Document e5OEKkw6GMnqryXxa74yXppKy

710 CHAPTER 52 1959 Guide Table 7 .... Exhaust Requirements for Woodworking Operations41 (Air Velocity: 4000 fpm at exfl itrandtat onion noted otfienme) Sell Feed Table Rip Saw Jointers Use 1--6 in. branch at bottom pulley; 1-4 in. branch at saw Up to 6 in. knives___ bead. 6 in. to 12 in. knives.. 12 in. to 20 in. knives. Large Self Feed Rip Saws Other Than Table Saws Over 20 in. knives.... Use 1-6 in. branch at bottom; 1-6 in. branch at top. 1-4 in. branch 1-5 in. branch 1-6 in. branch 1-7 in. branch Swing Saws Single Planners or Surfacera Up to 20 in. use 1-4 in. branch; over 20 in. use 1-4)4 in. branch. Up to 20 in. max. working width... 20 in. to 26 in. max. working width 26 in. to 32 in. max. working width Circular Saws ' 32 in. to 38 in. max. working width Up to 12 in. dia.................................................... 1-4 in. branch Over 38 in. max. working width___ Over 12 in. dia...................................................... 1-5 in. branch Dado head saws.................................................... 1-5 in. branch 1-6 in. branch 1-7 in. branch 1-8 in. branch 1-6 in. branch 1-10 in. branch Double Placers or Surfacers Gang Circular Saws Upper head Ventilation rate depends* on effectiveness of hood and maxi , Up to 20 in. max. working , mum number and diameter of saws. width.................................... 1-6 in. branch 20 in. to 28 in. max. working Disc Sanders Up to 12 in............................................................. 1-4 in. branch 12 in. to 18 in. dia........................................... 1-4)4 in. branch 18 in. to 26 in. dia.............................................. 1-5 iD. branch 26 in. to 32 in. dia.............................................. 2--4 in. branch 32 in. to 38 in. dia... .___ 1-4 in. branch and 1-6 in. branch 38 in. to 48 in. dia............. 1-6 in. branch and 2-4 in. branch width.................................... 1-7 in. branch 26 in. to 32 in. max. working width.................................... 1-8 in. branch 32 in. to 38 in. max. working width.................................... 1-9 in. branch Over 38 in. max. working width.................................... 1-10 in. branch Lower 1-5 in. branch 1-6 in. branch 1-7 in. branch 1-8 in. branch 1-8 in. branch Multiple Drum Sanders (over the table) Molders, Matchers, Sizers (see note) Up to 31 in. wide.................................... S in. branch (see note) Matcher head Top Bottom 31 in. to 49 in. wide............................... 6in. branch (see note) Up to 4 in.. 2--4 in. branch 1-5 in. Branch 1-6 in. branch 49 in. to 67 in. wide............................... 7in. branch (see note) 4 to 6 in-- 2-5)4 in- branch 1-6 in. branch 1-6 in. branch Over 67 in. wide. .. ............................. 8in. branch (see note) 6 to 8 in___ 2-6 in. branch 1-7 in. branch 1-6 in. branch Note: One branch of ese indicated required for each drum, Fever branch pipe* 8 to 18 in... 2-6 in. branch 1-8 in. branch 1-8 in. branch mayba uaed a* lost > total branch pipe crcva aectional area ia not reduced. Some Note: Where profiler ia uaed. provide additkmal pipe not km thanthat apedfind for manufacturer! taa 1 extra branch of equal cue on feed aide. 1-4 in. branch may be required far crhiinrtins bed rubber cuahiona or it-->K.n^.iiy operated bruab Single Drum and Spindle Type Sanders Wood Shapers Up to 50 sq in. sanding surface................ 1-3 in. branch 1-4)$ to 10 in. branch for each spindle according to size and 56 to 200 sq in. sanding surface........................ 1-4 in. branch character of work. 200 to 400 sq in. sanding surface...................... 1-5 in. branch 400 to 700 sq in. sanding surface...................... 1-6 in. branch 700 to 1400 sq in. sanding surface.................... 1-7 in. branch Tenoner 1400 to 2400 sq in. sanding surface................... 