Vessels, processing facilities

Gas processing facilities generally work best at between 10 and 100 bar. At low pressure, vessels have to be large to operate effectively, whereas at higher pressures facilities can be smaller but vessel walls and piping systems must be thicker. Optimum recovery of heavy hydrocarbons is achieved between 20 bar and 40 bar. Long distance pipeline pressures may reach 150 bar and reinjection pressure can be as high as 700 bar. The gas process line will reflect gas quality and pressure as well as delivery specifications. 

Process Facilities 15 Area electrical classification 16 Accessibility for mechanical integrity (sampling, maintenance, repairs) 17 Protection of piping and vessels from vehicles and forklifts 18 Protection of small-bore lines, fittings from external impact, personnel 19 Routing of process piping, critical controls cable trays, critical utilities 20 Vent, drain, and relief valve discharge locations... 

Hydrocarbon processing facilities pose severe risks with respect to fire, explosions and vessel ruptures. Among the prime methods to prevent and limit the loss potential from such incidents are the provisions of hydrocarbon inventory isolation and removal system. These systems are commonly referred to in the petroleum industry as ESD (emergency shutdown) and depressuring or blowdown. Although most standards and practices acknowledge the need for depressuring capabilities the exact determination of their requirement is not wholly defined. NFPA fire codes and standards rarely mention the subject. 

Industry literature typically cites concern with open air explosions when 4,536 kgs (10,000 lbs.) or more of flammable gas is released, however, open air explosions at lower amounts of materials are not unheard of. When the release quantity is less than 4,536 kgs (10,000 lbs.), a flash fire is usually the result. The resulting fire or explosion damage can cripple a hydrocarbon processing facility. Extreme care must be taken to prevent the release of hydrocarbon from vessels resulting in vapor releases and resultant blast overpressure. Measures such as hydrotesting, weld inspections, pressure control valves, adequate pressure safety valves, etc., should all be prudently applied. 

Floating exploration and production facilities are sometimes provided on jackup rigs, semi-submersible vessels or ex-crude oil shipping tankers converted to production treatment vessels. These facilities are essentially the same as fixed offshore platform or installations except they are moored in place or provided with a temporary support structure instead of provided with fixed supports to the seabed. The major process fire and explosion risks are identical to the risks produced on offshore platforms. They have one addition major facility risk, that is the maintenance of buoyancy of the installation. Should fire or explosion effects cause a loss of buoyancy (or even stability) the entire facility is at risk of submergence. Adequate compartimization and integrity assurances must be implemented in these instances. 

Fires in processing facilities may include vessel and equipment fires (internal or external), ground level pool fires, multilevel and three-dimensional fires resulting from spills or releases at elevated levels, liquid or gas jet fires from leaks, gas fires from vaporizing liquefied gas releases, or combinations of these. 

A number of flammable liquids and gases used in processing facilities are stored in refrigerated vessels. Common among these are liquefied gases, such as liquefied natural gas (LNG) and anhydrous ammonia, and a number of reactive or self-polymerizing liquids, such as acrylic acid and organic peroxides. 

In Effects of Motion on Design of Process Facilities for Floating Systems" Rice provides a theoretical analysis coupled with motion-simulation work in an effort to understand fluid motion inside process equipment on floating vessels. This work has led to the establishment of process-equipment sizing criteria for all types of vessel motion transmitted from the marine vessel. Design of internal baffling and other internals to dampen and control the fluid motion is reviewed. 

Major equipment factor estimates. Major equipment factor estimates are made by applying multipliers to the costs of all major equipment required for the plant or process facility. Different factors are applicable to different types of equipment, such as pumps, heat exchangers, and pressure vessels. Equipment size also has an effect on the factors. 

Figure 1.12 shows that an inverse relationship generally exists between consequence and frequency. For example, in a typical process facility, a serious event such as the failure of a pressure vessel may occur only once every 10 years, whereas trips and falls may occur weekly. 

Towers, also referred to as columns, are one of the principal pieces of equipment of any processing facility. Towers are cylindrical steel vessels that are used for distilling raw materials in the produaion of such products as gasoline, diesel, and heating oil. The plant layout designer must understand the internal structure of a tower and how it operates to produce a satisfactory design. ... 

Two major hazards may occur from high pressure vessel failures. The vessel itself may rupture and the formation of vapor cloud as a result of the rupture is possible. If the vessel ruptures, it will produce flying projectiles and usually release large quantities of vapors, and in the case of most hydrocarbons are combustible.The projectiles could harm individuals or damage the process facility, possibly increasing the incident proportions. Secondly, the release of a combustible gas from a pressurized vessel may cause the formation of combustible vapor cloud, which if a suitable amount of congestion is present or some turbulence of the cloud occurs, an explosive blast may result once the cloud contacts an ignition source. 

Pyrophoric iron sulfide is formed by the action of corrosive sulfur compounds on iron and steel in process facilities, particularly in vessels, storage tanks, and pipeline scraper traps. If such equipment has contained asphalt. 

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