Friday, September 30, 2011

Burkert Decentralised Automation at all Process Level

Intelligent control heads enable complete decentral automation of hygienic production processes, by Chris Hoey

In the food and beverage industry, and also in the production of medicines and cosmetics, excellent hygiene in processes and around the plant plays a key role. This is ensured by stringent legislative regulations. Standards such as HACCP (Hazard Analysis and Critical Control Points) for food processing and GMP (Good Manufacturing Practise) for FDA-compliant processes in the pharmaceutical industry define extremely stringent requirements for cleanliness, safety and product quality. In addition, legislation requires that all processes must be constantly monitored and documented in these areas. In an increasingly competitive global environment, companies of this industry are at the same time forced to make their production processes as efficient and cost-effective as possible, in addition to optimising processes. As a consequence, there is an ever increasing demand for automation at all process and auxiliary circuit levels.

Pneumatically actuated process and control valves play a key role in the manufacture of foods and beverages, in milk processing and in the pharmaceutical and cosmetic industries. They are the core element of practically every production plant, where they perform numerous different tasks. However, the economical and hygienic aspects of these process fittings in a centrally controlled automation process are not unproblematic. Classical control systems using switch cabinets with valve terminals, I/O system and field bus interface involve considerable expense especially in complex facilities. With this technology, the fittings at the field level are connected to the control units in the switch cabinets through a large number of long control air lines and discrete feedback connections. Apart from planning and installation requirements for such solutions, they are not entirely optimal as regards hygiene. According to HACCP, every additional control air and feedback line within the production plant is a potential source of contamination and other risks and must therefore be monitored, serviced, cleaned and documented regularly, which is a costly undertaking.

In shop floor practice the control air lines can be quite long, which increases air consumption and has a negative effect on the switching times of the fittings. The situation is worsened even more by the high power requirement - e.g. for evacuation of air from chambers and hoses - which is undesirable in terms of energy efficiency. The fact that the pilot valve operating level is at a distance from the fitting makes it even more difficult to commission, maintain and extend the plant. This also applies to the monitoring of processes.

Intelligent valve systems make switch cabinets superfluous
A viable alternative to the use of central switch cabinets is the integration of the required automation functions in the fittings themselves. In this case, the process control system is only in charge of control and status monitoring. At field level, pneumatically operated valves are used. These can be equipped with all required automation components such as pilot valves with manual actuation, electrical feedback units and optical status indicators, field bus interfaces and even positioners and process controllers. By integrating an AS interface as a field bus interface, the entire range of advantages of this approach can be fully utilised. All that is required for power supply, feedback and communication is a two-wire line connecting the PLC with up to 62 valves. Each process valve is individually connected to the main compressed air supply line installed in the field, whereby these connections are kept as short as possible. This minimises the number and length of hose and wire connections.

For auxiliary circuits such as steam, compressed air or cleaning media, the valve specialist Bürkert offers fluid control systems with the intelligent valve systems of the ELEMENT series for creating decentralised automation solutions. The latest addition to this solution portfolio is the new control head Type 8681, which was designed especially for use with pneumatically actuated hygienic media valves. The features of a decentralised automation solution in hygienic production processes can be used to good advantage not only in the auxiliary circuits, but throughout the plant at all process levels. In the planning of new plants, the use of conventional switch cabinets can be eliminated consistently. Existing plants can be converted from central to decentralised automation step-by-step, using the existing media valves.

New universal control head for hygienic process fittings
The Type 8681 control head is universally adaptable by means of adapters and can be combined with all commercially available valve types, such as flap valves, ball valves and single and double-seat valves, regardless of the manufacturer. Within the framework of a decentralised automation concept the control head, as a central unit for the hygienic process valves, performs all pneumatic actuation, feedback and diagnostic functions, as well as bus communication. Depending on the process valve, as many as three pneumatic driver chambers can be controlled separately.

The switching positions of the hygienic process valve are measured by the control head via an inductive analogue distance sensor for monitoring strokes of up to 85 mm and then transmitted to a master controller. After installation of the control head on the valve actuator the switching positions are automatically determined by a fast and reliable teach-in function, which eliminates the need for time-consuming manual configuration. If a fourth switching position is required, it can be read in by an externally mounted inductive proximity switch.

