Saturday, 9 January 2016

Tyseley: A Riveting Process...

Hi all. Today was a Volunteer Shed Day at Tyseley Loco Works. I was quite interested today to take part in some Steam Boiler Riveting which was going on. A boiler of one of the collections striking main line engines was having some Foundation Ring riveting carried out as part of a restoration to working order. Having experienced this riveting process ("see what I did there?") I thought it would be nice to talk a little about it. Steam locomotive boilers are held together using various means. A typical boiler will often include several hundred stays and rivets of various types and sizes which join forces to hold the plate-work together against steam pressure. With pressures up to and including 250 pounds per square inch on some locomotives, the amount of force trying to escape is staggering. During riveting, the rivet is heated with a gas torch until red hot and the runner (in our case me) must, using tongs, take the rivet to the boiler and, having given it a good bang against the plate to free off any material scale, feed the rivet into the hole that is to be riveted. The rivet is then driven into shape using two air fed tools, one of which retains the curved shape of the rivet head whilst the other in effect crushes the rivet down until almost flush. The holes in the plate-work are often countersunk on the none rivet-head side to allow the rivet material to be crushed further and thus the plate-work is held firmly together. There are however of course variants in the process of riveting as certain locomotive classes, on the foundation ring for example, will have less distance between the frames for the boiler in between once fitted. Yes, clearances can be that tight! There will also be variants in rivet materials, heads and sizes. The riveting process is demonstrated below on the boiler of 4472 "Flying Scotsman". This NRM video is available on YouTube...
As you make your way along the boiler, in our case the foundation ring, the rivets are calked between nuts and bolts which, during the process, act as holders for the plates. As the holes are gradually taken by rivets, the nuts and bolts can be removed and rivets crushed in their place. Eventually, you end up with a wholly riveted section of plate...
The rivet is often almost critical temperature-wise when being fitted and the process must be quick as the cold boiler steals the heat VERY quickly. I would estimate that from leaving the gas torch to reaching the end of the hammering the process takes little more than 10 seconds. Its the heating that takes the most time and I think we took most of the day to put in just over 100 rivets (probably about 1/3 of the foundation ring!). Its amazing just how many stays and rivets are inside a main line locomotive boiler and all have to be in A1 condition. The rivets are of course not only there to hold the plate-work but also to make a seal, in this case against water attempting to leave the 'water jacket' between the inner and outer firebox. However, this boiler is now another step closer to steaming and it was most interesting to see and take part in the riveting process first hand. I hate to think what it must have been like to hand rivet something like the RMS Titantic together with no air-fed tooling, just hammers! Best Regards all, Sam...

No comments: