The Post Grid
White Paper: Packing a Punch- Sealing Reciprocating Power Pumps
Reciprocating pumps vary significantly from centrifugal pumps in how they seal the high-pressure areas of the pump from the atmosphere. While the theory behind sealing is simple, practical implementation often leads to issues like leakage and downtime.
The successful operation of reciprocating power pumps hinges on a careful understanding of their sealing mechanisms and meticulous maintenance practices to ensure long-term reliability and minimal downtime.
Download our latest white paper published with Pumps & Systems magazine to read Dr. Gary Dyson’s discussion of how low flow affects performance and what can be done to optimize operation and reliability.
Learn more about Hydro’s engineering services or learn more about reciprocating pumps.
Strategies for Improving Life & Performance of Aging Equipment
Many of our aging facilities are still using the pumps that were purchased and commissioned during plant construction. Despite the age of this equipment, effective maintenance strategies and upgrade opportunities can extend useful life for decades more. Older pumps are often more robust than current designs, which take advantage of new manufacturing technologies to reduce the raw materials needed for construction. However, vintage equipment has its downfalls as well. It is important to understand the challenges we face when operating and maintaining vintage equipment so that we can stay ahead of potential sources for decreased reliability.
These challenges were at the forefront of an improvement project undertaken by a Canadian pulp mill. Most pulp and paper mills in North America have been in operation for decades, and many are still running with the original equipment. This facility had several BB2-style makeup liquor pumps (MULP) that were experiencing a low mean-time-between-failures (MTBF). To increase pump life and reduce the risk of unexpected downtime, the pulp mill approached Hydro’s Scotford service center for support in identifying the root causes of degradation. Hydro Scotford combined a thorough inspection process with experience in upgraded designs and materials to bring the MULP system reliability back to an acceptable level and improve overall performance. The major focus points of this project – standardization, material upgrades, and improved tolerances – can be applied to aging installations in all industries.
Read the full story in our recent case study published in World Pumps magazine.
Modifying Existing Equipment to Maintain Operational Standards
Many aging manufacturing facilities have witnessed changes in market demand that have altered their product slate and capacity. These changing system demands often cause equipment that was previously well-sized for the application to run significantly away from the operating range where peak efficiency and reliability are achieved. Running in this mode drives up the life cycle cost of equipment due to short maintenance cycles and wasted energy. In cases where reliability is severely compromised, equipment operating costs can also be accompanied by risk to production due to mid-cycle failures and unavailability of equipment.
To maintain safe, reliable and cost-effective operation, it is important to ensure pump systems are optimized. When approached with the need to optimize a pump system, many end users will look to purchase new equipment for the changed demand. This can be a costly and time-intensive endeavor, as new equipment installation is often accompanied by baseplate and piping modifications that require the system to be taken offline. In contrast, modifying the existing equipment to meet the new system needs provides a custom solution that maintains the original footprint, can be completed on a more aggressive timeline and often provides a more custom fit to the system.
The decision to perform one such modification was made by a major Gulf Coast oil refinery that was running at a significantly lower flow than the original system demand. The site reliability team worked with Hydro to design and implement an extreme downrating of the existing equipment. The result was an optimized system that improved reliability of not only the pump, but other affected system components.
Read our latest case study published with Pumps & Systems magazine where Hydro’s Sergio Ramos outlines how the process for this downrate and what the final outcome was for the end user.
Learn more about Hydro’s engineering services.
Ahlstrom Makeup Liquor Pump
Application: Make-Up Liquor
Pump Details: Ahlstrom Model 2LRS-20
Pump Type: 2-Stage Overhung
When a pulp mill’s make-up liquor pump failed, it was sent to Hydro’s Scotford facility for refurbishment and upgrade to restore reliability.
Hydro’s standard disassembly and inspection process uncovered a path for abrasives to reach the wear rings. Heavy localized wear was identified at the casing, behind the casing wear ring.
Additionally, the pump was experiencing excessive leakage of the seal water and black liquor. The millwrights were unable to properly adjust the packing gland because the 2-bolt packing gland follower was cocked on the studs due to the high pressure of the seal water. This misalignment also caused significant wear to the diffuser vane tips.
Hydro manufactured new wear rings without slots to prevent the abrasive material from damaging the case and minimize wear behind the casing wear rings. The worn areas of the casing and a new sleeve were overlaid with tungsten carbide to prevent further damage.
Hydro designed and machined a 4-bolt split packing gland follower to help maintain alignment of the packing gland follower with the stuffing box. A special material was installed to help cool and lubricate the seal to allow the proper distribution of seal water.
The diffuser vane tips were welded to restore them to their pre-wear length and the impellers were balanced to a stringent level of 2 W/N. The 2 stage pump was built vertically to ensure centerline compatibility of stationary components.
This engineered rebuild provided improved reliability for the makeup liquor pump.
Learn more about Hydro’s focused improvements for the pulp and paper industry here. Read more about Hydro Scotford here.
Blower Outboard Bearing Failure Identified through Advanced Condition Monitoring
Introduction:
Maintaining the reliability and efficiency of critical equipment is paramount. This case study highlights the value of continuous, real-time condition monitoring by describing the how a premature failure was identified and resolved in a blower unit installed at a specialty materials manufacturer. The proactive implementation of Hydro’s Centaur condition monitoring played a pivotal role in early detection, enabling swift intervention and preventing unnecessary downtime.
