This report summarizes the technical manual of plasma torch and anodic inoculation prototype developed by TECNALIA at FLEXICAST project.
The plasma (and anodic inoculation) torch is a heating system designed for cast iron casting units. This system, based on high power thermal plasma technology, consists of to take advantage of the heat of a plasma arc that occurs as a consequence of the ionization of a plasmagen gas between a graphite electrode (cathode) and the iron bath, electrically connected to another electrode (anode). The current goes through the gas ionizing it, being able to reach high temperatures in the cathode tip. The plasma arc is achieved by generating a potential difference between the two electrodes, so as to produce a chain reaction that ionizes the plasmagen gas, giving rise to the plasma arc. The necessary basic equipment is constituted by an electrical part (power supply equipment) and on the other hand a mechanical part (which allows movements of the electrode system). The refrigeration system, the plasmagen gas and the power control and regulation elements are also provided.
Optimum heat transfer is achieved by adjusting the electrical equipment which provides the desired power according to a series of parameters, the temperature setpoint and the measured temperature.
The heating of the metal by the plasma arc occurs in different ways:
- By radiation (which is derived from the plasma itself and the refractories).
- By heat transfer at the plasma / metal boundary (by convection and by
This system is a prototype not covered by CE marking, so only can be operated by authorized technicians of TECNALIA on controlled environments and situations. Specific human health and safety assessment of the implementation of the prototype into the casting unit is insistently recommended before operating the system in any industrial environment.
As all electrical equipment, only authorized personnel with electric systems knowledge and skills can operate at the prototype. Never operate the system without safety guard.
The information, diagrams and images that have been provided at this document are the property of TECNALIA. Its sole function is to facilitate the use and the maintenance of the material that has been developed by TECNALIA. This information should not be disclosed to third parties without prior written agreement of TECNALIA. It is forbidden any use or reproduction of the content of this documentation for purposes other than that related to the use of the material developed by TECNALIA in the Project. In case of non-compliance, appropriate legal actions may be taken.
Followed, some safety issues related to potential electrical risks.
2. General Electric Safety Aspects
Electrical Safety Rules: A safe work environment is not always enough to control all potential electrical hazards. You must be very cautious and work safely. Safety rules help you control your and others risk of injury or death from workplace hazards. If you are working on electrical circuits or with electrical tools and equipment, you should follow these safety rules:
Rule 1: Avoid contact with energized electrical circuits and treat all electrical devices as if they are live or energized.
Rule 2: Follow proper lock out/tag out procedures. Disconnect the power source before servicing or repairing electrical equipment and de-energize open experimental circuits and equipment left unattended.
Rule 3: Be sure your surroundings are dry, use matting and avoid wearing loose clothing. Always wear the correct PPE: rubber insulating gloves, hoods, sleeves, insulated shoes, industrial protective helmets, and use tools/equipment with non-conducting handles.
Rule 4: If safe, follow the one-hand rule keeping the other hand away from all conductive material to avoid making a complete circuit resulting in current passing through the chest cavity.
Rule 5: If water or chemicals are spilled onto the equipment, shut off power at the main switch or circuit breaker and unplug the equipment. Avoid placing or using equipment in high condensation (i.e. refrigeration) areas.
Rule 6: If an individual comes in contact with a live electrical conductor, do not touch the equipment, cord or person. Disconnect the power source from the circuit breaker or pull out the plug using a leather belt.
Rule 7: Enclose all contacts and equipment, short circuit capacitors before working. Do not rely on grounding to mask a defective circuit, or attempt to correct a fault by insertion of another or larger fuse/breaker.
Rule 8: When it is necessary to touch electrical equipment (for example, when checking for overheated motors), use the back of the hand. Thus, if accidental shock were to cause muscular contraction, you would not “freeze” to the conductor.
Rule 9: Do not store highly flammable liquids near electrical equipment.
Rule 10: Be aware interlocks on equipment disconnect the high voltage source when a cabinet door is open but power for control circuits may remain on.
