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  1. TrevorP

    Correlation of dew point of dry air

    Thanks folks. I have calc'd using 25362's method and using Antoine vp for ice also get -46°C. Cheers Trevor
  2. TrevorP

    Correlation of dew point of dry air

    I have a plant with a quoted ideal loading of 50mg/Nm3 of moisture in air post a drying tower. Any idea what this is in terms of the air dew point?
  3. TrevorP

    Storage Tank Inerting Required?

    What did you use to estimate the vapour pressure above the water? I remember reading an article some time ago that showed that, according to Henry's law, even at very low concentrations in the water phase, they can still be above the LEL in the vapour phase. I'll see if I can find a reference.
  4. TrevorP

    Vacuum Protection on Pressure Vessel

    I concur with reena1957. If it's a new vessel, specify full vac. Then you're covered, you don't have to worry about air ingress, or specifying the right size vacuum relief valve etc. If it's an old vessel not rated for full vac., then you need to consider what vacuum rate is required and size...
  5. TrevorP

    What interview questions are actually useful?

    This is usually the sort of interview that's carried out by someone from HR. They are often a fairly good judge of character, and that's more of what you seem to be looking for. I guess that your employers value your opinion enough to ask for it, and that's a real positive you can take...
  6. TrevorP

    Are patents worth anything?

    Dyson - patented the bagless vacuum cleaner. Took it to the big boys (Hoover, Electrolux etc.) to try to licence it to them but generated no interest. Decided to develop and make it himself, and started what is now one of the largest (If not the largest) vacuum cleaner companies in the world...
  7. TrevorP

    Software Piracy

    Toolpath, My hat off to you for taking such an ethical stance. I wonder why, though, you haven't been to your manager, or his/her manager to ask them to explain why you are being asked to use pirated software, and explain that you wouldn't think it ethical if you copied design details for their...
  8. TrevorP

    Software Piracy

    To take the analogy a bit further - suppose you had left something in someone else's car, by mistake, and then shortly after it was foreclosed on? Wouldn't you be justified in obtaining access to the vehicle to reclaim the item? Isn't this the same as accessing the software to retrieve data...
  9. TrevorP

    Chemical & Physical Properties of Liquids

    http://www.knovel.com is a good resource for this sort of information, for a subscription fee. You can trial it for free to see if it has what you need or not. I've often found it to be very useful.
  10. TrevorP

    Flame Arrester Materials of Construction

    Sounds like you probably need a detonation arrestor rather than a flame arrestor. In essence, a flame arrestor should only be used on an end of line application (or within a few metres of it) - e.g. on a storage tank. In line applications require a detonation arrestor. Check it out with your...
  11. TrevorP

    looking for a job, while you have one-and your emploer doesn't know

    QCE - need to be careful to make sure that people don't see this as the only way to get a pay rise. Otherwise, they'll always be looking for another job.
  12. TrevorP

    How much is gasoline/petrol costing you at the pump?

    Perhaps one of the reasons why people in the US and Canada are complaining more about the price of fuel now, is because there is a relatively low tax on it compared to the UK. In a relatively short period of time the price of crude has quadrupled. In the same period of time, the price of fuel...
  13. TrevorP

    PSVs...what's missing?

    Another thing from a purely practical point of view. Size a pump wrong, and your error is often immediately obvious as soon as you start up - or it is close enough to either modify or to live with it as it is. Usually, there is not a high cost involved, and the only thing damaged is your...
  14. TrevorP

    Employer Dishonest with Client

    Can you prove that you told your employer (i.e. the Project Manager) about this issue? Is there anything to stop your employer saying that you insisted all along to them that the product was SOX compliant, but now they have found out that YOU lied to them? Could they have told this to the...
  15. TrevorP

    Relief Valve Required?

    It seems from what you've said that you already have pressure relief on both shell and tube sides, protected from the only available sources of overpressure. Without knowing the full details, it seems that you do therefore comply with the code. Is the unit rated for full vac? You could get full...
  16. TrevorP

    Determining Design Flow Rates in General

    Check out thread798-113006 for some extremely useful pointers on dealing with historical systems with sparse design information. If you have thoroughly considered all the scenarios and believe 75 SCFM is the maximum possible, then design to this. A 10% additional allowance seems reasonable. It...
  17. TrevorP

    Better to Change Jobs Every Few Years?

    I've changed my job every 3 years almost exactly. However, I've only changed company once in 12 years. Not all changes have been at my request. The point is to keep learning and not to stagnate. I find it's been typically 1 year to learn the job, 1 year to improve the job, and 1 year to do...
  18. TrevorP

    determining pump pressure based on max pressure

    Correct me if I'm wrong, but is this a PD pump, rather than centrifugal? If it's the type I'm thinking of, the pressure will build up and up until one of the following happens: 1 A relief valve lifts. 2 Something - e.g. a flange or pump internals give way. 3 The back slippage through the pump...
  19. TrevorP

    NPSH for Separator Water Stream

    I agree that this is the conservative approach, but overly so. With a 4m head, gregg8 will require a NPSHR of 4m less frictional loss, i.e. the pumps will be inadequate. The NPSHA is (111 - ~20)/(sg * g)+ 4 - frictional loss, i.e. the pumps will undoubtedly be adequate. The NPSHR does seem...
  20. TrevorP

    NPSH for Separator Water Stream

    You can estimate the vapour pressure of the stream assuming it is an ideal mixtures (Raoult's and Dalton's law). It won't be an ideal mixture, but it'll probably be close enough. Easier still, (and more accurate) would be to use a software package like Aspen, HYSIS etc., if you have this. I...

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