20 



HARDWOOD RECORD 



January 25. 1921 



Engineering in Furniture Factories 



By B. A. PARKS, Grand Rapids, Mich. 



Associate Member of The American Society o( Mechanical Engineers 

 (Continued from Dec. 25 Issue) 



40. In most furniture plants the exhaust from the engine will 

 exceed the requirement for low-pressure steam during the summer 

 time and it therefore becomes a question as to how valuable this 

 excess of exhaust steam is and how great an investment is warranted 

 in cutting it down to the minimum. From a knowledge of the total 

 steam requirements of the plant the amount of fuel required can be 

 calculated, assuming that 20 to 2.5 per cent of the lumber cut finds 

 its way to the boiler room as refuse or waste, and that the fuel value 

 of the wood is about 20 per cent of that of the average bituminous 

 coal, weight for weight. It is then a simple calculation to determine 

 the cost of evaporating, the excess of exhaust steam during such 

 periods of the year as this excess exists. Any saving effected by re- 

 ducing the amount of the excess exhaust steam, which would go to 

 waste, should not only pay all fixed charges on any investment made 

 to reduce this excess but should also pay a return of at least 20 per 

 cent per year on this additional investment. As briefly outlined 

 above, then, it is fairly easy for the designing engineer to determine 

 how economical an engine it will pay to install and whether it would 

 be profitable to operate condensing, say, during the summer months, 

 or to install other means of utilizing or reducing the excess of exhaust 

 steam, thus effecting a saving in the coal pile. The type of engine 

 best suited for driving a lineshaft load where efficiency, economy 

 and continuous operation are permanent considerations is probably 

 the slow- or medium-speed releasing-gear simple Corliss engine or the 

 poppet-valve engine, which latter is similar in most respects to the 

 Corliss except in the valve gear. 



41. In many plants where breakdown service cannot be obtained 

 from the local public-service company, and in fact oftentimes when 

 Bueh service is available, it will be found economical and convenient 

 to install a small direct-connected high-speed generating imit to fur- 

 nish lights at night and operate a few machines without its being 

 necessary to operate the main engine. As the exhaust steam from 

 such a unit will generally be all used in the heating system and dry 

 kilns, the power generated is practically a by-product and the only 

 cost for the power generated is the fixed charge incident to the addi- 

 tional investment. Such fixed charges will often be found to be less 

 than the cost of breakdown service from the power company. 



42. With regard to the drive from engine to lineshaft, either 

 belt or rope transmission may be used, although the writer prefers 

 the American system of rope drive to the belt as being somewhat 

 smoother in operation and slightly more efficient; the total stresses 

 on engine and head-shaft bearings are less, also it requires less care- 

 ful alignment of engine and lineshafts. The main generator may be 

 either directly connected to the main engine shaft or be driven by 

 belt or rope. The writer prefers the latter arrangement as being 

 cheaper in first cost, allowing of operation of the plant in case of 

 breaK down to generator, and also of changing the generator for a 

 larger one should it be found that the electric load is going to in- 

 crease beyond the capacity of the original generator. 



43. In choosing boilers for the plant the capacity required may 

 be determined from the total steam demand, adding an allowance 

 of 10 to 15 per cent for pumps and other incidental uses throughout 

 the plant. By dividing the total maximum boiler capacity required 

 into at least three units it will always be possible to operate the 

 plant on two boilers, for even with a maximum demand for steam two 

 boilers wiU carry the plant by operating at 150 per cent of rating. 

 It is decidedly poor economy to provide just enough boiler capacity 

 to carry the maximum load, for this makes it necessary to do all clean- 

 ing and make repairs on Sundays. This means that such worK will 



seldom be done as thoroughly as it should and it is bad for the morale 

 of the jiower-plant crew for them to feel that they have got to spend 

 nearly every Sunday of the year cleaning boilers or doing other neces- 

 sary work on the boilers when out of service. An even greater argu- 

 ment in favor of providing sufficient boiler capacity so that one boiler 

 may always be out of service is in the interest of continuity of 

 operation, for the failure of one boiler due to accident or other cause 

 is very unlikely to cause a plant shutdown or even curtail production. 



44. As regards the type of boiler to select, there is no difference 

 in efficiency between a well-set horizontal retiirn tubular boiler and 

 a water-tube boiler. The choice is more dependent upon the capacity 

 required. For any plant requiring a maximum of 500 to 600 b.hp. 

 the writer would prefer the horizontal return tubular as being gen- 

 erally easier to care for and less likely to have accidents than the 

 water-tube boiler. Plants of greater capacity than the above should 

 generally consider the water tube as being preferable on account of 

 space requirements. 



45. The pressure to be carried depends on the type of prime mover 

 and as to whether the prime mover is to operate condensing or non- 

 condensing. In non-condensing plants 100 to 125 lb. gage pressure 

 should be about the maximum, although the addition of 50 to 75 deg. 

 of superheat will be found beneficial to economies of engines and 

 pumps. 



46. The location and arrangement of the power plant are impor- 

 tant as regards the economical transmission of power to the factory 

 and the allowance for increase in capacity. Where lineshaft drive 

 is used the power plant is located in a separate holding, preferably 

 near the center of the main lineshaft, though of course within easy 

 driving distance from engine shaft to main receiving shaft. This 

 location of power plant is also fairly near the center of distribution 

 for steam and electric current. By arranging the boiler and engine 

 rooms "back to back," that is, ivith center line of boilers parallel 

 with center line of engine and with back of boilers toward the rear 

 end of engine, and with the chimney at one end of boiler room, 

 provision is made for extensions to the power plant without any dis- 

 turbance of the original equipment. Whether the additional power 

 units shall be arranged to deliver power by belt or electrically depends 

 of course on where the additional power will be used. 



47. The utilization of the factory waste or refuse so as to obtain 

 the maximum fuel value is another problem which should receive its 

 fair share of thought and study. Of course, shavings and sawdust 

 from the various machines will be handled by an exhaust system to 

 a separator on the boiler-house roof and then spouted to the boilers 

 or shavings vault. In most plants the cuttings and culls are col- 

 lected in push carts by a crew of men and wheeled to the boiler house 

 where they are fed to the furnaces by hand. The above method of 

 handling this part of the refuse is not only expensive from the stand- 

 point of handling cost, but the full value of the refuse as fuel is not 

 realized due to the manner of firing. The installation of a few small 

 ' ' hogs ' ' or chippers, at convenient points in the plant where cuttings 

 collect, discharging into the regular exhaust system will in many 

 cases be found to be a paying investment. The power consumption 

 is considerable and a certain amount of maintenance is required, but 

 these disadvantages will frequently be found to be outweighed by 

 the decreased labor cost and the increased efficiency obtained in burn- 

 ing the fuel. Tests have shown that cuttings run through a hog and 

 spouted to the furnaces in the regular way are worth 25 to 30 per 

 cent more as fuel than when fed as cuttings into the furnace by 



{Concluded on page 24) 



