Global Container Kiln  - Copyright 2006 Global Energy

INTRODUCTION

Welcome to the world of drying lumber.

This guide will give you a detailed manual on the fabrication of your own lumber dry kiln. The construction of dry kilns is a relatively simple process once you know the procedure.

A. General Kiln Fabrication Structure

For years, the kiln industry has relied on permanent kiln structures which require a costly foundation and are not readily salable in case of upgrade or liquidation. Global has solved this problem by using ISO Shipping Containers.

Shipping Containers provide an excellent platform for building a dry kiln. Shipping Containers are self- supporting structures which are watertight, can hold approximately up to 60,000 lb. of contents, and can with- stand over 600,000 of weight when stacked.

Built of steel and aluminum, the containers are able to withstand the rigors of a hot, humid, at times acidic drying environment which hard and softwood exhibit. Aluminum can be easily sawed, drilled, and fastened. The installed doors provide a airtight fit which is better than most commercial kiln doors.

Components A kiln is a chamber which extracts water from lumber. The three critical elements for drying lumber are heat, humidity and airflow. As long as you get the desired effect of dried lumber in the end, the methods of achieving that do not matter. The biggest problem kiln operators face is lumber degrade-- or defects to the lumber while drying.

A properly constructed kiln with good operational components will produce quality dried lumber with the aid of a skilled kiln operator and a good kiln controller. The key to drying quality is consistency and experience. The major components of a dry kiln are:

• Moisture Removal Equipment / Heat Plant (Wood Burner, Steam, Hot Water, Electric Heat, Dehumidification, Vacuum, Solar, Hot Air, Microwave)

• Humidity Control -- Venting

• Air Flow -- Fans / Baffles

• Process Control -- Computer Controller with inputs from wet/dry bulb station, and outputs to heat control and vents

• Options -- Track Loading, Venting Heat Exchangers

The most cost effective kilns are natural gas (small scale), and wood heat. The Global Container Kilns are heated by either natural gas, wood heat, hot water, or electricity. When choosing a heat plant one must consider

(a) initial cost and

(b) operating costs.

 

In a small 5,000 BF kiln natural gas, propane, or electric heat provide ease in installation and low initial costs-- with moderate operating costs. At times it can be a tradeoff of convenience. A wood fired burner is most effective in larger kilns (15,000 BF and larger), but have high initial costs and are less convenient to operate. A good option is a Central Boiler Waterstove.

The waterstove can produce 200 deg. hot water while using batch fed wood scraps to fire the unit.

The advantages of a Container Kiln are:

• Fast installation time

• No Foundation

• Higher resale value

• Portable

• Modular and stackable

• Quality drying / good airflow through pack

• Prefab structure

Tools The tools required to build a kiln are basic hand tools which can be acquired through most hardware or home- center stores. Tools should be portable. Electric tools have the advantage of being more accessible than pneumatic tools, are are cheaper to acquire.

• Container Fabrication / Modification -- Sawzaw or jigsaw -- Small grinder with wire brush and abrasive wheel -- Electric Drill • Insulation Installation -- Electric Drill -- Driver bits (Phillips, and drywall driver) -- Utility Knife -- Hex-rachet and bits / Hand and Drill Attachments • Major Components Installation -- Electrical Drill (2-3) with assortment of bits and drills -- Set of Screwdrivers -- Hex-rachet and bits -- Assortment of wrenches -- Assortment of vise-grips -- Hammer / soft-head and claw • Miscellaneous -- Extension Cords (2-long 2-short) -- Halogen Lamps (3 500-Watt) -- Large Fan (it gets hot in containers) -- Step ladder (2) -- Paint brushes / rollers -- Manual sprayer -- Crowbar -- Circular Saw (wood cut blade, aluminum cut blade) -- Pliers / Wire cutters / Level / T-Square / Chalk-line

Enclosed with your kiln kit is a Fabrication Guide and Blueprints. Use one copy as a reference and keep inside your office. Use one copy as a "Working Copy" and keep on-site with your kiln for reference while building. Additional copies if needed are available through Global. Use the column to the right to jot down any notes you may add during fabrication.

