Document OJyYvVrzVJ47yxMLbRL0NmwjX

578 CHAPTER 31 1965 Guide And Data Book Table 11 .... Recommended Construction for- Rectangiilor Medium Pressure Ducts Between Joints Tronsverse Reinforcing* At Joint* Mtahmwi Rebrfordng Angle OifflARWOO Gedv. Sheet Size and Maximum Longi oflonged GopoUif tudinal Spacing Sid* Inches Series) . Inside clip . Joint Double 5 SEp -Jl Welded Welded 1 Standing Seam IL Reinforced Standing Seam - r Hanged Joint --iliu Pocket lode - Companion Angle Hanged Joint Op thn 13 - ' .24, 13-18 24 12-24 23 23-38 37-48 48-00'" ' 22- 22 20 41-72 20 With Tie Rods No tie rod* rv- 1 tie rod d 48 hkbtovwoo oUriri of Without Tie Tod* No aagb re quired 1X1X10 Gsge @48 fa. Min. Angle Size None required IXlXlOOsge Mia Height, fat. 1 i Mia Height, la Mlt Height, la Mia Size 11 Nooe Bcq'nL 1 - 1 Naee Req'rd. Mia Height, la 1 l Mia Height, la 1 t Mia Size UXUXI IlXHXt 1 tie rod d 48 la. intimi aa resto-line of dad ride IXlXt a 48 1X1X1 li U 1} Nooe Beq'rd. II U ixixia UXUXI b.r IJXUXj @40 fa. 1 i with tie rod H is aster 11 None Beq'rd. 11 M - uxuxi a UXUXI 30 m. 11 with tie rod 2 OR H with U. uxuxi 3 .tierodiscenter _ ;------- uxuxi a 3X3X1 a 14 1X3X1 24 ta. with tM OR 1| with tie rod 11 with tie rod is eater is ester H 3XH rod is center UX^Iwith lj^ with tie. 11X11X1 UXUXI UXUXI UXUXI uxuxi. a 2iX2|XA a 24 is. with he 24 m. S1** IjMrifh 3 tie 2 with tie red is rod b cents 'Se!/-X*"to ,11 , nxiixA 11^ with tie mxidb 73-84 ` 8S-M- ` 18 HXUXia ass?*' 24 ifl. with tie red is ceoter ;18 .. ams rod beater ijxnxA l|wtth2tic UXUXI with be rad is cen to lfwithlti* tie rod a ceeter IMrith tie red 11 2 with tie rod is center " 27 end Over IS 3X2X1 a 24 in. with tierah a 43 is. eioog eagle 3X2Xt with 11 with tie rode 2 with tie rods tie rods a 48 23 is. rioeg a 48 is. along is. rioeg eagi* just . HX2JXA 1) with tie rod b eato tl with tie rod is center 1 with tie rah a 48 is. along joist. 7X7XA OR Hx^xi with tw rod b eestm 8X2XA OR UXliXl with tie rod is eater . , 43 m.rioeg. * TmnwrcriB rrinfetciiig mutt be Applied on All four ridec And tied together At eeich corner by riveting, bolting or welding. *' - Tnsntne reinforcing n te determined by dimes*:cm of *id* to which eagle b Applied. Angle site* era bAsea on mild steel Reinforcing node in other'shapes or of other ***<i must bs cf equivalent etrenglh sod rigidity. Then is no restriction on tbs length of duct section* between faints, Daets sre oosmsOy msdo in section* of 4, 8, 10, or 12 ft is length. Tto longitudinal spsring of the trssswerss trinfarehig between ioints msy.neeeaArity be tees than the epsring* recommended in the tsUe in order to conform to the --wt--r length module. - . .... . ,j . , Hie fad discharge connections shown in Fig. 16 are rated: good, fair, and poor, in terms of efficiency. Flexible connections are recommended on both .the inlet and.outlet to. all fans. .An inspection .of the heater connec tions shown in Fig. 16 shows-that uniform velocity through the heater cannot be expected in.the diagram noted.poor. When obstructions cannot be avoided,,the duct area should, never be decreased more than 10 percent. iSiream-Jtned collars should be used around obstructions; however,-.round,,tie rods do not;require special treatment Larger obstructions require an increase in the duct size in order to minimise dy-s' namic losses. In systems .where the branch air quantities re main constant, the branch takeoffs should be arranged to cut into the air stream in order to reduce the losses in velocity head. This type of take-off should definitely be-avoided in dual-duct;Bystems where branch flow rates vary considerably. All materials and all Are and srpoke