For optimal adaptation to the respective valve and process, the switching speed of each driver chamber can be set individually for both directions of movement by means of a restrictor function integrated in the pilot valve. In addition, a non-return valve prevents faulty switching of other driver chambers of the process valves due to back pressure. Independent of the power supply, each pilot valve can additionally be switched manually by means of a mechanical control. Thanks to a patented magnetically coded manual control, it is possible to switch the main actuator for maintenance purposes from outside even in the case of a completely enclosed device - ensuring full IP protection at all times.

A highly visible three-colour optical status display with high-power LEDs, which is integrated in the control head, provides for an optimum overview at the field level. In addition to electrical feedback to the master controller, it also signals the current switching position of the process valve, facilitating diagnosis and maintenance within the system itself. Diagnostic functions such as required maintenance or errors are likewise signalled visually and can be read out in detail via a service interface. This communication can be wireless via a Bluetooth module or via the integrated USB interface.

Hygienic control valves are also suitable for decentralised automation
The use of one of the positioners or process controllers of the ELEMENT series allows the decentralised automation of control valves, in addition to the process valves. The ELEMENT process controllers are optimised for cleaning and use in the wet areas of hygienic processing plants; their outer geometry, materials, surface quality and sealing properties comply with EHEDG guidelines. The compact positioners are installed directly on the pneumatic actuator to save space and require no external hoses, thanks to the internal control air supply. Installation and commissioning are facilitated by the use of intelligent positioners with automatic adaptation and process controllers with automatic control circuit detection and parameter optimisation. Communication is achieved via Profibus DPV1, Device NET or the AS-Interface.

One decentralised system solution for all process levels
With the addition of the new Type 8681 control head to the ELEMENT series, Bürkert now offers a complete product portfolio for decentralised process automation in food and beverage production, breweries and the milk processing and pharmaceutical industries. The range of products extends from the process valve with an integrated pilot valve, as well as electrical and simple optical feedback all the way to the decentralised control of aseptic, hygienic control valves by means of a control head and process controller in complex production plants. decentralised automation can therefore be used in all processes for entire plants and installations, enabling users from these industries to combine the requirements for hygiene and safety with a high degree of automation and efficiency. Since the new control head can be used with virtually all available fittings regardless of the manufacturer, there are practically no limits to decentralised automation with uniform standards.
 To download the Burkert ELEMENT Conrtrol Valves datasheet: click here
The new flow transmitters at a glance

  • Beautiful stainless steel housing in standardized ELEMENT design
  • Long durability and outstanding availability
  • Removable, programmable display with backlight
  • Programming via joystick
  • New processors and software
  • Future-proof system architecture
  • Protection class IP 65/67
  • Resistant to cleaning chemicals
  • Up to two 700 mA transistor outputs
  • Analog outputs 4-20mA
  • UL approved

To receive more information on Burkert Element Valves please contact Forberg Scientfic customer service:
Phone: 855-288-5330Email:

Monday, September 26, 2011

Select a Diaphragm Seal or Chemical Seal

Selection Guidelines
When selecting a diaphragm seal assembly, the following details must be taken into consideration to ensure a safe and satisfactory operation. For specific technical assistance regarding temperature effects, volumetric compatibility, etc., contact the Forberg Scientific customer service department or send a completed diaphragm seal specification sheet to the factory for analysis.
  1. Process Composition
  2. Temperature
  3. Pressure Range
  4. Pressure Instrument
  5. Process Connection
  6. System Fill Fluid
  7. Mounting Positions
  8. Response Time
  9. Seal and Gauge Matches

1. Process composition
Since the diaphragm and lower housing of the diaphragm seal will be exposed to the process medium, it is critical to select materials for these components which will be compatible with this medium. Tables are available to assist in the selection of these materials (see Pressure Gauge Section); however, the customer is the ultimate source for specifying suitable materials. WIKA cannot guarantee suitability. For information, see numerous reference guides such as corrosion table reference books. If the pressure fluid is very thick, solidifies, or is full of solids, this should also be taken into consideration.