Background:
A large US chemical plant that creates a variety of specialty materials had ongoing troubles with the centrifugal blowers in their PVC division. The units are critical to production and do not have spare backup units. Hydro’s Centaur condition monitoring solution was deployed on these blowers to understand the nature of the failures as well provide insight into when the units needed attention. One of the blower units began exhibiting concerning signs on January 04, 2024. Vibration levels steadily increased over the subsequent weeks, reaching a critical point on February 9th, 2024. This prompted the decision to shut down the unit and perform a root cause analysis to quickly determine remedial actions and keep production downtime to a minimum.
Events and Details:
When elevated vibration amplitudes were first detected on the problematic blower, they were in the Blower Outboard Bearing in the vertical direction (BOBV). The velocity amplitude shown below crossed the warning threshold on January 06, 2024, alerting both Hydro and the end user’s site engineers that a condition was present and in blower was in the early stages of degradation. The observation was discussed during the weekly touchpoint between Hydro and the plant, where Hydro would review the health of all monitored assets and address any alarm events captured using Centaur with site stakeholders.
Figure 1: Velocity Amplitude as Several Alarm Thresholds Breached
The vibration velocity amplitudes continued to climb, and on January 25, 2024 they crossed the Alarm #1 threshold. The Alarm #2 threshold was breached on February 01, 2024. Continual touchpoint meetings highlighted the worsening conditions and provided an analysis of the suspected failure mode(s) affecting the blower mechanical condition. The below multi-spectrum chart shows the spectra at the BOBV location at various points along the trend – mapping the signature of the degradation.
Figure 2: Multi-Spectrum Chart of BOBV Location
The chart starts with the spectra during “normal” conditions, prior to the observed degradation. Peaks at 1X and several harmonics are present with an amplitude less than 0.15 ips RMS. As the problem is observed and continues to worsen, bearing fault frequencies and harmonic excitation appear and continue to get worse. The lowest spectrum in the chart shows vibration velocity amplitude during the final sample, when it is greater than 1 ips RMS – very severe. At this point, all the energy has moved to 1X or less than 1X frequencies – a common occurrence when a failure mode is in its final stages.
The following two spectra charts take a closer look at the condition, one chart showing the initial conditions prior to degradation and the other closer to the end of operation where bearing fault frequencies and harmonic excitation can be detected.
Figure 3: Initial Conditions
Figure 4: Near End of Operation
In parallel with the velocity measurement, Hydro and the plant reliability engineers reviewed the acceleration measurements at the same location. Acceleration often leads to velocity readings, particularly for bearing failure. The chart below shows the trend for acceleration with the amplitude shown in g’s.
Figure 5: Acceleration Trend
The following four charts show the spectra and waveform data for acceleration readings at two points during the degradation period. The first two charts show the early stages of failure with peak-to-peak amplitudes of ~6 g’s and harmonic excitation in the spectrum. The second two show acceleration data at a later stage of degradation with peak-to-peak amplitudes at ~30 g’s and increased discrete frequency amplitudes in the spectrum.
Figure 6: Waveform- Early Stage of Failure
Figure 7: Spectrum- Early Stages of Failure
Figure 8: Waveform- Late Stages of Degradation
Figure 9: Spectrum- Late Stages of Degradation
The observation noted throughout was that the blower outboard bearing was failing. Failure of this bearing could also translate to damage to the shaft and other blower components if not addressed in a timely manner.
Constant communication between Hydro and the plant prevented the issue from becoming an unexpected and catastrophic failure.
Root Cause Analysis & Remediation:
The data captured by Centaur during the monitoring period was instrumental in conducting a thorough root cause analysis. It provided a comprehensive overview of the conditions leading to the outboard bearing failure, enabling Hydro’s engineers to identify contributing factors, such as operating conditions, lubrication issues, resonance frequencies, and potential misalignments.
The root cause of the issue was found to be contamination. This PVC unit created a fine dust byproduct that was found in the atmosphere, with large quantities accumulating around the blower units. Over time, the fine PVC dust would penetrate the bearings, compromising the effectiveness of the lubrication and reducing the tolerance inside of the bearings. Plans for remediation included relocating the machines or redesigning the bearing and housing to eliminate the possibility of contamination. The plant ultimately decided relocation was not an option and consulted the bearing manufacturer for an improved design that included a sealed housing.
Hydro continues to monitor these units, with ongoing reviews of the oil quality, level, and possibility of contamination from moisture, metal, or other sources. In parallel, Hydro also recommended reviewing the load handled by this blower and the rated load of the specified bearings, as improper loading may contribute to premature bearing failure.
Results: Cutting Edge Tech and Real-Time Support
Centaur proved to be the first line of defense in identifying abnormalities in the blower unit’s performance. Leveraging real-time data analytics, Centaur detected escalating vibration levels and issued timely alerts based on preset alarm thresholds. This early warning system allowed the maintenance team to take proactive measures, and consult with Hydro’s engineers on the data, receiving immediate real-time support thus preventing a catastrophic failure and minimizing the impact on overall operations. The ability to pinpoint the issue before complete failure occurred significantly reduced the downtime and associated costs.
This case underscores the value of proactive maintenance strategies for rotating equipment. With a strong focus on customer needs, experience across brands and applications, and a commitment to innovation, Hydro’s capabilities and culture uniquely aligned with the customer’s goals for improving asset reliability and performance.
Learn more about Centaur and how it can help you reduce the cost of rotating equipment ownership.