General Assumptions

Id Activity Value Uom Description Remarks Source
1 Process Isolation 0.25 h/conn. Time needed to close a SBB and to check proper isolation expert judgment
2 Process Isolation 0.50 h/conn. Time needed to close a DBB and to check proper isolation expert judgment
3 Depressurization 0.50 h Time needed to reach atmospheric pressure by opening BDV and discharging to flare expert judgment
4 Cool down ○ ○ See dedicated table expert judgment
5 Electrical Isolation 0.25 h Time needed to locate and disconnect the circuit breaker and to verify isolation in field according to HSE procedures expert judgment
6 Draining 0.50 h Time needed to open connections to drain system (or to connect temporary lines) expert judgment
7 Draining 2.50 m/s Liquid velocity in the draining line expert judgment
8 Purging 0.50 h Time needed to connect the nitrogen generator expert judgment
9 Purging 2.00 bar Pressurization pressure (applicable to purging by pressurization/depr. cycles) expert judgment
10 Purging 1.00 bar Discharge pressure (applicable to purging by pressurization/depr. cycles) expert judgment
11 Purging 1,400.00 Sm3/h Nitrogen generator flow rate TO BE DEFINED BASED ON PROJECT PROJECT SOURCE
12 Purging 3.00 n/a Sweeping factor expert judgment
13 Blinding 0.50 h/conn. Time needed to apply/remove positive isolation devices (i.e. spectacles, blind flanges, spools) expert judgment
14 Ventilation 0.50 h Time needed to open a manway expert judgment
15 Ventilation 1.00 min/m3 Time needed for ventilation expert judgment
16 Ventilation 24.00 h Maximum ventilation time expert judgment
17 Washing ○ ○ See dedicated table ENI Std. 20560_430_rev02
18 Item Removal ○ ○ See dedicated table expert judgment
19 Reinstalling 0.50 h/conn. Time needed to remove positive isolation devices or to reinstall spools expert judgment
20 Reinstalling 0.25 h/conn. Time needed to open isolation valves expert judgment
21 Reinstalling ○ ○ Time needed to restore other mechanical connections: see dedicated table expert judgment
22 Leak test 0.50 h Time needed to connect the high pressure nitrogen generator expert judgment
23 Leak test 1.10 ○ Leak test pressure to operating pressure ratio expert judgment
24 Leak test 1,400.00 Sm3/h High pressure nitrogen flow rate TO BE DEFINED BASED ON PROJECT PROJECT SOURCE
25 Leak test 0.25 h/conn. Time needed to check each flange for leaks after the test pressure is achieved expert judgment
26 Air Removal 0.50 h Time needed to connect the nitrogen generator expert judgment
27 Air Removal 0.21 ○ Initial oxygen concentration (in case leak test has not been performed) expert judgment
28 Air Removal 0.03 ○ Target oxygen concentration expert judgment
29 Air Removal 2.00 ○ Pressurization pressure (applicable to purging by pressurization/depr. cycles) Assumed equal to Purging expert judgment
30 Air Removal 1.00 ○ Discharge pressure (applicable to purging by pressurization/depr. cycles) Assumed equal to Purging expert judgment
31 Air Removal 1,400.00 ○ Nitrogen generator flow rate Assumed equal to Purging expert judgment 342101BPST02508 34210ABPRV02054
32 Commissioning & Start up 1.00 h Temperature restoring time expert judgment
33 Commissioning & Start up 0.50 h Pressure restoring time Assumed equal to Depressurization time expert judgment
34 Commissioning & Start up ○ ○ Level restoring time Assumed equal to Draining time expert judgment
35 ○ 2.00 ○ Maximum numbers of crews working in parallel for isolation/blinding expert judgment
36 ○ 0.80 ○ Efficiency of maintenance crew Not applied to essentially labor-free activities (i.e. Cool down and Ventilation) expert judgment
37 Item conveyance to workshop 1.00 h Loading / Unloading expert judgment
38 Item conveyance to workshop 1.00 h Travel to WS expert judgment