Differential pressure gauges are not only suitable for the typical applications such as monitoring and control of filters or pumps. They can take on the function of a flow monitor, for example, in heat transfer oil plants. They thus control the volume flow of the medium. diaphragm seal of the measuring instrument can be attested for this application through a certification in accordance with VdTÜV (“Flow 100” code of practice).
Heat transfer oil plant
A look at its measurement principle makes it clear why a differential pressure gauge can be suitable as a flow control: It collects the pressure from two different points in the process and displays the measured value of the differential pressure. This information indicates the particular flow characteristics of the medium: The higher the value, the stronger the flow.
For the task as a flow monitor in heat transfer oil plants, however, only differential pressure gauges in a mechatronic design with switch contacts come into consideration. Plants with thermal oil are used for the tempering of processes in various industries. If the flow of the oil slows down, the differential pressure in the line between the two measuring points drops. The instrument indicates this and reacts automatically in the event of danger: Its pressure switch triggers an alarm when a preset critical measured value is reached and switches the heater off or stops the process. Thus, a block of hot medium of up to 400 °C and, as a possible consequence, an overheating of the plant at a single point, is prevented.
Up to two switch contacts
For the requirements for differential pressure flow monitoring in heat transfer oil plants, instruments like the WIKA model DPGS40TA from the DELTA-line product family are tailor-made (available both in an aluminium and a stainless steel version). The VdTÜV certificate confirms the reliability of the correct registration of the differential pressure and of the switch function. Given the potential risk in the process, plant operators require a component testing in accordance with the ‘Flow 100’ VdTÜV code of practice for such instruments. The DPGS40TA also has a shipbuilding approval, certified in accordance with DNV-GL, and is available with a SIL certificate for safety applications. It features up to two switch contacts and an integrated working pressure indication.
Further information on the differential pressure gauges of the DELTA-line product family (models DPGS40TA, DPG40, DPGT40, DPS40, DPGS40) can be found on the WIKA website and also in the flyer “DELTA-line” (PDF).