VARIANTS OF MOISTURE EXTRACTION. It is interesting to see that the Dessicant used back in the 1960's is virtually the same as used today. In the midsixies I bought a secondhand diving compressor that had a screw on brass container that was filled with silica gel and charcoal and through which the breathable air was pumped and a manual drain valve was fitted. This, as JK stated was , after so many pump ups was placed alongside the Sunday lunch in the oven to remove all traces of water present. I have seen this done many times more in the past than now because a lot of installations now have screw on filters rather than loose silica gel and perhaps a little charcoal added. Here in the photos of the compressor I now have, you will observe two manual drain valves, ( operated every 15 minutes running time ) are fitted. The properties of this silica gel are something else. It seems it attracts water from the atmosphere to the extent you would never believe unless you have ever played around with it. I depict a photo of a kit bought to reduce the moisture present in order to store electrical test equipment. The top tray contains, as shown, silica gel. The lower container contains the water drawn without fan assistance or any help at all the water content present in the atmosphere at all times. This was placed in a cupboard and left for several days. The silica gel seems to contain a unique property, the water appears to attach itself to the gel absorbing a minimal amount only. Gravity does the rest. This silica gel I left out overnight outside in about 80 degrees and the next morning the container had half an inch of water in it from being empty the night before. I have found in handling the crystals it is a very different substance to anything I have ever handled, from Macerator pumps upwards. It's a horrible sensation on your hands, you wash and wash but it's still there. Slimy weird stuff indeed. Amazing the properties of it, compressed air blown over the crystals seems to take nearly all the moisture away. I have worked on several different types of air compression systems as well as the standard two tower system over the years. Some air control systems were several HP receivers running at approx 130 psi and were linked lol together via check valves. As well as the Silica Gel installation cartridge each receiver had on the bottom of it a dump valve / condensate valve. Every time the max blow off pressure was reached the valve would lift and exhaust to atmosphere thereby dumping all the condensate , for that reason some people used to refer to it as the dump valve. ( It was a diaphragm valve ) Some systems had a sight glass filled with Glycerine to carry over into the system to prevent operating mechanisms and valves freezing up thereby bringing the whole installation to a halt which I have seen many times because the sight glass was allowed to get too low. The blowoff pressure was adjustable Upto about 150 psi. I enclose photos of a compressor I bought new in 1981 which has disposable screw on air filters fitted, these are supposed to be renewed every approx 240 bottle pump ups but you can cheat and weigh them to disclose any water content present. Hot sun or the oven treatment will prolong the filter life, and guess what's in them? Silica Gel. ( Plus a load of O rings ) I enclose a shot of the compressor being set up for a bottle being pumped up. The bottle needs to go in water really as the compressed air being pumped in generates heat, especially through the restriction of the bottle neck. This compressor splits in the middle with no tools for carrying purposes and although it may be small is not to be underestimated. No 450 psi here, it will pump Upto 3200 psi and if the bottle is faulty/ pitted/ rusted inside and it explodes it is more than capable of razing a house to the ground, I have seen pictures in old diving magazines of workshops/ houses flattened and people killed. Like the HP receivers on ships regular inspections are necessary. When I was about 10 years old I had a weekend job assisting a local man who established a diving centre in our area. I used to help him clear underwater sea suctions ( not running ones )on ships that had been laid up for 3 years swinging around destroyer buoys in our local harbour. Grating / Grill types ( not like all those holes drilled in a plate like you folks in Canada have, ) I think an air drill would be in order to clear all those drilled holes underwater and for many hours to boot it would appear. These diving bottles would, every two years be subject to a detailed internal inspection and a hydrostatic test. Pumping up the bottle with water to 3200 psi and the expansion measured and compared to a when empty situation. Caliphers were used for this pump up measurement test. Furthermore in writing I would perhaps consider that there could be some form of extraction similarity to my earlier article but can only give you my best assurances that any similarities are completely unintentional , but I leave it to you, the reader as to the how you would perhaps associate same. So you can clearly see from all the foregoing that this is the correct way to extract the moisture BP. I enclose an engine plaque quoting cubic feet per minute outputs etc for those of you who like a challenge, how long to pump up your smallest HP receiver to 450 pounds per square inch on your ship? ( No 100,000 hp quotes here please. ) so we can see various, different methods of extracting the moisture, but it would appear Ally based Silica Gel has not, to date been superceded . Variants indeed of Moisture Extraction.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.