Optimizing Process Safety for Petrochemical Plant with Fire and

Gas Mapping Solution This paper introduces the hazards involved with ammonia process facilities and discusses the benefits

of standardizing fire and gas mapping Jor process facilities in accordance with international guidelines. A solution is provided with the development o/new technical standard and customized 3D fire and gas mapping software,for which validation and test cases are also presented to demonstrate

Ihe success of the solution.

Chua Kien Kek PETRONAS Group Technical Solution

Tan Ping Yang PETRONAS Group Technical Solution

Introduction

W ith current fluctuating global crude oil prices, the oil and gas industry is facing uncertainty at thi s period of time. This increasingly competitive

environment has placed petrochemical plants, which operate on marginal profit, to rethink their strategies and also capital expenditures. Fire and gas systems (FGS) play an important role in ensuring the safety of Petrochemical and Ferti lizer p lants, like Ammonia or Urea. The in­herent toxic and flammable nature of the chemi­cals in the process for such plants are hazardous and cannot be fully mitigated with preventive safeguards. Hence, FGS has become mandatory to be implemented in each plant to mitigate the hazards.

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FGS triggers the earliest warnings of the haz­ardous situation upon detection, therefore as­signing the appropriate location of the detectors is crucial to allow effective detector coverage, and hence optimize the FGS of the plant.

Background

To warrant the safety of the plant, precise selec­tion and placement of detectors is crucial as in­appropriate selection and location would be det­rimental to the successful detection of a haza rdous incident. It has been observed that current industrial standards, such as ISA TR 84.00.07 and lEe 61511 does not provide a pro­cedural method in determining the optimalloca-

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tion of detectors. Thus, it has been largely de­pendent on each petrochemical plant or facility owners to detennine the design of the FGS based on their own operational experience and interpretation on the generic guideline provided by the aforementioned international standards. This situation has resulted in inconsistency among facility owners when it comes to design­ing and locating their FGS. Such disparity fur­ther invokes concerns on safety as there is no unifonn methodology to evaluate the adequacy of the respective plant's FGS in safeguarding against hazards for major oil and gas companies. Hence, there is a need to develop a manual or technical standard to address this issue.

Objective

A solution with a systematic approach using computer software to assess and calculate the FGS adequacy and efficiency was developed to provide petrochemical plants and facility own­ers with a standardized method to gauge the per­formance of their FGS. Such methodology should adhere to the guideline provided in inter­national standards such as ISA TR 84.00.07 and IEC 61511 and also take into account lessons learnt from operation.

Developing the solution

As a major oil and gas company, PETRONAS operates and maintains a number of facilities in­cluding Ammonia and Urea plants. From risk analysis studies such as Quantitative Risk As­sessment (QRA) and Hazard and Operability Study (HAZOP), it has been identified that flammable materials i.e. Natural Gas, Hydrogen, and toxic chemicals such as Carbon Monoxide, Hydrogen Sulfide and the end product Ammo­nia and Urea, are present throughout the pro­cess.

When dealing with a process, IEC 6 1511 sets out the technical standard for safety instrumen­tation, which also includes electronic devices

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such as flame or gas detectors. However, tEe 61511 focuses on the confonnance of the specif­ic device with the safety requirements laid out in it, but not the overall location of the detectors.

Other standards such as ISA TR84.00.07, pro­vides prescriptive guidelines to ensure the effec­tive design of FGS, which uses the perfonnance based technique to identify the coverage and safety avai lability. It defines the coverage into two categories, namely geographic based and scenario based. Geographic coverage is mainly concerned with the location and perfonnance at­tributes of detectors and obstructions to the field of view towards equipment. On the other hand, scenario coverage is defined as the fraction of fire or gas release scenarios that if they were to occur, would be detected by the fire and gas de­tection system.

However, to calculate and evaluate the coverage of the detectors, specialized software tools are required. To address this issue, PETRONAS has collaborated with Micropack Engineering (UK) Ltd to develop a 3-dimensional (3D) fire and gas mapping software for the purpose of calcu­lating the coverage of the fire and gas system, which is known as FnGMApTM. In addition, new PETRONAS Technical Standard (PTS) i.e. PTS 14.33.01 is also published to provide guidelines on fire and gas mapping for its pro­cess facilities. Both are specifically tailored to be consistent with international standards and to provide a complete solution for the design of optimal fire and gas detection system.

Validation of Software Results

As complex mathematical algorithms are im­plemented in FnGMAP™, it is crucial that the result of the software is validated with actual field scenarios to ensure the output of the soft­ware is desirable. Micropack Engineering (UK) Ltd. possesses a fire testing facility which simu­lates an actual plant environment, as shown 10

Figure I.

