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NG-EGN-13-KSEC-112001_rev01_ BD - Ahmad.doc

Doc. Ref.: NG-EGN-13-KSEC-112001

Egina FPSO Topsides Detailed Design

RELIEF AND BLOWDOWN

PHILOSOPHY

CTR Reference: NA

Revision: 01 Rev Date : 26 Feb2014

Discipline : PRO Document Type : PHI

Phase: DESystem / Subsystem :

SSEquipment Type :

NAStatus: IFA Class: 1 Page 29 of 51

Figure 6.1 Inlet Pressure Drop Calculations

Calculate P

from this point

Flare

Calculate P

from this pointCalculate P

from this point

High

Rating

Low

Rating

Refer to [Ref. 3, Section 7.3] for more details on PSV inlet pipe sizing and design.

6.8 Relief Valve Discharge Piping

The discharge line nominal diameter shall not be less than the nominal diameter of the PSV outlet flange.

When two or more PSVs in the same service (i.e. valves are operating in a 2 x 50% configuration) are

manifolded together into a common discharge line, the cross-sectional area of the common discharge line

should not be less than the sum of the cross sectional flow areas of the outlet flanges of the PSVs

discharging into it.

The discharge piping for each individual PSV shall be sized using the PSV rated relief rate for all

contingencies. This sizing basis also applies to any manifold that collects the discharge from two or more

PSVs in the same service. In the case of modulating pilot-operated PSVs, use required relief rate and not

PSV rated relief rate (refer Table 12 in section 8.3.1 herein).

All PSV discharge piping and headers shall be rigorously checked and sized using Aspen Flare System

Analyzer and in accordance with [Ref. 3, Section 7.3].

Where modulating PSVs are installed, the relief flow will be regulated and the discharge piping may be sized

using the calculated relief rate rather than the rated relief rate.

The actual back pressure at the PSV outlet must be consistent with back pressure limitations, and withflange / piping rating.

Discharge piping for PSVs (including relief headers) discharging to a closed system shall be installed to

continuously slope downward towards the flare KO drum. Refer section 8.2 for slope details.

If water may be present, the risk of ice or hydrate formation shall be assessed.

A pipe roughness of 460 m (for carbon steel) and 46 m (for stainless steel) shall be used in pressure drop

calculations for all PSV outlet lines and headers; this assumes heavily corroded service.