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  1. hrsgguru

    P91 Distortion

    I second the hardness testing. T91 is touchy about hardness in both ways - apply heat and force to straighten the tube you will see some work hardening. But if you get it too hot or over heat-treat it, you can also end up with it being too soft. A reasonable range for your finished product is...
  2. hrsgguru

    piping school

    All of the piping schools that I have come across are those offered by a company to bring their new hires or reassigned personnel up to speed in rapid fashion (or at least faster than on the job training). The class at Shell is probably a lot like the ones offered from time to time at Fluor or...
  3. hrsgguru

    Operating a balanced draft boiler on natural draft

    I assume that you've got a gas- or oil-fired boiler here since most solid fuel boilers are going to require at least one FD fan to move or support the solid fuel in the furnace. This seems like a very bad idea to me. For starters, I don't see how you can effectively accomplish a purge of the...
  4. hrsgguru

    Closed Cooling Tower System

    I believe another term for this type of cooling tower is: wet surface air cooler or WSAC If anyone's interested in such an animal, there's some good info at this manufacturer's website: http://www.niagarablower.com/wsac.htm (I am in no way affiliated with this supplier, by the way). I've...
  5. hrsgguru

    Deaerator Pressure Curve vs Boiler Load

    A CCPP deaerator operates, in theory, just like all deaerators (direct contact heating of feedwater with steam and venting of non-condesables). By "ancient deaerator" I assume that you are referring to a STANDALONE deaerator whose source of heating steam is from a pressure controlled source...
  6. hrsgguru

    Deaerator Pressure Curve vs Boiler Load

    In conventional power plants (regenerative Rankine cycle), the deaerator is part of the feedwater heater train and thus sees an decrease in its operating pressure as the plant load drops unless specifically pegged to a constant pressure. These DAs routinely operate at 150 psig and higher at...
  7. hrsgguru

    Steam quality and drum sizing

    I concur with davefitz here entirely. With the exception of low pressure boilers, steam-water separation is accomplished with static, mechanical separators. Typically there are two stages of separation. The first stage occurs at or near the normal water level and the second at the steam...
  8. hrsgguru

    oxidation catalysts- formaldehyde & HAP

    Davefitz: You'll probably find that most SCR catalyst vendors base their guarantees on a 20:1 NO to NO2 ratio (i.e., NO2 is 5% or less). This is common for most GT exhausts without oxidation catalysts. The addition of the oxidation catalyst (OC) will definitely affect that ratio, but the...
  9. hrsgguru

    Fresh air firing

    There are many examples of fresh air fired HRSGs that allow for continuous steam generation at or near normal combined cycle levels. However, I'm not aware of a system larger than a LM2500 in which this has been done in a non-interruptible approach. For a unit the size of a GE Frame 9E...
  10. hrsgguru

    Magnesium Hydroxide

    I have not heard of it being added to coal, but it is offered and used in heavy liquid fuels, as gaterine noted, to counter the effects of vanadium slagging in the furnace. Depending on the type of coal burner that your boiler uses, it may provide a similar type of effect.
  11. hrsgguru

    Deaerator water quality

    If you deaerator (DA) is operating correctly (under pressure with an open orifice/vent), you should see no deterioation of the condensate quality except for what is added by any make up water introduced to the DA. Since you're using demin water for makeup, the addition of hardness should be...
  12. hrsgguru

    BOILER BOOSTER PUMP

    Cast steel should be fine for this application. It sounds like more of a chemistry problem or hydraulic problem. How's the oxygen content in the system? Is this occuring in the suction or discharge or both sections of the pump?
  13. hrsgguru

    Steam

    Well, I think that your right to be a little confused here. For those conditions, the boiler should be rated for at least 4.53 MMBtu/hr heat input (that's a net figure). The gross heat input should be higher due to heat loss and other inefficiencies. So it should be rated at 135 HP or higher...
  14. hrsgguru

    water wash of HRSG - remove fuel oil sulphate deposits ?

    I would like to suggest that there may be a better alternative to water washing for this application. Several contractors are available that can do CO2 blasting - high pressure dry ice pellets. The ice pellets are very effective at removing the deposits and you are left with non-hazardous...
  15. hrsgguru

    Safety distances between boilers?

    If we're worst-case-scenario-ing the question, then I would say you'd have to assume a total loss for the one and significant damage to the other two, given the boiler size and proximity. For a downtime estimate, I'd call the boiler vendor or good local repair company and find out how long it...
  16. hrsgguru

    Questions on HRSG design

    Item D - if the HRSG is properly designed and/or specified with an adequate approach temperature for ALL operating cases, steaming in the economizer is not an issue. Commissioning also goes smoother with the feedwater control valves located upstream. And ZERO flexibility? That is far too...
  17. hrsgguru

    Questions on HRSG design

    davefitz: I feel that we're getting a little off-track from the original questions raised by ericwong which by now have been answered. The debate about horizontal versus vertical HRSGs could go on for days and days and still be inconclusive. Each design has its merits and each has its flaws...
  18. hrsgguru

    Questions on HRSG design

    1. The use of T91, and more importantly P91, for superheater and reheater tubes and headers/piping will help increase fatigue life in the hot end of the HRSG. Reducing the wall thickness reduces the thermal stresses imposed on the system every time the unit undergoes a temperature cycle...

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