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The validation is carried out with the following setup: • Fuel Size: O.lm2 pan fire n-Heptane • Flame Detector Specifi cation: Micropack

FDS301 • Horizontal Field of View: 9D degree • Vertical Field of View: 63 degree • Sensitivity: 10 kW @ 30 meters.

Figure I. Field Test Facility

FDS 301-02

FDS 301 -03

Figure 2. Software Simulation Result

Figure 2 shows the test facility modeled using FnGMApTM with three flame detectors, namely FDS 301-02, FDS 301-03 and FDS 301-04, rep­resented by the black dots.

The validation process is carried out by first simulating the coverage of the detectors for the equipment III the testing facility using FnGMApTM. The simulation in Figure 2 repre­sents the calculated coverage of the flame detec-

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tors as detennined by the software. Red repre­sents the area occluded from the detectors , or­ange represents detection of fire by single detec­tor (looN), and green represents detection of fi re by two or more detectors (2ooN).

Note: N is the total number of detectors at site

Next, six spots at the test ground are identified to be tested as looN, 200N or >20oN areas as per the mapping result shown in figure 3.

200N or >2ooN

looN

Figure 3. Test cases

The flame detectors at field are installed at the same location with similar elevation as the de­tectors in the software simulation. The D.I m2 n­Heptane pan fire is ignited and placed at the identified area as shown in Figure 3 for each test case. The detection by flame detectors at site for each spot is verified against mapping results shown in Figure 2 and the results are tabulated in Table 1

Table I. Field test result

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Discussion

From Table I, it is observed that the simulation result produced by FnGMApTM matches the per­formance of the flame detectors installed at the test facility for each of the test cases. The results confirm with the output from the calculation of the software. This indicates that the software is able to simulate and model the actual perfor­mance of detectors installed at field.

Implementation of Fire and Gas Mapping with FnGMApTM

FGS mapping study with FnGMApTM has been deployed for a new green field project. The ca­pacity of the new Ammonia and Urea plants is targeted to reach 2100 MTPD of liquid Ammo­nia and 3500 MTPD of granular urea.

The project was awarded to a contractor which is well experienced and had undertaken several similar projects around the globe. However, as detail risk analysis and mapping study is carried out, it was found that the FGS design for this current project does not meet the requirement of the owner and local authority 's regulation and law. This is a good example of experience could causes blind spot which results in under-design of the FGS.

The original design proposed is shown in Table 2, with a total of 52 detectors that included both flame and gas detectors combined. Detailed analysis of the process and potential risk associ­ated with FnGMApTM, has revealed that the original design does not provide sufficient de­tection coverage in accordance with PTS and in­ternational standards. This indicates that the de­sign could lead to a potential fire case or gas leak undetected by the FGS and the conse­quences could be catastrophic.

Hence, to reduce the risk and mitigate the possi­bility of hazard consequences, a new design of FGS is proposed which is compliant with PTS

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and international standards. The total number of detectors required by the new design is 95 de­tectors, which is 83% more than the original de­Sign.

Detectors Original Recommendation Fl arne Detectors 12 23 Gas Detectors 40 72 Total 52 95 Table 2. Number of Detectors requwed before and after

execution of mapping study

The original design was based on engineering judgment and experience by the Engineering, Procurement, Construction and Commissioning (EPCC) Company for the project. Comparing the numbers of detectors recommended and the original set by the EPeC Contractor, highlights the fact that traditional methodologies of citing detectors in plants may not always be adequate. By using the procedural methods and 3D map­ping software, gaps are identified and addressed with the addition of new detectors , which ensure the effective safeguarding of the facility.

Conclusion

The introduction of PTS and 3D mapping soft­ware standardizes the process of positioning of the detectors' to optimize the perfonnance of the FGS. By implementing the solution, the per­fonnance of the FGS is improved to meet inter­national standards requirement, as shown in the case of the new project. The goal of developing a solution to address the inconsistency in de­signing has been met.

Way Forward and Future Work

In view of dynamic demand in the oil and gas industries, improvements are required to be in­cluded into the software and methodology in or­der to meet new requirements. Hence, several new features such as incorporating a three­dimensional model from a third party engineer-

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ing software and taking into account new detec­tion technology such as ultrasonic are undergo­ing development. These new functionalities would be able to provide better mapping result to enhance the accuracy of the study.

References

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I. ISA TR 84.00.07 Guidance on the Eval­uation of Fire. Combustible Gas and Toxic Gas System Effectiveness

2. IEe 6151 1 Functional safety - Safety in­strumented systems for the process in­dustry sector

3. PTS 14.33.01 Fire and Gas Detection Mapping

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