Process vessels, processing facilities

General Considerations 1 Location of people relative to the unit 2 Location of critical systems 3 Dominant wind direction 4 Climate and weather extremes earthquake, flooding, windstorms 5 Site topography 6 External hazards or threats (fire/explosion/toxic release from nearby process or facility aircraft subsidence sabotage) 7 Traffic flow patterns and clearances from process vessels and lines 8 Security and reliability of all critical feeds and utilities 9 Command center and alternate command center locations 10 Evacuation routes, emergency exits, safe rally spots... 

The activation points should be located a minimum of 8 meters (25 ft.) away from a high process hazard location but not more than 5 minutes away from any location within the facility. 5 minutes is taken as the maximum allowable time since historical evidence indicates process vessel rupture may occur after this time period from flame impingement. If risk analysis calculations demonstrate longer vessel rupture periods are expected, longer time periods may be acceptable. 

In some instances it may be beneficial to maintain process inventories of certain process vessels until the incident is actually threatening the container. The inventory of the vessel may be crucial to the restart of a facility or the contents may be highly valuable. Loss of the inventory may be criticized if frequent false trips of the ESD blowdown system occur. In these cases an automatic fusible plug blowdown valve could be installed which would only activate from the heat of a real fire incident. In this way, a false disposal of the inventory can be avoided. 

NFPA requirements state that if equipment or process vessels, columns of tanks are suitably constructed of substantial steel construction adequately grounded, and do not give off flammable vapors, no other mechanism of lighting protection is required. This is also true of flares, vent stacks and metal chimneys by nature of their construction and grounding facilities. 

Process vessels and equipment should be provided with identification in the field that is legible from approximately 30 meters (100 ft.) away. It should be viewable from the normal access points to the facility or equipment and is of colors contrasting with the surrounding background. The identifications normally consist of the equipment identification number and the common name of the equipment, e g., "V-200, Propane Surge Drum". This is beneficial during routine and emergency periods where the quick identification of process equipment is critical and necessary from a distance. 

At 8 14 p.m. on February 19,1999, a process vessel containing several hundred pounds of hydroxylamine exploded at the Concept Sciences, Inc. (CSI), production facility near Allentown, Pennsylvania, USA. Employees were distilling an aqueous solution of hydroxylamine and potassium sulfate, the first commercial batch to be processed at CSI s new facility. After the distillation process was shut down, the hydroxylamine in the process tank and associated piping explosively decomposed, most likely due to high concentration and temperature. 

Sound practice dictates that storage tanks and process vessels containing hazardous chemicals be properly designed and used only for their intended purpose. They should also have, as a minimum, overflow alarms. Once these conditions are met, it remains to ensure the structural soundness of the containers, to enforce proper hazardous materials handling procedures, and to construct and maintain secondary containment and collection facilities (Shields 1980). 

In many areas of the unit, separation and processing vessels were operated at 3S psig (343.3 kPa). Hydrocarbons discharged from these vessels were flashed to stock tanks, and all vapors were vented to the atmosphere. Following consolidation of these conventional tank batteries, rich vapors were recovered by vapor-recovery equipment at the central treating facility. Total recovery over the life of the unit is projected to be 133,000 bbl (21 144 m3) of liquids and 262 MMcf (7.4 x I06m3) of gas. 

Oil and gas separators mechanically separate liquid and gas components that exist at a specific temperature and pressure, for eventual processing into salable items. A separation vessel normally is the initial processing vessel in any facility, and improper design of this component can bottleneck and reduce capacity of the entire facility. 

Where duplicate or similar process vessels occur at the facility the review team can refer to the earlier episodes of the review. If they and confirm that the analysis would be very similar, it could be essentially copied for the identical vessel. 

Insert the appropriate code (see below) that indicates the maximum quantity of the chemical (e.g., in storage tanks, process vessels, on-site shipping containers) at yourfacility at any time during the calendar year. If the chemical was present at several locations within your facility, use the maximum total amount present at the entire facility at any one time. 

Shipping casks, storage facilities, and process vessels involved in handling fissile materials contain neutronabsorbing materials—either for their neutron-absorbing properties or for structural reasons. These types of systems can be fiilly utilized, safely, only if the neutron absorbers are pnmcrly accounted for in the criticality analyses. The results from measurements on two such materials, copper and cqpper containing 1 wt% cadmium, were. .reported on previously. Since that time, the reactivity worths of several other materials, commonly considered for use as fixed neutron poisons, have been... 

All tank battery, separation, and treating facility installations (except for flowthrough process vessels) are constructed with a capacity to hold the largest single container plus additional capacity to contain rainfell. Drainage from undiked areas is safely confined in a catchment basin or holding pond. [ 112.9(c)(2)] ... 

The objectives of depressurization are to (1) prevent a vessel from rupturing during major fire exposure (from weakened condition of the vessel steel), (2) prevent further fire escalation, and (3) minimize the impacts to the vessel itself. It is therefore incumbent to depressurize a vessel so that its stress is less than the stress that would cause a rupture from fire conditions. These stresses and rupture periods can be estimated to determine the need for depressurization systems for process vessels. These estimates can provide a rough evaluation of the need of a depressurization system for a particular process plant or entire facility. 

The function of a relief valve is to protect a vessel, piping system, or heat exchanger from exceeding its maximum allowable working pressure (MAWP). The MAWP is shown on the code stamp (a metal plate) attached to each process vessel, and by design is determined by the size of the impeller on the pump upstream of the vessel (see Sec. 34.4.1 in Chap. 34). Normally, the relief valve is set to open at this MAWP pressure. The relief valve setting is adjustable and is done by a machinist at a shop pressure-testing facility. 

Recent national standards for hazardous air pollutants have placed strict controls on benzene emissions from coke-oven facilities. These regulations result in the requirement to enclose and seal all process vessels and tanks and to direct all vent streams to a collection system where benzene can be recovered and destroyed. The design of vapor control systems for coke-oven byproduct recovery plants to minimize the emission of benzene to the atmosphere is discussed by Kroll and Barry (1991). 

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