Risk Management System in Alumina Refinery

Hi Friends,

In earlier posts, we have already discussed the details about Hazid and Hazop studies in Alumina refineries.  Today we will discuss about the risk management system in Alumina refinery. In other chemical and petrochemical industries, this is popularly known as Risk-based inspection (RBI). Risk management system or Risk-based inspection is a dynamic tool to assess the future risk of plant / project based on current data and information gathered at the time of assessment. This technique helps us to prioritize the inspection of plant & equipment, pipelines and other associated facilities in optimizing the effective plan, procedure, frequency of maintenance and risk mitigation actions in business by quantifying the probability of failures and preventing the consequences. In Alumina refinery, high risk components are small percentage to the extent of about 5% of total facilities limited to pressure vessels, heat exchangers, co-generation plant and bauxite residue storage (red mud pond). 

Since risk is a function of probability and consequences, thus risk management system involves following three key issues-

(i) Assessment of risk,

(ii) Required level of risk reduction and

(iii) Development of plan to minimize risks to a acceptable level tending to zero.

The applicable relevant standards followed in risk-based inspection (RBI) as well as risk management system are detailed in API 580, API 581, API 510, API 570 and API 653 as elaborated below-

API 580, May 2002: Principle and general guidelines.

API 581, May 2008: Quantitative methods for inspection planning, probability of failure and possible consequences.

API 510 : Inspection of pressure vessels and heat exchangers.

API 570 : Inspection of piping.

API 653 : Inspection, repair and reconstruction of tanks.

Type of assessment may be either qualitative based on experience and engineering judgement or quantitative based on logic model and probability.

Risk associated with plant and equipment of Alumina refinery are influenced by following key parameters-

• Composition of process fluid,
• Volumetric flow rate,
• Process conditions like caustic concentration, caustic ratio, pressure, temperature, solid consistency etc.

Probability of failure can be assessed on the basis of following observations-

• Type and mechanism of deterioration,
• Rate of deterioration,,
• Estimated future rate of deterioration,
• Design tolerance provided for that deterioration,
• Severity of deterioration 

The consequences of failure are evaluated on the basis of following data / information-

• Safety and health impact,
• Environmental impact,
• Environment remedial cost,
• Production losses in monetary terms,
• Financial impact for maintenance / reconstruction / replacement.

Risk mitigation measures for major equipment of Alumina refinery are broadly outlined below-

• Adoption of technology developed by experienced team of professionals,
• No compromise on design margins and tolerances,
• Qualified erector for specified equipment and facilities,
• Periodic inspection and maintenance / reconstruction / replacement.

As such, there is no relevant standards for risk management associated with Bauxite residue storage pond, however, following guidelines in addition to those stated for equipment may be followed-

• Ensure a minimum free board of 1.5 meters in the existing residue pond operative with wet ponding method of residue disposal,
• Design of new pond to ensure no percolation of alkaline water into adjoining natural streams,
• Adoption of dry stacking system for disposal and storage of residue at plus 55% solids (w/w),
• Regular inspection of earthen dykes and seepage tests in nearby habitat areas and
• Immediate remedial action for repair.

Only a few Alumina refineries in the World are following these practices. Now, the time demands to strictly adhere to these guidelines with due seriousness considering the importance of safety, health and environment by all alumina manufacturers in the World.

Trust, the subject has been covered adequately. Please put your views / suggestions / remarks / comments, if any.

If you like this article and find it useful, then please press your rating as  +1  .

Kunwar Rajendra