Pilot flare

In the consideration of elevated flare pilots and igniters, proprietary flare tips are normally provided with the manufacturer s recommended igniter and pilot system. Usually, one to four pilots are used depending on the flare tip type and diameter. The forced air supply type of igniter system (described below) is normally preferred. Controls should be located at a distance from the base of the... 

Figure 6. Typical elevated flare pilot and igniter.

Flare pilot test stand. (Hong, J., Schwartz, R., Baukal, C., and Fleifil, M., Flare Test Facility Ready for the Challenge, presented at the John Zink International Flare Symposium, Tulsa, OK, June 11-12,2003.)... 

A new test stand (shown in Figure 28.17) was constructed specifically for testing flare pilots [29]. These are critical safety devices that must remain lit under severe weather conditions such as heavy wind and rain. The test stand is... 

Other systems such as the oxidation of H2S to SO2 and H2O are also used even though the SO2 produced is still considered a pollutant. The tradeoff occurs because the SO2 is much less toxic and undesirable than the H2S. The odor threshold for H2S is about three orders of magnitude less than that for SO2. for oxidation of HjS to SO2, the usual device is simply an open flare with a fuel gas pilot or auxiliary burner if the H2S is below the stoichiometric concentration. 

Flare systems are subject to potential flashback and internal explosion since flammable vapor/air mixtures may be formed in the stack or inlet piping by the entry of air, and the pilot constitutes a continuous ignition source. Flares are therefore always provided with flashback protection, which prevents a flame front from travelling back to the upstream piping and equipment. Design details are described later. 

Figure 1. Available pressure drop may in some cases dictate acceptance of a lower maximum velocity, but at least 75 m/s is recommended to insure good dispersion. Flare tips consisting of a simple open-ended pipe with a single pilot are subject to flame lift-off and noise problems at lower velocities, and should therefore be designed for a maximum velocity of 50 m/s.

Pilots and Igniters - Duplicate continuous gas pilots are required at each side of the flare, corresponding to the split burner grid layout. Selection of pilot and igniter systems follows the guidelines described below, and the controls should be located 15 m to 30 m from the windbreaker. 

Pilots and Igniters - Two gas-fired pilots with igniters are installed adjacent to the inlet distributor. The igniter assembly and pilot gas valves must be located remote from the flare for protection of personnel and equipment. This restricts igniter selection to the forced air supply type. Location of these components should be such that the calculated radiant heat density at maximum load does not exceed permissible levels for personnel exposure. Because of the potential hazard of release of unignited hydrocarbons at ground level, a flame scanner (suitably shielded and aircooled and cotmected to an alarm in the control house), is provided for each pilot. 

All flares must be provided with continuous pilots to ensure combustion of any releases discharged to them, and to prevent flame-out from occuring. Various designs of pilot burner are available, and proprietary tips for elevated flares are normally provided complete with pilots. 

Preferably, the HjS flare system should consist of a segregated header and separate line routed up the side of a conventional elevated flare stack, sharing the same structure, pilots and igniters. However, the HjS header may be tied into the regular flare seal drum if there are special mechanical design problems associated with the separate stack e.g., in the case of a flare which is to be dismantled for overhaul. Flare elevation must be sufficient to meet atmospheric pollution and ground level concentration requirements for the sulfur dioxide produced. 

The flare tip assembly shall be furnished complete with smoke suppression system, pilot and igniter assemblies, windshield, and flame retention assembly. 

The flare tip assembly shall be provided with at least two pilot assemblies to assure complete ignition of gases leaving the flare tip. 

Ignition controls shall include upstream (in flare header prior to knockout drum) dual flow sensing equipment which shall start the automatic flare purge, pilot ignition and the flare ignition cycle. N P Refinery will be responsible for the wiring between the flow sensors and the ignition control panel. 

Balanced bellows type valves are normally used where the relief valves are piped to a closed flare system and the back-pressure exceeds 10% of the set pressure, where conventional valves can t be used because back-pressure is too high. They are also used in flow lines, multiphase lines, or for ptu affinic or asphaltic crude, where pilot-operated valves can t be used due to possible plugging of the pilot line. An advantage of this type of relief valve is, for corrosive or dirty service, the bellows protects the spring from process fluid. A disadvantage is that the bellows can fatigue, which will allow process fluid to escape through the bonnet. For HjS service, the bonnet vent must be piped to a safe area. 

Flares are an attempt to deliberately burn the flammable safety relief and/or process vents from a plant. The height of the stack is important to the safety of the surroundings and personnel, and the diameter is important to provide sufficient flow velocity to allow the vapors/ gases to leave the top of the stack at sufficient velocities to pro ide good mixing and dilution after ignition at the flare tip by pilot flames. 

Flares ideally bum waste gas completely and smokelessly. Two types of flares are normally employed. The first is called the open flare, the second is called the enclosed flare. The major components of a flare consist of the burner, stack, water seal, controls, pilot burner, and ignition system. Flares required to process variable air volumes and concentrations are equipped with automatic pilot ignition systems, temperature sensors, and air and combustion controls. 

The main components of an elevated flare system are the flare burner with or without smoke suppression capability, pilot(s), pilot igniter(s), support structure, and piping. A number of optional features are available, such as pilot flame detectors air seals (buoyancy or... 

Smoke Signal Flare, used as navigation aids by pilots, is described on p SO of Ref 1... 

The shape is generally similar to the shape of a storage canister or dispenser from which the decoy flare is ejected by the aircraft upon command of the pilot. The decoy body generally has a circular or rectangular cross-section because of the cost considerations and ease of manufacture. The shaped flare is covered with a priming coat that facilitates ignition when the decoy is released from the aircraft. 

A pivoted, dual-flare boom can allow the tip and ignitor pilots to be serviced without need of special services or a complete process shutdown. 

Marine Flare Torch Pilot s Blue Light... 

As can be seen from the data in Table 3, little work has been done on recycling the majority of pyrotechnic basic mats with the exception of the Mg and Na nitrate in illuminating flares and dyes in smoke compns. Current investigations consist of attempts to recover P from signal flares (Ref 27). However, the work to-date can be considered as a pilot activity which can be further developed and applied to other pyrot items and compns... 

An SRV may release the process fluid directly to the atmosphere or release it via a pipe to a flare, scrubber, header or some other equipment. An SRV is always actuated by the upstream pressure and is usually characterized by what is described as a pop action upon opening in the case of compressible fluids. It is important to recognize that one should not expect a gentle release of gas proportional to valve lift, regardless of the design of the valve one possible exception is when a modulating pilot-operated SRV is used. 

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