June 2019

Maintenance and Reliability

Equipment life assessment—An exercise to help ensure plant equipment integrity and reliability

Numerous plants around the world operate with hazardous oil and gas, petrochemicals and refining fluids that have surpassed their design life.

Numerous plants around the world operate with hazardous oil and gas, petrochemicals and refining fluids that have surpassed their design life. The default design life of a plant and its major pieces of equipment is normally 30 yr. A plant reaching this design life must go through inspections to continue its operation. Failure to do so may lead to catastrophic consequences. However, when equipment has been inspected for years, what should be checked when the plant is close to reaching its design life? The facility will continue operating the way it has been since commissioning, so why should there be a need for a separate exercise?

The answer is that the records, procedures and systems that have been operating the plant may require a special check to ensure that each unit is safe to operate. This is an exercise/study that is called different things (such as an equipment lifecycle study or an asset life extension) in various parts of the world. However, it should be followed in the best way possible to ensure that aging equipment units are fit to operate.

The questions that must be asked include:

• Where to start?
• What to look for?
• Who is going to check the equipment?

Personnel operating the aging equipment may know everything about its performance, but may undermine some of the pending issues, since nothing has happened to date. An examination is required to identify any and all potential issues associated with all plant systems and to issue recommendations to address the same.

A list of black equipment

The stages to obtain a list of black equipment are shown in FIG. 1. These steps include:

Fig. 1. Stages to obtain a list of black equipment.

1. Forming a multi-disciplinary team
2. Examining operations, maintenance and inspection records
3. Consulting the defect register of the facility
4. Meeting with site inspection engineers should equipment reports be unavailable
5. Identifying the type of repair that will be needed
6. Making a list of black equipment at the site.

After assembling a team of multidisciplinary individuals—from process design, inspection, mechanical and maintenance—who all have a fresh perspective for the plant in question, the next step is to investigate the operation, maintenance and inspection records. These records may not always be available from the plant’s commissioning, and may not provide the full picture required to make a correct equipment life assessment. A procedure is required here to plan which records will be examined and, if they are unavailable, to determine the next step to bridge this gap and perform a reliable assessment.

A reliable assessment is one that has few or no unknowns during the assessment process—everything has been assessed based upon the full data available and by the right person on the team. At this point, the team will narrow down the records related to the static equipment of the plant. Once this is completed, the target is to ensure the life assessment of the plant’s static equipment. First, the team should consult the defect register of the facility. Typically, the defect register is meant to be a list of static equipment units that have been subject to damage affecting their performance (e.g., equipment corrosion forcing the inspection and maintenance team to perform necessary repairs before the equipment is put back into operation).

Facilities that have this kind of list for their assets will be able to get a jump start on assessing equipment life. For cases where this data is unavailable in a discrete form (e.g., in the form of a list clearly indicating the problematic static equipment at the site), a discussion with the concerned engineer is a great place to start.

After obtaining a list of static equipment having issues related to inspection and repair, the first to-do item is to identify the type of repair—a temporary repair is one meant to last for a specified time, and a permanent repair is one designed to make the equipment like new. If it is a temporary repair, then equipment validity can be confirmed through online monitoring and inspection. Whether it has passed its operational lifespan or there have been findings during online monitoring, equipment is still vulnerable to failure. Start making a list of black equipment at the site. If a permanent repair was completed, then a cause of failure should be determined (such as through a root cause analysis). If this exercise is not completed, the specified piece of equipment should move to the black equipment list.

While these checks are performed, it is also important to confirm that the repair work suggested was in line with internationally acceptable standards. If the suggested repair was not in line with acceptable standards and/or if the actual repair did not follow the suggested procedure, then this piece of equipment should be moved to the black equipment list. Personnel should document equipment records while performing this exercise.

After obtaining the list of black equipment, each piece of equipment should, at least, contain the following information:

1. Root cause of equipment failure
2. Actions taken previously
3. Recommended actions
4. Expected life after recommended actions
5. Special inspections required for the expected life
6. Budget required for implementing recommended actions.

Takeaway

Establishing the black equipment list after reviewing inspection and maintenance records is a landmark in an equipment life assessment exercise. Next, operational records must be checked. A similar strategy should be adopted to find the static equipment that has ceased operation due to damage. Furthermore, operational exceedance records should be obtained to determine if integrity operating windows have been exceeded. Although a record for the lifetime of equipment may not be available, a recent record can be taken with the assumption that a similar operational envelope may have existed.

Having this assessment ready to be presented to management for their information, review and approval will complete this exercise. Implementation of the recommendations will help the plant ensure its mechanical integrity and reliability. HP

The Author

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