by the existing Spent Regen Gas Compressor as a booster compressor. This will require connecting the AKG-1 EGC discharge line to SRGRC suction. SRGRC discharge, currently routed to AKG-2 AGRU, will need to connect to the existing 16” recycle line from AKG-1 EGC to AKG-1 AGRU.
- AKG-2 excess gas will be routed to AKG-2 AGRU through the existing AKG-2 EGC, operating in recycle mode. This will require a new line to recycle the entire AKG-2 excess gas to the AGRU feed preheater, together with the existing 6” recycle line from AKG-2 EGC discharge. Both recycle lines will operate together to eliminate the existing 6” recycle line limitation for full discharge flow from AKG-2 EGC to AKG-2 AGRU.
In summary, the project’s objective is to ensure AKG sales gas meets LNG production specifications by recycling excess gas to AGRU while addressing the Spent Regen Gas Compressor issue. This project aims to improve gas utilization, meet LNG specifications, and enhance safety measures through SIL Assessments.
Case Study 2 – SIL Study for installing filters in LR1 AND LR2 (Refinery) condensate line in Medgulf Construction Company W.L.L
Laffan Refineries LR1 & LR2 play a pivotal role in the Oil and Gas industry, receiving feed condensate from multiple producers in Qatar gas and Barzan assets. This feed condensate undergoes several processes before being utilized in the LR1 and LR2 plants. However, the facility has faced persistent challenges related to heater choking issues, which have led to operational disruptions and financial losses. To overcome these issues and enhance the reliability and availability of the LR1 & LR2 Feed Condensate Heater, it was proposed to install new feed condensate filters.
The primary objective of the SIL study was to evaluate the hazards and impacts associated with the proposed project, particularly concerning HSE considerations, and the company’s reputation. Furthermore, the study aimed to assess the reliability requirements for all Safety Instrumented Functions (SIFs) related to the project. This assessment was crucial for determining the adequacy of Independent Protection Layers (IPLs) in mitigating major process hazards.
- Addressing Heater Choking Issues:
- One of the primary issues faced by Laffan Refineries LR1 & LR2 was the choking of Feed condensate heater tubes due to debris present in the feed. This problem had a direct impact on the availability and reliability of the facilities. To address this issue, the project proposed the installation of new feed condensate filters at the inlet feed for both refineries. These filters would serve to eliminate debris that had been causing heater choking issues.
- Pilot Testing and Data Collection:
- Before proceeding with the full-scale project, a crucial step was taken in the form of a pilot project involving the installation of a filtration facility. The objective of this pilot testing was to gather essential data and analyze it thoroughly. This data would be instrumental in determining the design criteria for the filter elements, including their size and type. The successful execution of the pilot testing phase provided valuable insights and information necessary for the subsequent stages of the project.
- Reducing Financial Losses and Environmental Impact:
- The significance of this project extended beyond addressing operational challenges. Laffan Refinery recognized the financial implications of recurrent heater choking issues. These problems occurred every six months during continuous operation, resulting in production losses and financial setbacks. By implementing the proposed filtration facility, the refinery aimed to cater to local demand for refinery products while avoiding production losses. This not only reduced financial losses but also had positive environmental implications by minimizing shutdowns and start-ups.
The project’s scope encompassed several key aspects, including modifications to be made in the LR1 & LR2 Feed Condensate main header 18″ line that feeds the Feed Condensate pumps in LR1 and LR2 Asset. These modifications were essential to provide tie-in provisions on the feed condensate stream, flare header, and drainage systems of LR1 and LR2 to accommodate the new filtration facility.
The core of this project involved the Safety Integrity Level (SIL) classification and assessment study. Its primary goal was to evaluate the effectiveness of Independent Protection Layers (IPLs) in mitigating major process hazards. This study was instrumental in determining the necessary level of risk reduction for Safety Instrument Functions (SIFs) associated with the LR1 and LR2 Feed Condensate Line project. The risk reduction requirements were quantified in terms of SIL requirements.
Enhancing Design and Operation:
The SIL study aimed to establish the fundamental principles and extent of the Safety Integrity Level (SIL) for the project. It also sought to determine the SIL Rating and Risk Reduction Factor (RRF) for each Safety Instrumented Function (SIF). Throughout the study, the focus was on documenting the proceedings and recommendations. These insights and recommendations were crucial for facilitating the implementation of improvements that would enhance both the design and operation of the facility.
