Eliminating human error

Maintenance on safety critical plant and equipment should really be one of the safest jobs undertaken on a site. Given the nature of the working environment, it is generally well planned: checks and sign-offs abound (the permit-to-work system); risk assessments are done; senior engineering staff are involved; and dangerous substances are removed, flushed out and cleaned from the plant.

Many of the potential hazards are eliminated and, for those left, very tight controls are employed. This focus on the occupational safety of the maintenance personnel is highly admirable. But it should not be forgotten that for safety critical plant, it is vital to ensure that the plant or equipment following maintenance is once again meeting the design intent.

It is vital that the plant, process or equipment remains compliant with the design following maintenance - and the maintenance personnel must understand the criticality of the process, so that they are aware of the consequences of not doing a job properly.

For the routine changing of a pump, for instance, most maintenance personnel would ensure that the new pump gives the same rate of flow, the motor is the same size and so forth. However, dependent on the properties of the material, the most important criterion might actually be the construction of the pump internals. If replaced incorrectly, then a loss of containment event may ensue.

This is a clear demonstration of human error - most likely unintentional. The equipment was designed to have particular materials of construction and without these the design is compromised. Whilst this may not prove critical if the loss of containment is of an innocuous material, it is a far more serious matter if the substance released is toxic or flammable.

To guard against human error during maintenance operations, companies must first determine which equipment within the plant will have the greatest overall impact were it to fail. A full risk-based analysis covering all aspects of the plant should then be undertaken, taking historic reliability data and operating experience into consideration where possible. Based on the results of this analysis, planned maintenance should be scheduled for all safety critical equipment.

Personnel involved in the maintenance of these safety-critical areas need to fully understand the importance of regular maintenance and inspection of this equipment, rather than waiting until the situation reaches a near-critical level. Liaison between engineers, production operatives, maintenance personnel and procurement departments is also important to ensure that the correct levels of spare parts to the correct specification are kept in stock for maintenance purposes.

Relevant personnel should always be aware of why certain critical operations must be done in a particular order. If they fully appreciate the significance of their actions, then potential excursions should be reduced.

Training goes some way towards avoiding mistakes and system violations, but is unlikely to eliminate unintended omissions where the person has simply forgotten to do something that relates to a critical maintenance activity.

Educating personnel in the importance of doing tasks in a specified order or a particular manner is an essential element of the process safety management regime.

The degree to which a team or individual employee feels they have ownership of an area of plant or piece of equipment, the more reliable it is and the more likely it is to be operated and maintained in the correct manner. Again, the correct manner needs to be clear, unambiguous and understood; and related to the design intent, rather than based on picking up the historical practices of the old-hand operatives.

Article by Dr Julian Hought, managing director of HFL Risk Services Ltd