Leaking or overfilled tanks containing chemicals, fuel oil, sewage or hazardous materials can cause environmental problems, contaminate drinking water and cost a company millions of dollars in fines and lawsuits. This white paper discusses instrumentation and controls that can monitor the contents of a vessel and provide an alarm in the event of a leak or overfill event.
Without measurement there is no control. As with any type of measurement, results need to be expressed in a defined and clear way to allow everyone to interpret and apply those results correctly. Accurate measurements and good measurement practices are essential in industrial automation and process environments, as they have a direct effect on the success of the desired outcome.
Pressure, the measure of a force on a specified area, is a straightforward concept, however, depending on the application, there are many different ways of interpreting the force measurement. This white paper will identify the various units of pressure measurement, while discussing when and why certain pressure measurements are used in specific applications.
There are over two hundred pressure sensor suppliers around the world, offering products from a few dollars to thousands of dollars. A purchaser or engineer unfamiliar with pressure sensors can become overwhelmed with the price range, quality and options. The first step is to understand his/her application from the media being measured, to the desired electrical output for indication or control. The following is a guide through a variety of options to make a prudent decision.
Media is the most important item when selecting a pressure sensor for an application. Most sensor suppliers only sell sensors that are rated for benign environments such as clean, dry air. The next tier of suppliers will sell products that will handle mild environments through to difficult/corrosive environments. Clean water, steam, some forms of hydraulic oils and Freon can be considered mild environments. Difficult media tends to be corrosive liquids and gases such as hydrogen sulfide, hydrochloric acid, bleach, bromides, waste water and hydrogen. Wrongful selection of a pressure sensor can lead to catastrophic failure and serious injury. When unsure, ask the pressure sensor manufacturer to provide a chemical compatibility chart with their products. In fluidic systems, such as water and hydraulics, one must understand how the water hammer and pressure transients effect the pressure sensor.
Differential pressure (dP) sensors with electronic signal processing are increasing being used to monitor flow, filter condition and level. Since these devices offer linear and accurate output, they are also replacing the differential pressure switch that only support on-off condition and useless for closed loop control system. These dPs are often configured with expensive valves and fluid filled remote seals for added protection against corrosive media, radiation and/or extreme media temperature ranges when operating in demanding environments. In cold ambient environment specially operating in temperatures below -4 deg F (-20 deg C), the sensor need to be heated either by trace heater or within a heated enclosure to maintain the operation of the dP sensor. In addition to being expensive, these valves and seals tend to be bulky and require time to install and maintain. In many critical applications such as food and pharmaceuticals, filled fluids are a serious concern due to process contamination. In gaseous systems such as hydrogen and oxygen and semiconductor applications, fluid filled sensors are being banned since the leakage of fluid into the process could lead to an explosion and serious safety issues.
A new series of LVDT (linear variable differential transformer) based oil-less dP sensor with dual channel ASIC (applications specific integrated circuit) have been developed that can operate in a wide range of corrosive materials, radiation and temperature without any oil filling and bulky sealing systems. By encapsulating LVDT proven technology with digital compensation, the pressure sensors combine the benefits of friction-free operation, environmental robustness and unlimited mechanical life. By selecting the diaphragm thickness and material properties, Table 1 show the dP ranges that can be produced using the LVDT technology.
Ceramic pressure transmitters have proven to outperform standard metallic diaphragm transmitters in very demanding applications. Find out why in this white paper from Endress+Hauser that demonstrates the advantages of ceramic sensors, especially in vacuum and chemical service. See why the enhanced stability and lower maintenance of ceramic pressure sensors improve productivity, quality and the bottom line.
The use of Ceraphire pressure sensors may help plant operations and maintenance personnel realize optimum process performance and stability in process applications by identifying advantages that come with selecting ceramic pressure measuring cells. This white paper helps identify and demonstrate the inherent problems of using metal diaphragm pressure cells, particularly in vacuum and chemical service. It also brings awareness of enhanced performance and stability in pressure measurement to plant maintenance, quality assurance and operations personnel in order to improve their operations and the bottom line.
A Complete Precision Pressure Measurement Handbook Covering the Fundamentals of Pressure Measurement, Deadweight Pressure Testers, Calibration of Deadweight Testers, AMETEK's Deadweight Testers, Manometers, Secondary Comparison Pressure Standards and the Selection of a Pressure Measurement Standard.
The pH value is the most frequently used process variable in analysis. The pH value is of outstanding importance in water and environmental analysis and in almost all sectors of industry. Whether the cheese in a dairy is of the right quality, the water in a drinking water supply causes corrosion damage, or the precipitation in a treatment plant for waste water from an electroplating process occurs at the optimal point, all depend on such parameters as the pH value.
I/P transducers are relatively simple devices, but there are numerous factors to take into account before selecting one. This paper provides a complete understanding of the factors involved in making the correct product selection, installation, and maintenance.