Guest Editorial: Interpreting Reliability Metrics With Confidence
Authors: Renfroe Jim 
Published: February 2015

The intensity of today's global energy appetite requires our industry to become increasingly demanding in terms of innovative, cost-effective technologies and day-to-day performance. These requirements are growing almost exponentially as we go after deeper and less accessible reserves. As we stretch to achieve new limits, reliable performance in all facets of operations is pivotal to reducing downtime, improving efficiencies, and optimizing production. In short, now more than ever, reliability is a business imperative—and achieving maximum reliability does not happen without intentional focus and effort. There are no random acts of reliability.

Reliability has to be designed and built into oilfield technology, equipment, and processes by service companies that have made it a strategic imperative. Once achieved, reliability enables all of us to focus a bit more sharply on maximizing financial performance while never diverting our attention from minimizing exposure and risk.

What is reliability? Essentially, it provides an answer to the question, "How much reliance should you place on a particular product and/or technology?" Stated another way, it is the probability that a device will perform its intended function under known conditions for a specified time. I define it as consistently providing the expected results over and over. That is reliability.

Suppliers have a unique opportunity to improve reliability because it is an attribute influenced and affected at all stages of product and/or service delivery, including:Research, design, and testing procedures implemented during product development.Process controls for continual verification and maintenance of tolerance levels during manufacturing.Training for and continual evaluation of safe and efficient operating envelopes and procedures.

It is during the procurement process that operators have a unique opportunity to choose reliable technology to positively affect their overall economic equation. After all, service, maintenance, and repair often contribute the majority of total life-cycle costs. Factoring reliability into the procurement equation can result in economic improvements.

When reliability is a core value, it echoes throughout the organization—from engineering to manufacturing to operations—with all involved consistently working to eliminate even the smallest factors that lead to downtime and lost revenue. Reliability can be ascertained through metrics like functional details and life metrics. But a word of caution: metrics are open to interpretation.

What, then, are some factors to consider when assessing metrics? How can you be more assured of translating probabilities of reliability into actualities? How can metrics represent more accurate performance indicators to better assist in economic calculations during procurement?

Functional Details. Functional details relate to the boundaries of intended use such as temperature, pressure, and load. Primary functional details are easy to quantify and qualify and are typical of most engineering specifications. But are there other design parameters to consider? For example, a design specifies a small, 5/8-in.-diameter electric motor and gear train that will be used to manipulate a small, high-pressure shuttle valve in a downhole tool for use in pressures as high as 15,000 psi and in environments up to 149°C (300°F). The functional specification is easily matched for the environment and load requirements to shuttle the valve back and forth. However, in this example, a proper functional specification should note that the motor gear-train assembly will be powered to a hard stop. Without this latter specification, the motor gear-train unit would likely not be designed to withstand the inertia effect of a hard stop.

Life Metrics. Life-metric requirements define the retention of successful function to complete the planned mission. In this case, the electric motor and gear-train assembly should be specified with life metrics such as 99% reliability for 1,000 hours service or "X" cycles of maintenance-free service. Combining and documenting functional details with life metrics provides a greater probability of achieving the desired mission.