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← → There is a general feeling that safety is only a state of mind. Some think that it’s an attitude that individuals have while they are at work, play, or at home. When safety is involved, we are generally our own worst enemy. Sometimes injuries occur due to a lack of knowledge; however, injuries are caused more often because we don’t practice what we know about safety. We should use safety aids to protect ourselves from injuries. Gloves, safety shoes, and other proper clothing have prevented many serious injuries. Using the proper tools, the posting of safety rules in prominent areas of the workplace, and having the ability to recognize hazards have also prevented serious injuries. However, the most important thing is to have the proper mental attitude about safety while we are going about our daily activities. The proper mental attitude causes us to be more alert to effective ways to accomplish out tasks in a safe manner. SAFE SERVICING PRACTICES To avoid the possibility of personal injury and/or property damage, it’s important that safe servicing practices be ob served. The following are examples, but without limitation, of such practices: 1. Don’t attempt a product repair if you have any doubts as to your ability to complete it in a safe and satisfactory manner. 2. Before servicing or moving an appliance: a. remove power cord from electric outlet, trip circuit breaker to OFF, or remove fuse. b. turn off gas supply. c. turn off water supply. 3. Never interfere with the proper operation of any safety device. 4. USE ONLY REPLACEMENT PARTS CATA LOGED FOR THIS APPLIANCE. SUBSTITUTIONS MAY DEFEAT COMPLIANCE WITH SAFETY STANDARDS SET FOR HOME APPLIANCES. 5. GROUNDING: The standard color coding for safety ground wires is GREEN or GREEN with YELLOW STRIPES. Ground leads are not to be used as current carrying conductors. IT IS EXTREMELY IMPORTANT THAT THE SERVICE TECHNICIAN RE-ESTABLISH ALL SAFETY GROUNDS PRIOR TO COMPLETION OF SERVICE. FAIL URE TO DO SO WOULD CREATE A POTENTIAL HAZARD. 6. Prior to returning the product to service ensure that: a. all electric, gas, and water connections are correctly and securely connected. b. all gas and water connections are tested for leaks. DO NOT TEST FOR GAS LEAKS WITH A FLAME. c. all electrical leads are properly dressed and secured away from sharp edges, high-temperature components and moving parts. d. all uninsulated electrical terminals, connectors, heaters, etc. have adequate spacing from all metal parts and panels. e. all safety grounds (both internal and external to the product) are correctly and securely connected. f. all panels are properly and securely reassembled. SAFETY PROCEDURES The saying “safety doesn’t cost, it pays” is as true today as it was when it was first used. Following the proper safety procedures cannot be overemphasized, especially by workers in the appliance field. These workers generally work alone and help may be difficult to obtain if a serious injury were to happen. Safety may be divided into three general categories: safety of the worker, safety of the equipment, and safety of the contents. Safety of the Worker WELDING SAFETY (OXY-ACETYLENE) Caution: Always read the instruction sheets provided with the equipment before operating the equipment. Safety Precautions This is without a doubt the most important of all three. Machinery and materials are replaceable, but a human life is only a one-lime thing. The proper use of tools and machinery represents very little danger to the worker. When lifting heavy objects, always use the leg muscles. Never use the back muscles when lifting. When an object weighing more than 30 pounds is to be lifted, ask for help. The floor should always be kept clear of water and oil to prevent slipping. To slip when carrying heavy objects will almost always result in a serious injury. Major appliances use electricity as a source of power for operation. Make certain that all electrical circuits are turned off before working on them. The disconnect switch or the circuit breaker will usually break the circuit. Never work a “hot” circuit. Always wear safety goggles when working with refrigerants. Should liquid refrigerant get into the eye, a frozen eye will result. Liquid refrigerant should be washed from the eye with a gentle stream of tap water. When the eye has been flushed for about 15 minutes, have a physician properly medicate the eye. Also, the skin should be protected from frostbite when working with refrigerants. Safety of the Equipment Safety of the equipment is always of great concern to the technician. Many of the components on major appliances are easily broken. Some of these components are very expensive and all of them take lime to replace, usually at a lot of expense. When tightening bolts and nuts, use the proper torque to prevent breaking them. Use the proper sequence with lightening bolts and nuts. Be sure that all moving parts are free to rotate and all belts are clear of objects before starling the equipment. Safety of the Contents This is a basic requirement and will depend to a great extent on the care given to the equipment during the installation and servicing processes. It’s the responsibility of the service technician to make certain that the inside of the appliance is kept at the desired temperature. It’s the technician’s responsibility to know what the desired conditions are and to make sure that the equipment can produce these conditions. Most manufacturers provide