In addition to flow, pressure is without doubt the most relevant parameter and measuring factor in hydraulic applications. Measuring system pressure is therefore one of the most important and most frequently used methods for monitoring and controlling machinery and equipment. It is the prerequisite for reliable and economical operation. Analogue or digital gauges are generally used for this. While these are very inexpensive to buy, install and operate, they usually provide no option for recording data for subsequent evaluation and documentation. Users have to resort to more expensive and often also complicated pressure measuring systems with individually wired sensors where the time-consuming installation can sometimes already affect the economic efficiency of a measurement.
The PT-RF series of pressure transmitters presented by Stauff at this year’s Hannover Messe are an in-house development that has a patent pending. This new product in the field of universal pressure measurements for fluid technology applications will provide benefits for system operators, maintenance personnel and repair technicians as well as for original equipment manufacturers.
The use of these transmitters in a hydraulic system allows for the wireless collection of pressure data without having to connect any measuring devices to the user’s equipment, thus eliminating the possibility of introducing contamination into the system and significantly speeding up the process.
The operating principle of the pressure transmitters is based on the RFID (radio frequency identification) technology which has already become established in other areas of work and everyday life. The energy required for a measurement is transferred to the pressure transmitter via the antenna of the associated reading and display device so that the transmitter requires no internal or external power supply in the traditional sense (e.g. in the form of a battery) and no external wiring as it is common for conventional sensors. All that is required is a maximum distance of 1.5 centimetres from the antenna to the tip of the pressure transmitter for the duration of the measurement.
When the pressure transmitter is activated by the press of a button, the current pressure is determined in less than 0.5 seconds and then immediately transmitted back to the hand-held reader, displayed and stored for further evaluation. In addition to the pressure value itself, other relevant information is also transmitted as a standard, including media temperature, date and time of the measurement and the unique serial number of the pressure transmitter. When a continuous measurement is triggered, the MIN and MAX values as well as the average values for the respective time period are displayed in addition to the most recent pressure and temperature values. Over 15,000 of these measurement sets can be stored in the integrated memory of the reading device. The software included with the unit allows subsequent evaluation and further processing of the measurement results previously transmitted to the PC or notebook via the USB interface.
The pressure transmitters are available in five different versions and cover the usual measuring ranges for hydraulics between 0 … 16 bar and 0 … 600 bar (relative), depending on requirements, with a precision of max ±0.5 per cent full scale. The results can also be displayed in PSI. Temperature values can be displayed from -40 °C … +85 °C (or from -40 °F … +185 °F respectively).
Due to the stainless steel housing and the fully enclosed internal parts, pressure transmitters from the PT-RF series are hermetically sealed and can also be used under rough conditions (IP67 protection rating). As all parts that come into contact with media are also made of stainless steel, the system can be used with a variety of aggressive media as well. With a weight of only 220 grams, the reading and display device features a handy and most convenient design that is also robust (IP65 protection rating) and intended for regular use during a long lifetime.
The pressure transmitters are available with 1/4″ BSPP (with FPM profile sealing rings) or 1/4″ NPT screw-in threads thus ensuring easy integration with existing machinery during planning and design of the system, or in existing machinery or systems. Using suitable adapters based on straight 24°cutting ring fittings as per ISO 8434-1 and DIN 2353, the transmitters can also be easily installed in metric pipes with outer diameters between 6 and 42 millimetres which are commonly used in hydraulics. The corresponding connection pieces are available for the temporary or permanent use of existing test couplings with adapter thread M16x2 (e.g. from the Stauff Test 20 series).
The advantages resulting from the use of the new technology for system operators, maintenance personnel and repair technicians are clear: Measurements can be carried very easily, without extensive training and within a few seconds at the press of a button and then documented in a reliable process. Unscrewing and re-installing pressure gauges or other measuring and display devices – practically a temporary opening of the system – is not required. Potential hazards for people, machines and the environment, for example from emitted residual oil in the test hose or leaks at the measuring point, as well as ingress of dirt into the system (e.g. in dusty environments) can be effectively excluded.
If the pressure transmitters are installed directly in the system or pipeline for permanent use, they protrude only slightly more than conventional hydraulic test couplings and meet the highest demands with regard to space requirements and weight.
For original equipment, mechanical engineering companies and line builders will also benefit from this new product: If the pressure transmitters are installed at the factory, the innovative technology can provide a competitive edge over alternative suppliers and open up specific advantages for the users, increasing the value retention of their own devices in the long term.
Interested visitors of the Hannover Messe 2015 will find further information at booth D21 in hall 21, as well as at www.stauff.com.