TYPES OF AC GENERATOR ROTORS BASIC INFORMATION AND TUTORIALS

Synchronous AC generators are fitted with one of two different rotor designs depending on their intended rotational speeds.

Round rotors are solid steel cylinders with the field winding inserted in slots milled into the surface or the rotor. They usually have two or four poles. Round rotors can withstand the stresses of high-speed rotation.


Salient-pole rotors have multiple pole pieces (typically six) mounted to the rotor structure, and the field winding is wound around the pole pieces. Because of their more complex construction and larger diameter-to-length ratios, salient-pole rotors cannot withstand the stresses of high-speed rotation.


Electric utility steam-turbine–driven generators designed for 50- or 60-Hz AC output voltage have round rotors with two poles because they can withstand the stresses of speeds of 3000 and 3600 rpm.

Hydroelectric, diesel, and natural-gas engines have far lower shaft speeds than steam turbines, so the generators they drive usually have six or more pole rotors, requirements usually met with more complex salient-pole rotors.

Three-phase AC generators have a winding that is made up of three separate stator windings, each displaced from the other two by 120 electrical degrees. The three windings can either be wye- or delta-connected. The wye connection is more common because it is better suited for direct high-voltage generation.

ELECTRICAL OVERLOADING - THE HAZARDS OF OVERLOADING BASIC INFORMATION

Overloads in an electrical system are hazardous because they can produce heat or arcing. Wires and other components in an electrical system or circuit have a maximum amount of current they can carry safely.

If too many devices are plugged into a circuit, the electrical current will heat the wires to a very high temperature. If any one tool uses too much current, the wires will heat up.

The temperature of the wires can be high enough to cause a fire. If their insulation melts, arcing may occur. Arcing can cause a fire in the area where the overload exists, even inside a wall.

In order to prevent too much current in a circuit, a circuit breaker or fuse is placed in the circuit. If there is too much current in the circuit, the breaker “trips” and opens like a switch.

If an overloaded circuit is equipped with a fuse, an internal part of the fuse melts, opening the circuit. Both breakers and fuses do the same thing: open the circuit to shut off the electrical current.

If the breakers or fuses are too big for the wires they are supposed to protect, an overload in the circuit will not be detected and the current will not be shut off. Overloading leads to overheating of circuit components (including wires) and may cause a fire.

You need to recognize that a circuit with improper overcurrent protection devices—or one with no overcurrent protection devices at all— is a hazard.

Overcurrent protection devices are built into the wiring of some electric motors, tools, and electronic devices. For example, if a tool draws too much current or if it overheats, the current will be shut off from within the device itself.

Damaged tools can overheat and cause a fire. You need to recognize that a damaged tool is a hazard.

WORKS REQUIRING PERMITS BASIC INFORMATION AND TUTORIALS

What are the activities/ works that requires work permit?

The main types of permit and the work to be covered by each are identified below. Appendix 6.4 illustrates the essential elements of a permit form with supporting notes on its operation.

General permit
The general permit should be used for work such as:

S alterations to or overhaul of plant or machinery where mechanical, toxic or electrical hazards may arise
S work on or near overhead crane tracks
S work on pipelines with hazardous contents
S work with asbestos-based materials
S work involving ionising radiation
S work at height where there are exceptionally high risks
S excavations to avoid underground services.

Confined space permit
Confined spaces include chambers, tanks (sealed and open-top), vessels, furnaces, ducts, sewers, manholes, pits, flues, excavations, boilers, reactors and ovens.

Many fatal accidents have occurred where inadequate precautions were taken before and during work involving entry into confined spaces. The two main hazards are the potential presence of toxic or other dangerous substances and the absence of adequate oxygen.

In addition, there may be mechanical hazards (entanglement on agitators) and raised temperatures. The work to be carried out may itself be especially hazardous when done in a confined space, for example, cleaning using solvents, cutting/welding work.

Should the person working in a confined space get into difficulties for whatever reason, getting help in and
getting the individual out may prove difficult and dangerous.

Stringent preparation, isolation, air testing and other precautions are therefore essential and experience shows that the use of a confined space entry permit is essential to confirm that all the appropriate precautions
have been taken.

Work on high voltage apparatus (including testing)
Work on high voltage apparatus (over about 600 volts) is potentially high risk. Hazards include:

S possibly fatal electric shock/burns to the people doing the work
S electrical fires/explosions
S consequential danger from disruption of power supply to safety-critical plant and equipment.

In view of the risk, this work must only be done by suitably trained and competent people acting under the terms of a high voltage permit.

Hot work
Hot work is potentially hazardous as a:

S source of ignition in any plant in which highly flammable materials are handled
S cause of fires in all locations, regardless of whether highly flammable materials are present.

Hot work includes cutting, welding, brazing, soldering and any process involving the application of a naked
flame. Drilling and grinding should also be included where a flammable atmosphere is potentially present.

In high risk areas hot work may also involve any equipment or procedure that produces a spark of sufficient energy to ignite highly flammable substances.

Hot work should therefore be done under the terms of a hot work permit, the only exception being where hot work is done in a designated area suitable for the purpose.

PROJECT RISK CONTROL - HIERARCHY OF RISK CONTROLS BASIC INFORMATION AND TUTORIALS

When assessing the adequacy of existing controls or introducing new controls, a hierarchy of risk controls should be considered. The Management of Health and Safety at Work Regulations 1999 Schedule 1 specifies the general principles of prevention which are set out in the European Council Directive.