Burn Hazards Associated With Electricity
Human skin provides great protection from normal elements; however human skin provides poor protection from extreme heat which is a byproduct of exposure to electricity. Typically there exist three types of burns:
- Electrical burns happen when electric current flows through tissues and organs.
- Arc burns result from high temperatures (up to 35,000 F) when an arc flash event occurs.
- Thermal burns typically happen when skin touches a hot surface
Definition of “Arc Flash”
Simply put, an arc flash is a phenomenon where a flashover of electric current leaves its intended path and travels through the air from one conductor to another, or to ground. The results are often violent and when a human is in close proximity to the arc flash, serious injury and even death can occur. Working with plasma jets these kind of risks have to be taken into account.
Arc flash can be caused by many things including:
- Dropping tools
- Accidental touching
- Material failure
- Faulty Installation
Three factors determine the severity of an arc flash injury:
- Proximity of the worker to the hazard
- Time for circuit to break
Because of the violent nature of an arc flash exposure when an employee is injured, the injury is serious – even resulting in death. It’s not uncommon for an injured employee to never regain their past quality of life.
Typical Results from an Arc Flash
- Burns (Non FR clothing can burn onto skin)
- Fire (could spread rapidly through building)
- Flying objects (often molten metal)
- Blast pressure (upwards of 2,000 lbs. / sq.ft)
- Sound Blast (noise can reach 140 dB – loud as a gun)
- Heat (upwards of 35,000 degrees F)
Approach / Protection Boundaries
The National Fire Protection Association (NFPA) has developed specific approach boundaries designed to protect employees while working on or near energized equipment. These boundaries are:
- Flash Protection Boundary (outer boundary)
- Limited Approach
- Restricted Approach
- Prohibited Approach (inner boundary)
Flash Protection Boundary (outer boundary): The flash boundary is the farthest established boundary from the energy source. If an arc flash occurred, this boundary is where an employee would be exposed to a curable second degree burn (1.2 calories/cm2).
Limited Approach: An approach limit at a distance from an exposed live part where a shock hazard exists.
Restricted Approach: An approach limit at a distance from an exposed live part which there is an increased risk of shock.
Prohibited Approach (inner boundary): A distance from an exposed part which is considered the same as making contact with the live part.
This distance is not common between equipment. Some equipment will have a greater flash protection boundary while other equipment will have a lesser boundary.
How to Determine the Approach Boundaries
Since different equipment will have different approach boundaries, calculations must be made on each piece of equipment. There exists a number of ways to establish these boundaries and the method you select depends on personal preference, resources available and quality desired.
Here are a few of the methods available:
Since you’re referring to established tables, this method is the easiest and quickest however it provides the least amount of accuracy.
Formula Method: NFPA 70 E and IEEE Standard 1584 provides formulas that can be used to accurately determine the approach boundaries. This method is time consuming, requires an engineer level of expertise and is subject to human error.
Approach Calculator: IEEE has provided a spreadsheet based calculator to assist in determining approach boundaries. Although this calculator does help expedite the calculations, detailed information about the equipment and circuit is still required and this often necessitates the use of an electrical engineer.
Nature of Electrical Accidents
Electrical incidents are caused by many different events; however we can identify three common root causes for just about any electrical incident:
- Working on unsafe equipment and installations;
- Unsafe Environment (i.e. wet environment / presence of flammable vapors); and
- Unsafe work performance
Ways to Protect the Workers
There exists a number of ways to protect workers from the threat of electrical hazards. Some of the methods are for the protection of qualified employees doing work on electrical circuit and other methods are geared towards nonqualified employees who work nearby energized equipment.
Additionally, the use of alerting techniques are effective ways to warn employees (especially non-qualified) of the dangers present. Alerting techniques might include safety signs, safety symbols, or accident prevention tags. Often times, the use of such signs alone is not adequate as an employee (especially a non-qualified employee) may accidentally come in direct contact with an energized circuit. In these instances a barricade shall be used in conjunction with safety signs.
