1. Purpose
The electrothermal compression plant “EKU-N2” is designed for heating for soldering and heat treatment of assembly units of products under excess pressure.

2. Operating principle
The plant “EKU-N2” is a mechanized high-frequency induction muffle furnace, equipped with loading and unloading device, vacuum system, power source and automatic process control equipment.
The assembly unit is heated by radiation from a thin-walled muffle screen, heated by the energy of the electromagnetic field created by the inductor.
Loading of the assembly unit with technological equipment into the working space of the furnace is carried out by a loading-unloading device.
The rotation of the assembly unit with technological equipment is carried out by the spindle of the loading and unloading device from an adjustable frequency electric drive.
The atmosphere is evacuated from the cavity of the assembly unit through the hollow spindle of the vacuum system of the loading-unloading device.
The compression of the wall and jacket of the assembly unit is achieved by the excess pressure of the inert atmosphere created in the space of the furnace body.
Forced cooling of an assembly unit under excess pressure of an inert atmosphere is achieved by forced circulation of the atmosphere in a closed circuit: furnace working space - heat exchanger - fan unit - furnace working space.

3. Plant construction
The plant “EKU-N2” for soldering and heat treatment of assembly units consists of the following main components and systems:
- Vacuum compression aggregate (VCA);
- Loading and unloading device;
- Vacuum system;
- Water-cooling system;
- Hydraulic drive station;
- Gas filling cabinet;
- Control cabinet;
- Thyristor frequency converter TPCHT-250.

3.1 Vacuum compression aggregate VCA
VCA consists of a water-cooled housing, lid, inductor, magnetic cores, heat exchanger, fan unit, elbow, pipeline, control and safety device, manifold, seal and bayonet lock.
The inductor is three-section, water-cooled, the current leads of which come out through the flange holes of the rear housing.
The inductor is installed on the three lower magnetic cores. Electrical insulation (fiberglass) lais between the inductor and the magnetic circuits.
The purpose of the magnetic cores is to protect the compression housing from the influence of the magnetic field created by the inductor.
Shell and tube heat exchanger, cooled. Vane-type thermal dampers are installed in the central flanges of the heat exchanger, opening under the pressure of the circulating gas atmosphere in a closed loop. The purpose of the dampers is to reduce heat losses during natural convection of the gas atmosphere.
The heat exchanger is connected to the furnace body and the fan unit via a water-cooled pipeline and elbow.
A control and safety device is installed on the furnace body. Functions of the control and safety device:
- impossibility of opening the bayonet lock when the excess pressure in the housing exceeds 0.003 MPa;
- preventing the supply of compressed gas to the chamber seal when the lid is open.
The manifold is installed on the furnace body and connected to the gas filling cabinet to supply an inert atmosphere. The manifold is equipped with: a pressure and vacuum gauge, a valve for emergency pressure relief with a manual drive, a safety valve and a control valve for relieving excess pressure in case of deviation from the technical parameters. The manifold is connected by piping to a pressure transducer and an inflatable seal.
The drain valve (pressure relief) is installed in the upper part of the housing. The shut-off valve prevents the penetration of an inert atmosphere into the vacuum system when there is excess pressure in the working chamber.
The working space of the VCA is thermally insulated with lightweight fireclay.

3.2 Loading/unloading device
The loading and unloading device is a self-propelled unit that provides the following operations during the technological process:
- loading and unloading of the assembly unit with technological equipment from the furnace space;
- rotation of the assembly unit with technological equipment relative to the horizontal axis;
- vacuuming the cavity of the assembly unit;
- checking the assembly unit for leaks;
- creation of local excess pressure when heating the assembly unit.
The supporting structure of the loading and unloading device is a drive frame moving along a rail track by means of an electromechanical drive. Mobile vacuum pumps are attached to the side of the frame

3.3 Vacuum system
The vacuum system is designed for preliminary evacuation of the volume of the compression housing before filling it with an inert atmosphere.
The vacuum system includes:
- plunger and two-rotor vacuum pumps;
- emergency valve;
- vacuum valve with electromechanical drive DN100;
- emergency inlet with electromagnetic drive Du10;
- filter;
- pipelines.

3.4 Water-cooling system
The water-cooling system is flow-through, from the workshop water cooling system, and consists of two manifolds, valves for regulating water flow, a flow switch and pipelines.
Both collectors have a pressure and open drain line.

3.5 Hydraulic drive station
The hydraulic drive station activates the hydraulic cylinders of the bayonet lock.
The hydraulic drive station is turned on and off from the control panel.

3.6 Gas filling cabinet
The gas filling cabinet supplies an inert atmosphere to the volume of the housing, as well as compressed air to the seal and pneumatic cylinder of the control and safety device.
The gas filling cabinet consists of a frame, rear doors, front panel and front doors.
There are units inside the cabinet:
- reduction gearbox;
- safety valves;
- electromagnetic valves;
- check valve;
- air release valve.
There are pressure measuring tools and handwheels for shut-off and control equipment on the front panel of the cabinet.

3.7 Control cabinet
The control cabinet provides:
- carrying out the technological process in an automated mode under program;
- an opportunity to complete the technological process manually when the automatic control system failure.
The design of the cabinet is similar to that of the gas filling cabinet and consists of a frame, rear doors, front panel and front doors. The cabinet can be serviced through the front and rear doors.
There are plant controls, a mnemonic diagram, tools for monitoring electrical parameters, vacuum parameters on the front panel of the cabinet as well as an industrial computer.
PLC controller, relay blocks, circuit breakers, buzzer and other electrical equipment, together representing a control system for the electrothermal unit placed on the frame with electrical equipment.
The control system (CS) of the plant ensures that the requirements of the technological process are met in terms of heating rate, holding at certain temperatures, cooling rate, and the parameters of excess pressure in the installation casing and in the assembly unit. The control system based on modern computer technology.
The control system organizes the interface with the operator-technologist; serial-parallel control of the mechanisms of the vacuum system, software control of the heating process, identification of the state of the technological system, documentation of the technological process and dispatching of the above tasks.
The operation of the system at the lower level is controlled by a certified Direct Logic network controller. The operation of the system at the top level is controlled from a personal computer.
The control system ensures operation of the unit in the following modes:
- "Manual control"
- “Automated” (the control cycle includes operations from the moment the unit lid is closed until the housing is depressurized after the end of the technological process)
In the “Manual control” mode provides: setup and service operations.
An industrial personal computer provides the services necessary for work:
- multi-window ergonomic user interface with color graphics;
- effective system support for all application processes, the use of modern software products developed for the MSWindows operating environment;
- recording a report on the progress of the technological process; the report file can be called up on the monitor for visual analysis and printed in digital and graphical form (protocol) for inclusion in the accompanying documentation.

The protocol of the completed soldering and heat treatment process contains the following information:
- designation of the soldered assembly unit (AS);
- date of soldering;
- ambient temperature;
- soldering temperature;
- current time;
- thermocouple readings;
- pressure of protective gas in the cavity of the housing (furnace);
- shielding gas pressure in the internal cavity of the SB;
- vacuum in the SB soldering cavity;
- Full name of the operator.

The control system has a light alarm indicating deviations in the technological process:
- violation of water cooling;
- break of thermocouples;
- other deviations from the normal operation of the unit.
To ensure safe operation of the unit and operating personnel, and to prevent incorrect operator actions, the necessary locks have been installed.

3.8 Thyristor frequency converter
Thyristor frequency converter type “TPCHT-250” is designed for autonomous operation as a module in power systems for induction furnaces. Three units are installed in the plant.