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Lathe Talk #51: Air Compressor Replacement and Horizontal Pressure Pot Setup
April 25, 2013
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We’ve Been Up To Our Ears in Alligators: This year has started off with a bang… We’ve had our hands full of late getting quotes and replacing our roof after a severe storm came through and left our roof in a sorry nick. We obtained quotes from five different roofing companies for replacing our roof, but only two of the companies presented a professional quote. We finally settled on one company and we are very chuffed with their finished work. It took five of their roofers three and a half days to install 6,500sqft of roofing on our one-story home.
Over 25,000 roofing nails were hammered in by hand, one at a time. My arm aches just thinking about that… We chose to install a GAF Class 4 Impact Resistant (lots of hail in these parts) and a Class A Fire Resistant roof. This top-market roof allowed us to receive a hefty discount on our stratospherically high homeowner's insurance premium. I am glad it’s all finally sorted now and we’re on to other things.
Not So Fast Bruddah: I was looking forward to getting back in the saddle with a few things in the studio when we found out that we have to replace both of our aging HVAC systems on the main house. Once again, we looked at five different companies, but only one performed a thorough inspection and offered a professionally engineered solution to meet our needs.
Due to these extraneous time challenges, I have had no free time for writing Lathe Talk in the last few months. Things should start getting back to normal after all of the HVAC equipment is installed over the next two weeks. I for one cannot wait! My goal is to get Lathe Talk back to a monthly publication this year, if all of these outside time challenges will finally settle down.
Suggestions for Lathe Talk: If you have any suggestions for topics that you would like to see covered in Lathe Talk, feel free to send me an email. I’m always interested in your ideas and opinions. Complaints are appreciated as much as compliments. I have thick skin, so no worries. Please feel free to email me at: email@example.com
My upcoming plans for Lathe Talk include a new series of finishing articles, as well as new articles on tools and how to make some of your own tools. In addition, there will be articles on airbrushing, protocols for making your own cast resin blanks, free form sculptural carving tips, new articles on marketing your work, how to vacuum stabilize your wood and my continuing series on remodeling my studio. Whew!
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After more than sixteen years of heavy usage, my trusty 5HP Coleman 2-stage electric air compressor known as ‘Ole Red, has finally gone on to his greater reward. ‘Ole red’s specific demise was related to the 80-gallon ASME tank, not the electric motor or the compressor itself. I knew that ‘Ole Red was getting a little long in the tooth, but I never experienced any problems until recently…
Sorting The Problem
Last month, I began to notice that my compressor was losing air in the reservoir tank overnight. When I would close the studio in the evening, the 80-gallon tank would show full. In the morning, the tank would be completely empty. My cursory inspection did not reveal any apparent leaks in the tank or system piping, so I was ready to get stuck in and finally sort the problem. After pressurizing the tank up to a full 175psi, I began my inspection.
After a thorough going over, I was not able to find any apparent leaks or hear any air escaping from the piping. The compressor held its air during the day (although it was cycling of course during use, so who knows), but over the course of the night, it would lose its air. This air loss was intermittent, which made sorting the problem challenging. One day, I was out with my two Labrador pups in the back yard and I happened to hear the exterior water purge line hissing and gurgling. Ah-ha!
The compressor’s water purge line is fitted through an exterior wall. This allows me to easily evacuate the daily water accumulation outside into the grass, instead of mucking about with an old bucket. The intermittent hissing I heard lead me to believe that the quarter turn valve on the bottom of the tank was blocked by a flake of rust, or perhaps the seals inside the ball valve may have perished.
After exhausting any remaining air inside the reservoir tank, I removed the ball valve assembly and examined it closely. Everything looked in a proper nick, so I turned my attention to the condition of the ball valve seals. After dissembling the valve, I was able to closely inspect the seals. They did show signs of obvious wear and looked pretty well knackered. No worries, that’s an easy fix. I had another quarter-turn ball valve in the studio’s parts stores, so I grabbed it and headed back over to the compressor.
As I was getting ready to install the new ball valve, I thought it would be a good idea to take a look-see inside the tank to check its overall condition. I have not seen the inside of the tank since the compressor was new and I was keen to see the condition of the inner walls and the bottom of the 80-gallon reservoir tank.
Unfortunately, the petcock hole in the bottom of the tank is only about ½” in diameter. The only way I was going to see anything was with a tiny inspection camera. Luckily, I happen to have a 3/16" diameter inspection camera, so no worries. My inspection camera incorporates a tiny LED light on a flexible shaft that feeds images to a handheld control unit that is capable of taking still photos and video.
Photos and videos are stored on an SD card that you can pop into your computer to view the accumulated images or video. After inserting the flexible camera line into the bottom of the compressor tank, I began to examine the interior condition of the tank. What I found was a plethora of rust. The top of the tank (directly under the compressor motor) had only a wee bit of surface rust here and there. As I moved the camera around, the sides of the tank came into view. There was more rust here than on the top, but it was still in an acceptable nick.
