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FEED OFFICE

Standard Calculation for Input to Blowdown Calculations

Document No.: FEED-PX-CAL-003

01 14/01/2013 Issued for use RHB- UEP19P BP- UEP11P JN- UEP19P

Rev. Date Description Originator Checker Approver

CONTENTS:

1.0 EXECUTIVE SUMMARY...................................................................32.0 OWNERSHIP...................................................................................33.0 SECURITY......................................................................................34.0 USE OF STANDARD CALCULATION SPREADSHEET.........................35.0 THEORY AND METHODOLOGY........................................................46.0 REFERENCES.................................................................................47.0 APPENDIX A: STANDARD CALCULATION SPREADSHEET.................58.0 APPENDIX B: VALIDATION...............................................................6

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1.0 Executive summary

This standard spreadsheet is developed to provide inputs to depressurizing

calculation in case of fire/low temperature Blowdown. It calculate total volume, total

surface area, wetted surface area, liquid volume and mass work of a system to be

depressurized including pipes and equipments based on the relevant Design

Engineering Practices (DEP’s) and Perry’s Handbook Chemical Engineering.

2.0 Ownership

This Document is owned by Process Lead in Petroleum Development Oman FEED

Office (UEP1P).

3.0 Security

This Worksheet is password protected against unauthorized modification to the

Output cells. Input cells are only authorized for modification. Process Discipline Lead

and FEED Office Manager are only authorized to release the password for

modification if required.

4.0 Use of Standard Calculation Spreadsheet

This spreadsheet contains three worksheets:

1. Fire Blowdown Input

2. Low Temperature Blowdown Input.

3. Pipe Data

The first worksheet calculates wetted surface area and liquid volume based on

Normal Liquid Level of the system. The second worksheet calculates wetted surface

area and liquid volume based on Low Liquid Level of the system. The third

worksheet provides pipe ID and Thickness corresponding to pipe DN and schedule.

Input cells are highlighted in Yellow and red font. Output data is highlighted in blue

font. All calculation cells are protected.

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5.0 Theory and Methodology

Total volume, total surface area, liquid volume, Wetted surface area calculation and

mass work calculation are documented in Chemical Engineering Magazine and DEP

31.22.05.11. Heat Duty for wetted fire case calculation is based on API 521.

200% margin shall be considered on pipe length estimated from Plot Plan. No

margin shall be added if pipe length is estimated from PDMS or ISO Drawings.

Wetted length is considered within 300 m2 of fire circle.

20% is considered as a design margin on total pipe volume. No margin to be

considered on metal volume.

No margin taken on vessel volume/ wetted surface area calculation.

Metal Volume of vessels does not include head's volume.

Vessel Calculation depends on vessel orientation and type of vessel head. Types

considered in this calculation:

- Vertical vessel with Elliptical Head

- Vertical Vessel with Hemispherical Head.

- Horizontal Vessel with Elliptical Head

- Horizontal Vessel with Hemispherical Head

Other miscellaneous equipments (compressors, exchangers and air coolers) to be

calculated by respective calculation sheet.

6.0 References

- API521, Pressure-relieving and Depressuring Systems, Fifth Edition, January 2007- DEP.31.22.05.11

- DEP.80.45.10.11

- Chemical Engineering, Richard C. Doane, S&B Engineers and Constructors, Ltd, 2007

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7.0 Appendix A: Standard Calculation Spreadsheet

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8.0 Appendix B: Validation

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