Maintenance is an important activity for asset intensive industries. It enhances life and reduces operating risks of plant and equipment. Effectiveness of maintenance is reflected in the bottom line of organisations through reduced costs of operation, downtime, injuries, repair and replacements, asset loss and insurance premiums. It is difficult to accurately predict the degradation and wear and tear of long life assets. Accurate cost of risks linked to injuries and compensation is another complex area for quantification. Understanding of the magnitude of risk in financial terms makes it easier for decision makers to use executive judgement for choosing appropriate design from available alternatives and/or retrospective plant and process modifications. Quantitative risk models are helpful for cost effective operational and maintenance decisions. This paper is focused on how the failure characteristics of a component or assembly can be modelled mathematically. Quantitative approach to risk based maintenance decisions is proposed to estimate risks associated with failures and how to evaluate effectiveness of risk mitigation using alternative strategies