FLOWCHART Please refer to the pictorial flowchart diagramming the necessary steps to complete the container kiln. You may set goals for yourself by completing times and dates next to the steps of the flowchart. It is a good idea to fabricate you kiln using the "goal orientation" process.

Take one step at a time and perform each sequence as listed in this guide and the Blueprints. Taking items and installing them out of sequence may result in time lost or wasted. SEE FLOWCHART

KILN CHAMBER Set Up The kiln chamber itself provides a insulated capsule for the lumber to dry in. The chamber must be able to withstand the moderately high temperature and high humidity which accompanies drying lumber.

When your Container Kiln arrives try to set it down exactly where you want it. Since the Container itself weighs 10,000 lb., moving it may be an inconvenience without heavy lifting equipment. You may set the Container down on a cement pad or on ground with the support of railroad tie timbers supporting the corners.

It is important to have the Container level. Upon opening the Container thoroughly sweep out the interior. Next remove any plywood protective covering on the walls. Usually there is a 1/4" ply lining. Discard this plywood.

It is convenient at this time to put some packing grease on the hinges of the doors. This will make the doors swing open and shut without any friction. Next you will want to mark the centers of the aluminum studs on the walls.

Do this by using a very heavy black marker or wax pencil. Mark on the floor (a 6" mark perpendicular to wall) where the center of the stud is. You will need this reference point when installing the insulation and plywood shell.

You will notice that the walls of the container are made from a aluminum "C" channel "stud" and riveted with aluminum panels. They are spaced about 23" apart (on center). This stud allows enough room to affix a TEK self-driving screw (enclosed). Use the driver attached to a simple electric hand drill to affix TEK screws.

Insulating Installing the Thermax Insulation

You may purchase the 2" Thermax® or equivalent 2" R-14 insulation from a local building yard for approx. $30-35 per 4x8' sheet. You will need approximately 40 sheets. In addition you will need 40 sheets of 1/2 4x8' plywood, either straight edge or tongue and groove.

Step 1 -- The Interior Walls The first step will be applying the insulation to the walls. You may start at either end, but we recommend starting at the end where the doors are. Leave enough room for the door to close shut with about 3 inches to spare for the door insulation. At this point you may coat all the plywood with at least two coatings of Thompsons waterseal or equivalent waterproofing (both sides).

Use a manual pump sprayer you may purchase at your local hardware store for about $15.00 To begin start with one sheet of Thermax (insulation) and one sheet of plywood. You may use construction adhesive for a better hold by applying to both sides of the Thermax. Place Thermax against wall, 1/2 plywood on top, then screw into place with TEK (self tapping 3") screws.

Fasteners should go into aluminum studs only- 4 per stud. Use your markings on the floor as a reference where the studs are (as a reference for vertical). The TEK screws enclosed (or purchased) are 3" in length and have a hex head. Use a standard drill with a hex driver attachment to affix screws through plywood and insulation to aluminum stud.

With each additional sheet be sure to affix construction adhesive into the tongue and groove or straight edge of plywood to ensure a good seal. Once the side is finished, continue with the next side. Then with the back wall. Some cutting may be necessary here to make a snug fit. Next affix insulation and plywood to the doors. A rubber or foam gasket may be purchased at your local store for the edges.

Interior -- Ceiling Next affix insulation to the ceiling of the Container. This is a bit more complicated since you will need to hold the material up while affixing. Begin by marking where the studs are on the ceiling.

You may do this by marking on the plywood walls adjacent to the ceiling. Make the mark at least 6" in length for easy sighting. Next you will need a step ladder and a "T" shaped 2x4 "helper" to hold the insulation and plywood in place. Make two of these Ts out of 2x4's and make the top (horizontal) of the T about 4 feet in length. Make the vertical part of the T about 8 feet in length. You may prop up the ply and insulation with this simple device.