tables and charts showing the desired operating conditions and the required control settings. The safe and effective use of flame tool equipment depends on the user fully understanding and carefully following practical lime-tested safety and operating instructions to prevent and avoid unnecessary painful injuries and costly property damage. For adequate personal safety, the user must be fully aware at all times that the torch flame can reach almost 6000°F and the work piece can reach a high heat of almost 3000°F, which may produce flying sparks, slag, fumes, and intense light rays, all of which can be harmful to the user or nearby persons without proper precautions and protection. Practical proper “head-to-toe’ protection includes hair and head coverage, welding-and-cutting-type tempered lens eye goggles (shade 5 is standard). Body coverage includes proper gloves and proper shoes. Avoid wearing any thing flammable or clothing that has been exposed to flammables (oil, grease, solvents, etc.). Sparks and molten materials have a way of finding unprotected areas, so be prepared before starling work by being properly protected. Adequate ventilation must be provided, especially in confined areas, to remove harmful fumes and provide an adequate air supply for the user. Important: Oxygen rapidly increases the burning rate of almost any ignited material, especially oil and grease; therefore, it must never be allowed to saturate a confined work area. Oxy/fuel or air/fuel concentrations in confined areas can also be hazardous and explosive. Never use a torch on any kind of container or pipe until it has been properly cleaned, purged, or vented. Fire protection must be provided for the work area. The user must be fully aware of the impact that the torch flame, sparks, and molten materials can have on both close and surrounding areas; sparks can fly over 35 feet. Keep hoses clear of sparks and slag. Remove all flammables and care fully cover or shield, with fireproof materials, anything that could possibly catch fire, explode, or both. Note: Concrete can chip explosively when overheated by slag and molten metal. Carefully check out the work area after the work has been completed for places where sparks or molten metal could light and smolder. Douse any doubtful areas with water or a proper fire extinguisher. Have a bucket of water and a proper fire extinguisher available in the work area at all times. A water bucket is also handy for leak-testing hose and torches and for cooling the work. Important: To avoid a dangerous pressure imbalance and cylinder contamination due to the reverse flow of gases, don’t allow cylinders (especially oxygen) to become empty in use. Check for adequate gas supplies before starting work. Also, install reverse-flow check valves in the welding hoses. Checking out the Equipment Regulators New equipment in the original packaging has been inspected and tested and is ready for connecting. It’s standard safety practice, however, to check out and leak-test all connection points from the cylinder valves to the tips to assure safe, leak-tight service before using the equipment. This checkup and leak-testing is especially important after the equipment has been used and has been exposed to dust, dirt, oil, grease, and possible damage. The following guidelines for checking out, cleaning, and testing the equipment before using it are designed to cover normal working conditions. The proper procedures should be followed each time the equipment is set up and used. Cylinders The following procedures should be followed when working with cylinders: 1. The cylinders must be secured to keep them from falling over. 2. Fuel gas cylinders must be used in the upright position. 3. Don’t store cylinders and equipment in unventilated, confined spaces, closed vehicles, or near any source of heat or ignition. 4. The cylinder valves must be securely closed when not in use and also when empty. 5. To avoid a dangerous pressure imbalance and cylinder contamination, don’t allow cylinders, especially oxy gen, to become completely empty when in use. Check for adequate gas supplies before starting work. For added protection install external-type reverse-flow check valves on regulators and or torches. They are easy to install, test, or replace. 6. Valve protection caps should be replaced when the cylinders are empty, stored, or when the regulator is removed. 7. Don’t expose cylinders to torch flames or electrical arcs because they can seriously damage the cylinders. 8. Don’t use a cylinder, full or empty, as a roller or support. The cylinder wall may be damaged and result in a rupture or an explosion. 9. Don’t use a cylinder gas without a suitable pres sure-reducing regulator. 10. Don’t allow oil or grease to come in contact with cylinder valves, especially oxygen. Don’t use the cylinder if oil is on the cylinder valve; return the cylinder to the supplier. 11. Don’t use a cylinder with a leaking valve. Move it away from any source of ignition, preferably outdoors, and notify the supplier. 12. Handle all cylinders with care and protect the valves from damage. The following procedures should be used when working with regulators: 1. Use the regulators for the gas or gases for which they were intended. Oxygen regulators must be used only for oxygen service. 