Ammonia Relief & Vent System Appraisal

A supplier of high specification ultra pure chemicals to the semiconductor industry, appointed OSL to appraise an existing anhydrous ammonia relief and vent system to ensure its design suitability and compliance with applicable standards and legislation. 

Project Overview

A safety inspection carried out on an existing anhydrous ammonia storage facility built in the 1980’s raised a number of queries regarding the suitability of the existing relief and vent system and its compliance with relevant standards and legislation.

OSL carried out a design verification study using data gathered from site and from discussions with the site technical team regarding the operation of the facility.

The study findings were presented together with recommendations to bring the existing relief and vent system into compliance with standards and legislation. Improvements ensured the relief and vent system was able to provide overpressure protection duty and safe disposal of ammonia in an emergency situation.

Key Aspects of the Delivery

OSL explored a number of key aspects as part of the verification study in order to ensure the existing relief and vent system satisfied all necessary design requirements:

• Identification of credible overpressure scenarios
• Calculated required relief flow demands for all identified overpressure scenarios
• Relief valve vendor liaison to obtain the valve specifications and parameters vital for the relief valve sizing verification
• Review of the relieving capacity of the installed relief valves
• Hydraulic assessment and vent system modelling using Aspen Flare System Analyzer
• Dispersion modelling of the emissions from the vent to determine vent discharge height requirements
• Provision of the anhydrous ammonia storage and vent appraisal report.

Clever Thinking®

OSL combined their expertise in relief and vent system appraisal and their experience with anhydrous ammonia storage systems to tackle the challenge for the Client. A multidisciplined team was involved to ensure the technical solution was fit for purpose. This resulted in recommendations to separate the process vents and the relief valve vents to give a lower risk to site operators.