Gas Pipeline Blowdown Risk Assessment

Person inspecting Oil and Gas Infrastructure while review notes on a tablet

Case study

Upgrading a Natural Gas Utility Operator's Outdated Infrastructure

How can you keep your plant and piping safe during a planned or emergency blowdown?

If performed incorrectly, blowdowns can damage pipelines with low temperatures and excessive vibrations. Exponent's multidisciplinary team of mechanical engineers and thermal scientists can provide rigorous modeling to accurately predict piping temperature and vibration risk during blowdown. We also provide design and failure investigations related to these issues.

Venting flammable gas also carries an inherent risk of fire or explosion. Existing standards, such as NFPA 56 and API 521, only provide guidance for a limited range of venting scenarios. Exponent has extensive experience using commercial software codes and computational fluid dynamics (CFD) modeling to accurately predict the extent of the safe area during venting for scenarios outside the scope of the standards. We also provide design analysis and regulatory guidance related to fire and explosion risk during pipeline blowdowns.

Managing the environmental impact of pipeline blowdowns

Another blowdown risk is the environmental impact of releasing greenhouse gases from pipelines, which is significant and the subject of increasing scrutiny. These emissions can be reduced by flaring, transferring gas to a low-pressure system, or modifying processes to reduce blowdown events. We help reduce blowdown emissions by providing guidance on process changes.

Hydrogen blowdowns

Exponent also advises on issues related to hydrogen blowdowns. In particular, the hydrogen blowdowns include higher flame speed and a wider flammability range than natural gas. This leads to an increased risk of ignition near the point of release. Exponent has the experience to advise on transitioning to and safely operating with hydrogen.

SERVICES

For 50+ years, we’ve thrived on solving unstructured problems that require bespoke solutions. Some of our services include:

• Risk assessments and safety evaluations

• Computational fluid dynamics (CFD) modeling

• Consequence modeling, including computer modeling of fire radiation and vapor dispersion hazard zones

• Environmental impact studies

• Material selection and performance issues

Capabilities

Exponent offers rigorous pipeline blowdown process evaluations and modeling to address risks to facilities, people, and the environment.

Blowdowns of high-pressure gases from pipelines can cause vibration of the pipe wall and put the pipeline at risk of damage. Asymmetric discontinuities, such as small-bore connections, are most susceptible to failure due to vibration. Exponent's multidisciplinary team of structural engineers and materials scientists can provide qualitative reviews, in situ measurements, and rigorous modeling to assess vibration risk during blowdowns. Exponent also advises clients on both design and failure investigations related to this issue.
When performing blowdowns as part of construction, routine maintenance, or emergency operations, the potential risk and hazards introduced by the release of flammable material are of paramount concern. Exponent has experience investigating incidents related to the ignition of blowdown gas. Combined with our expertise in performing vapor dispersion, jet fire, and explosion overpressure calculations, we provide risk and hazard assessments that our clients can use to safely manage blowdown operations.
Blowdowns of high-pressure, flammable gases can present hazards to nearby structures, equipment, personnel, and, in some cases, the surrounding environment and general public. The ignition of a flammable vapor could result in either a flash fire with thermal radiation effects or a vapor cloud explosion (VCE) with potentially damaging overpressures if the flammable cloud migrates to a congested or confined area before being ignited.
Exponent has experience with industry tools, including computational fluid dynamics (CFD) modelling software (e.g., FLACS, Star-CCM+), to assess the potential flammable cloud dispersion, as well as determine the consequence of a VCE and mitigate the hazard. These studies have been published by Exponent staff in trade and technical publications. Additionally, as every real-world situation is different, we have the expertise to develop bespoke modeling solutions to give our clients the answers they need to safely manage blowdown operations.
Many energy projects require environmental assessments (EAs) or environmental impact assessments (EIAs). For pipeline blowdowns, EAs (smaller, focused assessments) and EIAs (thorough assessments) are formal analyses of the adverse impacts to the environment resulting from releasing hydrocarbons or other greenhouse gases. Such assessments are conducted to provide decision-makers and stakeholders with sufficient information about the environmental consequences of blowdowns before deciding to proceed.
An EIA, in general, contains a description of the proposed blowdown, a description of the impacts on the environment, mitigation measures, and alternatives to the proposed blowdown. Exponent's scientists and engineers have considerable experience performing EAs and EIAs. We can provide strategic direction for project needs and scope or perform the necessary studies to assess environmental impacts, critically review EAs and EIAs and the underlying studies used in the assessment, and provide support for public stakeholder engagements.

Our Capabilities Are Unparalleled

With expertise in over 90 disciplines and hundreds of capabilities, tools, and methodologies — we get to the root of even the most complex challenges and give you the objective answers you need.

Experts

Our global and comprehensive expertise across industries gives us a deep understanding of current challenges, best industry practices, and the implications of emerging technologies.