controlling features.ofduct systems must satisfy the requirements of applicable local. Air Duct Design Table 12 .... Recommended-Construction for Rectangular High Pressure Ducts Between Joints**' - Tronjverew Retnfordbg* At Joints 579 Minfamm Reinforcing Angle Size and Maxlnum Dhsendoo Gofv. Sheet Longitudinal Spodng of longest Gage(AO Side - ' Four Sided Indies-' Inside SCp Jobt Doubles SGp --It . Welded Welded - 1 Standing ' Reinforced Standing Seam .f Ranged Joint .JUU Companion Angle Ranged Joint Up thro 12 13-18 With Tie Rods Without Tie Mhv Angle Rod* Size Mb. Height, fav Mia Height, la Mfak Height, - la . Min.' Angle Size- Mia 'Height,' Mia Angle la ' - - Size ' 22 No^tb rode rw N^o eagle re- Nooe required l 1 1 None Beq'rd. 1 UXI1X1 21 ^brrigttfai. 1X1X14 Osge a 4s fa. 1X1X14 Qege 1 1 1 NoseBeq'rd. 1 UXliXl terJbe of daet 12-24 15-33 23 ' 2 tie roA a 4 lXIXi@48fa. 1X1X1 22 lixuxiau UXliXl "'OR' lixiixi a 40 11 11 11 11 with tie rod b cento 2 OR 11 with tie rod b eater U Nooe Beq'rd. 11 11X11X1 3 Uxuxi Uxiixi 37-4842-0 ' 41-72 73-81 . SS-flO 27 end Over 0. 2D - to 18 18 1. 2X2X1 a oC 1X2X1 if with tie rod 11 with tie rod b OR b cento cento 11X11X1 with- tit rod m ester iixMxia> b. with tie rod cestw JX2XA a 34 3Xo2aXA 1} with 2 tie rods 11 with tie rod m UXliXl with tie rod m eeato - lixiixi a 2i *fx2ixA a hk with tie rod 24 m. b cento .(X..XA 1) with 2 tierods 8 with tie rod b lixiixi with tie roa fa cetto iixnxi.en b. with to rod b emto fUasXrodliXfa lcewoittehr t) with2 tie rods 2 with tie rod fa 11X11X1 a 24 fa. with tie rod fa ceoter UXliXl with 1| with l tie rads 2 with tie rod fa tit rod a cento 3X2Xia>4b. with tie rode a 48m.doo*tngfe 3XJXi with lie 1} with tie rods 3. with tie rods rod* a 431 lo a 83 b. eloag a a fa. stag lling ugh joint U 2X2X1 .. 1} with tie rod UXUXI 11 3X2X1 u 21X21XA V". *" * 11 with tie rad 2X2X1 OR UXliXl with tie red b tester 11 with tiered 3X3XA 0B Uxuxi with tie rod u cater 2 with tie rod UXUXI with is eater tie rod m eater j^with tie rod UXUXI with tie roa b cento 3 with tie rods a 43 fa. aw fa. eloag eagle ^Tmwrena rrinlorang most be Applied an til four rides end tied together At eAch earner by riveting, lwiUw ar wridiag. "twreiw reinfarmng rite n determined by dimension of Aide to which angle is Applied. Arvgfa an "uH Rrinfondng mods fat other dmpee w t! Sr**- most be of equivalent strength end rigidity. .aw* > no restriction on the length cfduct section* between joints. Duct* ere niede in of 4, a 10. or 12 ft in length. The ^r*yng of the transverse reinforcing between joints mey neoeasertly be law than the epnaags h<j'iiiutiiu1i in table in order to to the wMffl length .regulations. Standard-No. 90A of the National Fire Protec tion Association11;gives recommendations for the of air-conditioning and ventilating systems of other residence type. This and-other NFPA standards are normally used as the basis for local building and fire regulations and for the guidance^of fire insurance rating organizations. HEAT LOSSES FROM DUCTS -- In duct systems, the heat gains or losses of the ducts can be quite considerable, not only if the duct passes through uncon ditioned space, but aJso.on long duct runs within conditioned .space. Proper insulation wp remedy this situation consider ably, but sometimes a redistribution of the supply air is neces sary b order to compensate for the heat exchanges that occur. The heat loss from a given length of duct can be expressed by: : - , ' T f Q..t7,,[(i^j-1)] ; (17) where ' Qm = heat loss through duet walls, Btu per hour. V " overall coefficient of heat transfer for.the duct.wall, Btu per.(hour), (square foot).(Fahrenheit'degree);:-:-.-.-