Relief Systems Management
- Description
- Services
- Profiles
- Experience
As global refineries and petrochemical plants continue to increase capacity to keep pace with worldwide demands, operators must keep a watchful eye on process safety - in particular, pressure relief systems management. These systems are a small part of a facility, but they serve as the final layer of protection when other control mechanisms have failed.
With more than 3,000 baseline studies conducted worldwide, Siemens offers expertise and powerful software to analyze, design, document and manage your relief systems. And because experience has shown us what to look for, we perform plant-wide audits quickly and efficiently, with minimal disruptions to your operations.
Pressure Relief Analysis (PRA)
The proper sizing, selection and installation of relief devices are necessary to ensure that overpressure protection is adequate and to reduce hazards in the event that the pressure relief device discharges. Further, proper documentation of these relief devices is required before conducting any process hazard analysis required by OSHA 1910.119 (d). A Phase I analysis provides a baseline study to ensure that a site has a properly sized and installed relief system, as well as to ensure that it is in compliance with industry and operating company standards.
PRA studies are typically equipment-based to ensure that a comprehensive study is completed. Data, such as process basis, equipment data sheets and U-1 forms, is collected to complete the analysis. Potential overpressure scenarios are identified for each piece of equipment, applicability of each scenario is determined, relief rate is calculated and associated relief device is sized based on industry standards such as API Std. 520 and 521. At the end of the study, Siemens provides a comprehensive database of potential sources of overpressure and a concern list summarizing any deviations from industry and operating company standards.
The collection header is also reviewed as part of the PRA. For each global (facility-wide) scenario, we calculate the built-up header backpressure, flare radiation, flare exit velocity, knockout drum liquid droplet separation, knockout drum retention time and dispersion modeling.
Concern Resolution
Any concerns or deviations from the standards can enter a Concern Resolution project, which is made up of three steps – a more detailed engineering analysis of the concerns, risk ranking of the concerns and development of mitigation options. A +/- 30% cost estimate for mitigation options can also be provided to assist in determining the best path forward
A Concern Resolution project typically involves a closer working relationship with the client site than a PRA project when determining the acceptable level of risk, safeguards and preferred mitigation methods.
Revalidation/Debottlenecking
A revalidation is similar to a PRA project in that the relief devices and disposal systems are evaluated for pressure relief adequacy. However, revalidations stem from an existing PRA project, where the relief devices and relief headers are reevaluated at different unit throughput rates. Therefore, the focus is on rate-dependent scenarios rather than holistic analysis of a process unit and associated pressure relief system.
An example of a revalidation study would be adding a new piece of equipment and determining if the existing relief system is adequate for the additional load.
Flare Quantitative Risk Assessment (Flare QRA)
Flare QRA takes credit for mitigating factors like instrumentation and operator action that could reduce the flare load during a global scenario. It also accounts for the reliability of these considered mitigating factors. Flare QRA solves the hydraulics of several (hundreds to thousands) permutations of the same global scenario in order to determine the vessel accumulation when these mitigating factors do and do not work.
Flare QRA requires a flare hydraulic network and that global scenarios be identified (this can be completed as part of a PRA study), as well as a list of the mitigating factors to consider for each system.
This is a systematic approach that will determine if a flare is adequate, the probability for vessel overpressure and the associated consequences. Flare QRA studies can address concerns with flare header hydraulics, flare radiation, flare tip exit velocity and KO Drum separation.
Evergreening
Evergreening projects typically take place after the baseline PRA project and/or after the Concern Resolution study is complete. PS PPM and PPM provide a living database of relief system data. An evergreening project helps to ensure that the database is current. The Siemens project team is included in the client management of change (MOC) work process to the extent that we are responsible for updating the PS PPM database, with approved MOCs.
The Siemens team can ensure that all relevant equipment and flare systems related to the MOC are updated. These updates enable the operating company to safely maximize operating parameters in response to market conditions and maintain accurate supporting documentation for OSHA compliance.
The motivation for evergreening is that safety depends on accessible, consistent and accurate information. Siemens’ evergreening support can help ensure this
Design Verification
Siemens consultants will review the relief system design prior to a project construction phase, which can prevent costly redesign errors. The Safety Systems team is trained on the API 520/521 and RAGAGEP (Recommended And Generally Accepted Good Engineering Practices) overpressure scenarios and calculations. We also look for potentially site-wide issues and can identify any under- or over-design with respect to the relief system.
Further, Siemens Safety Systems team can use our lessons learned from reviewing hundreds of poorly designed relief systems to support the Engineering Procurement Company in developing guidelines.
Additional services
- Cost estimating
- Relief device documentation gap analysis
- Dynamic simulations
- Develop heat and material balances
- Reaction modeling with respect to run-away reactions and relief requirements
FlareQRA
Client
U.S. Refinery
Project Description
FlareQRA: Calculated the effect of a new unit and tie-in of atmospheric valves on the existing flare header including hydraulics, Knockout Drum separation and radiation.
Outcome
A flare header that is confirmed to be adequate with supporting documentation.
Pressure Relief Analysis (PRA)
Client
U.S. Chemical Plant
Project Description
Pressure Relief Analysis: Performed on a nitrogen refrigeration system based on ANSI K61 guidelines.
Outcome
Detailed documentation of the relief system analysis and an itemized discussion list of deviations from guidelines.
Evergreening of relief systems documentation
Client
U.S. Refinery
Project Description
Evergreening of relief systems documentation: The Siemens Safety Systems team had previously completed a Phase I analysis for this refinery. During the refinery system modification process, approved MOCs were sent to Siemens to incorporate into the PPM data file. This project was continued as the Siemens Safety Systems team and site personnel worked together to develop a best practices approach for future evergreening efforts.
Outcome
A relief systems database and documentation that reflects the as-built configuration in the field and a customized program that emphasizes future evergreening of the relief systems documentation.
Revalidation
Client
Non - U.S. Refinery
Project Description
Revalidation: The Phase I analysis of a unit was reviewed for the effects of increasing the unit throughput rate. The project evolved into additional review to determine if other changes were made to the unit since the Phase I analysis three years prior.
Outcome
Documentation that the existing relief system is adequate for the increased throughput rate and a relief system database. Documentation was updated to reflect the as-built configuration in the field.
Flare analysis
Client
U.S. Refinery
Project Description
Flare analysis: Populated the PPM software with the client relief rate calculations and performed a flare hydraulics and radiation analysis based on these scenario relief loads.
Outcome
An organized and searchable relief system database and a report of the relief header and flare analysis.
Design Verification
Client
Crude Production Company
Project Description
Design Verification: Reviewed the EPC relief system design for several crude production sites.
Outcome
Independent review of EPC relief design. Provided recommendations for improvements where the design deviated from industry standard and operating company guidelines prior to the construction phase. Lessons learned were provided to the EPC when designing future crude production relief systems.
Facility-wide PSI work
Client
U.S. Refinery
Project Description
Facility-wide PSI work (P&ID walkdowns, file consolidation, etc) and PSV/Flare analysis.
Outcome
Current PSI elements that reflect the as-built configuration in the field.
Facility-wide verification and analysis of current relief system
Client
Corporate support for a major international production company
Project Description
Facility-wide verification and analysis of current relief system, as well as mitigation of potential deviations from operating company guidelines. Analysis and recommendation of tie-in locations of atmospheric relief to the existing flare header. Also analyzed the effect of consolidating multiple flare systems.
Outcome
Provided operating company with cost effective methods to mitigate concerns and consolidate the relief systems. Site personnel were trained on PPM software and the importance of updating documentation.
| Client | Description |
| Chevron | Flare modeling Flare QRA |
| ConocoPhillips | Pressure relief analysis Atmospheric dispersion modeling Concern resolution |
| ExxonMobil Refining & Chemicals | Design verification Refinery wide PSV and flare analysis Continuing support Concern resolution Training |
| Flint Hills | Relief system verification |
| Hess | Relief system verification |
| Irving Oil | Pressure relief analysis Flare modeling Flare QRA |
| Koch | Relief system verification |
| LyondellBassell | Pressure relief analysis Continuing support and evergreening Concern resolution Training |
| Marathon | Pressure relief analysis Concern resolution |
| Petronas | Pressure relief verification Flare QRA |
| SABIC | Pressure relief analysis Flare dispersion modeling Concern resolution Training |
| Saudi Aramco | Flare modeling Concern resolution Training |
| Shell | Relief system verification Concern resolution |
| Tesoro | Relief system verification |
| Valero | Pressure relief analysis Concern resolution |