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2013-10-10 00:22:55
formula DC3 exam

formulas for the DC3rd
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  1. The amount of heat required to Evaporate 34.5 of steam per hr. Boiler hp calculation 33.475 btus and 10ft squ of heating surface. Q: A Boiler has an output rating of 750 hp. what is its output in pounds of steam per hr?
  2. The Boiler pressure gauge reads 150psi. The pressure gauge is located 25ft below the top connection of the boiler. what is the actual pressure in the boiler?
    formula: 150-(25/2.31)=
    139.177489 round off to 139.18psi
  3. Feet of Head: A 10" pipe filled with water 250 feet high has a pressure gauge located at the bottom of the pipe. what is the indicate pressure on the gauge?
    • 250/2.31=108.225108
    • 108.23psi
  4. pump horsepower calculation: What is the required pump horsepower for a pump moving 150gpm to a height of 75feet at 93% efficiency?
  5. how much horsepower is needed for a pump that has 900feet of head from ground level and pumps 1250 gpm with an efficiency of 80%?
  6. Total Force: TF=psi x d x d d.7854=
    Q: what is the total force acting on a 3" pressure relief valve with a poping pressure of 500psi?
  7. GPM: GPM CAP.= slip%/100-1 x L x A x N /231
    L=Length of stroke
    A= Area of water cylinder
    N= Number of strokes per minute
    Simplex=rpm x 1
    Simplex=rpm x 2

    Q. A Duplex reciprocating pump runs @ 150 rpm. the pump is a 8 x 4 x10 operating with 8% slip. what is the capacity of the pump?
    .92 x 4 x 4 x.7854 x 10 x 2 x150/231=150.14
  8. Q: a 6 x 4 x x 8 duplex reciprocation pump makes 120  rotations per min with a slip 7%. what is its capacity?
    .93 x 4 x 4 x .7854 x 120 x 2 x 8/231=97.14
  9. GPM= V x D2/.4085

    V= Velocity

    D=Diameter of the pipe
    Q: what is the flow rate through 2" pipe with a velocity of 10' per second?
    10 x 2 x 2 /.4085=97.92gpm
  10. the flow rate in gallons per min through a 4" pipe with a velocity of 18 ft per second?
    18 x 4 x 4/.4085=705.02gpm
  11. pipe sizing: Maximum Allowable Flow Velocity:

    Low psi steam (up to 15 psi)=5,000fpm
    high psi steam=10,000
    superheated steam= 14,000fpm
    pipe size /density=___/60=___min/.7854/5k,10,14k=__sq.rootx12

    Q: A 15 psi steam boiler produces 8000 pounds of steam per hour. the minimum pipe size for the pipe leaving the boiler is ____ inches  (Density is o.037lb/ft3)
    8000/.037/60/.7854/5000/sq root x12=11.50inch
  12. Q: 150 psi steam boiler produces 18,000 lbs of steam per hr. the minimum pipe size for the pipe leaving the boiler is ____ inches (density .0727)
    18,000/.0727/60/.7854/10,000/squ root x 12=
    8698196.599 round to the next size pipe up 10" pipe
  13. steam psi x steam cyl area/ water cyl area

    Q: what is the maximum pressure that 12 x 6 x 15 duplex reciprocating pump can develop when operating with 200 psi steam?
    200 x 12x 12 x.7854/6/6.7854= 800psi

    • 12 steam cyl
    • 6 water cyl
  14. pipe expansion, in (T1-T2) x L x 12 .0000065

    T1= steam temp
    T2-room temp
    L= Horizontal length of pipe in"
    Q: the boiler steam is 350' long . during start-up the pipe is heated from 60 degrees f to 350 . the pipe will expand ___ due to the change in temperature.
    (350F-60F) x L x 12.0000065=7.92
  15. the boiler steam is 200' long. During start- up the pipe is heated from 75 to 400 degrees F. the pipe will expand___ due to the change in temp
    (400-75) x200 x 12x.0000065=5.07
  16. Exspansion Tank size (Temp x .00041) - .0466 x gallons
    14.7/fo -14.7/op

    Q: what size exspansion tank is needed for a hot water boiler system with 1000 gallons capacity, a 160 degree operating average temp a 75lb fill psi(makeup) and a 125 maximum operating psi?
    • 160 x .00041= .0656 - .0466 = .019 x 1000= 19
    • 14.7/75=.196 -14.7/125=.1176

    • .196-1176=.0784
    • 19/.0784=242.35
  17. Indirect boiler efficiency monitoring:
    Formula: Losses/input

    Losses= heat lost as flue gas and other losses

    Q: a 500 horsepower boiler is operating at 100 psi. the boiler burns 21,300 ft3 per hr of natural gas containging 975 btus per ft3. the chimeney recieves 12300pph of flue gas containging 405 btus per lb. what is the boiler efficiency through the indirect method?
    2,300 x 975= 20,767,500    12300 x 405=4,981,500

    • 2076500-4981500=157886000
    • 15786000/2076500=.760130011= 76.01%
  18. Safety valve capacity:
    RVC=1/3 x OC xVSPA
    RVC=1/2 xOCxBPA
    RVC=relief valve capacity required, ib steam/hr
    OC= orifice capacity, ib steam/(hr/in.sq)
    VSPA= valve-size pipe areas,in.sq
    BPA= bypass-size pipe area, insq
    the larger of the relief-valve capacites should be used for selecting the relief valve capacity.
     Note  Memorize chart on page 388 boiler operatro guide.
  19. Q: A reducing valve has no data on capacity on its nameplate. it is 3" in size with 125psi on the inlet side and 30 psi steam on the outlet side, which is the pressure rating of the low-pressure side connected equopment . Determine safety valve setting and capacity for the low side of the steam line if the reduceing station has a 1" bypass line.
    • RVC=1/3x7200x7.39=17736
    • RVC=12 x 7200x .86=3096
    • therefore safety valve should have a set pis of 30psi and a relieving capacity of 17736lb steam/hr
  20. heat loss:
    HL: heat lost by flue gas
    w=weight of gas going up the stack. usually ibs/hr
    Cp=mean specific heat of flue gas(.25)
    T2= Stack Temperature
    T1=air Inlet Temp
    Q: 9520 lb/hr of flue gas went up the stack. assume the stack temp is 650F and the air inlet temp is 80F. the heat lost up the stack is?
    • HL=9520 x .25 x(650-80)= 1356,600btus/hr
    • Q: what air temp must be provided to a burner for the following conditions? Stack temp 625F coal burned at 12,000ib/hr with a heating of 15,000 btus,ib flue gas formed 13.8ib,hr burned: boiler efficiency,80%
  21. heating surface
    4.14 x D x L x Qty of pipes
    Q: what is the heating surgace, in squ ft , for 145 boiler tubes, 2.5 diameter, and 12 feet long?
    2.5/12=.208333333 squ. ft x 12=2.5 x3.14= 7.85 x145=1138.25sq ft