New Current Interesting Links - Corrosion, Ball Valves, Temperature Measurement

Click through to the pages mentioned below via www.pipingdesign.com's "Current Interesting Links" feature at the main page (these links are also archived at http://www.pipingdesign.com for future reference):

Temperature Measurement
http://www.pipingdesign.com/transmitters.html

<<Temperature control is important for separation and reaction
processes, and temperature must be maintained within limits to ensure safe and reliable operation of process equipment. Temperature can be measured by many methods; several of the more common are described in this subsection. You should understand the strengths and limitations of each sensor, so that you can select the best sensor for each application. In nearly all cases, the temperature sensor is protected from the process materials to prevent interference with proper sensing and to eliminate damage to the sensor. Thus, some physically strong, chemically resistant barrier exists between the process and sensor; often, this barrier is termed a sheath or thermowell, especially for thermocouple sensors. An additional advantage of such a barrier is the ability to remove, replace, and calibrate the sensor without disrupting the process operation.>>

Flow Control With Ball Valves
http://www.pipingdesign.com/controlvalves.html

<<When a globe valve starts to open, it will always jump open rather
than move smoothly. In order to overcome linkage and internal resistance, more movement is needed by the actuator than low flow requires. Globe valves are installed with flow tending to push open the seat. As soon as flow is established, the pressure pushes on the seat, the stem rises, and more flow than needed occurs. There is a travel zone where about 10% of CV rating occurs on opening. Ball valves do not have this jump effect. Rotation is slow, rack and pinion linkage is used, the tendency of flow is to close a ball, and a high seal resistance, all contribute to smooth rotation without jumps, resulting in turndown ratios from 160:1 to 400:1, depending on quality of actuators, valves, and signal. Minimum flow is fully controllable under part load conditions. Ball valves with Belimo actuators are exceptionally good at control, and fully utilize the control signal.>>

Piping System Corrosion Control
http://www.pipingdesign.com/materials.html

<<Among other factors, the integrity and life of a piping system is
dependent upon corrosion control. As discussed in previous chapters of this manual, internal corrosion of piping systems is controlled by the selection of appropriate materials of construction, wall thickness, linings and by the addition of treatment chemicals. External corrosion can also be addressed through materials of construction. However, other methods may be required when metallic piping systems are applied.>> Received on Tue Feb 01 18:54:00 2005