That is an amazing set of photos. There is so much to see and appreciate in them.
The boiler shop photos are quite interesting. It looks like they were building solely Scotch Marine Boilers. No air tools in sight. The crew is going at it with hand hammers. One guy appears to be chipping or calking inside the flange of a "liner" or "doubler" in the fluesheet (or head) of a Scotch Boiler. The guys with sledges are either driving rivets by hand or simply getting a seam to "lay down". What is also interesting is the long seams on the boiler barrels. In the USA, we always used a straight "Welt Plate" on a long seam. The German practice seems to have been to use a welt plate with a zig-zagged edge, followign the line of the rivetting. The zig-zagged welt plate was probably done for better stress distribution, since the calking would put a "line" or "stress riser" into the shell of the boiler. At the same time, looking at the photo and thinking of the times, those zig-zagged welt plates were probably cut with some sort of notcher or shearing machine and hand finished. Then some guys had to chase along the edges of those zig-zags, hand calking them with a hammer and chisel.
All the sledging and hand hammering in that boiler shop must've deafened most of the guys who worked in there. Aside from that, no one is wearing safety glasses. I wonder how many guys came out of those shops hard of hearing or with eyes permanently damaged from taking too much scale or chips in them , or looking at white hot steel for too long.
The drilling machines for drilling the plates are probably one of the more modern things in the photos. They are on swinging arms, and look to be motorized. There is bin filled with chips from the drilling of the plates. In the days of rivetted boilers and rivetted ships, it was not uncommon to put thousands of rivets into a boiler and millions of rivets into a good sized ship's hull and framing. Any improvements in production for drilling or punching rivet holes was something a shipyard was almost sure to use.
The little marine engines in the 4th photo down may be for use in some sort of work boats or small canal boats. They look too heavy a design for launch engines. They appear to be compound or triple expansion engines, so I would not think they were windlass engines. In that same photo, there is a bigger marine engine with two men next to it. It is a partially assembled engine. It looks big enough for a ship docking tug. There are also parts for windlasses, an unmachined valve casting, and a smaller propellor as from a workboat or similar. From the looks of it, the yard must've handled everything and anything from small canal or work boats to large oceangoing vessels.
I agree that everyone in the photos is wearing a cap. Pre-hardhat days, so a cap might save a man's scalp from a laceration or at least keep the scale and grit out of his hair.
I worked in the old Rheingold Brewery when I was an undegraduate in Engineering School. The Rheingold Brewery was in Brooklyn, New York, but may as well have been in Germany. As I recall, most of the men wore some kind of cap. Mostly, we wore "engineer's caps". The chief engineer was a powerful man around the brewery. When you went in to see him, you waited at his office door until he barked: "Herein" (meaning "in here", short for "kommen Sie herein"). If you were wearing a cap, you had it off and in your hand at your side when you went in to see the chief engineer. One older guy, having some beef with the chief engineer, failed to take his cap off when he went in to see the Chief Engineer. The Chief chased the guy out of his office and was said to have wound up to throw a 1" bronze globe valve at the guy.
I was fortunate in that I was able to work with a variety of oldtimers in that brewery. Being a kid, the oldtimers taught me all sorts of things. One oldtimer had served his apprenticeship as a machinist in the "Weserwerft"- a firm similar to the "Howaldtswerke" in the photos. He came to America in 1923, so would have been the right age to have been working in shops like the ones pictured. Seeing these photos brought back a lot of what that oldtimer had told me.
It is an amazing set of photos. Thank you for posting them.
Joe Michaels