Overpressure Protection System Verification

We know major incidents like Grangemouth, Texas City, and Geismar were preventable, but why do they continue to occur? The incident investigations revealed inadequate safety system design, or a lack of thorough re-assessment after plant or operational procedure modifications. After each major incident, industry standards are reviewed and revised to ensure lessons are learnt, but many facilities are not checked independently to ensure compliance with the latest standards.

Verification protects your project and reputation

Overpressure protection system verification is a systematic review of a plant’s safety systems including:

• The pressure relief systems, compliance with Code, sizing and selection
• Depressuring valve systems, fire and low temperature effectiveness
• Collection headers, KO drums and flare systems capacity, material of construction and vibrational risks (AIV/FIV)

Verification is a critical safety review that should be performed by independent experts who are experienced in relief design and application of the latest industry standards. PSE extends the effectiveness of standard verification with the ability to use detailed analysis (including dynamic simulation using our industry leading gFLARE software) to solve problems with existing system capability or reduce the need to make unnecessary design changes.

Verify before key project checkpoints

Overpressure protection system verification ensures that the most important systems in your facility comply with the required standards. An investment in verification at the design stage prevents deferred production and risk of excess costs to correct design faults prior to start-up.

Verification is best completed towards the end of FEED once deliverables are sufficiently developed, then updated during EPC to inform final order procurement and construction.

As facilities age and change, verification is an important part of ongoing Process Safety Management (PSM) programmes, maintaining compliance with revised standards and best practices.

Verification systematically aligns design with best practice

Best Practice safety design requires a hierarchy of company documents supported by the relevant industry standards. For the specific facility it is expected that key safety documents are produced and maintained. A third party verification allows these documents to be checked for relevance and adequacy against any revisions to standards, or misinterpretations that may have occurred during the design process or subsequent plant modifications. The verification should be approved by the owners Technical Authority, as the actions can be far reaching and may require change to company documentation, standards and facilities.

Key Safety Documentation

The main focus for verification is the Relief and Blowdown report and calculations, which should reference all the supporting information in figure below. Documentation is checked to determine the correct scenarios have been evaluated and the methodology is suitable.

For completed designs, the documents listed in the ‘Essential Reference Data” are used to verify the capacity of devices and whether their installation complies with the required standards. However the level of documentation does vary and the level of verification is adjusted accordingly. Design Philosophies are also reviewed to ensure the devices comply with the company requirements and these represent best practice. Process Safeguarding schematics and narratives are checked for alignment with relief device designs. Through the process of verification, PSE are able to create and update any missing documentation if this is required.

Detailed analysis drives mitigation

PSE can reduce safety risks with detailed analysis or dynamic simulation to solve many of the problems with poor design or existing installations that are often overlooked, and avoid the need to make costly hardware changes.

• Relief Valves with >3% inlet pressure drop requiring “Engineering Analysis”
• Flare capacity assessment, upgrading and existing system verification
• Tailpipe Vibration assessments, AIV/FIV and finite element analysis (FEA)
• Calculation of Process Columns dynamic relieving loads and evaluation of HIPPS systems
• Heat Exchanger Tube rupture shock wave assessment
• Dynamic analysis of fire survivability depressurization and fire case relief protection

Deliverables include high level summary with detailed findings

Deliverables include a high level summary report providing the overall metrics, and detailed review proforma, providing an analysis of each valve according to a series of standard criteria. PSE analyses the findings and proposes mitigations to reduce or eliminate risks. These mitigations range from more detailed dynamic analysis to avoid hardware replacements or modification to valves and/or piping. All PSE calculations can also be supplied to supplement existing documentation.

Examples of Code 1 would be an undersized Pressure Relief Valve or total backpressure exceeding 10% for a conventional type PSV. An example of a Code 2 finding would be a credible scenario which was missed in the documentation, but cannot be quantified without further analysis. A Code 3 finding is generally a fault with documentation not affecting hardware or installation. All findings are documented in the detailed review proforma.