Whenever industrial plant equipment items are overpressurized, the pressure relief valves provided as essential safety devices on the equipment automatically release gases and sometimes liquids. A flare system generally consists of an elevated stack, means to maintain burning conditions at the top of stack, and means to prevent flashback within the system. Handling emergency releases from safety valves, blow-down, and depressuring systemsĭesigns will vary considerably, depending on the type of connected equipment and the complexity of the overall system. Depending on local environmental constraints, these systems can be used for: 1.Įxtensive venting during start up or shutdown 2. This is not limited to the SRVs directly related to the change but all valves connected to the flaring or discharge system The percentage backpressure in relation to the set pressure of the SRV will not only change the flow orifice but also determine the selection of the relief device (with or without bellows, pilot operated-modulating or snap action, etc.-see later in the backpressure chapter 9).įlare systems provide for the safe disposal of gaseous wastes. Changing and usually increasing the pressure in the flaring (or any other discharge system) system will have a direct (important) influence on the sizing of the SRVs and will usually result in the installed valves needing a larger flow orifice. The K b (backpressure correction factor) is in turn an important determining factor in the sizing and selection of the devices protecting the vessels. 3.įlaring systems are originally designed to a certain pressure which will be a determining factor for the backpressure on SRVs. ![]() 2.įor relief devices discharging to a flare header, the hydraulic analysis for the pressures developed in the header for any case where the relief device is expected to participate will need to be re-evaluated as the hydraulic analysis is typically based on the required relief rate. The cascading effects may include the following: 1.įor relief devices discharging to the atmosphere, the analysis performed to determine the acceptability of that release to the atmosphere will need to be reviewed as there may be additional risks associated with increased relief rates (reaction forces, built-up backpressure, etc.). This in its turn can have major effects on the calculation and selection of all SRV’s connected to the flaring system because of an increase in backpressures (see chapter 9) acting on the SRV. ![]() A more important fact to be considered is that when changes are made this will affect the behavior of the flaring system, not in the least the pressures therein. The immediate effect of this increased required relief rate may be the requirement for additional relieving capacity of the overpressure protection (note this does not necessarily mean a larger relief device is needed because the existing relief device may be adequately sized already). Implementation of HIPPS is a solution that can be considered in all of the above-mentioned cases in order to reduce flare capacity.įlare system – Consider a modification to increase required relief rates for one or multiple relief device(s) piped into a common flaring system or adding new devices piped into an existing flaring system. In some cases, a refinery or petrochemical plant may require expansion and an increase in the capability of the pressure relief valves and connected flare lines. Therefore the purpose of this chapter is to focus on using a high integrity pressure protection system (HIPPS) to reduce flare capacity and thus flare emission to the environment. Flaring is not applicable to the subsea oil and gas industry. Thus the discussion in this chapter covers refineries, petrochemical plants and onshore and topside oil field developments. Approximately one-fourth of the flare gas and greenhouse emission comes from offshore topside platforms. In some cases, the gas may contain hydrogen sulfide (H 2S) which is a very toxic compound. ![]() The main greenhouse gases that are released to the environment through flaring are methane (CH 4) and carbon dioxide (CO 2). The flaring of natural gas worldwide in the oil and gas industry produces 400 million tonnes of greenhouse gas emissions. Some statistics show that more than 140 billion cubic meters of natural gas are flared annually. 7.2, rather than releasing them into the atmosphere without burning them, is a more environmentally friendly solution, a great amount of greenhouse gas is released into the environment through flaring. Although burning hydrocarbons in a flare, as illustrated in Fig. Flare systems are elevated to keep the open flame away from ground level and reduce the effects of heat, smoke and noise.
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