2. Temperature
Each diaphragm seal measurement system (diaphragm seal, pressure instrument, and cooling element or capillary, if applicable) is filled with an amount of fill fluid at an ambient temperature of about 70oF. This temperature is referred to as the system fill temperature. The fill fluid will expand or contract according to temperature changes. This in turn causes the pressure in the sensing element to rise or fall, thus adding zero shifting effects to the instrument output. To reduce this effect, the temperatures of the process and the environment should be specified when selecting a diaphragm seal system (see Diaphragm Seal Specification Sheet). Special advanced calibration techniques can be used to ensure the best possible accuracy. At temperatures above 300 F, a cooling element or capillary is suggested to protect the pressure instrument.

3. Pressure range
The displacement volume on the diaphragm seal required to "drive" each diaphragm seal measurement system (diaphragm seal, pressure instrument and capillary, if applicable) must be greater than the displacement volume needed to move the pressure sensing element. Normally, the lower the pressure range, the larger the diaphragm is required to "drive" the system. Conversely, for higher pressure ranges, smaller diaphragms are sufficient. Pressure transmitters also follow the general rule of the lower the pressure, the larger the diaphragm required.

4. Pressure instrument
As mentioned above (Item 3 - Pressure range), the diaphragm seal must supply sufficient displacement volume to enable the pressure instrument to reach full scale. As a general rule, smaller size gauges are better suited to low pressure applications since less displacement volume is required on the part of the diaphragm seal to drive the pressure instrument.

5. Process connection
The process connection is specified by the customer. Most process connections are threaded, flanged, or clamped; however, additional connections are available. Teflon® coating and lining is only available in flanged connections, since tapered NPT threads strip off the Teflon® during installation. However, solid Teflon® threaded connections are available with NPT threads.

6. System fill fluid
WIKA offers a wide range of system filling fluids allowing temperatures from -130 F to 752 F. Chemical compatibility of the system fill fluid with the process fluid must be carefully considered in the event of a leak. In food processing applications a nontoxic fluid should be selected. Special fill fluids are also available for oxidizing media such as oxygen and chlorine.

7. Mounting position
Mounting position is important for diaphragm seal systems which include a capillary. The level difference between the diaphragm seal and the pressure instrument causes a hydrostatic pressure to act on the sensing element: a. For gauges mounted above the level of the diaphragm seal, the pointer on the dial of the gauge will be lower than the zero point. b. For gauges mounted below the level of the diaphragm seal, the pointer on the dial of the gauge will be higher than the zero point. The diaphragm seal system can be calibrated to compensate for the effect caused by the hydrostatic pressure, if the level difference is known in advance.

8. Response time
Response time, i.e., the time it takes the pressure instrument to indicate 90% of the value of a sudden pressure variation, is especially important for instrument/diaphragm seal assemblies which include a capillary. Response time increases significantly in systems with long capillaries. In applications requiring long capillaries, response times can be reduced by using larger diameter capillary tubing and reducing the viscosity of the system fill fluid. Be advised that increasing the inner diameter of the capillary increases the temperature influence of the measuring system. Forberg Scientific can consult WIKA if detailed information is needed.

9. Seal and gauge matches
For low ranges, gauge preference is 2XX.54 or 2XX.34 for access to perform calibration adjustments. Gauges with crimp rings might not be usable due to potential recalibration. The table below shows the common matches between gauge and diaphragm seal types recommended by the WIKA.

If you would like additional information about WIKA Diaphragm Seals or other WIKA Products please contact Forberg Scientific, Inc.
Toll Free: 855-288-5330

Friday, September 23, 2011

Diaphragm Seal & Chemical Seal Operating Principle

The drawing below illustrates the operating principle of a diaphragm seal assembly. A pressure measurementinstrument such as a conventional pressure gauge or electronic pressure transmitter is either mounted directly to the diaphragm seal or attached to the seal by means of a capillary or cooling element.
A diaphragm within the diaphragm seal separates the gauge / transmitter from the process medium. Any part of the diaphragm seal (i.e., diaphragm, lower housing, gaskets) which will be exposed to the process medium is selected from materials resistant to pressure, temperature and possible chemical attack by the process medium.

The diaphragm seal is also filled with a transmitting fluid or system fill fluid. Any pressure applied by the process medium to the seal diaphragm is hydraulically transmitted to the pressure element of the gauge / switch / transmitter thus generating a pressure reading.