2. Regulators and cylinder connections must be made free of dirt, dust, grease, and oil. Remember that oxygen reacts with oil or grease. Inspect the regulator and cylinder valve connections for damaged threads, dirt, dust, oil, or grease. Remove any dust and dirt with a clean cloth. Don’t use the regulator if it’s damaged or has oil or grease on it. Have your authorized repair station or Uniweld clean the regulator or repair any damage. Don’t use cylinders with damaged or dirty valves. Return such cylinders to the supplier. 3. Don’t crack fuel gas or oxygen cylinders near an open flame or any source of ignition. Make sure that you are in a well-ventilated area, and stand clear of the valve outlet when opening it. 4. Carefully crack (open briefly) the cylinder valves, one at a time, to clean the valves of dust, dirt, or foreign matter, then retighten. 5. To connect the regulator, attach the inlet connection nut to the cylinder valve. Make sure that the threads engage properly. Tighten the nut with a wrench, but don’t use excessive force. Excessive force could damage the nut and valve threads. 6. Turn the pressure-adjusting screw counterclock wise until the tension is fully released, to shut off the regulator. Note: The regulator should always be shut off when not in use to help in avoiding gas loss if the cylinder or torch valves leak. 7. Don’t stand directly in front or in back of the regulators when opening them. Open the cylinder valve slowly. Open fully only after the contents gauge stops moving. Note: Open the acetylene valves I to 1 turn only, all others are fully opened to seal the valve packing. Instructions for Cutting, Welding, and Brazing Use the following instructions when performing any of these procedures. Cutting steel--Position the preheat cone just above the work (about * inch) and hold it steady until the met al turns bright orange. Then slowly press the cutting lever and move the torch along steadily to avoid overheating and excess melting. To restart the cut, release the lever and preheat the metal before pressing the lever again. Piercing For piercing holes or cutting into confined spaces, the tip should be tilted over to keep the metal spatter from plugging the tip. Return the tip upright after the cut is started. Cutting thin steel--Tilt the tip over so that the preheat flames hit the surface at an angle which can be increased or decreased as needed to vary the heat. Move the lip fast enough to avoid overheating and excess melting of the metal. Use the correctly sized lip for the job. Welding steel--Note: Oxy-acetylene must be used for welding steel. Clean and assemble the parts with good fit- up. Position the flame cone just above the surface until a puddle forms and penetrates well into the joint. Then dip the rod into and out of the puddle to melt it as needed to fill the joint and move the puddle along the joint. When welding metal less than 1 inch, melt the rod ahead of the flame. Tilt the tip to decrease or increase the heat to the joint and slightly withdraw the flame as needed to avoid overheating the puddle. For metal over * inch, bevel the edge of the joints approximately 300 for good weld penetration. Brass welding--Brazing uses metals that melt and flow below the melting point of the base metal (brass at about 1600°F). When brazing, the proper filler rod and flux must be used. The joints must be clean and assembled with good fit-up. Be sure to provide proper ventilation to remove any harmful fumes. Heat the tip of the brazing rod and dip it into the flux (not necessary for pre-fluxed rods). Preheat the metal to a dull red color and apply the fluxed rod to the base metal and melt off a small amount of the rod. If it flows on the base metal, the heat is right, continue to heat and flow the rod on the joints. Note: Phos-copper brazing rod does not need fluxing when used on copper. Flux must be used on dissimilar metals. Silver brazing Silver alloys melt at lower temperatures (about 1200°F) than brass alloys. The joints must be clean and have a good fit-up. The joint must be coated with flux and the joint heated evenly. When the flux bubbles and melts clear, start applying the rod to the joint. If it flows, the heat is right, and the solder will flow quickly in and around the joint. Don’t overheat the joint. Remove the flame when the solder has flowed into the joint. Soft soldering--Lead solders melt at around 500°F. The joints must be clean, have a good fit-up, and be well covered with soft solder flux. Heat the joint until the flux boils, then apply the solder. If it flows, the heat is right, and the solder will flow quickly in and around the joint. Don’t overheat the joint. Remove the flame when the solder has flowed into the joint. Always heat the joint and not the rod. Flame Heat Control The oxy-acetylene torch flame has an inner cone with a widening brush outer flame. The highest heat transfer zone is just past the inner cone (about 1 inch) which is used to melt metal for welding or to preheat steel to a bright orange color, so the cutting oxygen can start burning and melting (about I burning of the iron to form iron-oxide slag and I melting caused by the heat of the burning iron, more melting if the travel is too slow). The outer brush flame spreads the heat out as it moves away from the inner cone. The flame heat can be controlled by moving the tip in or out from the work and also by moving it around so that it heats the joint evenly. Soft solder joints require less heat than brazed joints and brazed joints require less heat than welded joints. Larger tips and rosebud heating tips heat faster and can be used if the flame heat is controlled properly. Use larger-size tips for large tubing and for fuel gas brazing. Table 1 Flame temperatures (neutral flames):
