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  1. milltir

    What engineers do during FEED ?

    For oil/gas/petrochemical companies, the purpose of "Front End Engineering" is to do enough work to establish a cost estimate (to say a ± 10% certainty) and a detailed schedule. In parallel, their economists will try and determine the potential revenue. This is so they can determine whether to...
  2. milltir

    string test for turbocompressor (complete unit test)

    Like most things, the answer is "it depends". You need to consider what your perceived risks are and how far you are prepared to go to mitigate them. Examples to consider are: individual tests you are undertaking on the compressors (performance test in addition to mechanical running test?)...
  3. milltir

    When to Specify Torsional Analysis for Rotating Equipment

    API 610 for Centrifugal pumps and API 617 for Centrifugal Compressors both have criteria and requirements for torsional analysis.
  4. milltir

    Volume to Mass Conversion for Ideal Gas

    Contrary to one of the comments above, there is nothing wrong in engpes giving the molecular mass of methane as 16.043 g/mol, the mole is by definition the g mol. If using English (Imperial) units you state the molecular mass as 16.043 lb/lbmol - but the mole (g mol) and lbmol aren't the same...
  5. milltir

    stand by/duty pumps units

    99.94% not 99.74% if I had read my spreadsheet correctly (eyes going with age). (1 x p3) + (1 x 3p2q) + (0.5 x 3pq2)
  6. milltir

    stand by/duty pumps units

    I don't agree with the comment by BigInch above. If the individual availability of a pump is 98% then the availability of the system will always improve with standby pumps in parallel. In the instance described in this thread of 3 x 50%, the system availability will be 99.74% if an individual...
  7. milltir

    Centrifugal compressor suction piping

    Think about first running on nitrogen to both "clean up" the system andtest the system functionality.
  8. milltir

    Polytropic Head

    For T2 and volumetric flow you need to get your thermodynamics books out. However, in short to calculate the discharge temperature T2=T1*r^((n-1)/n) where r is the pressure ratio As you have the mass flow calculate the density at suction conditions from P1/(Z1*R*T1) where R is the Gas...
  9. milltir

    TurboCompressor Train Responsabilty

    My stock answer to questions like this is "it depends". Often the practice in Europe is to make the compressor vendor prime (but not always) whereas in the US the GT vendor is often prime (but again, not always). One party does need to take responsibility for the train and this can be done by...
  10. milltir

    centrifugal compressor efficiency

    As zdas04 said, you need to estimate the power on a stage by stage basis (I normally use polytropic equations, but as it is air, then adiabatic is OK). This gives you the "gas power". You need to add on an allowance for mechanical losses (bearings, seals). This will give you an estimate for...
  11. milltir

    Need help - Compressor preliminary sizing

    I'd encourage you to develop your own rather than trying to take somebody elses spreadsheets if only to develop your understanding of the theory (like doing a hand calculation). They can be quite useful for studies when you can quickly see the effect of say changing the suction temperature. I...
  12. milltir

    Fuel Gas Temperature to GTG

    The various gas turbine suppliers have differing fuel gas quality specifications, but the temperature requirement is generally around 28°C (50°F) above the hydrocarbon and water dewpoints at the supply point to the package (skid edge).
  13. milltir

    Distance between surge line and discharge NRV

    You want to minimise the inventory held between 3 points 1. Compressor discharge check valve 2. Anti-surge recycle valve (take-off for this, as pmover said, to be upstream of the discharge check valve) 3. Compressor discharge flange If this inventory isn't minimised the anti-surge control system...
  14. milltir

    Experience of Solar compressors

    Solar's compressors are for natural gas (you didn't stipulate the product). Solar aren't that renowned for their high pressure experience - they aren't in the "custom engineered" business and most of their experience is at lower pressures. I would get references for any conditions you are...
  15. milltir

    Determine Centifugal Compressor Torque

    Assuming this is a centrifugal machine, the theoretical torque demand is proportional to the square of the speed (rpm). However, theory doesn't apply from say 0 to 25% speed - there is a "stiction" effect to overcome - you need to get the rotor moving. The vendor torque-speed curve should look...
  16. milltir

    Dual/Tandem Seal Piping Plans

    The API 682 plan 52/53 arrangements for tandem and dual seals respectively show the buffer/barrier fluid inlet (BI)& outlet (BO) connections on the outboard seal with nothing connected to the flush (F) connection on the inboard seal. Will the buffer/barrier fluid always be able to remove the...
  17. milltir

    Polytropic efficiency of turbomachinery

    In general, positive displacement compressors are calculated on the adiabatic cycle (see API 618 Reciprocating Compressors), and rotordynamic compressors on the polytropic cycle (see API 617 Centrifugal and Axial Compressors). As with everything there are exceptions, single stage or air...
  18. milltir

    definition: Multistage compressor (Centrifugal)

    Vendors such as GHH Borsig, Dresser-Rand and Solar Turbines define a stage as an impeller and associated guide vanes & diffuser (it gets a little more complicated for parallel flow compressors). When gas is withdrawn, cooled and returned to the casing they will use the term "section", "process...

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