Flare report/flare and depressurization report

The report should be named "Flare report". If the depressurization design is included, name the report "Flare and Depressurization Report"

The flare report shall describe the design of the flare and vent system, and as a minimum include:

• Design basis for the system, e.g. system capacity and selection;
• Procedure for replacement of flare tip;
• Description of the flare and vent system segregation and disposal, e.g. wet vs. dry streams, high vs. low temperature, high vs. low pressure, emergency vs. maintenance flare/vent, flaring vs. cold venting and common vent vs. local vent;
  • For cold vents, selected/recommended methods to extinguish the flame (if the vent is ignited) shall be described;
• Descriptions of flaring scenarios including flare rates, e.g. operational flaring, relief cases, emergency depressurization and simultaneous flaring (operational flaring + relief/depressurization). The simultaneous flaring cases shall be clearly defined. The selected base load (e.g. long-term operational flaring) shall be explained;
  • The flare report shall list the largest flare sources, those that designs the flare headers/drums and the location of the flare tip;
• Operation of the system during long duration cooldown, e.g. cold ambient temperature, flowline depressurization;
• Description of the piping and equipment design, e.g.:
  • Hydraulic design (sizing of pipes);
  • Knock out drum;
  • Flare tip design (e.g. hydraulic performance, soot emission, noise, purge requirements, expected lifetime, maintenance requirements);
  • Flare gas recovery;
  • Flare ignition; - If flare gases are combusted for safety reasons (i.e. not only for environmental reasons), the reliability of the ignition system shall be documented to prove that the system has the required reliability and necessary requirements (assumptions) listed;
• Documentation of system design calculations, where the input data, results and the calculations shall be included in the report and in simulation files, e.g.:
  • Calculation of flare tip radiation to determine (a) the resulting heat exposure towards humans and (b) the resulting temperature on equipment, pipes and structures;
  • Calculation of gas dispersion;
  • The potential gas concentration resulting from an extinguished flare/vent shall be documented, and plant areas where operational activities are limited as a result (e.g. hot work) shall be defined;
  • Hydraulic calculation (pipe sizing);
  • Sizing of liquid knockout drums;
  • The main results are documented in the main report, the details in appendices.

The various simulation files defined above shall be a part of the delivery as executable simulation files (simulation programs to be agreed) reflecting the As-built design.

The flare report, including the simulation files, shall be updated whenever relevant modifications to the plant are performed, i.e. parallel documents shall not be established.

Documentation of the depressurization design

The depressurization report shall specify the information required to repeat/re-establish all dimensioning cases both with respect to fire depressurization and cold depressurization. Typical required information is input streams, system geometry (see list above), initial conditions (e.g. pressure, temperature, liquid volumes, ambient conditions), orifice specification, any delayed opening of BDVs, material properties used, fire loads and durations, the plant specific intolerable ruptures, assumptions made and other relevant information.

The report shall tabulate the following:

• Rupture conditions of pipes/equipment that will rupture during the dimensioning fire;
  • Time to rupture;
  • Pressure at rupture;
  • Instantaneous release of hydrocarbon fluid at rupture (kg/s);
  • Other relevant information;
• The initial flare rate from fire depressurisation and cold depressurization;
• System pressure 15 minutes after gas detection (no heat input, relevant delay of blowdown included);
• The minimum vapour and liquid temperature resulting from the cold depressurization;
• The minimum vapour wall and liquid wall temperatures resulting from the cold depressurization. The report should contain the following:
• The depressurisation rates for each depressurisation segment as function of time:
  • cold depressurisation, fire depressurisation and depressurisation from normal conditions;
• The total depressurisation rate (mass rate) for all segments that are feeding the disposal system simultaneously:
  • fire depressurisation and depressurisation from normal conditions.

The following shall be available for Company during project execution and shall be handed over to Company at project close out.

• A spreadsheet that describes the geometry of all depressurisation segments. See the below list for minimum content.
• A spreadsheet tabulating the pressure profiles during fire exposure/fire depressurisation for all depressurization segments and for all segments containing hydrocarbons but without depressurization.
• A spreadsheet tabulating the pressure profile for the flare header during depressurisation

The simulation file(s) used for calculation of temperature profile and stress/rupture (i.e. time to rupture calculations).

A spreadsheet that describes the geometry of all depressurization segments shall be made. The spreadsheet shall always reflect the current process design, include date of last revision and corresponding P&ID revision(s) used, and shall as a minimum contain the following information for each pipe and equipment (it is recommended to use one sheet for each depressurization segment):

• Line number or equipment tag number;
• Length (note 3);
• Inner and outer diameter;
• Liquid volume (see note 1);
• Gas volume (see note 1);
• Total volume of the depressurisation segment and volume of each sub-segment (note 2);
• Outside are:
  • total outside area of the depressurisation segment and outside area of each sub-segment;
• Dry area:
  • total dry area of the depressurisation segment and dry area of each sub-segment. See note 1;
• Wet area:
  • total wet area of the depressurisation segment and wet area of each sub-segment. See note 1;
• Insulated area and type of insulation;
• Wall thickness;
• Material;
• Weight:
  • total weight of depressurisation segment and weight of each sub segment.

Note 1: Liquid in sloped pipes will be drain to its nearest low point. Pipes that will be drained are treated as “dry wall” pipes.

Note 2: A sub-segment is e.g. a pipe or a vessel in a depressurization segment

Note 3: Line sizes that do not contribute to the system volume/area/weight, typically sizes less than 1’’, need not to be listed with length and can be listed separately on the same sheet.

The spreadsheet should in addition contain the following information:

• Name of depressurisation segment (e.g. 1ststage separator);
• Tag-number of the BDV (and the orifice);
• Which valves that determines the border of the depressurisation segment (PSD valves, ESD valves, PSVs, PV etc);
• Information about what, when and by whom the spreadsheet was updated, i.e. a change log.