The flame temperatures of natural gas and propylene are in about the same range as propane. Only the neutral oxy-acetylene flame can be used for welding steel—other gas flames become too oxidizing at higher temperatures. Oxy-acetylene provides the most versatile all-purpose flame tool for maximum heat and speed in getting the job done when the flame heat transferred to the work is con trolled properly. Air/acetylene, especially the high-velocity acetylene thruster-type tip, is the next best, followed by the LP thruster-type tip with air/mapp or air/propane. The flame temperature table, Table 1, shows the differences between the flame temperatures. Safety and Setup Checklist: Use the following steps to ensure a safe setup: 1. Review the previous information before using the equipment and use the outlined precautions and procedures. 2. Safety precautions--The safety precautions include personnel protection, adequate ventilation, and fire protection and precautions. 3. Cylinders--Cylinders should be secured and up right with an adequate gas supply to avoid dangerous empty cylinder conditions due to reversed gas flow, for safe storage, the valves should be closed when not in use or empty; use protective caps on stored or empty cylinders. 4. Regulators--Regulators should have leak-tight connections; they should be turned off before opening the cylinder valve slowly and closed after the work is completed to avoid leaks from the cylinder or torch valves. 5. Torches and tips--Before using torches and tips, make all connections wrench-tight and leak-test them; use proper operating pressures and clean, efficient tips. Purge the oxygen before each torch use. Purge oxygen before each torch lighting and use. Use the proper size and tip to fit the torch, job, and the fuel gas. Don’t use damaged or plugged tips—repair or replace such tips. 6. Operations--The torch connections should be checked for leaks before the torch is lit. Follow the proper tip lighting procedure with “no-smoke” fuel gas flame for adequate gas flow; maintain the proper neutral flame adjustment; use the proper tip angle and distance to decrease or increase the heat to the work for cutting, welding, or brazing; use the proper speed to avoid excess heating and melting on thin material when cutting or welding. Purge the oxygen before each torch lighting and use the “sniff test.” Purge the torch and the hoses after each cylinder change to vent out possible mixed gases. 7. Shutdown procedure--Shut the oxygen off first, fuel gas last and avoid backfire. The flame cannot burn in the torch without oxygen. Close the cylinder valves, drain off each gas separately, close the regulators and avoid leaks from the cylinder or the torch valves, close all torch valves, store the cylinders and equipment safely away from heat and ignition sources in a well-ventilated area. 8. Use the proper size tip cleaners to keep the tips effective and efficient for every job. Caution: The withdrawal rate of an individual acetylene cylinder should not exceed one-seventh (15 percent) of the cylinder contents per hour. Use an adequate size cylinder or an adequate acetylene manifold system to supply the necessary volume for large usage and to avoid dangerous reverse flow of gases due to unbalanced pressures. Don’t allow the gas cylinder (especially oxygen) to become completely empty while in use. SAFETY IN HANDLING REFRIGERANTS In operating refrigeration equipment, it’s necessary that only the type of refrigerant for which the machine was designed be used in it. When other types of gases are used in the system, it won’t operate as it was designed. In some cases the pressures may become excessive. Personal Protection Most of the refrigerants used today are nontoxic and present no personal hazard unless these is sufficient concentration to displace the oxygen in the air inside the space. Without oxygen the air won’t support life. The refrigerant vapors are three to five times heavier than air and will, therefore, tend to collect in a strong concentration near the floor or in low places and displace the air. The stronger the concentration of refrigerant, the less air there is to breathe and a person can actually suffocate. The deliberate inhalation of refrigerant vapors can cause a cardiac sensitization and death. This is an extremely dangerous act because death can occur without warning. When entering tanks or other places where there is the possibility of a strong concentration of refrigerant vapors, wear an air mask, use the buddy system, and attach a lifeline. At times it’s difficult to smell refrigerant vapors except in strong concentration. They have a faintly sweet odor which is difficult to detect. When you are working in an enclosed space where there has been a refrigerant leak or refrigerant has been purged into the air and you begin to feel a little dizzy, immediately get out of the space and into fresh air before it’s too late. Should refrigerant be drawn into the mouth, don’t induce vomiting. When vomiting is induced, there is a possibility that the refrigerant can be drawn into the lungs. Should refrigerant be drawn into the lungs, seek medical attention immediately. This condition could cause chemical pneumonitis, pulmonary edema, and hemorrhage. Most of the refrigerants used in modern equipment are in the vapor form at room temperature. These vapors have very little if any effect on the skin or eyes. However, those refrigerants that remain