Improvements in Kilns for Drying Lumber,

By Mr. Joe Steel, Moore Dry Kiln Company, Portland

The development of the steam-heated dry kilns for seasoning lurnber from the steam-heated roonr where only a dry heat was used into the present high-powered and flexible internal fan system of kiln has been a gradual process. Ilowever, within the last few years, several outstanding improvemerrts in dry kilns have been placed before the lumber manufacturers for giving them better drying results, These two outstanding developments have been the application of automatic humidity control and the perfection of the Reversible Circulation Internal Fan system of kiln for all classes of lumber seasoning.

In the old type "hot box" kiln, the only moisture or humidity in the air inside of the kiln was supplied by the water being evaporated from the lumber during the drying process. It has not been ma.ny years ago that a leaking stearu pipe inside of kiln was considered a serious drawback for good lumber drying. However, soon the value of humidity schedules for correct lumber seasoning was recognized, and humidity was injected irrto the kiln rooms by means of live steam sprays. The use of proper steam sprays unquestionably improved drying results, but hand control of the spray line valve v'as a hit or miss operation, and oftentimes desired results wcre not secured. The necessity for better control of steam spray operation led to the development of the present automatic humidity controller.

The Automatii Humidity Cbntroller combines the dry bulb temperature control, the humidity control, and the recording of b91h ihe wet and dry bulb temperafures into one practical and servicealrle instrument. This instrument is operated by air, and is very accurar'e in control and positive in operation. The humidity controller enables definite schedules of temperatures and humidities to be cari.ed, a'rd then duplicated on successive rtrns, thereby eliminating the hurliln factor in control of the proper drying schedules. It has also elinrinated the evils of too much spray being admitted into kiln, thereby slowing down the drying rate. More than.four hundred controllcrs of onJ of the populir hakes have been installed on dry kilns in various sections of the country within the last two ycars.

The Moore Dry Kiln Company has adapted the autonratic hrrmiditv controller 1o their improved design of Internal Fan Sysiem of Diy Kiln. These high-poivered kilns would be like engines with.out governors, without having hurnidity controllers made a Part crf tlieir"equipment. These corrtiollers also play an important part in securins the flexibility and drfing efficiency that can only be sg6sred with thi reversible circulation itrternal far.r type of kiln

Moore's Reversible Circulation Internal Fan kiln has been ihe outsrowth of intensive study and development in dry kiln design' ThJse kilns employ special reversible disc fans and work. agairrst very low static bressuie, giving a very large turnover of air inside of i<iln with an expenditure of a very moderate amount of enelgl'. By having a large fresh air inlet, schedules for -drying.woods-having a -hieh nioisture content, such as western yellow pine and su1:;; r oine'ind also redwood lumber, can be secured and maintained. I'lte i;;;r;bl. ;i;.ttitio" of "i. tlitoueh load of lumber also gives thii tvoe of kiln a distinct advantage over kilns employing only a onewiv circulation. When drying woods having a high initial moistttre "otitent it is a well-known fact that there is a considerable lag in drvins between the entering and the leaving side of the load. tly ha;in; reversible circulation, this lag can be cut down. thereby rea"ci"E the drying time required. These benefits from reversible circulition are-esplcially evident in kilns using edge stacked Iumber' where air is required to tra\el across from 8 to 10 feet of lunrber before being reconditioned.

The mec6anical features of Moore's Reversible Circulation itrternal Fan Kiln have been carefulty developed, and lumbermen can now be assured of a practical and foolproof dry kiln instatlation' Moore's Special self-oiling diy kiln bearings have demonstrated their efficiencv ind serviceability at over fifty installations that we have made of this type of kitn. - This bearing allows the shaft t-o -cxpe.nd fieelv when kilir is heated attd contract when kiln is cooled' Tl'e bearins is designed with replaceable babbitts, making it oossible- to chinei' bearins"without disturbing fans, ducts. shafting or requirirtg oouring of b;bbitt. We have tested these bearings alongside of ball arii roller type bearings, and have found them to be the most "i".tii"t iv;t .i'biarine for' drv kiln use. The use of direct conirected drive makes a simple and practical mechanical drive arran.<ement. . Because of the low static the fans are working ^inst. oniy " i"tt-itorsepower motor is required for the average length dry ltln i04 feet long. Reversible circulation is secured by oush button startins switch.

Reversible Circulation Internal Fan Kilns (fully covered t" ""ien[s), are used in drying atl kinds of Pacific C^ast woods' Mdi;-t;t Kiln Company hive'made installations of their improved t.'oe kilns-at the foltowing ptants:

Seven kilns, Owen Oregon Lbr. Co., Medford, Oregon; two kilrrs, East Oregon Lbr. Co., Enterprise, Oregon; eight kilns, Susar Pine Lbr. Co., Fresno, Calif.; twenty kilns, Cady Lbr. Corp., McNary, Arizona; two kilns, A. C. White Lbr. Co., Dover, Idaho; five kiLts, Western Lbr. Mfg. Co., Marshfield, Oregon; five kilns, I\{cCloud River Lbr. Co., McCloud, Calif.; one kiln, Pacific Lbr. Co. Scotra, Calif.. and two kilns, Pacific Veneer Co., Marshfield, Ore-on.

Lumbermen looking for improvements for their old dry kilns, or when in the market for atlditional drying capacity cannot afford to overlook the real improvenrents of automatic humidity control artd highly efficient Internal Fan Kilns.