Reviewing pressure gauge applications and installations can help increase instrument life and decrease total cost of ownership.

Pumps sustain the life of process plants as the heart sustains our bodies. Doctors use instruments to gauge the health of a human heart. Process plants (for example refineries, petrochemical, chemical, pulp and paper) use instruments to gauge the health of their pumps and processes.

A New Look at Pressure Gauges

Process plant operators understand the importance of proactively maintaining the health of their assets. World-class process plants prioritize their pumps. Should the gauges that monitor their performance not also have similar priority? Unfortunately, with time, the status of the mechanical pressure gauge has diminished to that of a commodity product.

Implementing a best practice instrument review program can elevate gauge status back to a level that enables plant personnel to understand how important they are to their processes. A best practice instrument review identifies gauge installations with unwanted conditions and recommends corrective actions to ensure optimum performance. In addition to identifying problems, this type assessment can help consolidate inventory, reduce maintenance costs and reduce process downtime.

The purpose of the best practice instrument review is to collect a reasonable sampling of pressure gauge applications, installed base and operating performance to identify trouble areas. This data is then used to create a plan that will accommodate the needs of the process plant while providing the highest level of instrument longevity, reliability and safety (see the sidebar, “Best Practice Instrument Review Process” on page 31).

Every process in a plant is unique. However, within the plant, processes can be—and usually are—interconnected and interactive. For this reason, the best practice instrument review examines plants holistically. Although the plant is viewed as a whole, the review’s initial and primary focus is pump systems.

Typically, vibration is the main cause of pressure gauge failure in process plants. Pump applications produce most of the vibration that affect gauges. Pumps are also responsible for spikes and over pressure—both of which shorten gauge life.

A gauge tagged for repair after an instrument review

When it comes to gauge failures, though, pumps are not the only culprits. Sometimes, gauges fail prematurely because they are misapplied or because of unintentional damage. A gauge may have been ideal for the application when it was installed. However, if equipment modifications or additional components change the process parameters, the gauge may no longer be right for the job.

Improper installation usually damages the gauge. Pressure gauges should be installed using the proper size wrench on the flats. Note that gauges should never be installed by turning the case.

Beyond the Gauges

If gauges cannot be read, they cannot provide critical windows into plant processes. The best practice instrument review identifies issues that affect pressure gauge reliability, longevity and safety.

Pressure gauges leave telltale signs describing their environment and providing details about the processes, pumps and other equipment that they monitor. Typically, an instrument review can uncover evidence of pulsation, vibration, pressure spikes, excess process or ambient temperature, installation damage, clogging or chemical incompatibility.

The review team understands that safety is one of the most critical gauge-related issues, and they educate plant personnel accordingly. When operators and process engineers realize that only a thin wall of metal stands between the people and the process, the process media becomes extremely important for two reasons: 

  • The process media could be under extreme pressure. 
  • The process media could be toxic, caustic, acidic or otherwise hazardous.

Typically, gauges are replaced when they fail. The person who replaces the instrument must understand that the replacement may not be chemically compatible with the process. The review team identifies misapplications like these and recommends appropriate gauges that are manufactured from corrosion-resistant materials or suggests adding a diaphragm seal to isolate the gauge’s element from the corrosive media.

The review team does not simply identify problematic instruments. They also look for, identify and acknowledge correctly installed and applied gauges. The team encourages plant personnel to use such installations as a benchmark.

In addition to solving problems associated with pressure gauges, the review team often solves process and system problems. For example, review team members help plant personnel understand the pressure spikes that result from pump startup and how to prevent these situations—or at least how to protect the gauges from them. The team also helps plant personnel understand how vibration and temperature affect gauge accuracy and longevity.

Managing Spares Efficiently

The best practice instrument review does not leave out the spares storeroom. Part of the review focuses on helping plant personnel rationalize, consolidate and manage their instrument inventory.

With time, storeroom inventory can get out of hand. If a plant stocks spares for 10 or more ranges, perhaps the review team can help reduce that number to five or six ranges. For example, a 200 psi gauge can easily and accurately accommodate a 60 psi application, with ample over range protection as a bonus.

Sometimes, plants change maintenance, repair and overhaul (MRO) contracts or obtain new equipment. The review team can help eliminate the redundancies that can result from not managing these changes efficiently.

Extension of the Equipment Life Cycle

Whether the equipment is a pump, valve, steam system or instrumentation, every piece of process plant equipment has a life cycle. Following best practices is important to plants that strive to be world class. World class process plants maintain their assets proactively. Pressure gauges should be given as much consideration as pumps or control valves.

Extending an asset’s life cycle saves money in the long run. The best practice instrument review was created to help process plants reduce the total cost of ownership—and extend the life—of the instruments that gauge the health of their pumps and processes.

Pumps & Systems, April 2012

BEST PRACTICE INSTRUMENT REVIEW PROCESS


A review team examines the gauges in a refinery in the northeast.

The five-phase best practice instrument review process involves observing a sampling of instrumentation on-site, collecting application and performance data and identifying areas of potential or immediate danger. The review team recommends corrective actions that plant personnel can take to reduce the total cost of ownership by ensuring the highest level of instrument longevity, reliability and safety. The process phases are:

  • Phase #1 is the interview. This step involves discussions between an instrument supplier review team and a member of the plant personnel. During the interview, plant personnel learn the purpose of the instrument review, how it will be conducted and how they will benefit from the program. The interview also helps determine the best way to match the program to the needs of the plant.
  • Phase #2 is the pre-meeting. This step involves determining the units or sections of the plant to review and the roles and responsibilities of the review team. It also identifies prohibited or exempt areas of the plant. The team reviews problematic instrument installations and discusses safety procedures with plant personnel.
  • Phase #3 is the instrument application review. This step involves key plant personnel who lead the instrument review team on an actual plant walk-through. The team reviews the target gauge installations, notes gauges that demonstrate unwanted conditions and identifies gauges demonstrating installation best practices.
  • Phase #4 is the post-meeting. This step involves explaining the instrument review results with key plant personnel, noting gauge installations that pose an immediate safety concern. Together, the review team and plant personnel determine which installations to investigate immediately and which to block out. The review team and plant personnel set schedules for the follow-up meeting.
  • Phase #5 is the follow-up meeting and presentation. During this step, the review team presents its general findings and the executive summary resulting from the instrument review. The review team also presents a spreadsheet that lists details about the gauges from the instrument review color-coded by severity. During this step the review team also provides recommendations for improvements based on experience and best practices. Together the team and plant personnel develop a strategy for moving forward.