How to Trap Steam Distribution Systems - Armstrong International, Inc.

More documents

Recommendations

Info

How to Trap Rotating Dryers Requiring Syphon DrainageProduct Inside a Rotating Steam Heated DryerThis type of dryer finds wide application in meat packing aswell as food processing industries. Common examples aregrain dryers, rotary cookers and bean conditioners.Their speed of rotation is relatively slow, usually limited to afew rpm, while steam pressure may range from 0-150 psig.These slower rotating speeds permit the condensate toaccumulate in the bottom of the collection chamber in practicallyall cases. Again, syphon drainage is required and flashsteam is generated during condensate removal.Trap SelectionThe condensate load generated by these dryers can bedetermined through use of the following formula:Q =N x L x RPWhere:Q = Condensate in lbs/hrN = Number of tubesL = Length of tubes in ftR = Condensing rate in lbs/sq ft-hr(typical 6-9 lbs/sq ft-hr)P = Lineal ft of pipe per sq ft of surface(see Table CG-26)EXAMPLE: What will be the condensate load on a rotarycooker containing 30 1-1/4" steel pipes 12' in length with acondensing rate of 8 lbs/sq ft-hr?Using the formula:30 x 12 x 8Q = = 1,252 lbs/hr2.30A differential controller is recommended on these dryersfor its purging and flash steam handling ability.The IBLV again requires proper sizing for certain applications.InstallationIn all cases, condensate drainage is accomplished througha rotary joint, Figs. CG-55 and CG-56. The DC should thenbe located 10"-12" below the rotary joint with an extended6" dirt pocket. These provide a reservoir for surges of condensateand also a pocket for entrained scale.Table CG-26. Pipe Size Conversion Table (Divide lineal feet of pipeby factor given for size and type of pipe to get square feet of surface)Pipe Size (in)Iron PipeCopper orBrass Pipe1/2 4.55 7.633/4 3.64 5.091 2.90 3.821-1/4 2.30 3.051-1/2 2.01 2.552 1.61 1.912-1/2 1.33 1.523 1.09 1.274 .848 .954Figure CG-56. Product Inside DryerRotaryJoint10''-12''DC6''A revolving cylinder drained with a syphon—an internal syphon surrounded by steam.Some condensate flashes back to steam due to the steam jacketed syphon pipe andsyphon lifting during evacuation.Armstrong Steam and Condensate Group, 816 Maple St., P.O. Box 408, Three Rivers, MI 49093 – USA Phone: (269) 273-1415 Fax: (269) 278-6555www.armstrong-intl.com45CG-40
How to Trap Flash TanksWhen hot condensate or boiler water, under pressure, isreleased to a lower pressure, part of it is re-evaporated,becoming what is known as flash steam. The heat contentof flash is identical to that of live steam at the same pressure,although this valuable heat is wasted when allowed toescape through the vent in the receiver. With proper sizingand installation of a flash recovery system, the latent heatcontent of flash steam may be used for space heating;heating or preheating water, oil and other liquids; and lowpressure process heating.If exhaust steam is available it may be combined with theflash. In other cases, the flash will have to be supplementedby live make-up steam at reduced pressure. The actualamount of flash steam formed varies according to pressureconditions. The greater the difference between initial pressureand pressure on the discharge side, the greater theamount of flash that will be generated.To determine the exact amount, as a percentage, of flashsteam formed under certain conditions, refer to page CG-4for complete information.Refer to Chart CG-3 (page CG-4) for percentage of flash steamformed when discharging condensate to reduced pressure.A third type of device that may be the preferred selectionin many cases is the automatic differential condensatecontroller. It combines the best features of both the IB andF&T and is recommended for large condensate loads thatexceed the separating capability of the flash tank.Safety FactorThe increased amount of condensate at start-up andthe varying loads during operation accompanied by lowpressure differential dictates a safety factor of 3:1 fortrapping flash tanks.Figure CG-57. Typical Flash Tank Piping SketchMake-upValve StrainerReducing ValveTrap SelectionThe condensate load can be calculated using the followingformula:Q = L -L x P100Where:Q = Condensate load in lbs/hr(to be handled by steam trap)L = Condensate flow into flash tank in lbs/hrP = Percentage of flashEXAMPLE: Determine the condensate load of a flash tankwith 5,000 lbs/hr of 100 psig condensate entering the flashtank held at 10 psig. From page CG-4, the flash percentage isP = 10.5%. Using the formula:AlternateVentLocationRelief ValveFlash TankGaugeCVTo LowPressureSteam UseAir VentTo DrainHigh PressureCondensateReturn Line46CG-41Q = 5,000 - (5,000 x 10.5) = 4,475 lbs/hr100Due to the importance of energy conservation and operationagainst back pressure, the trap best suited for flash steamservice is the inverted bucket type with large bucket vent.In addition, the IB operates intermittently while venting airand CO 2 at steam temperature.In some cases, the float and thermostatic type trap is anacceptable alternative. One particular advantage of the F&Tis its ability to handle heavy start-up air loads.Chart CG-21. Recommendation Chart(See Page CG-2 for “Feature Code” References.)Equipment BeingTrappedFlash Tanks1st Choice andFeature CodeIBLVB, E, M, L, I, A, FAlternate ChoiceF&T or *DC*Recommended where condensate loads exceed the separating capability of theflash tank.IBLV Steam TrapTo Low PressureCondensate ReturnFlash steam tank with live steam make-up, showingrecommended fittings and connections. The check valvesin the incoming lines prevent waste of flash when a line isnot in use. The by-pass is used when flash steam cannotbe used. Relief valves prevent pressure from building upand interfering with the operation of the high pressure steamtraps. The reducing valve reduces the high pressure steamto the same pressure as the flash, so they can be combinedfor process work or heating.Armstrong Steam and Condensate Group, 816 Maple St., P.O. Box 408, Three Rivers, MI 49093 – USA Phone: (269) 273-1415 Fax: (269) 278-6555www.armstrong-intl.com
Page 1 and 2: How to Trap Steam Distribution Syst
Page 3 and 4: How to Trap Steam Distribution Syst
Page 5 and 6: How to Trap Steam Tracer LinesSteam
Page 7 and 8: How to Trap Superheated Steam Lines
Page 9: How to Trap Space Heating Equipment
Page 12 and 13: How To Trap Process Air HeatersProc
Page 14 and 15: How to Trap Shell & Tube Heat Excha
Page 16 and 17: How to Trap EvaporatorsEvaporators
Page 18 and 19: How to Trap EvaporatorsTable CG-22.
Page 20 and 21: How to Trap Jacketed KettlesFigure
Page 22 and 23: How to Trap Closed, Stationary Stea
Page 26 and 27: How to Trap Flash TanksInstallation

How to Trap Steam Distribution Systems - Armstrong International, Inc.

Create successful ePaper yourself

Delete template?

Save as template?