It is helpful at this point to have a helper to hold the Thermax and plywood up while you arrange the T to temporarily hold up the material. Once these are in place you may affix both to the ceiling stud with TEK screws.

Do this starting from the opening end of the Container to the back end of the Container. You will find that once you have done a few you will have the "system" of installation down and it will go very quickly.

Painting Interior Paint

After affixing the insulation and the plywood shell you will need to seal and paint the interior. We recommend painting the interior white so that it is easy to see in your kiln. First begin by thoroughly sweeping the floor of the Container. Next paint the entire inside shell of the plywood with at least two coats (use an oil based paint). Next apply at least three coats of Thompson's Waterseal to the floor. Congratulations ! You now have a kiln chamber which is fully insulated and ready for the installation of the components.

Cutting Access Holes for Components Cutting Holes for Vents, Furnace and Wiring The next step in the fabrication of your kiln chamber is cutting the major holes for the components. This consists of two square holes for the vents, two square holes for the furnace, and access holes for wiring of the controller and electrical panel as needed.

Please refer to the Blueprints for locations. Procedure: To cut a hole use the following procedure:

(1) Use a Sawzaw® or similar cutting device with a medium tooth blade. You will need at least 2 3/4" cutting thickness on the blade.

(2) Using your grinder with an abrasive wheel attached, start from the outside of the Container and cut a 2-3" slot where you want to begin the cut.

(3) Using a drill, drill a hole through the slot big enough to accommodate a Sawzaw blade.

(4) Insert the Sawzaw blade and begin. It will help to mark out the area with a black marker or at least mark the corners of the cut.

KILN COMPONENTS The next step to completing your Container Kiln is to install the major components.

Vents: 1. Please refer to the Blueprints for location and instructions. 2. Mount motor on outside and build simple housing to keep rain off of motor. You may use a simple plastic bag for temporary use.

Heat Unit: 1. Please refer to the Blueprints for location and instructions. 2. Mount heat unit (with propane conversion if using such) with simple overhead cover to keep rain and weather out. 3. You may wish to contract a heating/mechanical contractor for the actual line hook-up. Be sure to follow proper CODE which may apply with the use (installation) of natural gas or propane.

Mount NEMA Enclosure for Controller: 1. Please refer to the Blueprints for location and instructions. Refer to the Installation Guide for proper procedure and hook-up. 2. We have included two units-- one for the monitoring of dry heat and controlling the gas furnace and one for the monitoring of the humidity (called depression and measures relative humidity) for controlling the vents. 3. Install two units. 4. Install the Dry Bulb (temperature probe which goes to the dry heat controller). 5. Install the Wet Bulb (temperature probe which goes to the humidity controller).

You may install the wet bulb "WB" by using the stainless steel WB well. This well holds water. The WB temperature probe is mounted horizontally above the level of the water using the clips enclosed. Be sure to place a non-heat conducting insulator between the clip and the probe when attaching (crimping) the clip to the probe.

The "wicks" (cloth material) is placed over the temperature probe and feeds water around probe. This gives a "wet" temperature reading called "dewpoint" and is your wet bulb reading. You must ALWAYS keep the well full of water so the probe does not dry out.

You may wish to install an automatic float valve which when connected to a small tank of water via a hose (mounted outside kiln) or directly to a water line via a hose-- it automatically keeps the well full of water. 6. We recommend that you get a small water tank (5 gal.) and mount outside kiln. Next feed a simple water-hose (2-3 feet length) from the tank to the float valve assembly in the well. This gives you the simplest, most reliable method of keeping the well full of water.

Be sure to keep the small water tank full of water by checking daily.