A barricade is an effective way to prevent or limit employee access to work areas exposing employees to uninsulated energized conductors or circuit parts. Conductive barricades may not be used where they might cause an electrical contact hazard. If signs and barricades do not provide sufficient warning and protection from electrical hazards, an attendant shall be stationed to warn and protect employees.
What if we Can’t Deenergize the Equipment
OSHA requires that live electrical parts be deenergized before the employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. OSHA has also made allowances for not deenreergizing electrical equipment when it would increase current hazards or create additional hazards, including such times as:
- interruption of life support equipment,
- deactivation of emergency alarm systems,
- shutdown of hazardous location ventilation equipment,
- removal of illumination for an area.
Lockout and Tagout
Because a deenergized circuit can easily be energized while an employee is working on it, the circuits energizing the parts shall be locked out or tagged or both. Electric equipment that have been deenergized but have not been locked out or tagged shall be treated as energized parts. The employer must develop and maintain a written copy of the lockout / tagout procedures and make it available to employees. Only qualified persons may work on electric circuit parts or equipment that have not been deenergized. Such persons shall be capable of working safely on energized circuits and shall be familiar with the proper use of special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools.
If You Must Work on Energized Circuits
If it has been determined that deenergizing a circuit is not feasible and the employee must work “hot”, the employer shall develop and enforce safety-related work practices to prevent electric shock or other injuries resulting from either direct or indirect electrical contacts.
The specific safety-related work practices shall be consistent with the nature and extent of the associated electrical hazards. These safety related work practices could include:
- Energized Electrical Work Permit
- Personal Protective Equipment
- Insulated Tools
- Written Safety Program
Who is a Qualified Worker
In an effort to limit electrical injuries in the workplace is compulsory that only are allowed a “Qualified” person to work on or around energized circuits or equipment.
Qualified person: One who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved.
Personal Protective Equipment:
Personal Protective Equipment is an integral part of any employer’s safety program. OSHA has determined that PPE although a good way to protect employees, should be used as a last line of defense and its important to understand the limitations of PPE in the workplace.
Prior to using PPE, the employer must determine if other mans of protection are available. OSHA uses the following sequence for employee protection:
- Engineering Controls (deals with equipment)
- Administrative Controls (deals with people or processes)
- Personal Protective Controls (deals with what you wear)
If no other method is available to protect employees, then PPE is an acceptable method. For those employees working in areas where there are potential electrical hazards, they must be provided with (and must use) electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed.
Main sources of this section: WPSAC and UC Electric Portal according to OHSA. For further information visit www.wpsac.org.
3. HPTP Plasma Torch and Anodic Inoculation System Description
The HPTP system is composed by:
- One electrodes support that controls the position of each electrode in relation to the metal bath. It includes for each electrode:
- An electric servoactuator (minimum stroke 500 mm and speed 50 mm/sg).
- A fastener made in copper where the graphite electrode is fitted. This fastener also receives all the fluids supplying the electrode, electricity, nitrogen as well as cooling water from the power cable.
- A grid surrounding the unit ensures the protection of the operator.
- Main held support of the unit for easy dissembling using the crane.
- Two electrodes (anode and cathode) made of graphite. The cathode is bored over all its length with a hole allowing the passage of the nitrogen. These two electrodes are consumable parts that the customer can find on the foundry supplier markets.
- An insulated cover against heat radiations to be positioned on the melting chamber. This cover has to be equipped with refractory materials. It is pierced with two holes of 60 mm for the passage of the electrodes. The cover weight is roughly 250 Kg and must be manipulated with a crane just in case any other movement system is not installed.
- Two junction boxes mounted onto a fixed support to the car, on the same side as the electrode holders. One junction box interconnects the power cables water cooled, the second one interconnects the other signals and the inlet of nitrogen.
