Heat tracing

Heat tracing can also be used however, it is usually best used if the problem is localized, for example around a valve. Points notorious for freezing in the acid gas injection scheme are the dump valves from the interstage knockout drums. 

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Storage tanks, lines, and pumps should be heat traced and insulated to enable product handling. Temperature control is required to prevent product degradation because of color alkan olamines have poor heat transfer properties. Exposure to air will also cause product discoloration. Storage tanks should be nitrogen-padded if low color product is required. 

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. 

The vast majority of heat-traced pipes are insulated to minimize heat loss to the environment. A heat input of 2 to 10 watts per foot is... 

Heat tracing for insulated pipes is generally only required for the period when the material in the pipe is not flowing. The heat loss of an insulated pipe is veiy small compared to the heat capacity of a flowing fluid. Unless the pipe is extremely long (several thousands of feet), the temperature drop of a flowing fluid will not be significant. 

The three major methods of avoiding heat tracing are ... 

Some combination of these techniques may be used to minimize the quantity of traced pipes. However, the majority of pipes containing ffuids that must be kept above the minimum ambient temperature are generally going to require heat tracing. 

High reliability. Many things can go wrong with a steam tracing system but, very few of the potential problems lead to a heat tracing failure. Steam traps fail, but they usually fail in the open position. 

In operating a coohng tower in the thermocycle or free-cooling mode, some precautions are necessary to minimize icing problems. These include fan reversals to circulate air down through the tower inlet louvers, proper water distribution, constant water flow over the tower, heat tracing of lines such as makeup lines as required, and maximum loading per tower cell. 

The heatable areas of the diyer are the vessel wall and the screw. The diyer makes maximum use of the product-heated areas—the filling volume of the vessel (up to the knuckle of the dished head) is the usable product loading. The top cover of the vessel is easily heated by either a half-pipe coil or heat tracing, which ensures that no vapor condensation will occur in the process area. In addition to the conical vessel heated area, heating the screw effectively increases the heat exchange area by 15-30 percent. This is accomphshed via rotary joints at the base of the screw. The screw can be neated with the same... 

Thermal expan sion. Equipment and pipehues which are liquid-full under normal operating conditions are subject to hydrauhc expansion if the temperature increases. Common sources of heat that can result in high pressures due to thermal expansion include solar radiation, steam or other heated tracing, heating coils, and heat transfer from other pieces of equipment. 

QUENCH LIQUID SELECTION The choice of the appropriate quench liquid depends on a number of fac tors. Water is usually the first quench hquid to consider, since it is nontoxic, nonflammable, compatible with many effluent vapors, and has excellent thermal properties. If water is selected as the quench liquid, the tank should oe located indoors, if possible, to avoid freezing problems. If the tank has to be located outdoors in a cold climate, the addition of antifreeze is preferable to heat-tracing the tank, since overheating the tank can occur from tracing, thus reducing its effectiveness. 

Samples may separate into two or more phases as they cool in the sample line precipitate, coagulate, and freeze. Laboratory sampling may result in nonrepresentative compositions. Heat tracing may be required and may not be installed on the nonroutine sample locations. 

Heat trace/insulate vessels and critical piping, as needed... 

Low ambient tern- Monitor temperature perature resulting. adequate heating in embrittlement and/or mechanical design system to accommodate minimum failure of reactor. expected temperature Provide freeze protection/heat tracing CCPS G-23 CCPS G-29 Lees 1996... 

Temperature con- Check heat tracing trol failure on, Perform periodic maintenance and inspection lines or equipment. CCPS G-29... 

Drumming at Follow operating procedures incorrect tempera-, Cool adequately before drumming ture. Possibility of flammable atmo- drums until material has cooled down sphere, or initia- sufficiently tion of thermally Provide adequate fixed fire protection unstable materials.. ventilation Check heat tracing for excessive heat input ACGIH 1986 Bossart 1974 CCPS G-15 CCPS G-22 CCPS G-29 CCPS G-30... 

Material solidifies Monitor and control temperature in feed system or is too viscous, Heat trace and/or insulate lines and plugs lines. Potential for proper line break procedures exposure while Use personal protective equipment (PPE) correcting, proper lockout-tagout and confined space problem. entry procedures CCPS G-23 CCPS G-29 Fisher 1990... 

Filters must be provided for all gas buffers in places where the gas will pass through the gas seal. The gas should be filtered to a nominal value of 2 microns. On most critical systems, dual filters will be required to permit servicing the filters without having to shut down the compressor. This requires the use of a transfer valve that can be switched without causing a flow interruption. If liquids are anticipated, heat tracing or an alternate gas source should be the first consideration. Should this not prove to be practi-... 

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