1-8 in. branch For cut-off saws: Up to 12 in. dia.................... 1-4 in. branch -Over 12 in. dia...................... 1-5 in. branch Horizontal Belt Sander or Edge Sander (see note) Drive Pulley Idler Pulley Use 1-5 in. branch minimum for each top and bottom tenon, cope, and dado bead. Up to 6 in. wide...................... l-4) in. branch 1-4 in. branch 6 in. to 9 in. wide.................... 1-5 in. branch 9 in. to 14 in. wide.................. 1-6 in. branch Over 14 in. wide...................... 1-7 in. branch 1-4 in. branch 1-4 in. branch 1-5 in. branch Automatic Lathes Use 1-3 in. to 1-10 in. branch according to work length. Note: Where mare thea one belt ia uaed, the pipe aisea tperified (ball be requited for each belt. Where a common bood te uaed far mere than one belt, a aincle pipe of an acta not tern than the cum of the areae el the pipea apeciffed may be * Where belt ia rarenibla, pipe at idler pulley eball be the aiae specified for the drive pulley. Air volume based on 50 cu ft per lb of refuse conveyed. Use 4500 fpm minimum conveying velocity. Vertical Belt Sanders (rear belt and both pulleys enclosed) Floor Sweeps Up to 6 in. wide................................ 4)4 in. branch on bottom Use 6 in. branch for fine dust to 8 in. branch for coarse ma 6 in. to 9 in. wide............................ 5 in. branch on bottom terial. 9 in. to 14 in. wide........................... 6 in. branch on bottom Mouth at floor, 10 X 4 in. to 12 X 6 in. Over 14 in. wide................................ 7 in. branch on bottom Note: Arm of floor sweep pipe need oat be included incomputing main pipe we*. Band Saws and Resaws Bottom Top Miscellaneous Equipment Up to 2 in. wide...................... 1-4 in. branch 1-4 io. branch Pulley pockets and chain mortises-3 in. branch: dovetail and 2 in. to 3 in. wide................... 1-5 in. branch 1-4 in. branch lock corner machines, dowel machines, duplex molding senders, 3 in. to 4 in. wide................... 1-6 in. branch 1-5 in. branch forming lathes, panel raisers (each bead), ploughs, rail shears, 4 in. to 5 in. wide................... 1-7 in. branch 1-5 in. branch routers, sash stickers (each head) 4 in. branch; pulley stiles-5 in. Over 5 in. wide........................ 1-8 in. branch 1-5 in. branch branch; glue jointer-6 in. braoch. Industrial Exhaust Systems 711 Table 8 .... Approximate Conveying Velocities Meferiof Cocvefed Oarign Velocity fpm 2,000 3,000 3.500 3,500-4,500 Large particles, heavy loads, moist materials 4.500 and over (Continued /ram p. 709) 4. Elbows and angles shall be a minimum of two gages heavier than straight lengths of equal diameter. 5. Hoods shall be a minimum of two gages heavier than straight section of connecting branches. 6. Where flexible piping is necessary, a non-collapsible type of flexible piping shall be used and its length shall be kept at a minimum. Construction 1. Longitudinal joints of ducts shall be lapped, and riveted or spot-welded on 3-in. centers, maximum Double-lock seams may be used on Class I application only. 2. Girth joints of ducts *bei1 be made with lap in direction of air flow with 1-in. lap for diameters up to 19 in. and 114-in. lap for diameters over 19 in. 3. Elbows and angles shall have an inside or throat radius of two pipe diameters whenever possible. Large radii are recom mended for heavy concentrations of highly abrasive dusts. Con struct elbows 6 in. or less in diameter of at least five sections, over 6 in. diameter of seven sections. Prefabricated elbows of smooth construction may be used. Angles' hjal] be pieced pro portionately. 4. Hoods must be free of sharp edges or burrs and hnll be reinforced to provide necessary stiffnpqi System Details 1. Connect duct to fan inlet with split sleeve drawband one pipe diameter long but not less than 12 in. 2. Transitions in mains and sub-mains are to be tapered; a taper 5-in. long for each I-in. change in diameter is recommended when possible. 3. All branches shall enter the main at the large end of the transition at an angle not to exceed 45 deg (30 deg is preferred). Connect branches only to top or sides of main, with no two branches entering diametrically opposite. 4. Provide dead end caps within 6 in. from last branch of all mains and sub-mains. 5. Provide access openings or cleanouts every 10 ft and near each elbow, angle, or auct junction in horizontal sections except for non-corrosive gases and vapors containing no particulate matter. 