Abstract
Hydrocarbons and Acid gases flares are common in Oil and gas processing plants. Main flame extinguishment is encountered as major concern in these flares due to the inability to re-ignite the main flame through pilots. This can result in serious HSE concern by release of toxic (H2S) and hazardous hydrocarbon into environment, causing harm to people and surrounding. This paper presents the approach followed in flare system design which will enhance reliability of flare system for safe plant operation.
Main issues in flares such as main flame extinguishment, failure of pilot, damage and burn of pilot, failure of thermocouples and blockage of pilot gas lines / fire ball lines were studied. All past inspection reports were reviewed to identify failure mechanism. Further aerial survey report were also reviewed. As flare pilots are exposed to severe operating temperature and service conditions, detail metallurgical study was performed to understand high temperature sulphidation corrosion. As existing flare were with old design, new technologies were explored and gap in current flare design were identified.
Material review concluded that existing Inconel material will prematurely fail in high temperature acidic environment. Hence new pilot assembly and flare tip of SS310S material were installed. To further enhance service life, Pilots were ceramic coated and thickness of pilot /FFG pipe were increased. Wind proof pilot design with weather hood and integral thermowell in single cast assembly were used to minimize welding. This approach avoided weld failures in the Pilot which have been observed earlier. Flare tip are provided with wind shields to minimize impact due to flame impingement which damages the Pilot Assembly. Instead of existing single ignition and monitoring system, Dual Ignition through High Energy ignition and FFG & dual monitoring System using ionization rod and thermocouple are provided to ensure availability in the event of a primary system failure.
Above new design improvements were successfully implemented in two of the existing flares. Continuous monitoring of the improvements confirmed reliable performance with no flare system failure in past 1.5 years. This will reduce cost by almost 50% due to decreased maintenance and increased life span. Further, it will optimize shutdowns and increase major maintenance cycles from 2 to 5 years.
Conventional approach of like to like replacement of flare system in case of failure do not address the issue and can affect people, plant and environment. However, implementation of the design improvements based on above approach will not only ensure reliable and safe plant operation but also reduce maintenance cost.
