|
|
Process Steam
Tracing |
|
|
|
|
Process Temperature Control
The ST valve can provide for temperature control of 150 feet or more of product line. Many process fluids require some degree of heating and temperature regulation in piping and storage tanks. Some products are affected by temperature changes; their chemical and physical characteristics (corrosiveness, color, viscosity, etc.) change. Other products will experience problems in pumping and handling if the product temperatures are too low or too high. And, many batch-mixing operations have to be conducted within some finite temperature range. Process temperature control of liquids in piping or tanks differs from the winterizing of piping, tanks and equipment (discussed in the previous section) because seasonal systems are primarily concerned with preventing damage due to freezing from low ambient temperatures. With process temperature control, it is necessary to guard against overheating as well as freezing conditions. Thus, in process temperature control the liquids must be maintained between a lower temperature limit and a higher temperature limit. Cost is another consideration. Significant energy is wasted in heating process fluids to higher than necessary temperatures.
Type ST valve. The thermal actuator is installed in contact with a process line or tank wall to control steam supply based on surface temperature. The results are product temperature maintained within specified limits and drastically reduced steam consumption. Traditional Process Pipe and
Tank Heating Three basic schemes have been employed for heating process piping and vessels: steam tracing, tracing with other heat transfer media such as glycol and Dowtherm TM, and electric tracing. The earliest and still most popular method of heating process lines and tanks is by steam. Steam is readily available in many processing plants. It is easily handled, and its cost can be distributed plant-wide. Steam needs no pumping and simply "distributes itself". Dowtherm TM and other high temperature tracing is usually employed only when extremely high (500°F+) temperatures are required. The third type of tracing, electric, has inherent disadvantages: operating costs can be very high since electric generation costs continue to rise; and maintenance problems can be immense since this type of tracing is susceptible to physical abuse, moisture, overheating and burnouts. In addition, electric tracing must be precluded in many hazardous areas. A New Approach To Process Temperature Control Steam tracing remains the simplest, most convenient method of heating pipes and tanks. Standard industry practice has been to simply keep the steam on in tracer lines without any control. But this practice of having uncontrolled tracers is very wasteful. Until the Ogontz ST surface temperature sensing control valve was developed, temperature control of tracer lines and tanks, if used at all, was limited due to the lack of simple, reliable controls. In process piping there was essentially no control at all. And with tanks, any temperature regulating system usually included some type of bulb and capillary system --incorporating a self-contained valve, a motorized valve or pneumatically operated valving. Remote bulb and capillary type controls have the same inherent drawbacks: not only are they delicate and thus somewhat unreliable, but they are also expensive. The ST valve provides a simple, reliable and inexpensive solution to the problem of controlling the temperature of liquids in pipes or tanks. The heat sensitive wax-filled thermal actuator of the ST valve is mechanically attached to a process pipe or tank wall to sense internal fluid ' temperature (as opposed to the Ogontz TL valve, where the thermal actuator detects ambient temperature). This totally self-contained valve becomes a complete temperature regulating "system". It eliminates bulb or capillary tubing, hazardous chemically filled diaphragms, thin-walled bellows, dirt-susceptible pilot valves, or the need for any external power. This state-of-the-art thermal actuator, when adapted for surface temperature control in the ST valve configuration, provides continuous monitoring of process fluid temperatures and regulates steam flow on an as needed basis. It is not necessary to penetrate the walls of piping or tanks with thermal wells. The ST valve provides a method of regulating steam flow that eliminates costly steam waste and prevents overheating process fluids. Process Pipe Temperature Control Before the ST valve was developed, any process line that required heating was steam traced without regard to temperature control. The usual reasons given were that since there is always a danger of reduced temperatures, heat is required constantly, and no control is needed. Just keep the steam on at all times. This is false and costly thinking, because overheating can cause serious problems to the product or the process, as well as wasting large amounts of energy. A Sensible Alternative - Add ST Valves to Tracer Lines Retrofitting existing steam-traced process pipes with ST valves or installing them in new systems is a relatively simple procedure. You don't have to drill and tap any pipe walls, or add thermal wells. The mounting bracket containing the thermal actuator can be attached to the pipe by banding or welding. The ST valve senses the temperature of the outside pipe wall, which is usually not more than a few degrees from actual product temperature |
|
|
2835 Terwood Road, Willow Grove, PA 19090 800-523-2478 E-mail: info@ogontz.com |