6. Support duets sufficiently to prevent placing of any load on connected equipment and to carry weight of system if plugged with material. Use maximum supporting interval 12 ft lor 8 in. or smaller ducts and 20 ft for larger ducts. 7. Provide 6 in. minimum clearance between ducts and ceil ing, wall, or floor. 8. Where blast gates are used for adjustment of system, place uiem near connection of branch to main, Provide means of locking after adjustments have been made. Butterfly-type dampers *hH qoI be permitted. 9. Fire dampers, explosion vents, etc- should be installed in accordance with NFPA Codes or local fire ordinances. 10- Rectangular ducts can be used only when clearances Erevent the use of round construction. Rectangular ducts must e as nearly square as possible. Weight of metal, lap, and other construction details are to be the equal of round duct con struction whose diameter equals the longest side. .11. Where State or local laws conflict with the specifications given, the more stringent regulation 6hall be followed. Any other deviation must Be approved before installation. AIR ROW PRODUCING EQUIPMENT The principal types of air moving equipment are cen trifugal fans, axial flow fans, and venturi ejectors. Chapter 22 includes information on fan types, arrangements, and application. Gravity stacks have application for some sys tems handling higher air temperatures or steam where no air cleaning equipment is installed.. Centrifugal fans are most frequently used for the bulk of exhaust system applications due to the system pressures involved. Where air cleaning equipment is included, fans are usually located on the clean air side. The paddle wheel or modified paddle wheel designs are heavily constructed and have few blades to make them more suitable if wear, corrosion, or accumulations are a factor. The higher efficiency backward-curved blade designs find application where relatively clean, non-corrosive air is handled. Forward-curved blade designs have limited application due to the number, shape, and metal thicknegi of the short curved blades. Belt driven fans are recommended by many designers because a change in fan speed is often needed where future changes of the system may be involved, where added pressure losses from air cleaning equipment im provements are anticipated, or where the fan may be used at some later date for another application. The axial-flow fan is used for systems having low-pressure losses. Propeller or disc designs develop pressures under 1 in., the vane-axial designs develop higher pressures but seldom are used where pressures exceed 3 in. The venturi ejector** is an inefficient method of air movement, but has the advantage of causing air flow without having the exhaust air pass through the air flow producing equipment. It minimi the explosion or cor rosion potentialities in certain types of system. Fans, motors, and drives should be located so that safe and easy access for periodic inspection, servicing, and maintenance is possible. AIR CLEANING EQUIPMENT As discussed in detail in Chapter 24, air cleaning equip ment should be considered in all systems where it can prevent property damage, neighborhood pollution, or re entry of polluted air to the working space, or where it can salvage usable material, reduce fire and explosion hazards, or make posable some recirculation of air to the working spaces. The present growing emphasis on air pollution control makes it desirable to remove all con taminants to the greatest practical degree based on reason able cost and maintenance. MAKE-UP AIR REQUIREMENTS A correctly designed exhaust system may be ineffective during periods when windows and doors are closed. This condition should be anticipated and prevented by making provision for an adequate air supply. Poor performance of exhaust hoods is caused by: absence of air supply systems; cold drafts due to high indraft velocities through cracks and openings in building construction especially at windows and doors; reverse air flow through lowpressure systems of roof ventilators or general ventilation systems; downflow through heater vent stacks preventing exhaust of flue gases to the outdoors. Systems for condi tioning make-up air do not necessarily increase boating requirements for the space, as cold air due to infiltration