Leaking oil tanks repaired in-situ with fast-curing epoxy composite

A UK oil supplier was faced with a major dilemma when a transformer oil storage tank began to leak in several places. As the tank was located in a confined space, it would be highly dangerous to repair the damage in-situ using hot work. If the tank was removed and repaired offsite, not only would this incur large amounts of downtime, but the cost of welding alone would be over £15,000.

The reliability of most rotating equipment is almost inevitably linked directly to bearing life, and it is estimated bearing failure is responsible for almost 21% of these equipment failures (Bloch, 2011).  

Research into bearing failures  shows that just over half of these are a result of contamination of the bearing oil (Fig 1). Clearly it is therefore essential to ensure that contamination of the bearing lubricant is minimised and if possible eliminated if optimum bearing life is to be achieved thereby improving the equipment reliability (MTBF).

Swedish paper mill Holmen Paper Hallsta has extensive experience in condition monitoring and has worked closely with SPM for many years. Now the mill is upgrading the monitoring of a number of Nash pumps to a newer online system. (Read More)

The art of measuring low-frequency vibrations

Rotor blades in wind turbines are growing longer – but also slower.

Multimegawatt wind turbines turn even more slowly. This means that reproducible low-frequency vibration monitoring will gain in importance not only for the main rotor but also for the slow-operating gearbox components and roller bearings. Reliably measuring low frequencies, however, can be rather tricky.

Molten sulfur is present in an ever widening range of industries and liquid sulfur storage tanks are used worldwide in crude oil refineries and natural gas plants to store liquid sulfur in very large volumes. Sulfur storage tanks are most commonly utilised as part of the Gas Treating System in sour crude oil refineries and gas sweetening facilities to temporarily store liquid sulfur produced in the sulfur recovery plant. These tanks are usually field erected and most commonly constructed of carbon steel.

Helium has the lowest boiling point of all gases at -269 °C. As a result, liquid helium is frequently used as a cooling medium. This is the case at the Jülich Research Centre (FZJ). “Nowadays we mainly use liquid helium for cooling superconductors in computer tomographs, for example for brain research and biotechnology”, says Ulrich Sieberichs, supervisor in the supply department for cryogenic gases at the FZJ.

At the Renström mine in northern Sweden, Swedish mining company Boliden monitors the mechanical condition of the multi-rope friction hoist using SPM HD and vibration analysis.

In 2012, Boliden tested a number of condition monitoring systems on an autogenous mill at its mine in Garpenberg, Sweden. The tests led to a strategic decision to implement condition monitoring solutions from SPM for mining equipment within Boliden. As a result of this decision, the Intellinova online system was installed on the mine hoist in the Renström mine last year. Mats Johansson, Maintenance Manager, about the investment: "The main hoist is critical equipment (A-rated) for us and the heart of our business. If the hoist malfunctions, production more or less comes to a halt. On this type of equipment, we need good control and that makes online monitoring necessary."

The hoist is a process critical application used in underground mines for transporting materials or personnel. This case study describes the friction hoist application in the Renström mine; currently Sweden’s deepest mine at 1340 m. Using the SPM HD measuring technique and vibration analysis, the online system monitors hoist bearings and gears to ensure around the clock operation and provide automatic alarms.

The combination of vibration and shock pulse technologies is optimal for this type of application. Shock pulse transducers pick up bearing related signals very clearly, yielding crisp and easily interpreted readings, while vibration transducers pick up gear mesh frequencies in the gearbox, unbalance in the drum and other low frequency vibrations.

Find out more here.