Viewing the very bottom of the tank proved to be a significant challenge, but I finally found the proper bend to use in the gooseneck and it came into view. The bottom of the inside of the tank was well knackered. I could see some areas that had lost quite a bit of their original wall thickness and as a result, I decided to scrap the entire compressor instead of trying to replace the storage tank.
A Better Look Inside
To get a better view of the interior condition of the tank, I decided to cut it into several pieces with a large abrasive cut-off disk mounted in a Fein 5” angle grinder. The inside walls and the top of the tank were rusty, just like I had seen with the camera but they were still in a good enough nick. The bottom of the tank however, was a different story. By my estimate, it had lost up to 40% of the original wall thickness in some areas. That’s not a good thing to see in a tank that holds air at 175psi.
Throughout the years, I was always diligent about purging the water from the tank each day. During particularly heavy usage, I would purge the tank several times a day. Even with that maintenance protocol, the tank rusted quite a bit in some areas. The inside of the tank was bare steel, which is the way many compressors are still manufactured. If you look hard, you can find a few compressors that have rust-inhibitor coatings on the inside, but they are not very common it seems.
Scrapping ‘Ole Red
Since the tank pieces were too heavy to easily lift, I used a two-wheel dolly to pack them down to the curb for recycling. As I was wheeling the pieces to the curb, I began thinking about what I wanted in my next compressor…
‘Ole Red 1.0 served me well through the years, but it was past time for an upgrade. Had I wanted to, I could have just replaced the knackered ASME tank and reinstalled the old electric motor and the compressor on a new tank. However, due the overall age of the compressor, I thought that would be throwing good money after bad. My compressor had seen very hard usage during my production turning days and I knew the compressor and the electric motor were getting well past their sell by date.
If you have an old compressor, you might want to safely drain all of the air out of the tank and inspect the tank interior. I used a tiny inspection camera that I bought last summer. It has been worth its weight in gold and I have used it many times to diagnose various machinery problems. Although I drained my tank daily, it still developed heavy rust in the bottom.
I am glad I decided to scrap the old compressor and I'm looking forward to getting ‘Ole Red 2.0 installed. The only problem with the new compressor is that it needs a 40amp breaker service, whereas the old compressor ran on a 30amp service. I have had three electricians out for quotes and I will need to get a new sub-panel installed with a new dedicated line to the compressor before I can get that bad boy up and running.
Stay tuned for part two of this article next month. As a side note, I will be keeping the old 5hp electric motor and repurposing it in the studio. The old compressor motor itself is primarily aluminum and will be recycled.
As many of you know, I pressure cast my own binary resins and I vacuum stabilize wood using various commercial products. I have had numerous emails asking about how I setup my horizontal pressure pot. I now have two 15-gallon pressure pots in my studio, one is dedicated to vertical use and the other is dedicated to horizontal use. The horizontal setup took a wee bit of thought to get right, but I ended up with an easy to use setup that performs exceptionally well.
Vertical vs. Horizontal Mountings
You might be wondering why anyone would ever need a pressure pot setup in a horizontal position. If you think about a vertically oriented pressure pot, you have a tall round cylinder. My 15-gallon pressure pot measures 14.5” in diameter (inside) and 21.5” inches tall (inside). No matter what I want to pressure cast or vacuum impregnate, it has to fit into that area. If you’re going to cast or stabilize round objects like bowls, platters, or large cylindrical blanks, you’re well chuffed since a vertically oriented pot can accommodate these shapes easily.
However, if you want to cast square shapes, you’re quite limited when the pot is oriented vertically. All of my castings for turning squares come from square molds. This presents a challenge because the round shape of the pressure pot limits square mold sizes significantly. If you want to use a square mold in a round pot, your overall size is limited to a mold that will fit within the available round opening.
This means that my 14.5” round pressure pot (oriented vertically) can only accommodate a 10.25” square mold and still leave enough free space to get the mold in and out easily. Compare this to a horizontally oriented pressure pot with the same 14.5” opening. This setup allows a maximum 12.125” square mold to be used. That is quite a difference. One of my favorite square molds is made from HDPE and measures 12.25” W x 13.0” L x 2.25” D. This mold would never fit into my vertically oriented pressure pot, but it slides into the horizontal pot easily.
Note: Yes, you could just pressure cast into square vertical molds set on end in a vertically oriented pot. However, it is much more difficult to pour and mix swirls and achieve well-defined coloured bands in a vertical square mold. Having the square mold laid on its long side makes it much easier to create visually provocative resins, with a greater degree of control.
If you want/need to cast in larger square molds than your vertical pot orientation affords, you have two options. 1.) Buy an additional/larger pressure pot (I have seen pots up to 80-gallons offered for sale), or 2.) You have to reorient your pot into a horizontal position. Reorienting the pot is an easy way to increase the maximum size of square molds that your pot will accommodate.
