Outline

  • Abstract
  • Keywords
  • Nomenclature
  • 1. Introduction
  • 2. the Details
  • 3. Procedure
  • 4. Example: Ammonia Synthesis Reactor
  • 5. Calculation of Offset F&ei (f&ei2)
  • 6. Modified Procedure for F&ei and Other Risk Analysis Information
  • 7. Advantages of Calculating Offset F&ei
  • 8. Conclusions
  • Acknowledgements
  • References

رئوس مطالب

  • چکیده
  • کلیدواژه ها
  • 1. مقدمه
  • 2. جزئیات
  • 3. روش کار
  • 4. مثال: راکتور سنتز آمونیاک
  • 5. محاسبه F&EI تصحیحی (F&EI2)
  • 6. روش اصلاح شده برای F&EI و دیگر اطلاعات آنالیز ریسک
  • 7. مزایای محاسبه F&EI تصحیحی
  • 8. نتیجه گیری

Abstract

The Dow Fire and Explosion Index (F&EI) is universally used in evaluating the hazard category of a process plant, area of exposure, expected losses in case of fire and explosion, etc. In the current procedure, the effects of the loss control measures (LCMs) on the F&EI value are not taken into account. This makes the plant look more hazardous, makes it more spread out, requires more elaborate emergency measures and alarms the public and the civil administration more than is necessary. It also affects the insurance premium.

We suggest taking the effects of the LCMs into account in the F&EI value. We call this the ‘Offset F&EI’ value. It favorably affects all the above items, and other related ones. To do this, we have developed the relevant equations and have proved the efficacy of the Offset F&EI by means of an example.

Keywords: - - - -

Conclusions

The calculation of the offset F&EI (F&EI2) gives a clearer picture of the fire and explosion hazards. There is no need to be extra conservative by having a greater F&EI than is actually the case with the LCMs installed. The calculation and use of the offset F&EI saves on insurance premiums, land cost, piping costs and all the losses associated with longer piping, if equipment is spread out much more than is necessary. It also gives a more realistic picture of the on-site and off-site emergency plans. The modified procedure (Fig. 4) looks more logical with the use of the RV2 directly to calculate the actual MPPD, MPDO and BI instead of interjecting the further calculation of Base MPPD1. The Offset F&EI brings out more clearly the inherently safer nature of the plant.

The MPPD, MPDO and BI remain the same in both the cases. This implies that the expected losses are confined to a significantly smaller area than the value given by the existing procedure. This also proves the validity of our procedure.

Users of the fifth edition of the Dow Guide would recall that for LCCF, one used to fill a form to get C1, C2, C3 and, using their product one had to read the actual LCCF from Fig. 9 in that edition. In the current edition (Dow, 1994), the values of C1, C2, C3 have been so modified that their product itself gives the value of the LCCF and the earlier Fig. 9 has been dispensed with.

We believe that the result will be similar to the suggestion in this paper to calculate the offset F&EI to get a better idea of the actual F&EI and to use the actual replacement value and thus delete two steps of Base MPPD1 and actual MPPD1 from the calculation of MPDO and BI.

Once the modified procedure, as suggested, is accepted, the subscripts 1 and 2 can of course be dropped and the nomenclature would revert back to the same as in the Dow Guide (Dow, 1994).

With the Base MPPD no longer necessary to calculate, the ‘actual MPPD’ can be renamed simply as ‘MPPD’ dropping the prefix ‘actual’.

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