Introduction
As a manufacturer of premium glass bottles, Allied Glass creates groundbreaking glass packaging for many world-leading brands of food and drink. With two state of the art factories, located in Leeds and Knottingley, Allied Glass has the capability to manufacture 13 million bottles each week.
From design through to manufacture, the company is committed to the highest production standards and the most stringent quality control procedures, as any defects in the glass can have very serious consequences for the consumer, brand owner and ultimately Allied Glass.
By its very nature, glass container production is challenging; therefore each container must undergo rigorous checks. This means Allied Glass lays great emphasis on automatic inspection and rejection equipment on the shop floor, which ensures that any issues are quickly identified and appropriate improvements made.
It was with this in mind that Allied took the decision to upgrade its factory information system Shopfloor-Online from Lighthouse Systems, to the latest version 4. It was first installed at the Leeds plant before being added to the Knottingley site, with an added complication - Knottingley was adding new lines at the same time.
The software tracks production runs, tracking the product being made and the specifications associated with it; it captures defect data and other quality measurements; and supports end of line audits. When defects are found it identifies the mould and section (the mould is located in a section in the bottle forming Shopfloor-Online Case Study machine) from which the defective bottle originated, and can highlight trends by machine, mould, section or product.
As the software is web-based, reports identifying such trends, and the tracking of potential issues, can be easily made available to production and maintenance teams for speedy resolution.

The Requirement for Change
The manufacturing process for glass bottles is fast and complex, therefore it is a very difficult process to control and improve. Once a bottle is formed, the production team focuses on identifying and removing defective bottles. The ability to quickly and easily spot trends and track issues delivers significant value in terms of process improvement. The 'trending' capability was one of the most important aspects of the Shopfloor-Online system to Allied Glass, as it promised better quality, throughput, and greater customer satisfaction. Richard Johnson, Continuous Improvement Manager for Allied Glass, comments:
"We wanted Shopfloor-Online to help us to improve trending. Removing paperwork from the process is the first step, this is because the software is highly adept at spotting trends or discrepancies in the figures. And, once the measurements from the shop floor are inputted into the system, it is simple to drill down into specific parts of the production process to find out information at any given point. With paper forms, our ability to pinpoint any disparities was arduous and time consuming. The new system gives us drill down capabilities at the press of a button. This not only enables the production team to alert operators to issues, but also helps us to focus resource where it is needed most and, Shopfloor-Online Case Study therefore, drive process improvements."
Integrating with Other Systems
As part of the project, several interfaces have been created to allow data from Allied's ERP (enterprise resource planning) system (PRISM) to be transferred to Shopfloor-Online automatically. This is used to provide better tracking of the production process. Production orders are automatically downloaded onto Shopfloor-Online along with other key data. This improves traceability and facilitates more exact/powerful reports.
The Lighthouse software also collects data directly from the 'Otto' measuring machine, an automated off line measuring device, which uses cameras to capture up to 600 measurements on any specific part of a bottle. The direct collection of data automatically into Shopfloor-Online, makes analysis possible that would have been otherwise impossible. It saves time, and the graphical representation of the data collected makes the identification of discrepancies much easier to see.

Benefits
With the upgrade of Shopfloor-Online, Allied can use the Inspection area data to pinpoint where problems are occurring, to the specific mould or section on the glass bottle making machine. This allows Allied Glass to react rapidly to production issues and to be confident that quality issues are not going unnoticed. This ultimately leads to reducing the impact of faults and the level of rejects, which improves production output and reduces customer complaints.
Richard Johnson continues: "The Lighthouse System makes our production teams more proactive. We use the information in Shopfloor-Online to put focus into specific areas where we see potential issues arising. Simply we are reacting to information and so that we can proactively fix faults. The net results should be two-fold, a reduction in customer complaints, which will strengthen our brand over the longer term."
Shopfloor-Online gives a real-time graphical representation of the equipment, showing the status. This clear visibility of plant performance is extremely valuable as everyone can easily discern what is taking place.
Previously, the creation of reports for management use was time consuming, as the information was held in paper form, which was complicated to cross-reference. Now they are created on demand with little effort and are more incisive and complete.

Looking to the Future
The implementation has been successful in achieving its goals, however Richard Johnson recognises that there is still more the company can achieve with Shopfloor-Online. Spoilage tracking is one area that he hopes to address in the near future. This will mean that all the machines on line are linked directly to the Lighthouse software to count production, spoilage and track machine status data in real time. This will assist Allied Glass in identifying problems at an individual machine level, which will help to prioritise staffing on lines. Also, the ability to schedule maintenance checks will enable Allied Glass to better manage the process and avoid potential problems.

