Reliability assessment of rotating equipment

Reliability optimization is an important part of plant revenue and profit. Reliability is the ability of the equipment unit to perform its stated duty without a forced (unscheduled) outage in a given period of time.

The major components of reliability improvement include 

optimization of site rotating equipment availability by implementation of practical:

Site reliability audits

Assessment methods

Availability improvement plans

Condition monitoring techniques

Preventive and predictive maintenance plans

Troubleshooting techniques

The objectives of the end user are:

• Maximum reliability (on stream time)
• Maximum product throughout
• Minimum operating costs

In order to maximize profit, a piece of machinery must have maximum reliability, maximum product throughput and minimum operating costs (maximum efficiency). In order to achieve these objectives, the end user must play a significant part in the project during the specification and design phase, and not only after the installation of the equipment in the field. Effective field maintenance starts with the specification phase of a project. Inadequate specifications in terms of instrumentation and the location of instrumentation will impact equipment reliability.

It is important to understand that the life span of rotating equipment is extremely long compared to the specification, design and installation phase. A typical installation will have a specification, design and installation phase of only approximately 10% of the total life of the process unit. Improper specification, design or installation will significantly impact the maintenance requirements, maintenance cost and availability of a particular piece of machinery. Proper screening of equipment vendor selection establishes the foundation on which reliability is built. Likewise, enforcing shipment, construction, installation and commissioning specifications, optimizes reliability and truly makes it ‘cost effective’ in terms of the life cycle of the equipment.

Optimizing reliability

The key to reliability improvement is to build a solid program foundation. The success or failure of any reliability improvement program directly depends on obtaining and maintaining management support.

1.       Clearly stating impact of problem on plant profit (cost of unavailability)

2.       Preparing a brief statement of

• Problem
• Impact on plant
• Reliability improvement plan

3.       Being confident

4.       Being professional

5.       Being autonomous (do not expect management to do your job!!)

6.       Providing timely updates

Input data

Once management support is obtained, input data forms the foundation of the program.

·         Include all the facts (operation, reliability, maintenance failure analysis etc)

·         Consider the machinery environment

·         Consider the entire system

·         Only use proven data (don’t guess)

·         Accuracy is most important-confirm data is correct

The environment or surroundings for any piece of rotating equipment play an important part in determining the availability of that particular item.

• ·         Process condition change
• ·         Piping and foundation change
• ·         ‘Unit’ (driven, driver, transmission, auxiliaries)
• ·         Ambient conditions

This shows that the rotating equipment environment is the process unit in which the equipment is installed. In any of these items are not taken into account, the accuracy of the conclusions reached during the assessment phase will be significantly reduced.

In my experience, most failures in predictive maintenance and troubleshooting exercises occur because the entire system in which the component operates is not considered. Every component in every piece of machinery operates in a system. Defining the system and all of the components contained therein is a very important step in successful problem analysis.

The concept of a system

• ·         Think system
• ·         Every component is a part of a system
• ·         In order to determine root causes, systems and not just components must be considered

Experience counts!

Having experienced analysts to determine the root causes of low reliability is the next step in building a strong program. Given below are ways to build and develop a practical, strong analyst group.

1.       Select experiences rotating equipment personnel

2.       Ideally, design and field experience are the best combination

3.       Provide site specific training

4.       Measure results

5.       Provide opportunities for networking with other specialists within and outside the company

• ·         User groups
• ·         Industry conferences
• ·         Regional conferences

6.       Include analysts in all phases of new projects

Utilize practical, correlated assessment techniques whenever possible. Today, many statistical methods are available to the analyst to determine causes of failure and to predict equipment and component life. The personal computer makes the use of these methods quick and easy.

However, the reader is cautioned to regard all statistical methods as only a part of the process. Whenever possible, actual data concerning failure rates should be used and the correlation of statistical methods should be defined. It should always be remembered that the basis for most statistical methods have evolved from industries where ‘production components’ are used, i.e. the electronics and automotive industries. However, the rotating equipment unit, regardless of type, always becomes customized by virtue of its environment. That is, each rotating equipment unit has its own signature. Consequently, care must be exercised when applying statistical methods to rotating equipment reliability assessment.

Since every rotating equipment unit, regardless of size, represents a ‘customized system’, care must be exercised when assessing the results obtained by statistical methods.