Distance Learning Steam Basics Answers

Session 1 (Thermodynamics of Steam), Self Quiz Answers

1. The saturation temperature of 100 PSIG steam is 338 deg-F.
2. False.  Steam quality refers to the % of dry steam in a steam/water droplet mix.
3. From Table 1, the 5 Flash is 11.7%, so flash quantity is 5,000 #/HR X 0.117 = 585 #/HR

4. Per Equation 1, Q = 1,000 #/HR X (hg @ 5 PSIG – h_f @ 160 deg-F)

           where hg @ 5 PSIG = 1156 BTU/#
           and hf @ 160 deg-F = 1.0 X (160 – 32) = 128 BTU/#
           So Q = 1,000 X (1156 – 128) = 1,028,000 BTUH               

5. Per the formula for “Heat Exchanger, Fluid, GPM Known” on Page 15:

BTUH = 500 X GPM X SH X SG X ΔT   
           = 500 X 40 X 1.10 X 0.88 X (140 – 70) = 1,355,200 BTUH
            H_fg of 2 PSIG steam = 965
            #/HR of steam = 1,355,200/965 = 1,404 #/HR

Mind Teaser A: Per Table 2, the steam is leaving Phil’s PRV at 311 deg-F, considerably above the 230 deg-F rating of the O-Rings.  Farron, on the other hand is using plain old saturated steam at 5 PSIG/228 degrees.  This is close to the rating but obviously the manufacturer has built in a little safety so his valves last.
Mind Teaser B:  The geyser if from flash steam, not a leaky trap.
Mind Teaser C:  A light loads, the control valve knocks the pressure of the steam down.  Because condensing takes place at the saturation temperature corresponding to the saturation pressure in the heat exchanger, at light loads there is insignificant flash.  When the load ramps up, the valve opens so that the steam enters the heat exchanger at a much higher pressure, which, per Table 1 results in more flash steam.  The traps are fine.
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 Session II, Steam Trap Basics
1.  Inverted Bucket   2.  F & T   3. Small hole in top of bucket
4.   2:1 at 1/2 PSIG, F & T    5.  0.43 #/ft.  6. Thermostatic bellows
7.  Thermodynamic and Inverted Bucket  
8.  Accumulation of condensate in mains results in steam hammer, which is noisy and can damage equipment.
9. 0.5" or 0.75" #1031-125 IB Watson McDaniel inverted bucket trap

Session III, Piping Details
1. D    2. Condensate Stall   3. It is generally not necessary to install vents on heat transfer equipment.  Air is heavier than steam and will usually eventually be vented to the condensate system through the trap BUT during start up the heat transfer system sees only air (it is pushed ahead of the steam) and lots of it.  To avoid extended start up times, separate air vents have a role because they have a greater venting capacity than traps.
4. This is a good application for both.  The vacuum breaker ensures that the collapsing steam in the heat exchanger will not cause a vacuum; without the air vent, the frequent start ups could be irritatingly slow and probably quite costly in terms of lost production time.  
5. The modulating valve is likely reducing steam pressure to a vacuum.  Make sure there is a vacuum breaker to ensure that a vacuum is not holding back condensate.  The 4" drip leg only results in a static head of 0.14 PSI so the trap is undersized.  A larger trap might work but a longer drip leg might be required, even if it means chopping a hole in the floor or raising the unit.  
6. The system has air in it.  Vent the air.
7. Double traps, an overflow trap in an extended (longer) drip leg.
8. Using one control valve is should be fine.  Trap the three coils separately, however.
9. Condensate is hanging up and surrounding the bottom tubes.  Steam bubbles are forming in the condensate next to the tubes and are imploding, causing the "ball peen hammer effect."  Things to check for to ensure that condensate drains: Properly sized trap, proper drip leg, condensate stall (is there excessive condensate lift?),  presence of  a vacuum breaker.  Also check for excessive pressure in return main and heat exchanger pitch (is it pitched toward  toward condensate outlet?

 NOTE:  Any and every question is welcomed.