In future, Allied Glass may explore linking its customer complaints database with the production data in Shopfloor-Online, enabling the production teams to cross reference information, aiding a faster and more comprehensive response to customers.
Richard Johnson concludes: "The upgrade to version 4.0 is a significant move for Allied Glass. The Lighthouse team have worked closely with us, delivering the expertise we have needed, whenever necessary. We now actively market the system to our customers, using it as contributing factor to our ability to deliver excellence in glass production. We are still building the system and our operators will continue to challenge it, to make sure that it continues to deliver more functionality and performance. We know we can achieve a lot more with it in time, but it is already proving to be a significant tool in our drive for process improvement."

For further information, please visit www.lighthousesystems.com

 
Lighthouse Systems Limited
Buchan Hill
Pease Pottage
Crawley
West Sussex
RH11 9AP
United Kingdom

Phone: +44 (0) 1293 605300
Fax: +44 (0) 1293 605301

www.lighthousesystems.com

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Schaeffler UK was part of the team that successfully completed the replacement of the main trunnion bearings on a BOS (Basic Oxygen Steelmaking) plant at Tata Steel Port Talbot.

By replacing the drive-side trunnion bearings with split rolling bearings, Schaeffler also helped to save the customer five extra days of work. If solid rather than split bearings had been used, the customer would have had to disassemble the bull gear unit (i.e. the main drive unit for the BOS plant vessel).

TATA Steel Port Talbot has two BOS Steel making vessels (V1 & V2) in operation. The original vessel was installed in the late 1960s by UK company Ashmore, Benson, Pease & Co and was subsequently upgraded in 1991/1992 by Mannesmann Demag, including trunnion bearing replacements. Each vessel has a steel making capacity of 330 tonnes. Loss of operation of a BOS vessel would result in significant lost revenue for Tata Steel.

Simon Life, BOS Plant Departmental Engineer at Tata Steel Port Talbot comments: “The bearing replacement work was very successful. The bearings were fitted to a high standard with expertise provided by Schaeffler throughout the installation process. During the bearing changeover, we encountered several problems with components being damaged and jacking issues. However, all problems were discussed with Tata, Schaeffler engineers and Central Engineering support, and between all parties, solutions were generated, action lists compiled and remedies implemented. Without Schaeffler’s expertise, the bearing change would not have run so smoothly.”

In July 2011, Schaeffler UK received a telephone call from an area works engineer at the BOS Plant, advising of a sudden bearing failure on the non-drive side (NDS) of the V2 BOS plant vessel.

The BOS Plant engineers arranged a meeting and a request was made for two engineers from Schaeffler Germany to be on site at Port Talbot soon afterwards. A meeting subsequently took place at Port Talbot to discuss action plans and how to replace the trunnion bearings.

           

As Dave Wall, Senior Applications Engineer at Schaeffler UK recalls: “A method statement document was drawn up by Schaeffler UK, which specified the sequence and method to replace the bearings and outline the TATA requirements. Included in this document was a detailed tooling list and a step-by-step procedure for the dismounting and mounting of the drive-side (DS) & non drive-side (NDS) bearings.”

“The standard ‘solid’ bearing on the DS was replaced by a special FAG split spherical roller bearing [SSRB], which is the recommended replacement spare, as this reduces the amount of downtime when installing the replacement bearing. The NDS bearing was to be replaced with a similar solid bearing. In addition, various surrounding components also required replacing, once the secondary damage caused by the bearing failure had been identified,” confirmed Wall.

Removal of the Drive Side bearing 

The cutting away of the existing bearing took a total of 36 hours. The distance between the trunnion spacers (bearing seating width) was measured in order to determine the thickness required for two special, TATA designed, split ‘dovetail’ spacers. These were required to ensure that the new split bearing would be correctly secured in place.