Mount Electrical Junction Box: 1. Please refer to the Blueprints for location and instructions. Mount next to NEMA Box. • This would be the "fuse" box or "load center" •

Also mount the Motor Starters

Fans, Heating Coils and Baffle Installation: 1. Please refer to the Blueprints for location and instructions. 2. The fans are installed by first assembling the motors to venturi mount, then attaching fan blades. Use locking washers and nuts to prevent loosening. 3. Be sure that fans are blowing AWAY from the walls for proper circulation. Wiring: 1. Please refer to the Blueprints for location and instructions. 2. Fans do require thermal protection. Usually this is in the form of motor starters which are included with the kit.

Conditioning System: 1. There are 10 humidity nozzles included with the kit. These are used as a "conditioning system" by taking water and misting (humidifying) water. This is accomplished by water under pressure being forced through a engineer nozzle which atomizes the water into a fine mist. 2. To install you will need a length of 1-1.5" diameter steel pipe. Space the nozzles equal distances along the pipe and tap into pipe. You may mount the pipe anywhere downwind of the fans-- even on top the fan rack itself. Install the pipe so that the nozzles are pointed in a 30-45% downward angle. 3. On the outside, install a on/off valve and connect to a pressurized water source.

FINISHING KILN In putting on the finishing touches to your kiln, we highly recommend that you read "Drying Oak Lumber." This manual is included with your literature package and describes the techniques in drying Oak lumber.

You may find several useful hints on drying lumber, in addition to many trade secrets for quality drying. You may apply some of these in the final stages of your kiln construction.

Calibration of Temperature Probes At this point you need to calibrate the temperature sensors to be sure that they are reading and reporting the correct temperature. Dry Bulb: You may calibrate with simple thermometer. Instructions in Controller Package tell how to compensate if reading is off. Wet Bulb: You may calibrate using a thermometer with a wet cloth wrapped around sensing end. Instructions in Controller Package tell how to compensate if reading is off.

Sealing Sealant and Insulating Strips

Be sure to seal and insulate the following with either silicon sealant or expandable foam. (A tube of silicon sealant is enclosed as an example.)

1. Vent openings between shell of container and vent.

2. Openings for return/outflow of heat furnace.

3. Openings for electrical wiring.

4. Openings for NEMA Controller enclosure and temperature probe leads.

5. Around bolts which go through the top of the container to hold the fan rack.

Drain Holes You may find that small pools of water form inside your kiln during the kiln drying process. This is normal. You should drill small 1/4" holes in the floor to accommodate this moisture to drain any pools which form.

Lumber Transfer and Handling The easiest way to load and unload your kiln will be through the use of some type of lumber handling system. We recommend using a rail or track type system. This system is composed of a rail on which lumber carts ride.

You may build these carts or purchase trucks to weld together to make carts. To make a rail, all you need is two types of steel: (a) 6" wide 1/4" thick flat steel, and, (b) "C" channel (2" wide or as per caster/wheel) or "V" stock steel- at least 1/4" in thickness. Simply weld the C or V stock upside down to the flat plate steel, then bolt assembly to floor "I" beams in container. This makes a very effective and inexpensive Kiln Track System.

On the outside, you may make a rail bolted to 6x6" timbers which can be moved with a forklift if you intend to put in several kilns.

Solar and Efficient Heating Options A seldom used technique for reducing the heating costs associated with kiln drying is probably the simplest and most overlooked. By painting your kiln top black and southern exposure black, you can have the solar radiation of the sun help reduce your gas bill.

By placing two kilns side-by-side and putting some insulation bats between them you can also help reduce heating bills. If you are next to an operation which uses steam heat, you may wish to contract buy a portion of the steam or even use their waste steam to heat your kiln.

A novel way to produce your own electricity and heat would be to cogenerate. Using a gas powered electrical generator fired by NG or Propane you could produce your own electricity and use the engine heat to heat the kiln.

You would do this by running the output of a hot water engine radiator into the kiln via finned piping which can be purchased through your local plumber.

Conditioning If you are drying furniture or cabinet grade lumber then you will need to condition your hardwood. In addition if you dry most woods below 15% you will need to condition. We have included water misting humidifier nozzles with the kit which will provide conditioning.