liquid at room temperature, such as CFC-11 and CFC-113, have a tendency to dissolve the protective fat from the skin which will cause a dryness and some irritation after prolonged contact or repeated con tact with the liquid form. Any time there is the possibility of coming in contact with liquid refrigerant, protective clothing should be worn. Always wear protective eye goggles when working with refrigerants to prevent their entrance into the eye. Should refrigerant get into the eyes, flush the eye with water, and seek medical attention immediately. Liquid refrigerant will freeze the moisture in the eye and possibly cause blindness. Should CFC-12, CFC-22, or any of the medium-temperature refrigerants come into contact with the skin, frost bite is probable. If treatment is started within 20 to 30 minutes after contact with the liquid refrigerant, soak the exposed area in lukewarm water. Never use hot or cold water. If the situation prevents starting of the treatment after 30 minutes have passed, apply a light coat of Vaseline petroleum jelly to the area. If the frostbite occurred in a place where it would be difficult to apply the petroleum jelly, then apply a light bandage to the affected area. Seek medical attention as soon as possible to reduce the chance of gangrene. Handling Refrigerants under Pressure Some of the hazards of handling refrigerants under pressure are as follows: 1. Don’t overfill a refrigerant container. Should an overfilled container be subjected to temperatures greater than 125°F, the container may become “liquid full” causing an immediately dangerous hydrostatic pressure to build up inside the container. The container may then rupture. 2. Don’t overheat or store a refrigerant container in the direct sunlight. There is the possibility of a buildup of hydrostatic pressure inside a correctly filled container when heated above 125°F. 3. Never connect a refrigerant container to the discharge side of a refrigeration system. The pressure inside the container may rise above the capacity of the relief device and possibly cause the container to rupture. This is very possible with the 14-ounce CFC-12 cans used to charge auto mobile air conditioners. It’s possible that they will explode when connected to the discharge side of the system. Cylinder abuse is the most common cause of pressure- related problems with refrigerants. Four recommendations are as follows: 1. Never heat cylinders above 125°F. 2. Never tamper with the valves or the safety devices. 3. Never refill disposable cylinders with refrigerant or convert them into compressed air tanks. The empty cylinders should be vented and discarded. Reusing disposable cylinders is a dangerous practice because of the possibility of corrosion and weakening of the cylinder walls. The corrosion is greater when it’s caused by water vapor in the refrigerant or in the compressed air. The greatest danger is that the damage may not be visible until the cylinder explodes. It’s then too late. 4. Disposable containers should always be stored in a dry place to prevent rusting and corrosion of the cylinder. Some Do’s and Don’ts for Handling Refrigerant Cylinders The following are some of the more important procedures for handling refrigerant cylinders: 1. Make certain that the cylinder is properly connected to the system. 2. Open the valves very slowly to avoid rupturing a hose or ruining a gauge. 3. Store the cylinder in a dry place to protect it from rusting. 4. Don’t tamper with the pressure relief devices. To do so may cause the cylinder to rupture when subjected to excessive pressures. 5. Don’t drop or otherwise abuse the cylinders. 6. Don’t use disposable cylinders for air tanks. The moisture in the air will cause the cylinder to corrode from the inside out. It may then rupture when least expected and cause serious injury. 7. Don’t refill disposable cylinders. They are de signed for one-time use only and any moisture in the refrigerant will cause corrosion on the inside of the cylinder. 8. Don’t force connections. This weakens the connection which may blow out when subjected to pressure and cause serious injury. 9. Don’t heat the cylinder above 125°F. To do so may cause the cylinder to become liquid full and a hydro static pressure will build up rapidly and possibly rupture the cylinder. 10. Make certain that the refrigerant, the cylinder color, and the label match. 11. The caps which are provided for valve protection should always be on the valve except when the cylinder is in use. 12. Never mix refrigerant gas in a cylinder. 13. When a cylinder is emptied, immediately close the cylinder valve to prevent the entrance of moisture, air, and dirt into the cylinder. 14. Never use refrigerant cylinders for rollers, sup ports, or for any purpose other than to carry refrigerant. 15. Never attempt to repair or alter cylinders or valves. Brazing or Welding on Refrigeration System Piping The following are some of the precautions used when attempting these operations: 1. Remove all of the liquid refrigerant from the part of the system that is to be heated. 2. Be sure to purge all refrigerant out of doors. 3. Provide plenty of ventilation to the space. Use an auxiliary vent fan if necessary. 4. Purge with nitrogen the part of the system that is to be heated to force as much of the refrigerant vapor out of the system as possible. 5. Leave the system open during the welding or brazing process to prevent a buildup of pressure inside the system and decomposition of the refrigerant. Decomposed refrigerant may cause toxic and irritating compounds, such as hydrogen chloride and hydrogen fluoride. 