Tank Farm Relief Assessment
Tank Farm Relief Assessment
The customer had a history of relief related incidents and releases to atmosphere. To understand the adequacy of the installed relief protection a study was commissioned.
With budgetary constraints, a high level screening exercise was carried out, consisting of an on-site survey and a focused desktop review.
Based on experience from similar studies our consultants quickly identified a number of areas of concern including:
- Incorrectly set devices,
- Poorly operated blanketing systems
- Installation related issues which compromised design capacity
- No inspection of rate limiting devices
- Inadequate vacuum protection
Project Management of a Gas Terminal Relief and Blowdown Study
Project Management of a Gas Terminal Relief and Blowdown Study
The customer had a number of near misses and was concerned that relief and blowdown barriers had eroded over time. A third party engineering contractor was engaged to provide resources to carry out a study, however, the customer had insufficient resources to provide technical and managerial guidance.
MF Process Safety provided a project manager to provide technical guidance and plan/coordinate activities around two key shutdowns. High consequence/higher likelihood issues were quickly identified and hardware mitigations implemented in the first available shutdown.
Longer term risks were reviewed and priorities assigned according to the customers risk matrix, and measures were put in place to minimise risk.
A design basis was created for each and every hydrocarbon relief system, together with a detailed hydraulic model and relief and blowdown summary.
Key associated protective devices were placed on a critical device inspection regime.
The project met the schedule and came in under budget.
Ground Flare Operational Issues
Ground Flare Operational Issues
The Customer had operational issues with a ground flare operating outside of its original design envelope.
The relief loads seen at the flare were excessive, with flames reaching well above the radiation fence at maximum relief loads.
Unlike conventional flares, the ground flare was very sensitive to changes in molecular weight, something which the original designer hadn't appreciated. The flare burner nozzles weren't sized for the higher molecular weight cases, and the longer flame lengths resulted in excessive heat outside of the fence.
Operational history and localised equipment damage bore evidence to this.
With the existing burner nozzle sizes, MF Process Safety calculated the maximum flow that could be tolerated for higher molecular weight cases, and in the short term proposed mitigations to limit flowrate.
A more comprehensive flare package design basis was generated which allowed the vendor to specify burner nozzle diameters without compromising the design capacity of the flare for lower molecular weight cases and avoided the need for expensive redesign.
Global Relief and Disposal Studies
Global Relief and Disposal Studies
An International Oil Company utilised MF Process Safety personnel to assist them in meeting their goal to conformance to their Engineering Technical Practices and to provide an appreciation of major operational risks on their upstream assets.
MF Process Safety's Technical Director assumed the role of Technical Manager for the project which spanned 5 years, addressing over 30 assets.
An updated design basis was developed for every hydrocarbon relief system.
A comprehensive suite of guidelines and tools was developed to ensure a level of consistency for multiple teams in offices throughout the world.
A multidiscipline approach focused very much on fitness for service.
Relief calculations and hydraulic models for the disposal system identified areas of non-conformity.
All major integrity risks identified were subject to risk assessment against the customers risk matrix.
Blowdown and Disposal Assessment of Offshore Platforms
A number of blowdown temperature and blowdown time issues were identified in a screening study. The customer wanted an understanding of the operational risks and how they could be managed.
The blowdown system was accurately modelled to get a clearer understanding of the non-conformances. A mechanical screening exercise was carried out to clarify the implications of the low temperature deviations against MDMT.
Survivability calculations were carried out for the blowdown time non compliances against customer agreed criteria.
The disposal system was analysed to understand the bottlenecks (hydraulics, effluent removal, radiation and dispersion).
Pragmatic mitigations were reviewed and agreed on with no downtime or disruption to production.
Chemicals Complex Disposal System Assessment
The customer had a major revamp of the process units planned and the flare system did not have an up to date hydraulic model
The Study required an assessment of the adequacy of the flare system pre and post revamp.
This required:
- the development of a Flarenet model
- a global scenario assessment
- an assessment of the hydraulic limitations
- a knockout drum assessment
- radiation and dispersion checks
- purge and sealing checks
The study identified significant bottlenecks which needed to be overcome prior to the revamp. A number of potential modifications along with the implementation of measures to reduce significant relief loads were proposed.
Tank Farm Relief Device Non-compliance and Blanketing Issues
The customer wanted to understand their operational risks on one of their large storage tank facilities. If deficiencies were found, the remit was to provide measures that could be implemented quickly without significant mechanical modifications or downtime.
A site survey and a desktop review identified a large number of relief devices which were incorrectly set. Additionally inspection and historical trends suggested that the blanketing systems required adjustment as excessive nitrogen usage and valve damage was evident. The second stage of the work entailed a more in depth analysis to calculate relief device size requirements.
Modifications to the purge device settings resulted in immediate savings in purge gas usage and a significant reduction in releases to atmosphere.
Although a number of devices were shown to be undersized, various mitigating measures were proposed to limit the relief requirement without constraining operational capacity.
Additional relief capacity was installed by rationalising tank nozzle usage and/or changing to dual service devices.
Cold Eye Review of Flare and Vent System
The customer requested MF Process Safety to carry out a review of the flare and venting design basis for a new facility.
Options proposed in certain parts of the plant were compared and contrasted to identify the most appropriate solution.
Flare package and detailed design documents were reviewed and recommendations made to improve the integrity of the systems proposed, advising of best practice in a number of areas. Dispersion and radiation study results were reviewed for acceptability, as was the hydraulic model.
Recommendations were made for corrective actions and a high level overview of the installation identified the need for AIV and FIV studies to be carried out.
Oil and Gas Terminal Debottlenecking Study
The customer was faced with the challenge of introducing a new gas plant onto a 30 year old oil and gas facility. To ensure that the existing flare could accept the additional blowdown and relief loads, a flare debottlenecking study was commissioned.
Our consultants developed an up to date basis of design, supported by hydraulic and radiation models. These were used to assess the limitations of the flare system.
Options were generated to resolve radiation excursions at the property boundary, proposing segregation of higher pressure fluids to minimise piping modifications and mitigate MDMT issues.
Prioritised Flare and Relief Assessment
The customer had a limited budget, and a full evaluation of all hydrocarbon systems was out of the question.
Extensive experience from similar studies gave MF Process Safety insight on where to focus attention. Systems were prioritised in terms of expected safety severity and likelihood of occurrence. Known concerns were also included as part of the assessment.
The study provided a cost effective way of identifying operational risk. Site inspection provided useful information to qualify some of the issues identified.
Short and long term mitigating measures were proposed to minimize ongoing risk.
MF Process Safety Ltd
Flare & Relief Consultancy
© 2017 MF Process Safety Ltd
© 2017 MF Process Safety Ltd