Q&A from our downstream optimisation webinar ‘Peak performance’

By Stephen Hall, Jordan Grose and Duncan McLaren

Disclaimer: The answers below were given in the context of the webinar and may not address all aspects of the issues discussed. For more comprehensive information or application support, we encourage you to contact us directly

Reliability, maintainability, and availability (RAM)

What are the fundamental (and simplistic) differences between RBI and RAM analysis?

RBI is directed toward determining the risk that failure of equipment and piping poses the health, safety and the environment from releases from the pressure envelope.

RAM is directed towed addressing the loss of production posed by the failure of components, systems, and facilities. It can consider rotating machinery, fixed equipment, electrical, I&E, piping, human factors, and external events in determining total risk.

How can RAM analysis can be used to reduce our maintenance frequency?

RAM can be used to identify drivers of current turnaround frequency. Once identified, RCM can be used to determine what maintenance tasks require shutdown. Finally, RAM can be used to determine the marginal risk of decreasing the turnaround.

What are the definitions for availability, unplanned down time, etc used in your calculations?

Availability is uptime/(uptime + downtime); it is only a measure of what percentage of time a component or systems is operating or not. Since systems, units and facilities can be less than totally down, terms such as production efficiency (PF) or equivalent availability (EA) have been defined. PF is a measure of the level of production in a given period of time.

What failure rate data did you use to develop the RAM model?

The data comes from multiple sources. IEEEE standards 493 and 500, NERCGADS (power plant data), Oreda (offshore and subsea), previous studies, CMMS data, expert opinion, and potentially from vendors.

What is the timescale of a typical RAM case study?

The time scale for A RAM Analysis is dependent on the scope. Typically, they will run from 45 to 90 days for a medium-sized facility.

Risk-based inspection (RBI)

Can RBI be done on rotating equipment?

Yes, this can be accomplished on parts that are part of the pressure boundary, such as pump barrel, seals, valve internals, etc

How is RBI done for piping systems?

Define piping circuits based on process conditions and metallurgy. A defined circuit becomes an entity which is assessed for risk through determination of likely damage mechanisms, process conditions, and maintenance and inspection history.

How to choose an inspection program by RBI analysis?

Inspection frequencies are determined by equipment or piping risk; the higher the risk, the more frequently it should be inspected. The inspection techniques are determined by which method is most effective in monitoring the onset or growth of damage mechanisms.

How effective is RBI in managing CUI (corrosion under insulation)?

RBI methodically looks at insulated components and piping circuits, addressing the likelihood of failure based on insulation quality and state, external environment (eg, hot, humid or arid) and surface operating temperature range.

Can any RBI study achieve the amount of savings shown earlier or does Wood have some unique capabilities or tools to enable them to achieve such savings?

The savings shown in the case studies can be achieved by any RBI program using best practice, assuming it is properly implemented and sustained. While we do not have a magic formula, our experience, domain knowledge and tools allow us to identify improvement opportunities, evaluate risks, and overcome implementation challenges with higher efficiency, accuracy and confidence.


Have you studied pro-active maintenance approaches for thermal fatigue cracks and vibration-induced cracks on vessel and piping?

Yes, we engage in proactive approaches to de-risk vibration-induced fatigue in existing and new facilities. It is based upon the Energy Institute avoidance of vibration induced fatigue failures  (AVIFF) and we regularly help clients with these types of programmes.

What is the vibration guideline used in the case study for limits? Are there any ISO standards?

VDI 3842 are the guidelines used in the piping/structural vibration case study. The Energy Institute AVIFF guidelines can also be used and are similar to the VDI guideline.

Did you used Design Approach 3 to solve the piping vibration issue or pulsation study?

API 618 Design Approach 3 is for reciprocating compressor applications and was not used in this case, as the vibrations were due to multi-phase flow-induced excitation, not pulsating flow from a reciprocating compressor.

What software do you use for multipoint analysis vibration?

We use our proprietary software PostPro that can process the huge amount of data from over 100 channels (we recently analyzed over 200 channels). PostPro reduces the analysis time from what used to take weeks to months down to only a few days or less.

What pipe supports were used to control vibration while allowing some thermal / pipe stress movement?

In this case, our novel ThermaGlide anti-vibration clamps were used to allow for thermal expansion of the pipe while controlling its vibratory movements. Learn more about our anti-vibration products and which clamp is best for your application.


Is the going ‘digital platform’ proprietary to Wood?

The digital case study presented utilized commercially available software best suitable to the client. The platform was created based on client needs and budget.

More questions?