6. Don’t breathe the vapors produced when welding or brazing on refrigerant lines. These vapors are acidic and will irritate your nose and throat. Anyone exposed to these vapors should be taken to fresh air immediately and given medical attention. 7. Some silver-brazing alloys contain cadmium. These alloys are very dangerous to use. Most silver-brazing alloys contain large quantities of cadmium and when these alloys are melted they emit cadmium-oxide fumes into the air. These fumes are very toxic and must be avoided. An increase in the temperature above the molten state will cause an increase in the amount of fumes produced. Because oxy acetylene gas burns at a temperature of about 6000°F, higher concentrations of the cadmium-oxide fumes are produced than with other types of welding and heating fuels. You cannot smell cadmium-oxide fumes, thus making it even more dangerous. A lethal dose does not necessarily need to be irritating enough to cause discomfort until after enough has been absorbed by the worker to place his or her life in immediate danger. Some of the more common symptoms of cadmium poisoning are headache, fever, chills, irritation of the throat, vomiting, weakness, and diarrhea. These symptoms may not appear for many hours after the exposure to the fumes. The primary injury is to the respiratory system. Those who breathe the air within 5 feet of where the silver brazing is done are in the most dangerous area. When these materials are used in production work, precautions should be taken to protect workers from the fumes. How ever, when appliance technicians are working in the field, these precautions are not available. It is, therefore, up to the technicians to protect themselves. Lunches should not be stored or eaten in the area where silver brazing with these materials is done. The workers should be sure to wash both their hands and faces before eating, smoking, or leaving work. The nice thing is that today no one must use these types of silver-brazing materials. There are materials avail able that don’t contain cadmium. However, technicians must make certain that the type they are using is safe. There are several companies that manufacture cadmium-free silver-brazing materials. SAFETY IN WORKING WITH HEATING EQUIPMENT Heating equipment is probably the most dangerous of all the equipment used in the industry, especially natural and liquefied petroleum (LP) gases. The danger is in the combustion process that provides heat for the operation of the appliance. Electricity is probably the least dangerous of all the heat sources used for appliance operation. However, all of these heat sources must be treated with respect. There fore, appliance service and installation technicians must know the combustion process and they must practice safety procedures to prevent loss of life, property, and equipment. The following are some of the more common safety procedures to follow when working on heating equipment: 1. Don’t tamper with the safety controls. If a problem arises with one, replace it. Tampering may cause delayed ignition which could cause an explosion or an over heated condition which could cause a fire. 2. Don’t light the pilot until the firebox has been cleared of all unburned fuel. 3. Follow the manufacturer’s directions carefully. The manufacturer has invested much time and money developing these directions and they should be heeded. 4. Always follow the local building safety codes. 5. Be sure the unit is grounded electrically. 6. Don’t make adjustments without knowing what the results will be. 7. Don’t alter the venting system in any way. 8. Never reduce the size of the vent pipe. 9. Increase the vent pipe size only when it’s needed to provide proper ventilation of the products of combustion. 10. Be sure that the proper ventilation air is supplied to the appliance. 11. Never allow the unit to be operated when a bad heat exchanger is suspected. The products of combustion will enter the building and possibly cause death or illness of the occupants. A bad heat exchanger should be suspected when the occupants of the building complain of having headaches which are relieved when they leave the building for a short time. 12. Never leave a malfunctioning appliance in operation. To do so is inviting an explosion, fire, or other damage to the building and/or its contents. 13. Always check the venting system and remove any obstructions before lighting the burners. If an appliance is fired with a restricted venting system, the products of combustion will be forced into the building. 14. All safety devices must be in excellent working condition and be properly adjusted. Never leave a safety device bypassed. 15. It’s never a good idea to work on “hot” electrical systems. However, at times it’s necessary to find a problem with the equipment. Take precautions to avoid becoming grounded and receiving an electrical shock. 16. The equipment and its components must be in stalled according to local, state, and national electrical codes. The electrical circuits should be installed by a licensed electrician. If there is a local licensing code for appliance technicians, it must be adhered to. The equipment should have Underwriters’ Laboratory (UL) approval. 17. Leak-testing should be done with soap bubbles or a liquid leak detector. Never check for leaks with an open flame. If a leak is present there will probably be a flame out of control. 