Order of carrying out electrowelding works
During the electrowelding works there is the danger of defeat by electric current. Besides, damage of eyes, the surfaces of skin on open parts of the body beams of the electric arc, receiving burns thaws of the melted metal and slag and poisoning with the noxious gases which are emitted at electric welding is possible.
For safety the electric welder has to be provided with special clothes and protective prispoyosobleniye. The special clothes consist of the jacket, trousers, boots with deaf top, mittens and the headdress without hood.
Asyobestovy or tarpaulin oversleeves are necessary for performance of ceiling welding. The respirator is necessary for welding of the non-ferrous metals and alloys containing zinc, copper and lead. The face and eyes protect the guard helmet or the mask. Guard helmet glasses (YEW) or masks have to podyobiratsya on sight of the welder.
To take the necessary security measures when performing electrowelding works, it is necessary to know the device of the most widely applicable at these rayobota of the equipment and equipment and also the instruction for use them.
For arc welding istochyonik of current usually are welding transformayotor or special welding units. Tension of no-load operation of the transformer has to be dostatochyony for emergence of the arch and safe for the person, and after emergence of the arch has to decrease to the znayocheniye corresponding to tension of burning of the arch. At change of length of the arch the size of the welding current should not change considerably, and at short circuits the circuit current should not exceed the working current of welding more than for 20 — 40%.
It is necessary that the welding transformer obesyopechivat the opportunity easily and to smoothly regulate the veliyochina of current and to react quickly to changes of current and tension in the welding arch.
Welding transformers have the transformatoryony and throttle windings placed on different rods of one general core. Between transforyomatorny and throttle parts of the core the third rod - the magnetic shunt is placed. For regulation of the welding current move the magnetic shunt or the podyovizhny part of the throttle half of the core.
Primary winding of welding transformers vyyopolnyat with the rated voltage of 220 and 380 Century. From the power line welding transformatoyora have to be protected by safety locks. The wires bringing current to electrodes have to be flexible, have isolation from the vulcanized rubber, and over it the rubber hose. Naimenyyoshy section of wires on each phase and their protection go to networks of primary voltage of 220 and 380 V according to the power of the welding transyoformator or the unit.
Widely use the automatic devices for shutdown of welding transformers at no-load operation (fig. 1) ensuring safety of work of the electric welder when changing electrodes.
The main eleyoment of the device are two-winding relays P, the contactor To and the boiler transformer T. The contactor has two main contacts and one normally zamknuyoty interlock contact. The main contacts are expected current intensity 50 A. The coil of the two-winding relay consists of two obmotokab icd.
At the opened E1 electrode from E2 welded деталью (the welded part in this case yavyolyatsya by the electrode) the main kontaka of the contactor are opened and therefore the welding transformer отсоединен from network. At the same time vspomoyogatelny voltage of 12 V from secondary winding of the kotelyyony transformer T is attached to electrodes.
At short circuit of electrodes (the beginning of welding) the branch circuit of 12 V via normally zamknuyoty interlock contact of the contactor on obmotkuab the two-winding relay zamyyokatsya. At the same time the anchor is involved and closes the normally opened contact which turns on the contactor's coil K. Kontaktor works and vklyuyochat the welding transformer, welding process begins.
At inclusion of the contactor its normally zamknuyoty interlock contact is disconnected, and obmotkaab the two-winding relay is deenergized. However the two-winding relay remains included as the second quickens obmotkacd the relay, fed from the throttle, streamline by svayorochny current. At disconnection of electrodes (the end of the svaryoka) obmotkacd the relay is deenergized, the contactor disappears and switches-off the welding transformer. The scheme vozvrayoshchatsya in the starting position.
The described device works reliably and at dliyotelny operation gives big economy of the elektroyoenergiya as during change of electrodes or kratyokovremenny breaks in work the welding transforyomator is automatically disconnected.
For welding in the joint, spot and sutural welding widely use stationary connection, dot and sutural machines of electric contact welding at the vtorichyony tension of no-load operation of their transformers not higher than 36 in and alternating-current primary voltage not higher than 500 Century.
