Equipment venting

Although the ethyleneamines ate water soluble, soHd amine hydrates may form at certain concentrations that may plug processing equipment, vent lines, and safety devices. Hydrate formation usually can be avoided by insulating and heat tracing equipment to maintain a temperature of at least 50°C. Water cleanup of ethyleneamine equipment can result in hydrate formation even in areas where routine processing is nonaqueous. Use of warm water can reduce the extent of the problem. 

Figure 17-9. Process equipment vent in a nonenclosed, adequately ventilated area (top), and instrument or control device vent in a nonenclosed, adequately ventilated area (bottom). (Reprinted with permission from AW RP 500.)...

Chemical plant equipment—including tanks, pressure vessels, piping, rotating equipment, vent systems, and safety instrumentation—should be identified and categorized into different degrees of hazard potential. Classification systems could be simple or very complex. A complex system could be a matrix of increasing severity ratings on one axis and the... 

Nitrogen or other inert gas, used for blanketing or purging, must be positively removed and equipment vented with air before personnel are allowed to enter equipment. 

Electrical lines and water Maintenance done on wrong equipment Inadequate isolation of equipment venting of atmosphere removal of toxics... 

Will flame arresters be installed where needed on equipment vents ... 

Valves on RCS support systems, e.g., on equipment vents, should not be left open even if other valves in series could prevent a loss of coolant through them. 

Hand Tools Portable Power Tools Proper tools available Tools in good condition Power tools grounded or insulated Gas powered equipment vented ... 

Materials of construction for ancillary systems are commonly carbon steel, fiberglass-reinforced plastic (FRP), epoxy-or phenolic-lined, stainless steel, and concrete. Many times waste transfer lines will change from a product contact material (near the process equipment) to carbon steel, stainless steel, or polyethylene (near the ancillary equipment). Vent tines are particularly troublesome and require special attention. Smooth surfaces (noncorrugated) with proper sloping to avoid areas for condensation and debris accumulation are essential to minimize corrosion. Smooth and sloping surfaces are cJso needed to aid in cleaning between campaigns. 

Apparatus 2-1 three-necked flask, equipped with a dropping funnel, stirrer and thermometer, combined with a vent. 

A twin-screw extmder is used to reduce residual monomers from ca 50 to 0.6%, at 170°C and 3 kPa with a residence time of 2 min (94). In another design, a heated casing encloses the vented devolatilization chamber, which encloses a rotating shaft with specially designed blades (99,100). These continuously regenerate a large surface area to faciUtate the efficient vaporization of monomers. The devolatilization equipment used for the production of polystyrene and ABS is generally suitable for SAN production. 

A filter cake from the wringer is washed to remove absorbed acid, transferred to a slurry tank of water, and quickly submerged, after which the nitrocellulose is pumped to the stabilization operation as a diluted water slurry. Exhaust systems are installed to protect personnel and equipment from acid fumes, and water sprays and cyclone separators are used for acid fume recovery before venting to the air. 

The third type of storage for anhydrous ammonia is pressurized storage without refrigeration. This is used at small terminals, ia some transport vehicles, and ia field appHcation equipment. For safety reasons, maximum allowable storage pressure ia vessels at retail locations and ia the field has been set at 1.83 MPa (265 psig) (8). This pressure is sufficient to prevent boiling at temperatures up to 46°C. Safety pop-off valves are provided to vent ammonia should higher temperatures be encountered. 

Most small Hquid helium containers are unpressurized heat leak slowly bods away the Hquid, and the vapor is vented to the atmosphere. To prevent plugging of the vent lines with solidified air, check valves of some sort are included in the vent system. Containers used for air transportation are equipped with automatic venting valves that maintain a constant absolute pressure with the helium container in order to prevent Hquid flash losses at the lower pressures of flight altitudes and to prevent the inhalation of air as the pressure increases during the aircraft s descent. Improved super insulation has removed the need for Hquid nitrogen shielding from almost all small containers. 

Fig. 2. The Dow magnesium cell. The steel container. A, is equipped with a ceramic cover, B, through which graphite anodes, C, pass. The magnesium is deposited on the cathode, D, and is diverted as it rises into the collection sump, E. The chlorine is withdrawn through a vent, F.

Mercury vapor discharge from vents of reactors or storage tanks at normal atmospheric pressure is controlled readily by means of activated carbon. Standard units (208-L (55-gal) dmms) of activated carbon equipped with proper inlet and outlet nozzles can be attached to each vent. To minimize the load on the carbon-absorbing device, a small water-cooled condenser is placed between the vent and the absorber. 

Finish removers are manufactured in open or closed ketdes. Closed ketdes are preferred because they prevent solvent loss and exposure to personnel. To reduce air emissions from the solvents, condensers are employed on vent stacks. Mild steel or black iron ketdes are used for neutral or basic removers stainless steel (316 or 317) or reinforced polyethylene ketdes are used for acidic removers. The ketdes are heated to increase dispersion of paraffin waxes and aid in the mixing of other ingredients. Electric or air driven motors drive either sweeping blade or propeller mixers that give sufficient lift to rotate and mix the Hquid. Dispenser-type mixers are used to manufacture thick and viscous removers. Ketde, fittings, mixer, and fill equipment must be fabricated with materials resistant to the chemicals in remover formulas. 

Storage of Flammable Materials. The preferred storage for flammable Hquids or gases is in properly designed tanks. Floating roof tanks frequently are used in the petroleum industry for flammable cmdes and products (see Tanks and pressure vessels). The vents on cone roof tanks should either be equipped with flame arrestors or the vapor space above the contents should be inerted with a nonflammable gas or vapor, unless the flash point is weU above the maximum ambient temperature, the contents are not heated above the flash point, and the tank is not exposed to other tanks containing flammable Hquids. 

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