18. Always allow the appliance to stand open for at least 5 minutes before lighting the pilot or burner. This is to allow any accumulation of fuel to escape to the atmosphere without an explosion. 19. Always exercise care when working around heating appliances to prevent burns because almost all of the surfaces are hot when the appliance is operating. 20. When in doubt about a heating appliance, check the vent products with one of the meters which are available for this purpose. Be safe not sorry. 21. When servicing heating appliances, before leaving the job, check all safety devices to make certain that they are operating properly. SAFETY IN WORKING WITH ELECTRICITY AND ELECTRONICS Appliance technicians are involved in the installation, ser vice, and maintenance of equipment in which dangerously high voltages are present. This work is often done in con fined spaces. Among the hazards of this work are electrical shock, electrical fires, harmful gases which are sometimes generated by faulty electrical and electronic devices, and injuries which may be caused by the improper use of tools. Because of these dangers, appliance technicians should formulate safe and intelligent work habits since these are fully as important as knowledge of the electronic equipment. One primary objective should be to learn to recognize and correct dangerous conditions and avoid unsafe acts. These persons should also know the proper procedures for dealing with fires of an electrical origin, for treating burns, and for giving artificial respiration to persons suffering from electrical shock. In some cases, artificial respiration may have to be accompanied by cardiac massage (CPR) to restore heart beat. Electrical Shock Electrical shock may cause burns of varying degree, the stoppage of breathing and unconsciousness, ventricular fibrillation or cardiac arrest, and death. If a 60-hertz alternating current is passed through a person from hand to hand or from head to foot, the effects when current is gradually increased from zero are as follows: 1. At about 1 milliamp (0.001 amp), the shock will be felt. 2. At about 10 milliamps (0.01 amp), the shock will be severe enough to paralyze muscles and a person may be unable to release the conductor. 3. At about 100 milliamps (0.01 amp), the shock is usually fatal if it lasts for 1 second or more. It’s important to remember that, fundamentally, current, rather than voltage, is the criterion of shock intensity. It should be clearly understood that the resistance of the human body will vary. That is, if the skin is dry and unbroken, body resistance will be quite high, on the order of 300,000 ohms. However, if the skin becomes moist or broken, body resistance may drop to as low as 300 ohms. Thus, a potential as low as 30 volts could cause a fatal electrical shock. Therefore, any circuit with a potential in excess of this value must be considered dangerous. Note: The intentional taking of an electrical shock should be avoided. Care of Shock Victims Electrical shock is a jarring, shaking sensation resulting from contact with electrical circuits or from the effects of lightening. The victim usually experiences the sensation of a sudden blow, and if the voltage is sufficiently high, unconsciousness. Severe buns may appear on the skin at the point of contact. Muscular spasms can occur, causing a person to clasp the apparatus or wire which caused the shock and to be unable to let go. Electrical shock can kill its victim by stopping the heart or by stopping breathing, or both. It may sometimes damage nerve tissue and result in a slow wasting away of muscles that may not become apparent until several weeks or months after the shock is received. The following procedure is recommended for rescue and care of electrical shock victims: 1. Remove the victim from electrical contact at once-- Don’t endanger yourself. This can be done by: (1) throwing the switch, if it’s nearby; (2) using a dry stick, rope, leather belt, coat, blanket, or any other nonconductor of electricity; or (3) cutting the cable or wires to the apparatus, using insulated tools while taking care to protect your eyes from the flash when the wires are cut. 2. Determine whether the victim is breathing. If so, keep the victim lying down in a comfortable position. Loosen the clothing about the neck, chest, and abdomen so that the victim can breathe freely. Watch the victim carefully and protect him or her from exposure to cold. 3. Keep the victim from moving about. After shock, the heart is very weak, and any sudden muscular effort or activity on the part of the victim may result in heart failure. 4. Don’t give stimulants or opiates. Send for a medical person at once and don’t leave the victim until he or she has adequate medical care. 5. If the victim is not breathing, it will be necessary to apply artificial respiration without delay, even though the victim may appear to be lifeless. WORKING ON ENERGIZED CIRCUITS Insofar as practical, a technician should not undertake working on energized circuits and equipment. However, as when making operational adjustments, one should carefully ob serve the following safety precautions: 1. Ensure that you have adequate illumination. You must be able to see clearly, if you are to safely and properly perform the job. 2. Ensure that you are insulated from ground by an approved-type rubber mat or layers of dry canvas and/or wood. 3. Where practical, use only one hand, keeping the other behind you or in your pocket. 