Far too little has been done over the years to sustain the performance of control valves once they go into operation, despite widespread agreement on the impact that valves have on process efficiency. Rather than considering control valves as assets to be preserved, too many plants treat them as liabilities — frequently replacing critical valves during shutdown for no reason other than length of service. As a result, millions of dollars have been wasted and perfectly good control valves often have been discarded.
This happens largely because chemical processors historically have had little knowledge of their control valves’ condition. For example, more than half of the valves in some 7,000 profit-critical control loops audited in refining and petrochemical plants by Emerson Process Management were delivering poor performance. Plant personnel didn’t know how to optimize those under-performing valves and had no idea how much they were costing the overall operation. However, a benchmarking study conducted by Monsanto and 11 other chemical companies  showed that improvements to final control elements could reduce the cost of goods sold by 1.5% which meant an additional $15 million return annually on average to each of the plants studied. Another study , performed by Solomon Associates at more than 100 olefin plants in North America, found that overall plant reliability was best in plants that had the highest level of working, effective process control. The loss of production due to reliability issues ranged from 2% of plant capacity in the best facility to about 16% in the worst plants.
If you are searching for a way to reduce costs by improving the efficiency of your process, it’s time to start thinking of control valves as assets to be preserved <em dash>—<em dash> and to begin maintaining them accordingly. It’s as simple as this: process efficiency and reliability are influenced by control valve performance, and sustaining good valve performance can be achieved through predictive maintenance.
An ARC study  reported that “the cost of performing predictive maintenance on valves can be up to five times less expensive than preventive maintenance and 10 times less expensive than corrective maintenance, even before the costs of downtime are figured in.” There’s little wonder that “best cost companies” are increasing their reliance on predictive maintenance. Some companies are even achieving proactive maintenance, which builds on predictive monitoring to identify and eliminate the root cause(s) of maintenance problems.
The road to an effective predictive maintenance program for your control valves can be bumpy. However, common errors can be avoided through a combination of strong leadership, technology and training.
The role of leadership
Leadership is easily the most important factor. Every successful application of predictive maintenance to control valves has rested upon a strong leader or champion inside the company. This person (or sometimes a small group) is committed to the pursuit of excellence, deeply involved in selecting a new approach and insistent on comprehensive training. The leader plays a key role in keeping efforts on course and, so, needs to have the authority to implement the needed changes.
The quest begins with recognizing the need for change and developing a vision for an improved maintenance plan. A review and understanding of current work practices will help you determine what changes are necessary. The vision created should clearly define what you are going to do that’s different.
Several steps are crucial for turning that vision into a reality:
- Focus your initial efforts on critical problem valves where predictive technologies deliver the biggest payback. For example, a pilot program at the ChevronTexaco Refinery in El Segundo, Calif., targeted 103 critical valves and saved the company nearly $275,000 in one year, including $90,000 from improving the performance of just one steam control valve. That pilot program is now being expanded to cover much more of the huge refinery.
- Identify key implementation resources. You need to address the impact of new technology on plant personnel, especially the maintenance staff. Questions such as “what does this mean to me (or to my job)” will be on the mind of those involved with using the new technology. The early involvement of key individuals results in a much quicker buy-in and acceptance of changes to be implemented later.
- Be willing to make changes and have the will to make them permanent. You can expect to encounter resistance. You may need to insist on new practices and procedures and that employees strive to make the unfamiliar system successful. Banish the phrase “but we’ve always done it that way.”
- Establish measurements and use them. Benchmarks are essential for showing progress and communicating success/importance, but they don’t need to be complicated. They might include before and after monitoring of the number of reactive work orders in a particular process area, charting overall process uptime versus maintenance hours spent, or tracking overall maintenance hours required in a particular area.
- Publicize results throughout the organization. Communication, especially with measurement data, is critical for gaining additional support and ongoing success.
- Revisit the vision to ensure that the maintenance program is meeting stated objectives. After review of early results at a Canadian chemical plant, the initial plan for data collection was modified to provide full-time monitoring and faster diagnosis of about 30 critical valves. Predictive intelligence gathered in this way has driven control valve maintenance costs lower for each of the last three years.
Smart valve technology
With the advent of microprocessor-based valve instrumentation and sensor technology, the health of control valve assemblies became much more visible. Data collected by the valve provide never-before-available diagnostics (see sidebar), which many plants have used to improve their processes.