If you would like additional information about WIKA Diaphragm Seals or other WIKA Products please contact Forberg Scientific, Inc.
Toll Free: 855-288-5330

Wednesday, September 21, 2011

Diaphragm Seal or Chemical Seal Application

Diaphragm seals, also referred to as chemical seals, are used to isolate pressure gauges, switches, and transmitters from clogging and/or corrosive media. Standard diaphragm seal bodies and diaphragms are made of stainless steel; however, a variety of materials from carbon steel to Hastelloy® C-276 are available to meet the demands of most applications. WIKA diaphragm seals can operate in pressure applications from 10" H2O to 20,000 psi and media temperature between -130°F and 752°F.

  • The media is corrosive and may damage a sensitive element such as a Bourdon tube gauge, pressure switch or transmitter diaphragm.
  • The temperature of the media may be too high for a standard gauge, switch or transmitter to operate properly.
  • The media is highly viscous or tends to crystallize, or polymerize and may clog the pressure port of a gauge, switch or transmitter.
  • The media is non-homogenous or contains suspended matter such as wood pulp which may clog the pressure port of a gauge, switch or transmitter.
  • Remote reading is required. A diaphragm seal with a capillary line will allow remote installation of a pressure instrument.
  • The sanitary cleanliness level is critical. A flush mounted or INLINE SEAL™ sanitary type diaphragm seal avoids dead space and cavities.
  • The media is toxic or hazardous and may pollute the environment. A suitably designed diaphragm seal will provide additional protection.
  • The application requires high overpressure protection. A diaphragm seal with a contoured diaphragm bed can be configured to provide overpressure protection and protection to the instrument.
WIKA diaphragm seal systems are an excellent value and offer savings by:
  • Meeting fugitive emission requirements
  • Extending the service life of the pressure instrument
  • Reducing the cost of installation
  • Reducing or eliminating maintenance costs
If you would like additional information about WIKA Diaphragm Seals or other WIKA Products please contact Forberg Scientific, Inc.
Toll Free: 855-288-5330

Friday, September 16, 2011

Commercial Roof and Gutter De-Icing Nelson Heat Trace

For commercial grade protection against ice dam formation on roofs, gutters and downspouts, look to our selection of cut-to-length, and pre-terminated heating cables. Nelson Heat Trace offer a wide range of choices in terms of voltage, power and construction, including mineral insulated cables that provide exceptional protection of the heating element. Solutions are available for corrosive and hazardous locations, along with all the accessories you need for a simple installation and the controls your customers need to operate the system easily and reliably.

SMMC‐3 Control Panel. This three‐zone control panel allows each snow melting zone to be controlled independently or on a priority mode basis.

SS‐1 Automatic Snow/Ice Melting Controller. This controller senses both moisture and temperature, automatically energizing the heating cable only when snow or ice conditions exist

SLT‐D Downspout Hanger. For use with all versions of Nelson’s SLT and CLT‐JT heating cables. This kit contains material for five complete downspout hangers

SLT‐C Universal Roof Clips. Are for use with all versions of Nelson’s SLT and CLT‐JT heating cables.

SLT‐RC Roof Clips. Are designed to fasten heating cable to most types of roof and gutter materials.

AT-50 Aluminum Foil Tape- may be used to secure the heater cable to the bottom of the gutter. Each roll of tape will accommodate 46M (150’) of gutter. Gutter must be clean for foil tape to adhere properly.

Description SLT Heating Cable:
Nelson Type SLT heating cable is a parallel circuit, self-regulating electric heater. An irradiated crosslinked conductive polymer core is extruded over two multi-stranded, tin-plated, 16-gauge copper buswires. The conductive core material increases or decreases its heat output in response to temperature changes. Three jackets provide extra dielectric strength, moisture resistance, protection from impact or abrasion damage, and flame retardancy. The inner thermoplastic jacket is extruded over and bonded to the core material to prevent moisture penetration and wicking along the core. A waterproof thermoplastic elastomer outer jacket is then extruded over the inner jacket for dielectric protection and additional moisture resistance. A tinned copper braid is installed over the second jacket providing a continuous ground path. A flame retardant, UV stabilized polyolefin overjacket is then extruded over the braid.

If you would like more infomation about Nelson Heat Trace Products please contact Forberg Scientific, Inc.
Email customer service at