4. If the system voltage exceeds 150 volts, rubber gloves should be worn. 5. An assistant should be stationed near the main switch or circuit breaker, so that the equipment may be immediately deenergized in case of an emergency. 6. A person qualified in first aid for electrical shock should be standing by during the entire operation. 7. Don’t work alone. 8. Don’t work on any type of electrical apparatus when wearing wet clothing or if the hands are wet. 9. Don’t wear loose or flapping clothing. 10. The use of thin-soled shoes and shoes with metal plates or hob nails are prohibited. 11. Flammable articles, such as celluloid cap visors, should not be worn. 12. All rings, wristwatches, and similar metal items should be removed before working on the equipment. Also, ensure that clothing does not contain exposed metal fasteners such as zippers, snaps, buttons, and pins. 13. Don’t tamper with interlock switches, that is, don’t defeat their purpose by shorting them or blocking them open. 14. Ensure that the equipment is properly grounded before energizing. 15. Deenergize the equipment before attaching alligator clips to any circuit. 16. Use only approved meters and other indicating devices to check for the presence of voltage. 17. Observe the following procedures when measuring voltages in excess of 300 volts: a. Turn off the equipment power. b. Short-circuit or ground the terminals of all components capable of retaining a charge. c. Connect the meter leads to the points to be measured. d. Remove any terminal grounds previously connected. e. Turn on the power and observe the voltage reading. f. Turn off the power. g. Short-circuit or ground all components capable of retaining a charge. h. Disconnect all meter leads. 18. On all circuits where the voltage is in excess of 30 volts and where metal is present, the worker should be insulated from accidental ground by the use of an approved insulating material. The insulating material should have the following characteristics: a. It should be dry, without holes, and should not contain conducting materials. b. The voltage rating for which it’s made should be clearly marked on the material, and the proper material should be used so that adequate protection from the voltage can be possible. c. Dry wood may be used, or as an alternative, several layers of dry canvas, sheets of phenolic insulating material, or suitable rubber mats. d. Care should be exercised to ensure that moisture, dust, metal chips, and soon, which may collect on insulating materials are removed at once. Small deposits of such materials can become electrical hazards. e. All insulating materials on machinery and in the area should be kept free of oil, grease, carbon dust, and so on, since such deposits destroy insulation. QUIZ 1. Why is it especially important for a worker in the appliance field to practice safety? 2. What should be done before operating any piece of equipment? 3. What temperature can the acetylene flame reach? 4. What is the standard shade of eye protection used when welding? 5. What must be done to a container or pipe before using a welding torch on it? 6. What must be done with welding hoses when welding or cutting? 7. Name two uses for a bucket of water in the welding area. 8. What should be done before using new welding equipment? 9. In what position must a fuel gas cylinder be used? 10. Should the fittings and valves on welding equipment be lubricated with oil or grease? 11. What should be done when a cylinder valve becomes dirty? 12. Where should the operator be standing when opening the valve on a welding cylinder? 13. How far should acetylene cylinder valves be opened? 14. How far should oxygen cylinder valves be opened? 15. What is the maximum acetylene pressure that can safely be used on welding equipment? 16. Is it safe to light the welding torch with a match or a cigarette lighter? 17. What must be done to prevent flame backfiring or flashback inside the welding torch? 18. What is the first step in the welding unit shut down procedure? 19. What is the maximum withdrawal rate of a single welding cylinder? 20. Is it proper procedure to use more than one type of refrigerant in a system? 21. What is the greatest personnel hazard when using refrigerants in a confined space? 22. What could be the result of inhaling refrigerant vapor? 23. Describe the odor of refrigerant vapors when in heavy concentration. 24. What will direct contact of liquid refrigerant with the skin cause other than frostbite? 25. Should hot water be used on refrigerant frostbite? 26. What could possibly happen if the temperature of an overfilled refrigerant cylinder were exposed to temperatures over 125°F? 27. Why should a refrigerant container never be connected to the high side of the refrigeration system? 28. Why is reusing disposable refrigerant cylinders a bad practice? 29. Why should a refrigeration system be left open during a welding operation on tubing? 30. Why are cadmium-oxide fumes dangerous to breathe? 31. What type of equipment is probably the most dangerous with which to work? 32. What complaint is a good indication of a bad heat exchanger in a gas-fired appliance? 33. Is it good practice to leave safety controls by passed? 34. With what should natural or LP gas be leak- tested? 35. List the possible results of an electrical shock. 36. At what amperage is an electrical shock usually fatal? 37. What is the most dangerous to people, electrical current or voltage? 38. What is the first step to follow when a shock victim is discovered? Home top of page |