Larger pressure pots like 30 and 60-gallon are readily available, but they are huge and heavy beasts and they are extremely expensive. My two 15-gallon pots cost approximately $1,250.00 each (£818 Quid), with the large oil filled stainless steel pressure gauges installed. A single 30-gallon pot by comparison, can easily relieve you of $6,000.00 (£3,930 Quid) or more.
Horizontal Orientation Challenges
Reorienting a pot on its side is not as easy as it sounds. Whilst it is easy to reorient a small pot like a 2.5-gallon model, a heavy 15-gallon pot is a different kettle of fish. You have to design a secure mounting for the heavy pot and install it perfectly level, or your resin castings will not come out level. In addition, you need some way to store the lid (which on my 15-gal pot weighs 26 pounds by itself) until you can get the pot loaded with your molds.
You also need some type of internal shelf on which to place your molds, preferably one that can be removed, if necessary. Then, you need to find a way to quickly and easily centre the pot lid on the horizontal rim opening. This will ensure that the pressure gasket is depressed in the centre of the lid gasket. Last but not least, you have to find a way to dog down the five lid wing nuts quickly, so you can begin the pressurization or vacuum process in a timely fashion. This is particularly important when casting so called “hot batch” resins that are specifically formulated to cure rapidly.
Fast Lidding Protocol
Some of the resins I work with will cure in less than five minutes. That sounds like a lot of time until you consider that most of that time you are mixing the two component parts together and incorporating the dyes, micas, or adjunct materials into the resin. You have to be quick, or you will end up with air bubbles in your finished casting. You have more time when vacuum stabilizing, but you still need to work efficiently with your time depending on the product you use for stabilizing.
You can only stir and incorporate materials into the base resin so fast. Aggressive mixing produces homogenized colours, whereas we are usually striving for elegant swirls, distinctive colour bands, or precisely inlaid alternative materials. Some resins require specialized mixing protocols using multiple coloured resins of various temperatures that must be added into the base resin in a particular order to achieve the proper visual effect. This takes time and time is something you have very little of when working with hot batch resins.
To save a bit of time in setup, I came up with a way to attach the top lid, centre it perfectly and dog down the wing nuts on the lid faster than you can say “Bob’s you’re Uncle, Sally’s your Aunt.” My fast lidding protocol saves quite a bit of time versus manually locating the lid on the centre of the pot rim and securing the wing nuts by hand. I use a high-density plastic (HDPE) strip that is taped to the outer rim on the top of the lower pot rim to accurately place the lid on the centre of the sealing gasket. Easy Peasy, Lemon Squeezy.
To save time locking the wing nuts down, I use a large modified 50mm socket and a wrench. The socket has two cutouts (cut with a standard cut-off disk) in the side of the wall to allow the oversized wing nuts to fit in the socket. Using a socket wrench to tighten the wing nuts is much faster than doing them by hand. You also save your fingers, because it’s much easier to securely tighten a large wing nut with a wrench than using your fingers. Fast lidding is the most efficient way I have found to get the pot ready for pressuring or vacuuming. Seconds count here and my protocol gets the lid secure in short order.
Securing the Mounting
Needless to say, when you use a pot in the horizontal mode it needs to be securely mounted and it must be level. I used regular 2” x 4” Southern Yellow Pine lumber (2x4’s) to build the frame for my horizontal pressure pot. The existing holes in the wheel mounts (where you would insert wheels if vertically mounted) were used to attach the pot to the reinforced 2x4 frame. The entire frame was then bolted to a heavy exotic wood workbench top to complete the assembly.
Once the pot was bolted to the reinforced frame, I checked it for level again. When you tighten the nuts on the mounting bolts, it slightly compresses the wood fibers on the 2x4 around the bolt/washer/nut. This throws the pot slightly off level, so you have to re-level the pot and add shims as necessary to maintain a level pot. In my case, I had to add shims (ground down washers) to two of the bolts to re-level the pot. Keeping the pot level is necessary for level castings.
As I was building the horizontal mounting, I thought I should incorporate a shelf for the lid. The lid weighs 26 pounds and there is no available space to set the lid whilst loading the pot. Therefore, I decided to add a shelf over the horizontal pot mounting to hold the heavy lid. This shelf doubles as a storage space for the lid when the pot is not in use. Since the lid is quite heavy, I routed several dadoes in the top of the shelf and added HDPE runners to help protect the shelf from damage. This worked a treat!
If you fancy casting in the horizontal mode, take a look at this mounting setup. It does not lend itself to removing the pot however, so you will have to dedicate a pot to this mounting if you use it. This may require investing in two pressure pots, which is a significant expense. To reduce your costs, look on the Internet for machinery, tool and equipment auctions, or on private sale websites.
Companies that liquidate bankrupt business equipment are another possible resource. If you scrounge around, you can find a good pot on the cheap and save yourself a monkey (£500 Quid) when buying your pots. Cheers!
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