At present, the rise of domestic brands has brought confidence and benefits to the people of the country, and in the field of domestic equipment, detection instruments such as automatic nitrogen determination instruments have also started a lot of domestic production, but even though the domestic automatic nitrogen determination instrument is a fast, Low-cost instruments for testing nitrogen content and protein content are widely used in food, beverage, soil, feed, food and other fields. However, the market acceptance is still low, and many companies will still use the imported automatic nitrogen analyzer at a higher price. In summary, the main reason is that the inherent quality of domestic automatic nitrogen determination instruments is not high. After several years of use, there are often many problems and the reliability of users is reduced. Therefore, to revitalize domestic equipment brands, it is necessary to first Starting from the quality of homemade automatic nitrogen determination instruments, it is becoming more and more important to improve the intrinsic quality of automatic nitrogen determination instruments.
Due to the harsh environment in which the automatic nitrogen determination instrument is used, negative pressure is generated by the corrosive body such as concentrated sulfuric acid, boric acid, sodium hydroxide and heating. This has very high requirements for the intrinsic quality of the automatic nitrogen determination instrument. Therefore, to extend the service life of the automatic nitrogen determination instrument and improve the stability and accuracy of the instrument, it is necessary not only to start with the spare parts materials but also to use the instrument for a long time. The materials used, through a large number of tests to ensure the material off, but also in the production process for excellence, through the development of strict inspection standards, starting from the details, pay attention to every detail, to ensure that the qualified equipment to the user's laboratory.
Nowadays, the intrinsic quality of automatic determination instruments and other instrumental products is increasingly valued by domestic companies. Therefore, on this basis, through the rational design of products, the selection of high-quality materials, strict production processes, and meticulous product inspections, it has greatly improved. The quality of the domestically-made fully automatic nitrogen determination instrument is increasing compared with that of the users of the domestically-made automatic nitrogen determination instrument. Topcon Yunnong, a professional enterprise dedicated to the research and development and production of agricultural instruments, has always been a customer. The greatest degree of satisfaction for the purpose, through efforts to improve product quality, improve after-sales service, etc. to provide users with high quality and cost-effective instruments, subject to many users.
The clamp with earth cable is used to make the electrical connection between the power source and the base material to be welded. The section and length of the cable are determined by the maximum current from the power source.
What does Grounding have to do with Arc Welding Safety
?
Grounding of electrical circuits is a safety practice that is documented in various codes and standards. A typical arc welding setup may consist of several electrical circuits. Applying and maintaining proper grounding methods within the welding area is important to promote electrical safety in the workplace. Associated processes such as plasma cutting will also benefit from proper grounding. The important grounding topics in a typical welding environment are discussed.
Grounding and Arc Welding Safety
Welding Machine Ground
Welding Machines that utilize a flexible cord and plug arrangement or those that are permanently wired into an electrical supply system contain a grounding conductor. The grounding conductor connects the metal enclosure of the welding machine to ground. If we could trace the grounding wire back through the electrical power distribution system we would find that it is connected to earth, and usually through a metal rod driven into the earth.
Grounding and Arc Welding Safety
The purpose of connecting the equipment enclosure to ground is to ensure that the metal enclosure of the welding machine and ground is at the same potential. When they are at the same potential, a person will not experience an electrical shock when touching the two points. Grounding the enclosure also limits the voltage on the enclosure in the event that insulation should fail within the equipment.
The current carrying capability of the grounding conductor is coordinated with the overcurrent device of the electrical supply system. The coordination of ampacity allows the grounding conductor to remain intact even if there is an electrical fault within the welding machine.
Some welding machines may have a double insulated design. In this case, a grounding conductor connection is not required. This type of welding machine relies on extra insulation to protect the user from shock. When double insulation is present it is identified by a "box within a box" symbol on the rating plate.
Grounding and Arc Welding Safety
For small welding machines that utilize a plug on the end of a power cord, the grounding conductor connection is made automatically when the welding machine is plugged into the receptacle. The grounding pin of the plug makes a connection within the receptacle. The use of adapters that effectively remove the grounding pin connection at the plug is not recommended. Furthermore, do not cut off or remove the grounding pin from the plug. All safety benefit of the grounding conductor is lost without the connection.
Grounding and Arc Welding Safety
