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News of Blackmore Vale's Repair

Initial work on the repair of Blackmore Vale concentrated on the boiler, which is now certificated. Work is now progressing on the engine sheeting and fittings, and on the tender. At a later stage the wheels will be dropped to check the axleboxes etc, but as it has run little mileage since its last major repair in the 1960s no great work is expected in this area. These pictures were taken on 28 February 1999.

Left side of loco A view of the left side of the engine, showing the boiler lagged and pipework being fitted.

Right side of loco A view of the right side of the engine. The boiler feed pipes have been replaced with new piping from the unions just in front of the firebox up to the clacks. (The copper looks dull because they have been annealed by heating to red heat.)

View into cab A view of the cab showing boiler fittings in place. The roof sheeting has been replaced with new.

View of cab side New steel sheeting in place on the cab side, and the injectors and pipework reinstalled.. All of the sheeting will be replaced so that the whole engine will look like new.

View of tender side Repairs have been made to the tender side sheeting.

View of reverser The steam reverser, previously one of its most unreliable components, has been thoroughly overhauled. Here Mike Carroll prepares it for refitting on the engine where few people will be able to see the workmanship which has gone into it.

View of stay testing The firebox stays have been tested using an ultrasonic instrument which detects breaks by measuring their length. Here Andrew Wilkens is testing some in the combustion chamber. For many years it has always been the practice to test stays by tapping them with a hammer and listening to the resulting tone. What we are using is a modern development of that same technique by injecting a sound wave down the stay and displaying the resultant echos on an oscilloscope in the same way that sonar works. The equipment used is an "Ultrasonic Flaw Detector", a comercially available instrument that is universally used to test welds and platework for defects and is used throughout industry. The one that we are using can be calibrated to test any length between 5mm and 1m. The sound wave is reflected by a surface which can be the other end of the stay or it could be a fracture.

View of stay testing instrument display An example of the display obtained from a sound stay. The X axis of the screen is a time base and the instrument is effectively measuring the time taken for the ultrasonic signal to travel from the probe to the reflecting surface and back again. The speed of sound is different for different materials and hence if you tested an 8 inch copper stay and an 8 inch steel stay you would get a trace at a different position on the screen. In order to test a row of stays we calibrate the machine so that the trace for a complete stay is set at 75% along the screen. We then lightly clean each stay head with a wire brush and put a small dab of grease on the head to act as a couplant. Each stay is then tested and the traces should all appear at the 75% point on the screen. If a stay has a trace at say 50% of the screen this will show that the stay has a reflective surface part way along its length which will indicate that it is either fractured or cracked. There is still some further work to perfect the technique and we will be looking to try this application on crown stays but it has already detected broken stays in boilers which have then been confirmed visually.

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