- Two power cables being able to lead a DC current of 500 A, water cooled. These cables circulate from the electrodes holder onto the ladle to the junction boxes on the car. The wiring and the assembly is oversized for the possibility of employing one power cabinet to a maximum of 80 kVA.
- A set of power cables with appropriate section for DC currents to be installed between the junction box and on the power cabinet.
- Power cabinet, to deliver the electrical energy to the electrodes. Its characteristics are:
- Maximum total current 500 A.
- Voltage: 10 to 160 Vdc.
- Supply: 400 Vac (3 phases without neutral, 80 kVA).
- Working ambient temperature: 40ºC, relative humidity without condensation 85%.
- Cooled with forced ventilation of 2000 m3/hr. Equipped with particle filters.
- Weight: 300 Kg.
- An electrical cabinet equipped with a standard PLC Omron CJ Series and the software to control the system.
- A HMI screen equipped with supervision software of the installation associated with a data acquisition system. This system ensures the control and the monitoring of the arc plasma source.
- A control panel receiving the buttons and lights to pilot the installation by the operator furnace, including:
- Move up and down for each electrode.
- Emergency stop.
- Lights to indicate that the arc plasma system is powered on or off.
Plasma Torch Actuator: Plasma torch is equipped with two servoactuator which allow an accuracy better than 0,1mm for electrode movement.
Selected power rectifier has following characteristics:
- V: 400 V AC (-10/+15%) + G.
- F: 50/60 Hz.
- I: 128 A rmc.
- Power: 88,9 kVA.
- Power Factor: 0,96.
- Standard Circuit Breaker and Protections.
Supplies required for plasma furnace operation at end user facilities are:
- 1. Power Supply and Rectifier:
- i. V: 400 V AC (-10/+15%) + G.
- ii. F: 50/60 Hz. I: 128 A rmc. Power: 88,9 kVA.
- iii. Weight: 240 Kg.
- iv. Dimensions: 600x600x1400 mm.
- v. “Clean” and “cold” Environment. Air forced cooling.
- Nitrogen: 99,5%. Purity (lower values suitable).Q: 5-40 l/min.
- Cooling Water: Q: 5-40 l/min. Quality: Industrial. Maximum Working Temp.: 50 ºC.
- Compressed Air: Industrial. 6 bar.
Anodic Inoculation system is extremely linked to HPTP plasma heating device. In fact anodic inoculation is produced in any case using plasma torch heating combined with submerged graphite electrode as anode in contact with the molten metal. But to obtain maximum inoculation effect using this technology needs development of specific control of the torch and, above all, of the anode electrode position and performance. There are three key parameters which determine the Anodic Inoculation process.
Heating Mode (TC): According to this parameter the plasma equipment works without effective heating (or minimum heating), standard heating electric parameter table, or anodic inoculation specific parameter table, which is higher intensity developed control curve. Direct measurement of the effect of this parameter over Anodic Inoculation technology is related to the fact that higher electric intensities produce major anodic inoculation effect.
Inoculant Power (PI): This parameter represents the medium length of electrode (anode) material submerged at molten metal in operation. At previous WP2 tasks submerged length of approx. 50 mm was set as standard, and 80 mm as optimal length. So high PI should be approx. 50% higher than standard and minimum or low PI should be 50% lower. The standard value can be adapted on demand at torch control. Direct measurement over effect of this parameter is related to the fact that higher length of electrode submerged represents higher contact surface between electrode and molten metal and so, higher crystalline graphite particle interchange surface (improved anodic inoculation).
Inoculant Degree (GI): One of the innovations of this stage of the project is the effect of moving up and down the anode electrode without taking it out from the molten metal. At standard configuration of the torch the anode is static, with high GI the electrode moves at 5 mm/s speed and with very high GI at 10 mm/s speed. Direct measurement over effect of this parameter is related to the fact that the movement accelerates the dissolution of crystalline graphite particles in the molten metal, improving the anodic inoculation effect.
