VacDry Kiln Chamber Construction

• VacDry kiln chambers are manufactured of stainless steel with a heavy-duty external, carbon-steel frame. Doors are fitted at one or both ends, and engineered to open on an articulating hinge, lift straight up or roll sideways dependent on customer requirements.

• Door seals are fabricated by milling a 0.5” channel into the stainless steel flat and pressing a half-round, solid neoprene extrusion in the slot. Insulation is applied according to local ambient conditions

• VacDry kiln chambers are available in two configurations: Singlewide and doublewide. VacDry Models 2.5 and 4.0 are singlewide, Models 8.0 and 10.0 are doublewide. All chambers are 28’ long. Singlewides are 54” wide and doublewide are 120” wide. Doublewide chambers use two side-by-side heating plates for each layer of the kiln charge.

• All kiln charges are 26’ long and either 40” or 80” wide, respective of the chamber.

Control System

• The VacDry kiln precision control system is accessed through a convenient LCD touch-screen connected to a PLC and I/O board. The control system constantly checks chamber-mounted sensors against a wide range of parameters to provide the operator with total control over every aspect of the drying process. In combination with the VacDry software package, the system displays visual data and allows operator access to each variable, control switch and status indicator. The entire system can be remotely monitored and controlled through an Internet-connected PC.

Heating System

• Heating requirements for VacDry kilns are very low. The source can be hot water or low-pressure steam. However, if you plan to dry cold or frozen wood, the boiler needs to be oversized.

• The heating system is a closed loop through an all stainless steel corrugated shell and tube heat exchanger. High quality Crane Deming 3110 series end suction pumps are used to circulate the heating water. The system includes a low-pressure regulator for make-up water, anti-backflow valve, air release valve, pressure release valve, expansion tank, brass ball valves and sensors to monitor water temperature in and out.

• To provide uniform heat throughout the charge, aluminum-heating plates are used between each course of lumber. Fabricated from a custom design, the plates are designed to reliably and repeatedly deliver maximum BTU’s with minimal water pressure. When the heating source is hot water, a 3-way diverter valve is set by the heating control. When the source is steam, a globe valve is set proportionally by the control system.

Vacuum Pump

• All VacDry models use variable speed vacuum pumps to reduce energy consumption and allow a tighter control on vacuum pressure. The vacuum system includes a copper and brass shell and tube heat exchanger to prevent wood vapor from reaching the vacuum pump. Pumps are a 2-stage, liquid ring SIHI LPH series pumps with cast iron case and bronze impellors. These pumps are liquid ring using water as the seal. If the ring of water is thrown out of the pump, a PVC separator allows any air bubbles to leave the water. The PVC separator is connected to the discharge side of the pump. Air leaves through a vertical pipe coming out of a tee pipe arrangement. Water runs out of the end and is re-circulated through a cooling water storage tank. Where climate allows, an evaporative cooling tower is used. If the unit is installed where the climate is hot and humid, a chiller is recommended.

• Vacuum pumps can be installed on top of the kiln for easy drainage of seal water back to the cooling water storage tank. If mounted on the floor, the seal water can routed to the cooling water storage tank or may need to drain into the sump from which it is pumped to the cooling water storage tank.

Condensate Collection

• A shell and tube heat exchanger condenses water vapor drawn from the chamber. The cooling water enters through a Y strainer and exits past a thermometer and pressure gauge. The water travels from the pump condenser into a condensate collection tank. Two level switches mounted in the tank are monitored by the PLC. When the water level reaches the upper switch, the PLC energizes a condensate pump until the water drops to the lower level.

Cooling Water

• VacDry kilns use evaporative cooling towers where climate permits. When the local climate is hot and humid, chillers are recommended. Cooling water is needed for the condensers and vacuum pump to operated efficiently. The water is continuously circulated through the kiln and returned to a polyethylene cooling water storage tank. Two submersible pumps are installed in the storage tank — one to circulate water continuously through the kiln, the second to pump warm water to the cooling tower.

Note: VacDry kiln do not need to be full to operate and the aluminum-heating plates do not need to be fully covered. You can also mix similar species (exhibiting similar drying characteristics) on different layers and run on the least demanding schedule for the species involved.