Novel handheld vibration monitor enables optimum
maintenance of traction motor bearings at Siemens Mobility

A novel, handheld vibration monitoring system has been developed, which enables maintenance engineers at Siemens Mobility to check train traction motors for early signs of damage to the bearings.

The two handheld FAG Detector III vibration monitoring systems supplied by Schaeffler UK have already paid for themselves within just two months, by minimising disruption costs to rail operators and by significantly reducing the number of traction motor repairs due to bearing deterioration.

Under-floor wheel lath at a Siemens rail maintenance workshop.

"If we detect early signs of wear to traction motor bearings, we can repair or replace that motor at our own convenience before more significant damage occurs," says Peter Ridgway, Production Support Engineer at Siemens Mobility, Rolling Stock. "The cost of repairing a damaged traction motor would be many times the cost of a standard overhaul."

Prior to investing in the FAG Detector III handheld vibration monitors, Siemens had been experiencing bearing deterioration problems on some traction motors, which are fitted to the Desiro electrical multiple units. The bogies on these trains are all driven by the same traction motor. What Siemens needed was some method of monitoring the condition of the traction motor bearings in order to predict their remaining operational life and to take the appropriate corrective action before damage is caused to the motor.

"In theory, these traction motors have a service life approaching one million miles before they need overhauling, but we were experiencing some bearing issues earlier than this. In March last year, I therefore started to search for a suitable solution and came across Schaeffler's UK website, which was very helpful," said Ridgway.

After talking to Schaeffler UK's Engineering Manager Dr Steve Lacey, Ridgway decided to work with Schaeffler on developing a suitable condition monitoring solution.

Between March and October 2010, Schaeffler carried out a comprehensive program of measuring vibration from around 100 traction motors. This involved measuring vibration on the traction motor housing and assessing the condition of the bearings and other associated mechanical components.

The vibration measurements were carried out whilst the trains were positioned over an Underfloor Wheel Lathe at two of Siemens' rail maintenance workshops in Southampton and Ilford. These wheel lathes are used to perform routine wheelset skimming in order to maintain the correct tread profiles.

As Dr Steve Lacey states: "At the onset of the investigation, I wasn't very hopeful that simple vibration-based parameters could be used to give a reliable indication of motor condition. However, after carrying out detailed vibration measurements on the traction motor housing, it became apparent that simple characteristic vibration parameters related to the raw signal and signal envelope could be used to give a very reliable indication of the condition of the motor, even in the presence of high background vibration from other sources within the transmission system and the Wheel Lathe such as the gearbox and axle box, as well as the belts, conveyors and bearings within the lathe itself. We believe this novel solution for assessing the condition of rail traction motors is an industry first and we're very excited about the potential benefits that our FAG Detector III can bring to rail operators."

Following this in-depth analysis and reporting, Schaeffler developed special software for its FAG Detector III. The aim was to provide Siemens with a device that would be easy to use and that didn't require a vibration monitoring expert to interpret the measurement results.

The modified Detector III now enables maintenance engineers at Siemens to implement vibration measurements on a routine basis. The device has a new 'Rail-Measurement' menu option with pre-set limits for the Desiro traction motors.

The train normally comprises four cars (coaches), each with two bogies, two axles per bogie. Each train has eight driven axles each with their own asynchronous traction motor.

Vibration measurements on the Class 444 and 450 trains (power collection DC third rail) were undertaken on the Southampton Wheel Lathe at a surface speed of 80m/min. For the Class 360 train (power collection AC overhead), measurements were obtained on the Wheel Lathe at Ilford, at a surface speed of 60m/min, which was the maximum speed available. The Desiro motor bogie has two axles, each fitted with a 250kW traction motor driving the wheelset through a 4.15:1 ratio gearbox.

"Initially, we took measurements horizontally on the traction motor housing at both the drive end and non-drive end positions by attaching an accelerometer with a magnetic base. Prior to attaching the accelerometer, the surface area had to be cleaned with a solvent to remove as much grease and dirt as possible," recalls Dr Lacey.

"We then collected vibration data using our FAG Bearing Analyser over three frequency bands: 0-200Hz, 0-1kHz and 0-5kHz and using 8,096 data points. The results demonstrated that, even amongst the very high background noise and vibration levels, it is possible to detect vibration frequencies that are related to the drive end bearing," adds Dr Lacey.

It was proved that simple based parameters such as the RMS (root mean square) of the signal envelope (RMS Env) and the carpet level of the envelope spectrum (CL Env) gave very reliable indications of motor condition.

In most cases it was the drive radial ball bearing that seemed to be experiencing most of the problems, including some deterioration of the raceways and rolling elements. The cause of the damage is still being investigated but is thought to be due to a number of possible reasons, including degradation of the lubricant and possible electrical erosion.

