ione,
Thanks for the info. However, the issue here is not how to determine the specific heat ratio. Rather, what is the required "specific heat ratio" to be used for the ISA/IEC sizing equations (ie. is it ideal gas specific heat ratio, isentropic exponent, or even real gas specific heat...
hsbcn,
Thanks for the link. Yes, I have a copy of this. Unfortunately it does not state how to calculate the "actual specific heat ratio". Note that the "actual" specific heat ratio mentioned in the link and the isentropic exponent are not the same value.
All,
ISA 75.01 and IEC 60534 use the "specific heat ratio" for control valve sizing. Does this "specific heat ratio" mean the ideal gas specific heat ratio (evaluated by k = Cp (Cp-R) ) or does it mean the actual isentropic exponent (same isentropic exponent used in orifice sizing and relief...
We have an air cooled propane condenser. The condenser is located at the high point in the discharge piping of the compressor. The inlet and outlet piping to/from the condenser are from the bottom. Short of CFD analysis, is anyone aware of calculations that can be done to confirm if...
My previous statement on the flare header DCS temperature measurements was to rule out any high temperatures coming from the flare header (as you suggested as possible cause earlier).
We have separate DCS temperature measurement at the discharge of the compressor.
1) Molten-As mentioned previously, the PRV's are at the discharge of a centrifugal compressor. Based on the acutal measured power absorbed by compressor it is impossbile for the temperature to exceed 160 C. The measured temperature agrees with Hysys simulations of the compressors based on the...
To address your previous query:
1) The DCS readings can be exported in Excel numerical format. It is easy to find the maximum values of the readings in Excel.
2) We had an identical PRV (in a duplicate unit) also lift for only a few minutes about 1 month later. When this PRV was inspected it...
FYI - the sample was sent to two independent labs. Both labs concluded the damage was due to high temperatures. The DCS historical data archives data in 5 second scans, so it is very unlikely that a high temperature reading would not be picked up.
We have 4 DCS temperature indicators/recorders at the immediate discharge of the compressor (before PRV takeoff) so we know the temperature history throughout the life of the PRV. PRV has been in service for less than 1 year and no temperataure above 110 C have been recorded.
An update: The damaged soft seats were sent to a lab for detailed analysis. The lab confirmed the melting was due to heat damage (temperature > 200 C). However, there are 4 independent temperature indicators on this stream and none have indicated temperatures above 110 C. The PRVs are on the...
We had a pilot PRV stick full open for about 12 hours. When the PRV was taken offline fore repairs it was noticed that the PRV soft seat had partially melted along the outside edge. The melting temperature of the soft seat is > 160 deg C, however, the measured gas temperature during the...
Asme B31.3 allow use of carbon steel and low temperatures based on stress ratio. However, my reading of Asme B31.3 is that for low temperature carbon steel grade material (LTCS) that is already impacted tested at -46 C, it CAN NOT be used at lower than -48 C if the stress ratio is above 0.3...