The new split SRB inner ring halves with clamping rings, outer ring half and bottom roller cage halves, were fitted without any problems.

Removal of the Non-Drive Side bearing 

The original bearing on the NDS had failed during operation, which had caused the BOS converter to drop down. It was now resting on the bearing housing and the housing covers.

After lifting, parts of the damaged bearings were removed, including cage pieces; outer and inner ring fragments and rolling elements. All the components were sent for forensic examination to TATA Central Engineering Metallurgy & Inspection Dept. The housing back cover, bearing pressure plate and sleeve spacer were found to be seriously damaged. New ones had to be urgently manufactured by Tata Steel’s Central Engineering Shops (CES). The bearing inner ring had disintegrated and the sleeve had to be cut off due to its deformed shape. After removing the damaged bearing, it was also discovered that the trunnion back spacer was in need of repair. Again, machining work was urgently carried out by CES.

Due to the subsequent damage to the bearing housing, Schaeffler expertise was required to manually repair this surface to restore it back to an acceptable condition.

During the dismounting process the NDS Ladder Expansion Bearing Rollers had to be replaced. To facilitate the Ladder Roller replacement and installation of a TATA manufactured solid inner bearing housing cover, the bottom half of the housing had to be moved away from the journal using specially manufactured crossbeams.

Mounting of the new Non-Drive Side bearing 

The new bearing was first pre-mounted to determine the correct sleeve spacer width. The bottom half of the housing was then moved back into position and the crossbeam construction removed.

Mounting of the new bearing was challenging, as the collapse of the original bearing had caused the vessel to move out of alignment.

The lowering of the converter was also a challenge as the vessel had to be moved sideways by 40mm to achieve the correct installation position. Side shifting was initially a problem for the vessel lifting contractor but the problem was successfully overcome.

Final mounting steps for the NDS and DS bearings 

For the DS bearing, the remaining roller cage and outer ring halves were installed. For both bearings, the housing caps were fitted and each bearing was 100 per cent filled with grease, including the surrounding free space.

The housing covers were bolted in position and new seals with their tensioning devices were fitted. After having successfully completed the work in under 2 weeks, Schaeffler engineers were pleased to be leaving behind a very happy customer.

After the bearings were installed, the work didn’t finish there. Schaeffler UK prepared a recommended practical maintenance schedule list and forwarded this to the BOS Engineers, which was well received. In addition, customer “as built” cross-sectional drawings were updated to show the actual parts (with measurements) now in place at V2. Schaeffler UK participated and contributed to the Bearing Failure Review meetings with Tata Steel that followed the bearing replacement for the BOS vessels.

“Since replacing the trunnion bearings, engineers from Schaeffler UK have also supervised two further BOS vessel bearing changes in a very short timeframe of just two months: Converter C at SSI UK / Teesside and Converter 1 at Tata Steel Port Talbot. Schaeffler has now been selected as the preferred supplier of main trunnion bearings for the two BOS plant vessels at Tata Steel Port Talbot,” confirms Dave Wall.

Schaeffler (UK) Ltd,                         

Forge Lane                                                              

Sutton Coldfield                                                        

West Midlands B76 1AP                                          

Tel:   0121 313 5870  Fax:  0121 351 7686
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.This email address is being protected from spambots. You need JavaScript enabled to view it.       
www.schaeffler.co.uk

By Paul Uher and Ernesto Wiedenbrug, Ph.D.
Everybody who is responsible for maintenance of VFDdriven application knows the feeling… The application was running well, and now it acts up and trips sometimes, and the drive’s trip message isn’t much help. Now what?

This paper discusses such a case, and how being able to see the dynamic interaction of voltage level and frequency changes led to the solution.

Situation:

Paul Uher from SKF Industrial Market in Sweden was called into a major bearing manufacturing plant to offer service for a VFD-driven application that was causing problems.

