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Recent content by petrotrinsmerv

  1. petrotrinsmerv

    Thermocouple performance on Visbreaker Furnace outlet

    I hear you. However, we did place the thermowell in the middle of the coil outlet, and it did work, for a while. As a matter of fact, the thermowell tip near the wall also worked for a period of time. The deterioration of the accuracy is where the question arises. The only thing that happens to...
  2. petrotrinsmerv

    Thermocouple performance on Visbreaker Furnace outlet

    We have a Visbreaker furnace with four coils. On each outlet the temperature is monitored (COT) and also on the main transfer line. A year or two after startup, we noticed spurious COT readings, i.e. 30 to 60 degF lower than the transfer line. The instrument department checked using a test...
  3. petrotrinsmerv

    Rotating pipe/drum skimmers for API separators

    I understand that the removal of the oil is the main objective. However, the ammount of water removed along with the oil has implications for downstream processing, especially for equipment/vessel sizing. That's why the manufacturers make the claims they do. Also, there are alternative...
  4. petrotrinsmerv

    Rotating pipe/drum skimmers for API separators

    At our refinery we have an API separator that skims separated oil using slotted pipes. In looking into rotating pipe/drum skimmers, I have seen certain claims for the oil recovered being <10 v/v % or even <5 v/v %water. Oil extracted using the slotted pipes generally has >50 v/v % water, unless...
  5. petrotrinsmerv

    Corrosion Control for Vacuum Overheads

    Thanks for the reply orenda1168. Ammonia is something we use extensively in the refinery and is something we can set up quickly without chemical vendor input. We still have to make a decision on whether we want to go long term with metallurgy changes (we have changed some sections already)over...
  6. petrotrinsmerv

    Corrosion Control for Vacuum Overheads

    We upgraded a small vacuum column (26,000 BPSD) a few years ago and changed the overhead from direct contact ejector condensers to shell and tube ejector condeners. We are experiencing severe corrosion problems due to low sour water pH problems (column uses stripping steam). Can we use ahhydrous...
  7. petrotrinsmerv

    Choose a process simulation model.

    Once difference between PRO II and HYSYS, the output data provided by HYSYS is more user friendly. Actually, HYSYS is more user friendly overall. I have dealt with 2 consultants who used PROII. They seem to have more confidence in it, however, reading the output to analyse it is murder. All the...
  8. petrotrinsmerv

    GRAY-BOX VERSUS BLACK BOX

    Currently we are preparing to implement a new MPC controller on one of our process plants. Generally, the approach used is where the relationships between manipulated variables (MVs, also called 'handles), controlled variables (CVs, or targets) and disturbance variables (DVs) are defined based...
  9. petrotrinsmerv

    Sour Water Stripper Internals

    Thanks to both of you (robslav & 25362) for the information. I suspected there would be a problem. The stripper is Carbon Steel with a cement-type lining. We will be processing FCCU water but we use a pumparound. To my knowledge, this may well be the first use of this material for trays in our...
  10. petrotrinsmerv

    Sour Water Stripper Internals

    We have plans to revamp a Sour Water Stripper using 316L stainless steel internals. However, we anticipate that at times there may be high Chloride content in the sour water due to leakage on seawater condensers, of which we have a few. This may be more for a metallurgist, but if anyone has...
  11. petrotrinsmerv

    Vacuum Column Overhead Design

    Thanks for the reply. Actually, the designers assumed 95% of the steam condensed with a vapour outlet temp of 99 degF from the condenser. This was actually a 'wet' column so the steam load was quite high. I don't know but its possible that the load on the 2nd stage ejectors may have been above...
  12. petrotrinsmerv

    Vacuum Column Overhead Design

    We have a vacuum column designed with a three stage overhead (ejector/condenser) system. From inception the pressure obtained in the column was above design (40 mmHgabs compared to design 20 mmHgabs). This was so whether the first stage ejectors were on or not. We had three first stage ejectors...
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