32 



HARDWOOD RECORD 



Jauuary 25, 1922 



YARD AND Kl LN 



c^ Section Intended to Promote Efficiency^ 

 and Economy in Lumber Drying ^ 



Short Stories of the Kiln 



By C. J. M. 



ThciC little talis o) the lumber kiln may carry iivitluyr humor nor ro- 

 mance, but they arc true, and possibly contain, here or there, a little sug- 

 gestion, of dormant value, until remembered at the right moment, what it 

 m^y repay the trouble oj reading and remembering. — Author. 



A Poor Heating System Quickly Corrected 

 Sometime during tlie war, the writer was requested to supervise 

 the drying of artillery wagon, materials in large quantities, mostly 

 very green oak of southern origin. 



Several blocks of war emergency dry kilns had been previously 

 constructed and recently completed, and the first charge was due 

 to come out of same, when contrary to all hopes and expectations, 

 it was discovered that the kilns contained but a very small per- 

 centage of usable material, most of it having contracted nearly all 

 of the ills which follow severe casehardening. Needless to state this 

 condition greatly increased the immediate need for such materials 

 as the kilns contained. Of course the expert was requested to pro- 

 duce the same in record time. 



An analysis of the kiln records and schedules merely disclosed 

 that temperatures and humidities had been very irregular and the 

 former too high for the materials in the kilns. Inspection of the 

 methods of operation indicated lack of system and the physical 

 fact that one man cannot keep track of more than eighty kilns 

 without serious consequences to the kiln contents. The operator 

 testified his inability to obtain anything like a fair temperature ad- 

 justment and blamed the heating systems of the kilns. 



And the operator had to be sustained. He was right. An inspec- 

 tion of the heating arrangements of these kilns disclosed that inci- 

 dent to the hurry of construction of these kilns, somebody had 

 really overlooked something slightly important. 



Each heating system consisted of 30 1%-inch pipes, running full 

 length of the kiln, and subdivided into five equal sections of six 

 pipes each, of the header coil type, and whenever the operator de- 

 sired to make an adjustment of temperature, he would either add or 

 subtract a full 20 per cent of the entire heat producing capacity. 

 Try as he may, the operator naturally could not obtain the tempera- 

 tures prescribed by his schedules, he would be either too high or too 

 low by a good many degrees. 



An effective remedy had to be found, such as would without de- 

 lay, and without attracting too much attention to somebody's pre- 

 vious error, make the heating sj'stems as flexible as necessary for 

 me materials to be dried. 



A sufficient number of l^^-inch pipe plugs were obtained, and 

 four of the coils were trimmed to proper size by the complete 

 removal of five pipes from the central header, leaving but one pipe 

 on it, four pipes were taken from the adjoining next, leaving but 

 two pipes on same, three were taken from the next, leaving three, 

 and two were removed from the fourth header, leaving four pipes. 

 Thus out of a total of thirty pipes, but sixteen remained, and the 

 operator was able to effect by the use of single headers or by com- 

 binations, anything from one to sixteen pipes under heat, and this 

 was just about sufficient to give him from 100° to 130° during sum- 

 mer weather. 



From, each kiln had been removed 14 pipes, and these with some 

 additional piping were reassembled into similar header coils and 

 installed on top of the coils already in the kilns at a later time, as 

 the kilns came to be unloaded, so as to provide a reserve for the 

 cold season. Practically no drying time was lost and immediate 



good results were obtained from systemaiic operation of these 

 kilns under proper schedules. 



Question — Vacuum Eetum System for Heater Coils 



In your issue of Dni'niber 2.5th I note a question regarding the 

 advantages of a Vaeuum System for Bemoval of Condensation from 

 Heater Coils of Dr}' Kilns. I felt very much interested in this but 

 found that in the answer you did not explain just how such a 

 Vacuum System is arranged and how it works. If not too much 

 trouble I would greatly ajipreciate learning this. 



Kiln Operator. 

 Answer to Question 



As explained in the answer to question 3, issiie of December 25th, 

 air accumulates in all heater coils of any steam heating system, 

 and this must be removed, if the heater coils are to perform their 

 service. 



Good Automatic Air-Valves connected at the right place to eacli 

 Heater Coil Kcturn Header and also to the Steam Trap itself, will, 

 if properly installed and maintained, remove this air when it ap- 

 pears. They will do so slowly but surely. Unfortunately these air- 

 valves are of a more or less delicate construction not intended to 

 the rough usage in a dry kiln and sooner or later, but mostly sooner, 

 the}' forget to function and call for attention which somotinies they 

 do not receive. 



A good Vacuum System, properly installed, will do all that the 

 steam trap and the air-valves can do but will do this much more 

 surely and thoroughly without any interference by the severe kiln 

 conditions, and will thus maintain uniform heat conditions in the 

 kiln, regardless even of any small fluctuations in the steam pres- 

 sure, because this latter is not required to move tho condensation 

 through the trap or in the pipe lines, this motive power being sup- 

 plied by the Vacuum, or rather by the jiump which produces this 

 Vacuum and maintains the same in the condensation return line. 



With a good Vacuum system it is possible to utilize all of the 

 exhaust steam from the engines and pumps for the heating of the 

 dry kilns, at a pressure as low as one jiound or even lower, thus 

 reducing back pressure on the steam app.-iratus to a minimum. 



In a Vacuum sy.stcm a pump is attached to the main condensation 

 return line, at the power house or other suitable place, so that it 

 pulls constantly on this pipe line, maintaining a vacuum of about 

 8". The return header of each heater coil is directly connected to 

 this return line, without check valve, but in each of these connec- 

 tions is installed a vacuum return valve, which in effect is a simple 

 trap, so constructed as to ])ass instantly any water or any air which 

 may enter it, but to close just as instantly when steam touches it. 



Thus by the action of the vacuum pump and the vacuum return 

 valves any slight accumulation of condensate or of air is promptly 

 removed from the heater coils, as soon as formed, without waste 

 of steam, or without assistance from the steam pressure. The result 

 is uniformity of heat conditions and instant response when a heater 

 coil is cut into service. 



The cost of operating the vacuum pump is practically restricted 

 to the cost of the lubricating oil, if it is driven by steam and the 

 exhaust turned into the heating supply of the kilns. Once properly 

 installed, the vacuum .system requires practically no attention, 

 aside from the continuous operation of the pump. Cons. Engr. 



