– Model 2704 vacuum controller
– 2704 expansion i/o
– Advanced features
– Triple independent control loops
– Supports up to 3 vacuum gauges
– Vacuum probe switchover
– High vacuum gauge power up
– Gauge status inputs
– Leak detection
– Roughing pump timeout
– Gauge calibration
– Advanced programmer
– Expandable i/o
– Modbus rtu or profibus-dp communications
|Data Sheet||HA026916 Iss 6 09/2004 (512KB)|
|Glossy Sales Brochure||HA026750 Iss 2 07/2002 (4,317KB)|
|Installation and Operation Handbook||HA026502 Iss 5 10/2004 (2,588KB)|
|Addendum to User Guide||HA026502 Iss 4 06/2003 (583KB)|
|Engineering Handbook||HA026933 Iss 5 09/2004 (7,729KB)|
|OEM Security Engineering Handbook Supplement||HA027482 Iss 1 07/2001 (56KB)|
|Low Voltage Addendum||HA026502 Iss 2 12/2000 (8KB)|
|Vacuum Furnace Controller/Programmer Data Sheet||HA027551 Iss 2 08/2002 (242KB)|
|Vacuum Furnace Handbook Supplement||HA027655 Iss 2 08/2002 (1,867KB)|
|Vacuum Control Handbook Supplement||HA027186 Iss 1 08/2000 (158KB)|
TIBC149 – Downloading 2704 Vacuum Curves (60Kb)
Other Related Pages
Click here to go to the 2704 page.
Complex heat, pressure and vacuum cycles, such as those found in advanced heat treatment furnaces, usually require the use of high specification programmers or PLCs. In such cases the temperature control function alone may be handled using one or more temperature controllers, either in cascade or single loop mode. Sometimes where vacuum bags are used, pressure can also be regulated by the same controller.
However, In addition to separate temperature and pressure control facilities, systems of this type will also usually have a dedicated vacuum control unit, designed and built to traditional standards, adding considerable cost and bulk to the equipment.
The introduction of the 2704 vacuum option has enabled Eurotherm to integrate both the temperature and vacuum control functions into one unit, providing both OEMs and heat treatment specialists with a more economic and compact control solution than they have available at present. Removing the need to buy separate expensive vacuum controllers can reduce the size of a system control PLC, or in some cases remove it completely. Eurotherm claim that the 2704 is the first DIN format temperature controller to offer this feature.
Operationally, the use of a single 2704 in this type application can offer clear advantages in processing efficiency. The unit provides provides a more informative display than more traditional vacuum control units, and in addition provides a smooth switchover function between high and low vacuum levels. This function is not generally available with traditional designs of vacuum controller, a weakness which has been known to cause problems within some heat treatment processes. The 2704 vacuum function is available in two levels:
- The 1-Gauge option (V1) provides an input for a single vacuum gauge, six on/off setpoints, roughing pump timeout, leak detection and a vacuum summary page.
- The 3-Gauge option (V3) provides all the facilities of V1 plus the facility to measure two other gauges.
As part of the V3 option, one of the additional gauge inputs is directed at high vacuum gauges which need to be powered off at low vacuum in order to prevent damage to the sensor. A dedicated gauge switchover software block allows both high and low vacuum gauge inputs to be used for a ‘bumpless’ measurement of the chamber vacuum.
The vacuum function also incorporates a number of vacuum-specific measurement and display options, including displays in scientific notation (range 9.99E-9 to 9.9E+9), a Log10 input option for gauges with logarithmic type responses, storage of process specific sensor linearisation tables, and selection of the programmer mimic as either a main or summary display page.
Of the many techniques that are used to evacuate vacuum chambers, the most common is the use of a diffusion pump, although the cryogenic pump is now growing in popularity. When using a diffusion pump it is necessary to place it between the furnace chamber and a mechanical rotary (roughing) pump. The area between the diffusion pump and the mechanical pump is referred to as the backing chamber.
The mechanical pump reduces the backing chamber pressure to below the maximum intake pressure of the diffusion pump. Only when this low level of pressure is achieved can the diffusion pump start to operate correctly.
In a typical single chamber furnace system, there will be three vacuum gauges: In the main vacuum (or furnace) chamber there will be two gauges, one for low vacuum (pirani gauge>10 -3 mB) and the other for high vacuum (Active Inverted Magnetron AIM) gauge <10 -8 mB. The backing chamber gauge, another Pirani, is treated as a separate input.
The two main chamber gauges will be required to perform an automatic switchover, similar to the way in which thermocouple & pyrometer sensors are required to switch at high temperatures. Both types of vacuum gauge (each of which require a 24vdc power supply) give a 2-10vdc logarithmic output covering separate vacuum ranges. Most common units are calibrated in mB, Torr or Pascals. In order to be able to display high vacuum values to the operator, scientific notation is always used, and this function forms part of the 2704 vacuum option.
In a typical sequence, a plc in conjunction with the vacuum controller will isolate the backing chamber from the furnace and switch on the backing pump. When this chamber reaches a set vacuum, the plc will change its interlocks to enable the diffusion pump to evacuate the furnace. Again when the furnace reaches a set vacuum, the plc will allow the designed temperature profile to begin, while continuing to monitor that the necessary vacuum is being maintained.
The JAVA Applet below enables you to create a configuration string for the Model 2604 and 2604f. Select the options you require from each field from the drop-down list box. Invalid choices are displayed with an error message in the text box at the bottom of the Applet.