Simply install a 20 or 40' long 1" water pipe through the kiln in front (downwind) of the fan rack. Tap the nozzles into the water pipe and install a on/off valve outside the kiln. Follow guidelines on conditioning in the "Drying Red Oak" manual or as recommended by the kiln schedule.

Another method of conditioning is to purchase a hot water boiler (gas fired and used to save money) or make yourself a simple conditioner by using an old water heater-- purchase extra elements to install in water heater to raise steam.

Economizing Energy / Efficient Operation

A new product is out which economizes motor operation. The device makes the motor operation 25% more efficient saving you 25% of your electrical bill. If you notice that you have more than 500-600 FPM airflow you may wish to disconnect one of your fans. In drying hardwoods, you can turn OFF most of your fans below 20% moisture content as directed in the "Drying Red Oak" manual. Up to 40% of your electrical bill can be saved observing this technique. This will save you 1/5 of your energy bill.

You may also wish to switch from a standard billing rate to a capacity rate to save even additional money. Using solar options will assist in reducing your heating bills. Remember a kiln which isn't full still uses the same amount of energy.

KILN OPERATION Kiln Operation and Drying:

We highly recommend that you read "Drying Oak Lumber." This manual is included with your literature package and describes the techniques in drying Oak lumber. If you are drying softwoods or other species please refer to the specific Drying Schedules provided with this package. Schedules: Included in our literature package are the complete drying schedules for all species of wood in North America and most Tropical woods.

It is important that when you start drying that you follow these closely since these schedules represent the best quality drying in the most time effective manner. Many schedules may be modified according to your expertise in drying lumber.

In starting you may wish to lower the dry bulb temperature by 5 to 10 degrees F to act as a buffer area to prevent possible degrade. Once experience is gained in drying, you my follow the schedules or even experiment within small percentages of the target temperatures.

Furnace Type Kiln: If you are interested in converting your kiln to wood energy we highly recommend you read the manual titled, "A Furnace Type Kiln" from the USDA Forest Products Lab. Using A Computer to Track, Monitor and Control:

You can use a IBM or Mac computer to monitor (remotely) your kiln. With automatic moisture and temperature probes you can chart and control the kiln process more precisely and fine tune the drying time. However there is no substitute for a good kiln operator.

How Effective is End Coating Lumber? Is end coating a worthwhile technique to reduce end checking in air drying oak lumber? Gene Wengert (now of Univ. of Wisconsin Madison) and Fred Lamb of the Brooks Forest Products Center in Virginia did a study on the effectiveness of end coating that was paid for by U.C. Coatings of Buffalo.

They found:

1. End Coating immediately after sawing reduces the average length of end checks by 2-1/8". On a 8 foot piece of lumber, this is a potential increase of 4 percent.

2. 62 percent of the pieces of lumber that were end coated immediately had end checks that were one inch or less in length. Only 4 percent of the uncoated pieces had end checks that were this short.

3. A delay of three of more days in coating the ends reduces the benefits of the coating by a significant amount. This applies whether the lumber was stickered or tight piled.

End coating is a well established practice to reduce end checking in lumber. This practice is occasionally used on high value logs as well. I know one small mill that harvests, saws and dries for the retail market. He has his logging crew promptly end coat the logs after bucking.

The result was lumber which appeared to have only a few short end checks an needed less trim allowance. End coating gives the greatest benefits when used on thick, valuable, easily split (Oak and Ash) species, that is stacked in the sun during dry, windy, hot weather.

Other useful techniques to reduce end checking involve:

• Placing the stickers right at the end of the pile.

• Placing the lumber under a shed to get the boards out of the sun and rain. Pile covers are a cheap way to get some protection from the elements.

• Consider covering the windward side of the pile with burlap or an industrial textile designed for that purpose.

• Don't put valuable, easily check lumber on the edges of the yard or top of the pile, where too-rapid drying is likely to occur. The spacing between piles also can be used to get a little control over drying rates. May of these techniques will also help prevent other surface checks.