The LR1 and LR2 Feed Condensate Line project, inclusive of the installation of filters, was a comprehensive initiative driven by the need to address persistent heater choking issues. The project aimed to improve the reliability and availability of the LR1 and LR2 Feed Condensate Heaters, thereby reducing financial losses and minimizing environmental impacts
Case Study 3 – SIL Assessment & Verification for Barzan Onshore Asset – Qatar Gas Operating Company Ltd
The Barzan Onshore facility is a vital component of the oil and gas sector, responsible for producing treated sales gas for national transmission and local fuel gas systems, along with the recovery and export of various hydrocarbon products such as ethane, LPG, untreated and plant condensate, and liquid sulfur. This complex onshore facility comprises two identical trains with a combined inlet capacity of 1.9 BSCFD Full Well Stream (FWS) on a dry basis. Barzan also includes utility facilities, off-plot facilities, and an extensive network of pipelines.
One of the key challenges faced by the Barzan facility was the need to address potential hazards associated with its operations. The SIL Assessment Study had a multifaceted objective, including assessing the hazards and impacts of the project on health, safety, the environment, and the company’s reputation. Additionally, the study aimed to ensure that all SIFs met the target SIL requirements, and any gaps were identified and mitigated with practicable solutions. The review process adhered to Qatargas’ SIL Assessment Procedure.
Reliability Requirements and SIL Ratings:
The SIL Assessment Workshop commenced with a rigorous evaluation of xx Safety Instrumented Functions (SIFs). Using the Qatar gas SIL Risk Assessment Matrix and risk matrix methodology, the team identified various SIFs with different SIL Ratings. Some SIFs were rated as SIL 1, SIL 2, and even SIL 3, based on their criticality and potential consequences. Scenarios related to these SIFs were further assessed using the Layer of Protection Analysis (LOPA) methodology to ensure comprehensive risk management.
The scope of the project was extensive and involved modifications to the LR1 & LR2 Feed Condensate main header 18″ line, which supplied the Feed Condensate pumps in LR1 and LR2 Asset. These modifications were essential to accommodate the new filtration facility and included provisions for tie-ins on the feed condensate stream, flare header, and drainage systems of LR1 and LR2.
Enhancing Safety and Mitigating Hazards:
The Safety Integrity Level (SIL) classification/assessment study played a pivotal role in enhancing safety measures at the Barzan facility. By evaluating the effectiveness of Independent Protection Layers (IPLs) in mitigating major process hazards, the study ensured that the facility adhered to the highest safety standards. The quantification of risk reduction requirements in terms of SIL was a critical aspect of the study, guaranteeing that Safety Instrument Functions (SIFs) met specified risk reduction levels.
In summary, the Barzan Train-1, 2 & Utilities Onshore project faced complex challenges related to safety, reliability, and environmental impact. The collaboration between iFluids Engineering & Consultancy W.L.L. and QatarGas resulted in a comprehensive SIL Assessment Study that addressed these challenges. By evaluating hazards, assigning SIL Ratings, and recommending mitigations, the project aimed to enhance safety, protect the environment, and safeguard the company’s reputation. This thorough assessment and commitment to safety principles contribute to the overall sustainability and success of the Barzan facility in Ras Laffan Industrial City.
Introduction to SIL Assessment
The SIL Assessment is a critical process in risk management, focusing on the necessary risk reduction for each process system to safeguard against various hazards. This assessment involves calculating the difference between the current risk level associated with a process or equipment and the desired, target risk level. Achieving risk reduction is facilitated through process and mechanical integrity measures, the implementation of independent protection layers, and potentially the inclusion of Safety Instrumented Systems (SIS), if required.
SIL Assessment Methodology
Various methodologies are available for performing SIL Assessments. Qatar Gas, for instance, follows the SIL Assessment Risk Matrix methodology in its initial SIL Assessment exercises. This approach results in identifying SIL 2 and 3 loops, which are then further assessed using the Layer of Protection Analysis (LOPA) methodology. The assessment of the Safety Integrity Level is accomplished through the collaborative efforts of a multi-disciplinary team, which evaluates the risks associated with specific scenarios and determines the necessary risk reduction provided by the Safety Instrumented System.
Identification of Safety Instrumented Functions (SIFs)
Before starting the SIL Assessment exercise, it is crucial to identify the Safety Instrumented Functions (SIFs). SIFs are safeguards associated with an instrumented system that performs a shutdown to mitigate safety, environmental, or financial consequences. Each initiator in the Cause & Effect (C&E) matrix is considered as one SIF, with the exception of Manual Push Buttons.