Combination of these three parameters give us the value of the AIR (Anodic Inoculation Ratio), which is maximum when heating stage is using Anodic Inoculation electric parameter table, Inoculant Power is high (maximum deep penetration of the submerged anode in the molten metal) and the Inoculant Degree is very high, which means that the anode is moving up and down at maximum speed, always inside de molten metal, in order to increase dissolution process of the electrode.
Anodic Inoculation Ratio
|Medium||Standard||Standard||Normal / High|
|High||Anodic Inoculation||High||Very High|
Fig.5.- This table summarizes the AIR values related to the three key parameters (Heating Mode, Inoculant Power and Inoculant Degree).
The intelligent control of the torch, specifically developed for this application, will make possible the balance between both, heating and inoculation processes.
As described before, main differences between a standard HPTP plasma torch and Anodic Inoculation HPTP Plasma Torch are based on the capabilities of heating mode and anode operation performance. In order to control these aspects specific sheets or screens have been developed at control system.
4. Torch Assembly for Starting-up
- A first position, called work, is located in the furnace, where it is fixed in a specific base that guarantees an approximate positioning of the torch with respect to the lid located in the bathtub.
- A second position, called maintenance, is located on the platform together and allows to carry out an early maintenance of the system or leave it free access to the furnace for maintenance operations.
The displacement of the torch from one position to the other is carried out by raising it carefully with the crane of the bridge. During these operations of displacement it is necessary to pay attention to the cables that permanently connect the torch to the rest of the installation. Once the torch in its working position, it is necessary to verify the correct placement of the electrodes with their respective holes in the cover of the bath. If the alignment is incorrect, try:
- Either repositioning the torch chassis before fixing it.
- Either adjusting the position of the electrode holder arm using available screws under each of them (not recommended). Side adjustment and angle adjustment of each arm. Attach the torch chassis to the platform once the working position is found. Check the condition of the electrodes. If necessary, replace or adjust your positions by means of the handle screw elements of the clamps to optimize the useful length before that another adjustment operation of its position is necessary. Install the cap on the cathode that allows nitrogen feed and check the conduit connection.
The start of the torch requires that the protective cap is in position in the vessel, with refractory caps, gaskets and nitrogen supply if necessary. The steps to follow are:
- Check the cleaning of the plasma cap ducts and clean them if necessary.
- Place the refractory brick in front of the plasma chamber.
- Place a refractory cap or high temperature gasket in each hole.
- Put an insulating gasket in each refractory bushing.
- Place the nitrogen input on the assembly (if necessary).
- Insert the torch and connect the nitrogen supply to the lid.
- Verify the correct alignment of the electrodes with the lid inlets and lowering them manually.
- If this operation is not possible, check the correct align of the torch in the oven and correct if necessary. If this continues being insufficient, adjust the position of the arms (see section 4.1). Also, seizing the holes in the lid may cause similar effect.
- Use the electrodes in the required working stroke.
- Then proceed to clean the ducts. Check chimney flue and, if necessary, clean it to ensure the evacuation of fumes can take place correctly.
- Place the chimney (if necessary). The plasma is operative and can be started.
- The reset blue button on the control panel on; The system is ready to work (mode which allows manipulation of the electrodes and rectifiers).
- The two emergency buttons on the torch panel and control panel must be raised to allow commissioning of the installation.
The inverters are switched on (Var. Cathode, var. Anode, var. Pyrometer), provided that the conditions required. When maintenance mode is not activated, manual guidance
of the electrodes is only possible if the torch is in manual mode. Maintenance operators should be careful of the executed movements.
- Pressing of the “RUN” button (green) (either from the control panel, or from the torch panel) puts the rectifiers on if the water cooling of the two electrodes is active and that the
electrode protection door is closed. This pulse must be maintained during start-up of the rectifiers feed, time corresponding to the operation of the acoustic indicator, which warns people that there will be voltage at the electrodes. The [Command] screen on the control allows to check the operating status of different main elements, and the [Conditions] screen allows you to quickly diagnose conditions which may not occur at that time, as well as the different stages for the laying in running the torch. If all conditions are met to authorize then the facility is declared ready to operate at the operator screen.
