The Key to Your Reliability Centered Maintenance Approach May Be Missing
by Paul Lesnau, on 4/7/20 8:45 AM
California’s Air Resources Board has set aggressive climate target policies that continue to demand increasing efficiency for refineries across the state. The prevention of leakage is key to meeting these per-barrel efficiency benchmarks, making preventative maintenance a front and center challenge. But the question remains: Is your maintenance plan comprehensive enough?
Considering the number of pumps operating throughout a plant, every opportunity to improve reliability positively impacts productivity and efficiency. A commonly employed reliability-centered maintenance approach uses a structured framework for analyzing asset functions and potential failures. Let’s take a deeper look at some improvement opportunities for this approach that you may have overlooked.
Enhancing Your Reliability Centered Maintenance Approach
One method of reliability centered maintenance analysis poses seven questions to identify potential causes of failure and develop plans to prevent asset failure.
- What are the expected functions and performance metrics of the asset?
- What can cause the asset to fail?
- What causes each type of failure (failure modes)?
- What happens at the time of failure?
- What are the consequences of each failure mode?
- What can be done to predict or prevent failure?
- What can be done when failure cannot be prevented?
These seven questions are a powerful method for developing scheduled maintenance plans that cost-effectively balance risk and efficient operability with regard to a petrochemical plant’s critical assets.
Let’s take just two of these questions—#3 and #6—and apply them to the problem of pump leakage. Depending on the extent of leakage, this may also be equivalent to pump failure, particularly in light of more locally-stringent Bay Area Air Quality Management District (BAAQMD) emissions regulations.
What causes pump seal failure?
When pumps, seals, and seal support systems are properly engineered, installed, and maintained a plant should expect years of reliable service. However, between the time of installation and the current day, process changes, operating conditions, and equipment age can lead to declining performance. Eventually, this may lead to asset failures.
Pump seal failures account for more than one-third of pump failures. Several factors precipitate seal failure and attention to these problems is the first step in reducing the chance of unplanned downtime. Here’s what to look for:
⇒ Excessive vibration: Too much vibration in a pump, coupling, or drive will cause seal faces to wear and eventually fail. Vibration can be caused by a broken or damaged impeller as cavitation or particulates taking their toll. The source may also be a bent or misaligned pump shaft. Other components to take a close look at include the coupler, motor shaft, worn thrust or radial bearings, or loose anchor plate bolts.
⇒ Materials and supporting systems that are no longer suitable for current process demands: The characteristics of process fluids may have changed since a system was first installed. For instance, California Bay area refineries must now contend with sour crude that has a higher acidic content (H2S) that may cause pump seals to become brittle and fail. Seal support systems installed years ago can no longer adequately maintain the required seal chamber environment.
What can be done to predict or prevent pump seal failure?
A reliability-centered maintenance approach addresses the vibration problem through a planned maintenance schedule, checking for vibration and the underlying causes mentioned above. Maintenance schedules should be data-driven, with intervals based on repair records of similar classes or types of pumps and their processes.
Plants adopting an Internet of Things (IoT) strategy can instrument critical pumps to monitor vibration and other performance metrics like pressure, flow, speed, and torque. This will alert you to potential problems in real-time, allowing you to remedy the problem well before pump seal failure brings a process to a standstill. Historical performance data obtained via IoT systems can be analyzed and used to predict pending pump failure well in advance, providing a new dimension to a plant’s reliability centered maintenance approach.
The second issue—suitability of materials and supporting systems—is often the missing key in maintaining pump seal assets. With a focus on improving reliability through better maintenance practices, you may overlook the benefits of material and design advances that further improve seal reliability.
Advances in material science have led to the development of seal materials engineered specifically for certain chemical processes and are far more resilient in harsh environments.
If your pumps are showing signs of leakage, either as a result of age or changes in process fluids that stress your current environment, it may be worthwhile to consider seal upgrades. Improved designs and resilient seal materials carefully matched to your processing needs are a critical factor in preventing pump failure.
Similar improvements have been made to seal support systems, offering capabilities to further enhance pump seal reliability. Any plans for upgrading pump seals should be accompanied by an investment in upgraded seal support systems. Advantages of this approach include:
- A wide range of seal support systems solutions and configurations to more closely match your specific processing needs
- Seal support plans that follow API 682 Plan Standards, yet can be customized for your specific plant processes
- Increased pump seal reliability (especially for barrier or buffer seals) to meet stringent fugitive emission standards and avoid sanctions
- Designs that avoid pipe threads and limit the number of connections wherever possible while efficiently and accurately maintaining a proper seal chamber environment via temperature, pressure, and flow instrumentation, and cooling units
- Isolation valves and bypass loops that facilitate easier system maintenance
Design improvements and a wide range of seal support system components and configurations give reliability and rotating equipment engineers an additional means of enhancing pump seal reliability, and strengthening the reliability centered maintenance approach.
Local Partners Complement Your Reliability Centered Maintenance Approach
Advances in material science and seal and support system designs give you ever-better means of enhancing the reliability centered maintenance approach. To gain the optimum value from the investments in new seal support systems, collaborate with local partners who have decades of petrochem industry experience. Expect a deep understanding of your specific needs when designing and assembling the seal support systems to meet those specifications. A local partner is a key part of your reliability centered maintenance approach, with replacement parts and technical support readily available.
To find out more about how Swagelok Northern California can complement your reliability centered maintenance approach and help you increase efficiency with local seal support systems design and assembly, contact our team today by calling 510-933-6200.
About Paul Lesnau | Sales Manager, Business Development Manager, and Field Engineer
Paul holds a B.S. in Mechanical Engineering from North Dakota State University. Before joining Swagelok Northern California, he was the West Coast Regional Sales Manager for an organization based in Illinois involved in pneumatic and hydraulic applications where he supervised product distribution throughout the western United States, Canada, and Mexico. While in this role, he was able to help provide technical and application-specific expertise to customers and distribution to drive specifications.