The drive is a 400V 30hp manufactured by Danfoss, and the load is an eccentric press which creates the rollingelements for bearings. Paul’s customer had explained that the application worked well for about two hours and then it started slowing down, finally coming to a stop, even though no changes were being made on the load-side.

Torque and Speed vs. Time

Frequency and Voltage vs. Time

Figure 1: Torque, speed, frequency and voltage level vs. time during healthy operation.

Action:

This description clarified that the problem had to be in one of two spots: Eitherthere was something wrong with theexternal control signals/programming tothe drive, or the issue was internal, in thedrive control itself. In order to answerthe question as to which of thesealternatives was causing the slow-down,it was necessary to get “eyes” onto whatwas happening. Obtaining a clear pictureof dynamic VFD application problems likethese is only possible by seeing howfrequency variations, voltage levels,torque requirements and motor speedinteract with one another. This is what
the software component VFD4000 delivers for the SKF Dynamic Motor Analyzer - EXP 4000. Fig. 1 shows these four traces for 40s of healthy operation, where fifteen 2s cycles of the eccentric press are followed by a short no-load period.

The application started to slow down after roughly two hours of successful operation. The difference in the healthy signature of Fig 1 is apparent in the frequency and voltage vs. time plot in Fig 2. The traces show that the voltage ramps down towards the end of each stroke of the eccentric press, while the drive tries to maintain a constant frequency until it shuts down for a very brief instance.

Figure 2: Frequency and voltage vs. time during faulty operation.

Volts per Hz:

One control technique internal to VFDs is called “Volts per Hertz” [1]. It means that voltage level gets changed in proportion to the frequency changes for frequencies below nameplate, as shown in Fig 3. In other words, if the motor runs at half nameplate frequency, it should be supplied by half nameplate voltage. A Volts per Hertz control typically doesn’t raise the voltage level above nameplate for frequencies higher than the nameplate frequency of the motor. This type of control has the ability of delivering full torque for the low speed range, and full nameplate power for the speeds above nameplate – at the expense of dropping torque capabilities in the high-speed region.

Even if a drive had a different control strategy than V over f, this rule of thumb will still apply for applications that have relatively small frequency changes as is the case being analyzed here. The voltage and frequency vs. time traces of Fig 2 show that there are times where the expected normal behavior of the drive falls apart: voltage level ramps down while the drive attempts to maintain constant frequency output. This answers the question – the problem is originating internally in the VFD.

Figure 3: Voltage level and torque vs. speed for V/f control.

Correction:

Since now it was clear that the problem somehow originated internally in the drive, and wasn’t caused by the external control signals, the next step was to approach Danfoss application support and ask for help. The VFD manufacturer’s application engineer was able to diagnose the issue by looking at the voltage, torque, speed and frequency plots vs. time of healthy operation and during the slow-down. The problem was that the eccentric press required a very high peak torque to manufacture this particular batch of rolling elements. Over time the motor started heating up, causing the stator resistance to rise – ultimately starving the magnetic flux and the torque-generation capability.

The solution was described in an application note that was emailed by the Danfoss application engineer, explaining which two drive settings needed to be set differently to shift the drive from the default high-efficiency settings towards peak torque settings that this application required [2].

Results and Conclusion:

Changing the two parameters in the VFD setup as suggested by the Danfoss application engineer solved the issue upon first try. The eccentric press has been working reliably ever since.
This case study shows how VFD applications can introduce unique complexities never offered by line-operated motor applications. The voltage level and frequency vs. time traces were key to diagnose the root cause problem being in the drive control. That data, together with the torque vs. time plots were the information that allowed the Danfoss application engineer to diagnose the issue, and realize the simple solution. The “VFD Details” plots of the VFD4000 gave eyes to the maintenance engineer, allowed him to isolate the problem, and gave eyes to the VFD application support to solve the issue.

References:
[1] “Application Guide for AC Adjustable Speed Drive Systems.pdf”, pg. 14, NEMA 2007.
[2] “Instruction Manual – VLT 5000”, Danfoss.

 

For further information, please visit http://www.whitelegg.com