SYSTEMATIC FRAMEWORKS FOR RELIABILITY, AVAILABILITY, AND MAINTAINABILITY (RAM) CONSIDERATIONS IN CHEMICAL PROCESS DESIGN
Abstract
Failures in the chemical process industry may lead to severely negative impacts on sustainability, health and wellbeing of workers and adjacent communities, company profit, and the stability of supply chains. The conventional approach in handling equipment failures has usually been focused on operational strategies. This approach overlooks the critical role of process design in mitigating failure. When availability is considered in a proposed design, it is traditionally through fixed availability values. This leads a design team to generate single-point estimates regarding the potential economic performance of the design. The aim of this dissertation is to present systematic methodologies that account for failure, and the uncertainty around it, early enough during the conceptual design stage. Availability models are developed using a simple Markov process with each item being in one of two states: operating or under repair. Since failure and repair rates are uncertain inputs, two methods of incorporating uncertainty are presented: Bayesian updating and Monte Carlo simulation. Critical process subsystem(s) that are more failure-prone than others are identified. An availability-weighted profitability metric is also presented to include the effects of the failure-repair cycle on revenue and profit. Then, design alternatives that improve the availability of the subsystem(s) in question can be evaluated based on their economic potential. This problem is presented by an optimization formulation with the objective of maximizing the availability-weighted incremental return on investment.
After examining the effects of equipment failures on process profitability, a wider look at other factors affecting the reliability of the oil and gas supply chain is performed. One of the most important considerations for the safe and continuous operation of process plants is the reliability of feedstock supply. Feedstocks are primarily transported to plants using an extensive network of natural gas transmission and hazardous liquids pipelines. Shutdown incidents of those pipelines impact supply delivery to dependent plants and can lead to production shortfalls or disruptions. In process design, a team often has a number of pathways to consider selecting from. These pathways may have different feedstocks, which are transported by pipeline systems. The economic risk potential of pipeline failures or incidents is a consideration that needs to be accounted for in the selection process. Most existing works on pipeline economic risks examine the topic from the viewpoint of the costs of lost commodity, cleanup and recovery, and litigation. To address economic risks from the perspective of the commodity customer, a systematic framework to determine the impact of pipeline shutdowns on process plant production and economics is presented.
Citation
Al-Douri, Ahmad (2021). SYSTEMATIC FRAMEWORKS FOR RELIABILITY, AVAILABILITY, AND MAINTAINABILITY (RAM) CONSIDERATIONS IN CHEMICAL PROCESS DESIGN. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /195231.