4.4. Power Supply Disconnection
When the installation is on, simply press the stop button once to stop the power rectifiers. If the button is held down for 2 seconds or more, the system stops completely (rectifiers, drives, translation).
4.5. Emergency Stop
Pressing one of the emergency buttons instantly stops all movements, as well as rectifiers. The installation is stopped. To return to start the installation, first you need to make sure that it is possible doing it without risk to people. You must then unlock the emergency has been triggered, restart the system with reset blue button, and then start up as indicated in the section Power Supply Connection.
When the power is switched on and the control panel restarts, the electrodes have to be indexed rising them with the indexing option of the main screen, then ascend completely at low speed and are initialized
In the +10 mm position. As long as this initialization is not done, it is not possible any movement, neither manual nor automatic. This initialization only takes place when putting the cabinet on voltage or at the request of the operator from the maintenance screen. This screen also allows you to adjust the different parameters of the configuration of the cylinders.
Once initialization is done, it is possible to perform manual or automatic movements from the torch panel at any time. In automatic power control mode or automatic temperature control, the electrodes are controlled by the regulators depending on the system configuration. It is possible to perform manual actions but the regulatory conditions will change.
The automatic starting up phase starts automatically when the operator presses one of the two buttons of automatic control of power or temperature and both electrodes should be correctly placed in the vessel. During the automatic starting up phase, the torch executes a predetermined sequence destined to create the plasma jet. It must first be verified that the electrodes are correctly aligned with the holes in the lid causing them to come in and out without difficulty by manually controlling from the installed panel.
Automatic Power Control Mode:
The classic mode of operation for the use of the torch is the automatic control mode of input power at plasma torch, which involves the activation of the automatic power control mode. In this case, the power is not set as a function of the temperature measured by the pyrometer, but as a constant over the time with the operator supervision. There are two automatic power modes, one with maintenance power (selected by administrator of the system) and the second one with power adjustable from screen from 1 kW to 80 kW. The power regulation determines the voltage. Physically, the cathode is mobile and is the control of its position which makes the voltage vary and allows maintaining the power constant.
Temperature Control Power Mode:
This mode is activated by pressing one of the «Auto temperature» buttons at operating screens. If this mode is active, the corresponding indicator lights up. The stop is done either at request of the operator by pressing the buttons of other modes, or by failure of the installation. In automatic temperature control mode, the first control loop remains active of the power, but a second control loop is activated which, this time, determines the power setpoint as a function of the measured temperature. Then, the installation permanently set its power setpoint so that the temperature of the is maintained at the desired setpoint value.
5. Control Panel
Plasma torch and anodic inoculation system is equipped with control touch panel (OP) which allows online configuration, data gathering and view of system main parameter.
5.1. Start Screen
When the control panel is started, the next start page is displayed. From this screen, you can access the general overview of the installation and the maintenance, consult the event log messages or open the operating system installed at touch screen. At this screen selection of different working positions is possible.
5.2 Screen organization
Switching from one screen to the other is done using the navigation buttons visible in the bottom of each screen. The organization chart allows the organization of the control panel displays. The screens are grouped into two large families:
- Operational part.
- Maintenance part.
Both are accessible from the synoptic screen on the home page. All screens of each family can be accessed directly from the menu below. To switch from one family to another, you need to return to the start window (key Start, “Home”, top left). All values that can be modified are written in blue characters, pressing the numeric value to display the following window. To introduce the new desired value must pay attention to the indicated minimum and maximum limits above the image and validate.
5.3 Event Screen
A certain number of events are recorded in the historic of the touch screen (OP).
This event log is available from the main working screen. The “Reset” button allows reset the message list.
