Building Something Different
A PVC Wood Steaming Boiler system
This is my adventure into woodsteaming and wood bending, I am shearing this info in hopes to help others interested. I have a complete 28 page set of Free plans for this system at “firstname.lastname@example.org”You should start by reading everything printed about steam bending, searching the internet, books and talking to a few people who have done steam bending.
I first got the idea to build this woodsteaming system from a book I read, the book showed a steel pipe used to form a boiler system to create steam for bending wood, this started the wheels turning..
The first thing to do is find the material needed for this steaming system. However, when I start looking and realized the cost and problems involved with steel pipe, I soon decided it is time to look at some other alternatives. I do believe the system in the book would work just fine, but the cost of steel pipe today just does not make it piratical for this project and the heat build up with the steel pipe is not what I wanted in my shop.
So, whats a guy or lady to do; well some research on other types of pipe produced some interesting info. I looked at some cheap pipe like conduct and found it to be that, cheap, cost is low but it will rust if you just talk about water in front of it, but this pipe is not made to be used with water. Conduct will rust in a heartbeat. Aluminum was another choice, but the cost was too high. Copper is just untouchable, cost wise, for pipe large enough for this project. I looked at my last and option, PVC. This was an education all of its own, I even learn what the letters PVC stand for, “polyvinyl chloride” most of my info about PVC comes from the ’’‘AWWA Research Foundation’’’, Denver, Colorado, 1994. This info led me to other info and I began to see what was and was not possible in terms of using the schedule 40 PVC in my steaming system, and the cost is in the ballpark for the do it yourselfer. It has many variables and if you’re going to use PVC, you need to learn the limits of these variables. I did look at my very first thought on PVC, schedule 80. However, when I seen the cost of schedule 80, I soon changed my mind. Schedule 80 PVC is 3-4 times the cost of schedule 40 PVC. Although it is a good chose for this project, it’s just too expensive for the average do it yourselfer to make it practical for this project. Also, remember if you are using schedule 80 you must use the proper schedule 80 fittings as well as the proper cleaner and cement. Each type of PVC uses a special types of cleaner and cement, this is an important issue. No one size fits all!!!
After much research and studying of schedule 40 PVC, I now had enough info and understanding about PVC to go forward with my idea. However, that did not help me build a great steamer the first time. I did a lot of experimenting and after a few flops, and near misses, I finally came up with a way to do the job. What I found out about how heat affects PVC is amazing. Trying parts of different types, sizes and lengths, (all sch. 40) made it either work or turn into a large white sticky ball. The trick here was to be able to use it time after time with no problems or damage and with complete safety. PVC is a chemical compound that is affected by heat depending on its stresses. This steaming system is a somewhat simple system, but putting it together in a manner that lets the PVC do what I wanted and not having the problems associated with heat, this was not so simple. I also had to know if it would stand up to long hours of use, repeated heating and cooling and yes, sometimes just plain abuse. I did not want something that would work a few times and then fall apart, but something that would be around many years from now and still doing its job. The system I built is still working after 4-1/2 years ,it’s still steaming along. After extensive use and testing, which included many 12 hour runs, this is the steamer running more than 12 hrs. in a row without any interruptions. It’s still steaming along, without any signs of fatigue or damage of any kind and completely safe. With any tool or electrical system you should always be awear of safety!!!!
What I built was a PVC boiler with an electric heating element built into it. The PVC is in the form of a schedule 40 (90) degree fitting, a Santee (sanitary fitting, ) and a straight section of PVC pipe. I did this several times and as I soon learned the location of parts to each other and element size makes a boiler that works or turns into that white sticky ball. I did use a lot of PVC, but that is just part of the learning process. In addition to the boiler, it is important to have the proper water supply feeding the PVC boiler as water is used, (turned into steam). I found that a 5ga. plastic container works fine, its large enough to supply water for several hours without having to constantly watch the water level. The main thing here is that the container must have a smooth bottom; it makes a great difference in how the 5 gal. container is used and ease of supplying the water. Having a water supply to feed and how its feed to the system without interrupting the heating and steaming made all the difference for success of the intended process. It should be noted here that the container isn’t glued, screwed or attached in any way to the platform its setting on.
As with most wood steaming systems, the steam box is the big pay off. I did the research on this also and the number and types of boxes out there, you would not believe, some are just plain dangerous. I did look at the use of PVC for the steam box. PVC can be used for a steam box if care is taken in its construction. Plugging the ends of the PVC pipe can cause a real dangerous problem, a rag stuffed loosely into the end of the pipe or loose fitting cap on the end will prevent any problems of pressure build up. I do believe that a wooden box is a better chose, what I wanted here was a box that would stand up to the water, hold the heat, and move steam from back to front in an even flow. Yes, PVC will do this to. Also, provide the space for several pieces of wood to be steamed at one time and be able to be of many different lengths of say 3ft to as long as 20ft. This provided me with a few problems and options. Use a very rot resistant wood, wood heavy enough to stand up to the constant use, one that was easy to find, and not going to cost me the farm. Keep in mind that if you use wood for a steam box, the box will have to be replaced after the wood becomes waterlogged over years of use. This is a disadvantage to using wood.