Receptacle circuit testers will easily check the continuity of the grounding conductor. Receptacle circuit testers for 120-volt circuits are available at electrical supply or hardware stores; these inexpensive test devices plug into an electrical outlet. Indicator lights show whether the grounding circuit is available at the outlet, as well as other circuit tests. If the test device shows the absence of a ground connection or other circuit problem, call a qualified electrician for assistance. This is a simple test and should be done periodically. Consult with a qualified electrician to test circuits greater than 120 volts.
Grounding and Arc Welding Safety
Workpiece Ground
The welding circuit consists of all conductive material through which the welding current is intended to flow. Welding current flows through the welding machine terminals, welding cables, workpiece connection, gun, torch, Electrode Holder and workpiece. The welding circuit is not connected to ground within the welding machine, but is isolated from ground. How do we ground the welding circuit?
According to ANSI Z49.1, "Safety in Welding, Cutting and Allied Processes," the workpiece or the metal table that the workpiece rests upon must be grounded. We must connect the workpiece or work table to a suitable ground, such as a metal building frame. The ground connection should be independent or separate from the welding circuit connection.
Grounding and Arc Welding Safety
Grounding the workpiece has similar benefit to grounding the welding machine enclosure. When the workpiece is grounded, it is at the same potential as other grounded objects in the area. In the event of insulation failure in the arc welding machine or other equipment, the voltage between the workpiece and ground will be limited. Note that it is possible to have an ungrounded workpiece, but this requires the approval of a qualified person.
The Workpiece Connection is not a Ground Clamp
"Ground clamp" and "ground lead" are common terms used by many welders. The workpiece is connected to a welding cable typically by means of a spring loaded clamp or screw clamp. Unfortunately, a workpiece connection is often incorrectly called a "ground clamp" by many welders and the workpiece lead is incorrectly called "ground lead." The welding cable does not bring a ground connection to the workpiece. The ground connection is separate from the workpiece connection.
High Frequency Ground
Some welding machines utilize starting and stabilizing circuits that contain a high frequency voltage. This is common on Tungsten Inert Gas (TIG) welding machines. The high frequency voltage may have frequency components that extend into the megahertz region. In contrast, the welding voltage may be as low as 60 Hertz.
High frequency signals have a tendency to radiate away from the welding area. These signals may cause interference with nearby radio and television reception or other electrical equipment. One method to minimize the radiation of high frequency signals is to ground the welding circuit. The welding machine instruction manual will have specific instructions on how to ground the welding circuit and components in the surrounding area to minimize the radiation effect.
Portable and Vehicle Mounted Welding Generator Grounding
Portable and vehicle mounted arc welding generators often have the capability to supply 120 and 240 volt auxiliary power. These generators are used in remote locations away from an electrical power distribution system. A convenient earth ground is not usually available for connection. Should the generator frame be grounded?
The rules for grounding depend on the specific use and design of the auxiliary power generator. Most applications fall into one of the two categories summarized below:
1. If all of these requirements are met, then it is not required to ground the generator frame:
The generator is mounted to truck or trailer
The auxiliary power is taken from receptacles on the generator using a cord and plug arrangement
The receptacles have a grounding pin
The frame of the generator is bonded, or electrically connected, to the truck or trailer frame
2. If either of these conditions are met, then the generator frame must be grounded:
The generator is connected to a premises wiring system. For example, to supply power to a house during a blackout.
The auxiliary power is hard wired into the generator without the use of cords and plugs.
The summary above does not go into details and the reader is urged to consult their local electrical codes and ANSI/NFPA 70, "National Electrical Code" for the specifics.
Extension Cord Grounds
Extension cords should be periodically tested for ground continuity. Extension cords lead a rough life while lying on the ground; they are under foot and prone to damage. The use of a receptacle circuit tester will confirm that all of the connections are intact within the cord, plug and receptacle.
Welding Circuit Shock Hazards
Utilizing proper grounding in the welding environment is a good practice, but it does not remove all possibility of electrical shock. The welding circuit is energized by welding voltage. A person will receive a shock if they become the electrical path across the welding circuit. Precautions must be taken to insulate the welder from the welding circuit. Use dry insulating gloves and other insulating means. Also maintain insulation on weld cables, electrode holders, guns and torches to provide protection.
Similarly, electric shock originating from the electrical supply system can be prevented. Proper maintenance of electrical equipment and extension cords will insulate the welder from electrical sources.
Information Sources
American Welding Society, ANSI Z49.1:2005 "Safety in Welding, Cutting, and Allied Processes."

National Fire Protection Association, NFPA 70, "National Electrical Code", 2005.

American Welding Society, Safety and Health Fact Sheet No. 29, "Grounding of Portable and Vehicle Mounted Welding Generators", July 2004.

American Welding Society, AWS A3.0-2001, "Standard Welding Terms and Definitions."
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