5.4 Plasma Torch Operating Screens
Plasma torch operating main screen presents visual values of main parameters of the equipment and provides direct access to different control and configuration screens. Direct information about electric supply (power, voltage and intensity), selected power mode, selected anodic inoculation mode, electrode position and evolution, system general status, instant molten metal bath temperature and average of last cast molds.
Auxiliary systems are available from “Aux Gas” button in the bottom left of the screen. Main parameter values are storage for further assessment in a continuous way at .csv format files.
Anodic Inoculation System:
Anodic inoculation system is available from “Inoculacion” button on the bottom left of the screen. In an easy mode different parameters can be selected on demand as shown in images below.
Maintenance and Others:
There are two main screens related to the maintenance, system status and setting of main parameters of the system. Main parameter configuration screen is selected from second level, and it is mainly focused for administration role. At main screen, in the bottom left side, “System Status” and “Com Status” buttons provide access to information about the system and the communication status among different parts of the device.
6. Maintenance and prevention actions
Operational operations and electrical and mechanical maintenance must be executed by qualified persons.
ATTENTION! RISK OF BLINDNESS:
If there is a failure of the insulation in the cover, there is a very high risk of propagation of UV light that can cause irreversible damage to the eyes. Check the condition of the cover regularly (several times a day). Said lid is subjected to intense thermal contrasts, and can become red hot and punctured
It is also necessary to pay attention to the seals that ensure the tightness of the lid with the bottom bracket. In case there is no watertightness in the chamber, leaving the operator exposed to the arc, it is necessary to suspend immediately the operation of the plasma torch and correct the problem before restarting the system.
ATTENTION! BURNS RISK:
When the torch is in operation, certain parts of the installation rise to elevated temperatures (electrodes, tweezers, nitrogen cap, cover, chimney, etc.) and can only be manipulated with the aid of protection (insulation face shield, gloves, safety footwear, etc.). Attention must also be given to the high temperatures of the gases from the holes of electrodes when the torch is not in
position. Regularly check and clean the flue gas evacuation chimney. Cover (adjust the frequency of the controls according to the speed with which they are produces sticking, which may vary depending on the metallurgical composition of the casting). This chimney seizes, and can end up being clogged, which favors the undesired rise of the gases from the electrodes holes.
ATTENTION! RISK OF HANDLING:
During the movements of the equipment between their positions of maintenance and work, it is necessary to pay attention to the risk of shock / interference / obstacles that may occur along the way (people, clothing, bulky objects, etc.). In the maintenance phases, it is important that there are no elements of obstruction in the casting platform and limiting the number of personnel in the latter. For all maintenance stages in the torch is preferably to work in maintenance stage.
ATTENTION! RISK OF ELECTRIC SHOCK:
For any intervention that takes place in conductive components of the installation, it is mandatory to place and stop the installation through the operator control panel. Maintenance operations shall be distinguished from normal (replacement or modification of the position of the electrodes) operations in the electrical circuit from rectifiers to the electrodes. In the second case, it is also necessary to cut and block the rectifier through their respective general switch. In case of maintenance operations on the
rectifier, ensure the electrical installation in the front of the process according to the professional rules of action. The plasma torch has been designed to withstand a severe industrial environment and work on it, however it is necessary to inspect the installation regularly, in particular if it has been subjected to an unforeseen event (mechanical shock, for example) that may have caused the deterioration, so we recommend to inspect regularly:
- The electrical circuit: state of cables (in particular the parts subject to torsions and frequent contacts), clamps and fittings, check the tightening of the terminals in the polarity box and at the rectifier output, clean the cabinet and rectifier (in particular the filters of the latter).
- Cooling circuit: Check for cleaning and, if necessary, clean water circuit. Check that the flow rate is sufficient and check the tightness of the different splicing points.
- The nitrogen injection circuit: Check the pipes and fittings as well such as the correct operation of the injection control.
- Mechanically: check the unimpeded movement of the torch between their working and maintenance positions, as well as the movement of the two electrode arms throughout their entire career. Never operate the torch without safety grid.