Reliability and maintainability: Questions for suppliers about their equipment

Companies frequently ask suppliers of critical equipment about the reliability and maintainability of their equipment. The questions cover a number of topics and often include queries about Mean Time Between Failure (MTBF), recommended spares, PM requirements, the role of reliability and maintainability in the design of equipment, and so on.

12/15/2002


Companies frequently ask suppliers of critical equipment about the reliability and maintainability of their equipment. The questions cover a number of topics and often include queries about Mean Time Between Failure (MTBF), recommended spares, PM requirements, the role of reliability and maintainability in the design of equipment, and so on.

My experience has been that the answers, while pretty standard, are often little more than "sales-speak," and perhaps more importantly, the questions are often not sufficiently specific to solicit an adequate response. These observations are not intended to be overly critical, but rather to observe what has been traditional in the supplier-buyer relationship. Below are some common examples of questions put forth by the buyers, and typical answers from the suppliers of critical equipment.

Specifications

A common question included in a request for proposal might be something to the effect of "What roles do reliability and maintainability play in the design of the equipment you are quoting? A typical answer might be something to the effect of "We've designed this equipment many times and work with many plants to make our equipment reliable." Of course, I'm summarizing, but this seems to be the gist of the questions and answers, and they aren't very satisfying.

Let's be more specific, and use the following kind of language:

We're currently experiencing some __ % maintenance downtime with equipment similar to that which you are quoting. This is considered at least in part to be due to poor reliability and maintainability. Likewise, the lack of ease of changeovers is also affecting our ability to provide for rapid setup and reduced changeover and transition losses. We estimate this at some __%. This totals over __% of our production losses. We find this unacceptable for new equipment, and will make the purchase of this new equipment untenable. (Note: you might also consider their initial reply as nonresponsive to your question). In order to fully address these issues, please provide or respond to the following:

A. Provide your definition, criteria, and standards for reliability and maintainability of the equipment being supplied; e.g., SAE, SMRP, etc.

B. Provide a description of the most common failure modes, and the consequence of each, for this type of equipment. Also provide a description of those failure modes that are infrequent, but have severe negative consequence for this type of equipment. The description of consequences should include a discussion of the potential downtime (or mean time to repair) and repair costs that are typically experienced for each failure mode.

C. Provide the key operating and maintenance practices required to mitigate and minimize these failure modes.

D. Describe the critical spares that are needed in light of these common failure modes. What is the risk or consequence without these spares?

E. Describe the methodologies being used for analyzing the reliability of the equipment; e.g., RCM, RCFA, FMEA, Pareto, etc. Give a specific example of each method being used for the equipment proposed.

F. Where and how is this data collected for applying the methodologies described in paragraph E. above, and how does the proposed equipment compare to the baseline equipment for which the data was collected?

Designing

A typical question might be, "How can future downtime be prevented during the design and engineering phase of the equipment procurement? And what can be done to facilitate future troubleshooting and problem solving efforts?" A typical answer might be something to the effect of, "We'll let you review the drawings for your approval and/or our processes are highly automated for ease of troubleshooting." Or they might say, "We spend considerable time in plants working with operators and maintainers, understanding their problems, and getting their ideas on how we can improve the design." Certainly these are important, but not likely to be sufficient.

Let's ask the following:

A. In light of the failure modes analysis described above, how will you modify the design of your equipment to eliminate, mitigate or better manage (through condition monitoring methods that allow early detection of problems) these failure modes? If condition monitoring technologies or methods are applied, please describe those that apply, including their potential costs and benefits. Include in your discussion a review of the application of continuous monitoring.

B. Describe 3 or 4 design changes that have been made as a result of working with your customers, and why. What additional efforts are currently ongoing for improved reliability and maintainability in the equipment?

C. Attached is a listing of several problems that we have had in reliability and maintainability. Please provide us with a description as to how you will address and resolve these problems in the design to assure improved reliability and maintainability.

D. Will approval of your drawings be permitted, and if so, in sufficient time to allow for equipment modifications and while still meeting the project schedule? Please outline your plans.

Experience

When asked about their specific experience in providing reliable, readily maintainable equipment, or more to the point, when asked about the reliability of the equipment being procured, a typical reply from the supplier might be "This equipment has been installed in many places throughout the world, and has operated very reliably. In particular, this equipment was installed at the First-Up plant, and had few difficulties during commissioning, and is currently running reliably. It's also been installed at the Next-Other plant."

Let's ask the following:

At the First-Up and Next-Other plants, please respond to the following for each plant:

A . What has been the historical average percent unplanned maintenance downtime?

B. What is the mean time between repair?

C. What is the mean time to repair?

D. What are the five most common failure modes?

E. What is being done in the design to mitigate or eliminate these reliability and maintainability issues?

F. How long did the commissioning process take to achieve full, sustainable production rates? How many failures, and of what duration, occurred during that period? Did any supplied parts exceed the guaranteed failure rate?

G. What were the major problems encountered during commissioning?

H . What design changes have been made to minimize these commissioning problems?

I. What is the standard commissioning process? We desire that the equipment run at least one full production cycle while maintaining full production requirements. We also desire that this same test be repeatable within 6 months of initial commissioning. Please describe your process for meeting these requirements.

J. We desire a mean time between failure (MTBF) of not less than __ hr. For our purpose, a failure is defined as anything that occurs with the equipment that results in any downtime, production rate reduction, or quality loss. For example, at a __ % confidence level, this requires that we have no more than __ failures during a __ -hr period. Please affirm your commitment to running a commissioning test over the period stated with these specific confidence limits, and predetermined number of failures, or offer your alternative that will meet this need.

K . Could you arrange for our engineers and purchasing people to visit these two plants, and perhaps other plants, to review their practices and performance?

Summary

Using the model outlined should be an integral part of an overall strategy for minimizing the total cost of ownership for major capital equipment. The key to using this approach is having a good understanding of your current operating results and problem areas, the failure modes most likely to result in lost production, downtime, or high costs; or that may have the most severe consequence to your overall operation. Having a good understanding of these issues will assure that you can work with your supplier to eliminate, mitigate, and manage these risks; and that you can minimize your total cost of ownership, and be more profitable.


Author Information
Ron Moore is managing partner of The RM Group, Inc., Knoxville, TN, and author of Making Common Sense Common Practice: Models for Manufacturing Excellence. He can be contacted at RonsRMGp@aol.com




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