Post by Jim Scott on May 9, 2015 14:29:00 GMT
For anyone visiting North Yorkshire there is another ‘too good to miss’ museum at Glaisdale. www.museumofvictorianscience.co.uk/ It is a few years since I visited but I recall a couple of literally ‘hair-raising’ hours for our group of three in the small but wonderfully over-filled museum which is an annexe to his home. Absolutely fascinating but must be booked in advance...!
If visiting the North Yorks Moors Railway, Glaisdale station is not far away from Grosmont on the Esk Valley line out of Whitby.
Back again to valves....
Most folk think of old radio receivers when mention is made of valves in an electrical context. Tony’s superb photo and description of the transmitter valves reminds us of just how far the technology has progressed over the years. We should also remember other applications nearer to our common engineering interests; RF induction heating has already been mentioned but the use of high voltage (typically 150kV) triodes for radiographic use was (is?) commonplace. Also, the development of the electron gun, in which the electron current or ‘beam’ passes through the anode instead of being collected by it, led to the cathode ray tube (CRT) for use in oscilloscopes and eventually to commercial TV tubes.
At higher powers an electron beam has considerable heating capabilities and has found applications in welding, drilling, machining and heat treatment of metals. In an electron gun designed for welding most of the electron beam passes into a work chamber which is generally evacuated to a high vacuum. The beam can be electro-magnetically focused to a very small spot size resulting in a very high power density, typically 10,000 – 100,000 W/mm2 , high enough to evaporate most metals. By manipulating the workpiece within the chamber and using appropriate beam power, focusing, weld speed etc, welds can be produced having high depth to width ratio with minimal heat input, often allowing finish machined components to be joined without further work. I’m sure we have a few members who have a background in aerospace/engine manufacture and will know of the extensive application of EBW in jet engine production.
I became involved with Electron Beam Welding in the early 1970’s when the R&D company I worked for inherited some redundant laboratory equipment designed and produced by Vickers Research Establishment at Sunninghill. Rated at 10kW beam current (150kV x 67mA) this was still quite a capable bit of kit and I had an interesting 20 years looking after it as an operational facility for the associated group companies.
Cheers
Jim S
Note to Alan re anode cooling. The thin stainless steel anode wasn’t cooled at all but the copper beam stop /collimator immediately below was, fed by pressurised mains water. The 150kV supply was effectively ‘floating’, with (IIRC) the anode held at earth potential by two back-to-back diodes...!
If visiting the North Yorks Moors Railway, Glaisdale station is not far away from Grosmont on the Esk Valley line out of Whitby.
Back again to valves....
Most folk think of old radio receivers when mention is made of valves in an electrical context. Tony’s superb photo and description of the transmitter valves reminds us of just how far the technology has progressed over the years. We should also remember other applications nearer to our common engineering interests; RF induction heating has already been mentioned but the use of high voltage (typically 150kV) triodes for radiographic use was (is?) commonplace. Also, the development of the electron gun, in which the electron current or ‘beam’ passes through the anode instead of being collected by it, led to the cathode ray tube (CRT) for use in oscilloscopes and eventually to commercial TV tubes.
At higher powers an electron beam has considerable heating capabilities and has found applications in welding, drilling, machining and heat treatment of metals. In an electron gun designed for welding most of the electron beam passes into a work chamber which is generally evacuated to a high vacuum. The beam can be electro-magnetically focused to a very small spot size resulting in a very high power density, typically 10,000 – 100,000 W/mm2 , high enough to evaporate most metals. By manipulating the workpiece within the chamber and using appropriate beam power, focusing, weld speed etc, welds can be produced having high depth to width ratio with minimal heat input, often allowing finish machined components to be joined without further work. I’m sure we have a few members who have a background in aerospace/engine manufacture and will know of the extensive application of EBW in jet engine production.
I became involved with Electron Beam Welding in the early 1970’s when the R&D company I worked for inherited some redundant laboratory equipment designed and produced by Vickers Research Establishment at Sunninghill. Rated at 10kW beam current (150kV x 67mA) this was still quite a capable bit of kit and I had an interesting 20 years looking after it as an operational facility for the associated group companies.
Cheers
Jim S
Note to Alan re anode cooling. The thin stainless steel anode wasn’t cooled at all but the copper beam stop /collimator immediately below was, fed by pressurised mains water. The 150kV supply was effectively ‘floating’, with (IIRC) the anode held at earth potential by two back-to-back diodes...!