Termex in Weighing Technology

Intrinsically safe weighing technology with calibration facility and Pepperl+Fuchs EXTEC operating terminals for the dispensing of carbon dioxide, propane gas and refrigerants.

A. Friedrichs Industriebedarf is an old established company in Bremerhaven. It was founded in 1921, in the east fishing harbour, as a commercial ship fitting enterprise. The rapid development of shipboard technology led, little-by-little, to its restructuring as a supplier of industrial commodities. A. Friedrichs now supplies almost anything from asbestos gloves and high-pressure hosing, to ball bearings, etc., as well as CO2 for dispensing plants.

Variety of Business Areas

The decision to add the filling of refrigerants to the product portfolio was taken in 1969. A. Friedrichs provided the locally based polar research organisation with refrigerants for ice core boring. Then in 1978 the dispensing of propane was added. In addition to research laboratories, A. Friedrich’s regular customers also include camping enthusiasts.

Other business areas are:

• The dispensing of carbon dioxide (CO2) for companies engaged in fire extinguishing technology and dispensing plants
• The provision of forklift trucks with industrial gas for the locally established fish market halls and for various local scrap dealers

In order to cater for continually increasing demands, the management decided to erect a new sales building with a new dispensing plant for CO2, refrigerants and propane gas.

Project Requirements

Up till then a pneumatic technique had been employed for weighing the filling quantities. The plan now was to use a more precise electronic weighing technique in its place. The prerequisite for this was that an accuracy of at least C3 (3000 scale graduations) should be achieved for the balance calibration function. The gases to be filled are classified for Ex-Zone 1 as hazardous substances (Category II G). As a consequence the whole of the system had to be appropriate to Ex protection in Zone 1, II T4.

Because of the explosion protection requirements for the balance technology, it was not possible to use standard products. The search for the combination of calibration-capable balance technology for weights up to 1,500 kg and explosion protected operating terminals in one unit led to Pepperl+ Fuchs EXTEC as the possible supplier of this technology.

The Pepperl+Fuchs EXTEC balance measurement amplifier, Ex-AWU, in combination with the graphics-capable, intrinsically safe TERMEX operating terminal was the ideal solution for the dispensing plant application. The operating panel was devised as a stainless steel housing with wall-mounted devices with approval for Zone 1 hazardous areas. A particular advantage of the system is the use of display and operating panels, combining a balance display, which can be calibrated, with station operation and visualisation in a single display unit.

Implementation

Altogether, three dispensing stations are in use, each incorporating TERMEX equipment. The simple operation and the user-friendly panel were decisive arguments in the decision to employ Pepperl+Fuchs EXTEC technology. The display is characterised by excellent readability, ease of operator control and also the display of text and measured values. To this end, the largest possible text character size of 20 mm was selected.

The balance platforms were constructed in-house, with four ring torsion balance cells (One cell in each corner), in order to ensure a high level of robustness of the platforms for the purpose of weighing a very varied assortment of steel flasks and containers. A 10 mm thick steel plate protects the Ex balance system, embedded in a sturdy steel frame. On the old systems increasing difficulties were encountered with the balances over a period of time, because the mechanical components were not adequate to contend with the loading of the heavy steel cylinders and containers. The consequences were repeated problems with the routine calibration of the balances. In view of this, the A. Friedrich’s management decided to opt for an in-house construction, which would be capable of withstanding this heavy loading.

Universal Operating Terminals for Explosion Hazardous Areas

When the operating terminal of a plant or machine is installed in a hazardous area, naturally enough the safety aspects are given prior consideration. Our devices are certificated in accordance with the applicable European directives (II 2G EEx ib IIC T4 for application in Zones 1 and 2). Then, in addition, user friendliness has an essential part to play. An easily understandable operator/machine interface, clear demarcation of the operating steps and clear representation of the machine/plant data make a significant contribution to plant safety. Only when the operation is presented in a clear and unmistakable way can false interpretation and incorrect operation be avoided on safety-relevant plant components. An important contribution in this respect is provided by the richly contrasting text and graphics displays employed in the TERMEX product family. Depending on customer requirements, plant layouts and input fields can be presented on the display screen in various text sizes and in interplay with appropriate symbols.

Robust Nature

The devices in the TERMEX product family are designed for use in coarse industrial environments and as a consequence they are of very robust construction:

• IP65 protection on the front
• Safety glass display screen
• Stainless steel housing
• Anodised front panel with polyester film and appropriate resistance to chemicals

Integrated Control Technology

Various physical interfaces are available for incorporation in the PLC or a control computer, e.g. RS232, RS485 and TTY. For data exchange, in addition to the ASCII terminal coupling, the TERMEX operating devices accommodate the customary automation technology communication protocols: Siemens S5 programming interface AS511 and 3964R/RK512, Siemens S7 MPI, Allen-Bradley DF1, Modbus/RTU and PROFIBUS DP.

Programming and parameter assignment of the TERMEX devices are achieved with the graphics-oriented TERMEX pro programming tool. The transparent structure of this tool enables fast and intuitive programming.

The functionality includes:

• Adaptable use of text and graphics
• Incorporation of bit maps for process symbols
• Extensive alarm options
• Variable-controlled dynamic bar graphs with configurable limit values
• Use of dynamic graphics elements

Intrinsically Safe Interfaces

Digital and serial interfaces are integrated in the TERMEX product series as standard. Optionally, up to three serial peripheral devices, such as Ex balances and barcode readers, can be directly connected in this context. Also, three digital NAMUR inputs and three digital insulated outputs are available for the coupling of external switches and push buttons or valves, flasher lamps and alarm sensors.

As an established EX area man-machine-interface, the TERMEX family of products is the modern, future-oriented system solution for small to medium-sized applications.

Our Products

Intrinsically Safe Operating Terminals Termex pro Configuration Tool

Additional Information

A. Friedrichs Industriebedarf A. Friedrichs Kältemittel