Initial SIL Assessment Process
The initial SIL Assessment follows the SIL Matrix Methodology using the Qatar Gas SIL Assessment Risk Matrix. This matrix comprises five levels of consequence classification and five levels of likelihood evaluation. A typical SIL Matrix, as shown in Appendix A, must be validated by an LP engineer before usage. To determine the target SIL for each SIF, the team first describes the consequences of the event, assuming no safeguards are in place. This step is crucial to understand the event that the SIF is intended to prevent or mitigate. Once the event consequences are outlined, the team determines the consequence category for each area of consideration. The worst of the four categories is used for the assessment, with financial consequences given equal importance, potentially governing the SIL level for the SIF under consideration.
Risk Evaluation in SIL Assessment
The second step in risk evaluation involves estimating the event likelihood. This estimation considers various factors, including the frequency of potential causes or initiating events, the effectiveness of existing safeguards (excluding the SIF under consideration), and the probability of conditions necessary to generate the consequences being present. The likelihood evaluation is conducted both before and after considering safeguards or independent protection layers. This approach aids the team by breaking down the estimation into manageable steps.
LOPA Methodology
Steps to Conduct LOPA
- Step 1: Select Hazard Scenario from HAZOP based on its severity level.
- Step 2: Select Target Mitigated Event Frequency (TMEF).
- Step 3: Identify cause(s) from the HAZOP and quantify Initiating Event Frequency.
- Step 4: Determine Intermittent Hazard(s) credit if applicable.
- Step 5: Identify Independent Protection Layers (IPLs) from HAZOP safeguards.
- Step 6: Quantify the Probability of Failure on Demand (PA) for each IPL.
- Step 7: Identify and quantify Conditional Modifiers / Vulnerability Factors if applicable.
- Step 8: Calculate the SIL level based on Probability Failure Demand.
LOPA is a simplified risk assessment method, functioning as a measure of both the consequence of an accident scenario and its frequency. Developed to examine selected scenarios, LOPA focuses on individual causes and their progression to a scenario of concern. It evaluates the effectiveness of protection layers in reducing the frequency and/or consequence of a hazardous event. When a Safety Instrumented System (SIS) is used, LOPA is employed for SIL determination of identified Safety Instrumented Functions (SIFs).
The primary goal of LOPA is to establish sufficient layers of protection against potential risk scenarios, ensuring that at least one layer is effective for each scenario. However, no layer is perfectly effective on its own, necessitating the development of adequate protection layers to maintain tolerable accident risk levels. LOPA is consistently used to judge the sufficiency of Independent Protection Layers (IPLs) in controlling risk. In cases where the estimated scenario risk is intolerably high, additional IPLs must be added. While LOPA does not directly suggest the addition of IPLs, it assists in evaluating various risk mitigation alternatives.
Application of LOPA in Risk Assessment
As a risk assessment tool, LOPA is utilized within a company to provide an order of magnitude estimation for any identified scenario. It is also used cautiously as a justification for the removal of a safeguard or IPL. LOPA may not be suitable for scenarios heavily reliant on transient operation modes, such as those dependent on administrative controls, operating disciplines, and equipment design.
Consequence Analysis in LOPA
An essential component of accident scenario risk is its consequence, estimated to an order of magnitude of severity in LOPA. This enables the comparison of risks from separate scenarios. Consequences are defined as the undesirable outcomes of an accident scenario, varying in application across organizations. In the chemical industry, for example, consequences may manifest as loss of containment, caused by leakage, pipeline rupture, or relief valve activation. Consequence endpoints include the dispersion of hazardous materials, the release of hazardous substances, and the physical effects of explosions, fires, and toxic releases, along with the impacts of such releases. These endpoints are typically quantified using various estimation methods.
LOPA Methodology Structure
In LOPA, a scenario is defined as an event with the potential to lead to a concerning outcome. It leads to a chain of events that may result in a significant consequence. A scenario is an unplanned sequence of events or a singular event, each comprising two parts: an initiating event and a consequence. The initiating event starts the chain, while the consequence is the result of the chain continuing without interruption. Each scenario must have a unique initiating event/consequence pair. If an initiating event is linked to multiple consequences, additional scenarios are developed. Most scenarios will include at least one safeguard, considered an IPL for LOPA purposes. The structure of the data in a LOPA analysis is critical for accurately assessing and managing risk.
