Optimization of instrument maintenance

Safely reducing the length of annual shutdowns


Planned Maintenance Routines (PMRs) on a 3-stage compressor with excessive instrumentation was lengthening the customer’s annual shutdown duration.

DNV GL was asked to determine if maintenance intervals of non-safety critical compressor related instrumentation could be extended without undue danger or production impact.

DNV GL solution

Compressor instrumentation was analysed against the HAZOP to ascertain which were safety critical, safety related, or were only for production, or asset protection. Instrumentation that was safety related, but not safety critical, underwent reliability assessment to determine if the maintenance interval could be lengthened whilst complying with the client’s tolerable risk criterion. Asset protection instrumentation underwent economic assessment to determine the optimal maintenance interval, i.e. the lowest summed cost of maintenance, incurred costs due to spurious trips and cost of equipment failure. 

Outcome and benefits

The outcome of the analysis was that a high proportion of safety related instrumentation PMRs were extended by one year. Several asset protection instrumentation PMRs were extended by two years. This enabled the customer to reduce their annual shutdown duration, with a minimal impact on production uptime and minimal safety impact, saving millions of dollars.