Peter Ridgway concludes: "Siemens is committed to undertaking maintenance to the highest standards of integrity. We have been extremely impressed with Schaeffler's commitment to this project and cannot fault the company's drive and dedication to finding a reliable and practical solution for us. The cost of purchasing the two FAG Detector III units is modest compared to the cost savings we will make due to fewer motor repairs, eliminating the possibility of in-service traction motor failures and the disruption that would cause to our rail operators and networks."

"In addition, we can now properly survey the fleet of trains to assess the condition of their traction motors and to make more informed decisions as to when to overhaul a particular motor."

For further information on the Schaeffler Group, e-mail: info.uk@schaeffler .com or view website: www.schaeffler.co.uk  Refer to page 380 

Oil recycling plant turns to Babcock Wanson thermal fluid heating system for high efficiency

Eco-Oil, a leading UK industrial waste oil recycler, has installed a TPC1000B thermal fluid heating system from industrial process heating specialist Babcock Wanson in its Ipswich oil recycling plant.

A fully automatic coil type, multi-pass thermal fluid heater complete with integrated burner, control system and safety devices, the TPC1000B has been installed in Eco-Oil's process area and is being used to generate heat for the production of Processed Fuel Oil.  Eco-Oil is one of the largest suppliers of this type of fuel product in the UK.

The TPC Heater has been supplied with a dual fuel burner facility, running on gas oil but with the option to switch to the recycled Processed Fuel Oil Eco-Oil produces at the plant.

This is the first time Eco-Oil has opted for a thermal fluid heating system having relied on steam boilers previously.  Allan Goulden, Engineering Director at Eco-Oil, explains his company's decision to switch: "Reducing energy costs was at the heart of our decision and we knew we could make considerable savings by moving from steam to thermal fluid as the heat source for our process.  We investigated the options thoroughly and decided Babcock Wanson offered the best solution.  To date we have been proven right: the system has reduced our energy costs and is easy to use with very good control."

The TPC1000B can achieve 20-50% energy savings when compared to the transfer of the same amount of heat using traditional steam boilers.  The system precisely matches fuel input to plant energy requirements for high efficiency.  With lower energy input demand also comes lower total exhaust emissions so it's a "win-win" solution for both operating costs and the environment.

Babcock Wanson offers a complete range of products and services for boiler houses and other process heating needs, from steam boilers, thermal fluid heaters, rapid steam generators and hot water boilers to VOC and odour treatment by thermal oxidation, water treatment or process air heating solutions.  The company aims to help optimise customer's energy production with high quality products and efficient service.

For furtherinformation, e-mail: info@babcock-wanson.co.uk or view website: www.babcock-wanson.co.uk

Metal finishing company opts for Babcock
Wanson steam generator for safety and efficiency

Metal finishing company Amfin has chosen a Babcock Wanson ESM4000 Steam Generator for its new factory in Hinckley.

The ESM4000 Steam Generator will be used to heat tanks for a variety of immersion metal treatments, including anodising, electroplating and etch inspection predominantly for the aerospace market.

The ESM4000, fitted with a high efficiency economiser and fired on natural gas, was the ideal solution for Amfin due to its combination of safety, efficiency and compact size, the latter being a particular issue due to the relatively small size of the boilerhouse.  Paul Bennett, Managing Director of Amfin,
explains: "we had been using thermal fluid heaters in the previous plant, but with the purchase of a new factory it provided the opportunity for change.  We have relied on Babcock Wanson for ten years or more and have been happy with the service they provided so we worked with them on this project to determine the most suitable means of heating the tanks.  We went for coil boiler technology rather than firetube to raise steam as it has a much smaller footprint and is very efficient."

A coil type steam generator, the ESM provides operating efficiencies of circa 96- 97% overall and low emissions.  It utilises modern controls to maintain a close ratio between the burner firing rate and water input with inverter drive of both the combustion air and feed water pumps.  This ensures close control of both steam output and steam quality and lowest practicable consumption of electrical power.

The ESM4000 also has many safety benefits.  The chance of a pressurised water explosion is virtually eliminated with a coil steam generator such as this as the steam generation process takes place in a small tube.

Babcock Wanson offers a complete range of products and services for boiler houses and other process heating needs, from steam boilers, thermal fluid heaters, rapid steam generators and hot water boilers to VOC and odour treatment by thermal oxidation, water treatment or process air heating solutions.  The company aims to help optimise customer's energy production with high quality products and efficient service.

For further information, e-mail: info@babcock-wanson.co.uk or view website: www.babcock-wanson.co.uk