In use machines have to keep constancy of current and secondary voltage. Change of these parameters does not exceed for installations of connection and spot welding ±6%, and for installations of sutural welding of ±3%. Heating temperature of separate parts of the machine should not be higher than 75 °. For each machine необходимо to have the separate breaker and safety locks. By the welding machine it is necessary to install the voltmeter.
All parts of the welding machine which are under the peryovichny tension need to be protected ograzhdeyoniy, and it is reliable to ground the body of machines. The floor about the mayoshina should be held dry, to cover with the wooden reyoshetka or the rubber rug.
As defeat by electric current perhaps as directly in the course of welding works, and at connection to network of welding units, constitutes naibolyyoshy danger simultaneous prikosnoveyony one hand to the electrode, and another to the welded subject. In this case the welder will appear under the nayopryazheniye of the secondary circuit of installation where tension fluctuates ranging from 25 up to 90 Century.
The increased danger is constituted also by change of electrodes when the full tension of no-load operation of the transformer (65 — 90 V) is between the electrode and the welded part. At the same time the welder is forced to touch with the hand the electrode or the bared parts the electrode holder who is energized.
Electric current of the welder it is necessary for prevention of defeat that in mobile elektroyosvarochny installations both wires to the transformer and the wire from the transformer to the welding post had the reliable isolation which is regularly checked in eksyopluatation and also sufficient section of wires.
Welding installations can be connected to the general network only by means of operational plug soyediyoneniye and breakers of the closed execution.
The design of the electrode holder has to obespechiyovat reliable clipping and fast change of the electrode. The handle of the electrode holder has to be manufactured from heatresistant, badly carrying out heat and the elektriyochestvo of material. It is forbidden to use electrode holders whose handles have the broken isolation.
It is necessary to consider that change of electrodes proizvoyoditsya in the course of welding quite often - through the promeyozhutka of time calculated for minutes. Increase in the veyoroyatnost of hit under tension aggravates the opasyonost of this operation.
As measure of protection serve the dry tarpaulin mittens protecting the welder at the same time from the burn metalyoly and the radiant energy. In dry normal svarochyony rooms this measure is quite dostatochyony. When welding in metal boilers, rezervuyoar or in especially dangerous rooms where conditions for defeat by current promote it, it is necessary применять other, more reliable measures of protection. One of such measures is application of the safe elektrodoyoderzhatel.
From harmful effects of the electric arc the welder needs to apply guards or fiber masks with protective walls (light filters) to protection of eyes. Besides, from the outer side of zayoshchitny glass it is necessary to place safety ordinary white glass. The guard has to cover the face without gleams in avoidance the popadayoniya in light eyes from the next electric arcs from all directions.
At placement of several welding machines the distance between current carrying parts of adjacent welding machines has to be not less than 1,5 m.
For protection of surrounding people from the oblucheyoniya the place of work of electric welders should be otgorazhiyovat boards or to perform electrowelding works in special cabins.
Drops of the melted metal can ignite clothes and cause body burns. For protection of welders against burns and splashes of metal work needs to be proizvoyodit in tarpaulin mittens and overalls.
On the handle of the guard there is the additional fibroyovy hood (it is easily replaced at its damage), which protects mittens from fire.
At arc welding the dust and gases which are harmfully influencing health of welders are emitted. For the preduyoprezhdeniye of poisonings it is necessary to apply the bezvredyony plastering to electrodes and gumboils at poluavtomayotichesky welding. Welding posts have to be equipped with the supply and exhaust ventilation for removal of dust and gases.
It is necessary to remember that during the works in the boilers and other metal designs having connection with the earth, the welder has to avoid touch to metal designs and to neizolirovanyony current carrying parts of the welding chain. In these conditions the welder is obliged to perform work on rubber mats, in the rubber helmet, galoshes and dielektrichesyoky mittens.
Due to special danger of works the person responsible for their production is obliged to install special observation of work of the electric welder in boilers and similar metal designs and to provide immediate interruption in supply of current on its signal.Top