I chose to use treated lumber and treated plywood covering it with foam/glass insulation. Most any rot resistant wood as cedar and cypress can be used here to provide a long lasting steam box life. The box I built has an outside size of 11-1/2” x7-1/4”x 3 ft to 10 ft. this size is compatible to the boiler system I built. It is possible to use a steam box up to 20ft long if you use the larger 4” PVC pipe to build the boiler. The steam box must also be set at an angel to induce good steam flow inside the box, the back bottom side of the box where the steam enters sets lower than the front. This tilt helps lets the condensate drain from a small hole near the back end of the box. Too steam wood in a box it is necessary to keep the wood up and as close to the top of the box as possible, this is where most of the heat and steam is and it keeps the wood up off and out of the condensate on the bottom of the box. With the wood up off the bottom, the steam can
surround the wood and better penetrate. Another problem with the steam box is that most people try to seal it up, WRONG; it becomes a bomb if the steam cannot escape easily. Leaving an open area in the front, say at the front door lets steam flow and not make a bomb. However, this dose brings up issues of keeping out the cool air while steaming the wood. It is important to seal all the holes on the box, but let the steam escape in an even flow. All the dowels used to hold the wood up off the bottom must each have holes to pass through and each hole must be sealed. The door on the front of the box is also an issue. The door must not be completely sealed, by leaving a ¼ -gap at the top of the door; you can get a bellowing flow of steam through the box. This steam flowing through the box also helps keep out cool air that tries to enter. If you get too much cool air inside the box form holes or other openings, you lose a lot of heat and steaming efficiency, you also get a lot of condensate, which is not good for anything. This is another reason why it’s important to keep the wood up off the bottom of the box as you will get condensate water in the box. The drain hole in the back of the box could have a small hose in it for draining the box back into the supply tank. What you want here is a steam box that is safe, effective and will not fall apart while giving you good bendable wood time after time. Another method of draining the condensate is to tilt the steam box down at the front and leave the gap at the bottom of the door. This will let the condensate run out and still gives the steam an easy exit, just not my preferred method. I believe having the box tilt up at the front gives a better steam flow. This is a matter of personal options and thoughts on the steaming effect.
The steam box stands over the steamer (boiler) and water supply tank with support legs attached to the sides of the steam box and to the platform below. The legs can be of any length, but they should be tall enough so it is easy to add water to the supply tank when necessary and to have good access to the wood being steamed. It should be fair to add here that a large section of PVC pipe could be used as a steam box, wrapped with insulation to contain the heat and used in the same manner as the wooden box. Using a PVC push on cap with a slot or hole in the top front end of it will help provide good steam flow, let the steam have an easy exit from the steam box no matter what type you use. The biggest disadvantage here is that the round PVC pipe doesn’t provide the space for several pieces of wood to be steamed at the same time, unless you use very large pipe, that’s expensive also, it’s your choose.
The next item is the water supply tank for the system; it has to hold enough water for several hours of steaming without having to add water. As stated, a 5ga. plastic container with a smooth bottom, one with a lid is a good idea, so it can be covered when not in use. Cover the supply tank when not in use, this keeps out all the dirt and small objects that seem to find their way into the supply tube on the bottom of the tank. I don’t believe it’s a good idea to cover the tank while in use, as this makes it difficult to see the water level inside the tank, you don’t want to run too low on water. Note here that with this system you can run it for about 4 hours and only use about 3” of water level. The supply tank will need a connector on the bottom with a hose attached and constantly providing water to the steamer (boiler) as needed. The supply tank needs to be in a safe and relevant location to the steamer so water can be added to the supply tank at any time with ease and not interrupt the steaming process; this system will let you do that.
Setting the supply tank at the right height will keep the water supply in the boiler at a safe level and provide constant steam.
This whole operation sets on a ¾” plywood platform with a 2×4 frame under it for the wheels that make it quite portable, but only use wheels that will lock and prevent the system from moving when in use. This makes it safer and easy to roll out of the way to store when not in use. When you are ready to steam some wood, having wheels makes it easy to roll it right over to the job. Being portable and being able to move it close to the job means that when removing wood from the steam box you lose less heat, bending time is extended and seconds count at this point.
The average woodworker of some experience could build this system easily in a couple of days. The small cost of materials is far out weighted by the ease and safety of use which it provides. The efficiency, durability, productivity and just plain fun, makes this a rewarding and useful project. But then, anything having to do with boats or woodworking is fun.
Some other ideas I have seen on the internet that use a gas can (a new gas can if you must) and a used or new burner of some type is far less efficient and cost more when you take into account the cost of propane, an open flame and lack of efficiency. The fact that a system with an open flame in a wood shop is just plain dangerous, especially if there is saw dust or other flammable material close, which makes the open flame type very unappealing. I am not putting down anyone for using any of these other systems, just saying it’s not in your best interest to do so. Some are dangerous and very costly. If you insist on using these other methods, do so with care. There is not any project worth getting hurt for or burning down your shop. Do not replace safety with being cheap or uninformed!!! Not trying to be rude here, just do not want to see anyone get hurt, it just is not worth it. A few other facts, when you are using your wood steaming system, when you open the door on the front of the steam box, be sure to wear good heavy leather gloves, safety glasses and always stand off to the side when you first open the steam box door. Steam burns deep, it is hard to see and if you ever get a steam burn, you will remember it. ’’‘Steam can cause very serious injuries!!!’’’
I am not sure if the electrical heating element is cheaper to run than using propane, but I do believe that it is safer and provides a more consistent heat.
Never move the steaming system while in operation. Keep the wheels, if you use wheels, on the platform locked when you’re using the system. When you are working and enjoying your work, time seems to fly by, but if the water supply to your boiler, gets too low, it could cause extreme damage to the system, it is necessary to have a water level marked on the supply tank so you know when to refill the tank. Working with wood is fun, but don’t lose track of what is happing around you.
Its Always a good idea to keep the area around the steamer clean, especially if you are using an open flame system. One seems to work better if things are in order and clean.
I could go on and on here about safety, but you must be your own keeper, “think before you leap” . Good luck with your projects and Stay Safe!!! I have a complete 28 page set of Free plans for this system at “email@example.com”