These principles are:
1. avoiding risks
2. evaluating the risks which cannot be avoided
3. combating the risks at source
4. adapting the work to the individual, especially as regards the design of the workplace, the choice
of work equipment and the choice of working and production methods, with a view, in particular, to alleviating monotonous work and work at a predetermined work-rate and to reducing their effects on health
5. adapting to technical progress
6. replacing the dangerous by the non-dangerous or the less dangerous
7. developing a coherent overall prevention policy which covers technology, organization of work, working conditions, social relationships and the influence of factors relating to the working environment
8. giving collective protective measures priority over individual protective measures and
9. giving appropriate instruction to employees.

These principles are not exactly a hierarchy but must be considered alongside the usual hierarchy of risk control which is as follows:

S elimination
S substitution
S engineering controls (e.g. isolation, insulation and
ventilation)
S reduced or limited time exposure
S good housekeeping
S safe systems of work
S training and information
S personal protective equipment
S welfare
S monitoring and supervision
S reviews.

POWER CIRCUIT BREAKER TYPES FOR SAFETY INFORMATION BASICS

The five general types of high-voltage circuit breakers are as follows.

1 Oil circuit breakers use standard transformer oil, an effective medium for quenching the arc and providing an open break after current has dropped to zero. There are two general types of oil circuit breakers: dead-tank for the higher voltage ranges and live-tank for lower voltages.

Oil circuit breakers have been improved by adding such features as oil-tight joints, vents, and separate chambers to prevent the escape of oil.

Also, improved operating mechanisms prevent gas pressure from reclosing the contacts, making them reliable for system voltages up to 362 kV. However, above 230 kV, oil-less breakers are more economical.

2 Air-blast circuit breakers were developed as alternatives to oil circuit breakers as voltages increased. They depend on the good insulating and arc-quenching properties of dry and clean compressed air injected into the contact region.

3 Magnetic-air circuit breakers use a combination of strong magnetic field with a special arc chute to lengthen the arc until the system voltage is unable to maintain the arc any longer. They are used principally in power distribution systems.

4 Gas circuit breakers take advantage of the excellent arc-quenching and insulating properties of sulfur hexafluoride (SF6) gas. These outdoor breakers can interrupt system voltages up to 800 kV.

These circuit breakers are typically included in gasinsulated substations (GISs) that offer space-saving and environmental advantages over conventional outdoor substations. Gas (SF6) circuit breakers are made with ratings up to 800 kV and continuous cur rent up to 4000 A.

They are alternatives to oil and vacuum breakers for metal-clad and metal-enclosed switchgear up to 38 kV.

5 Vacuum circuit breakers, more accurately termed vacuum-bottle interrupters, are generally used for voltages up to 38 kV and continuous current ratings to 3000 A.

They are used for higher system voltage, current, and interrupting ratings, and are typically specified for metal-clad and metal-enclosed switchgear in distribution systems.

TRANSFORMER TERMS GLOSSARY BASIC INFORMATION AND TUTORIALS

The following technical terms apply to transformers.

BIL: An abbreviation for basic impulse level, a dielectric strength test. Transformer BIL is determined by applying a high-frequency square-wave voltage with a steep leading edge between the windings and between the windings and ground.

The BIL rating provides the maximum input kV rating that a transformer can withstand without causing insulation breakdown. The transformer must also be protected against natural or man-made electrical surges. The NEMA standard BIL rating is 10 kV.

Exciting current: In transformers, the current in amperes required for excitation. This current consists of two components: (1) real in the form of losses (no load watts) and (2) reactive power in kvar. Exciting current varies inversely with kVA rating from approximately 10 percent at 1 kVA to as low as 0.5 percent at 750 kVA.

Eddy-current losses: Contiguous energy losses caused when a varying magnetic flux sets up undesired eddy currents circulating in a ferromagnetic transformer core.

Hysteresis losses: Continuous energy losses in a ferromagnetic transformer core when it is taken through the complete magnetization cycle at the input frequency.

Insulating transformer: A term synonymous with isolating transformer, to describe the insulation or isolation between the primary and secondary windings. The only transformers that are not insulating or isolating are autotransformers.

Insulation system temperature: The maximum temperature in degrees Celsius at the hottest point in the winding.

Isolating transformer: See insulating transformer.

Shielded-winding transformer: A transformer with a conductive metal shield between the primary and secondary windings to attenuate transient noise.

Taps: Connections made to transformer windings other than at its terminals. They are provided on the input side of some high-voltage transformers to correct for high or low voltages so that the secondary terminals can deliver their full rated output voltages.

Temperature rise: The incremental temperature rise of the windings and insulation above the ambient
temperature.

Transformer impedance: The current-limiting characteristic of a transformer expressed as a percentage. It is used in determining the interrupting capacity of a circuit breaker or fuse that will protect the transformer primary.

Transformer voltage regulation: The difference between the no-load and full-load voltages expressed as a percentage. A transformer that delivers 200 V at no load and 190 V at full load has a regulation of 5 percent.

BUCK BOOST AUTOTRANSFORMERS BASIC INFORMATION AND TUTORIALS

The buck-boost transformer is a simple and economical means for raising a voltage that is too low or decreasing a voltage that is too high. This transformer can raise or lower voltage being supplied to the load more than ±5 percent, to improve the efficiency of the device or system.

Buck-boost transformers are small single-phase transformers designed to reduce (buck) or raise (boost) line voltage from 5 to 20 percent. A common application is boosting 208 V to 230 or 240 V AC.

For example, there might be a requirement to power the motor in an air conditioner with a 230- or 240-V AC motor from the 208-V AC supply line. This can be done with a buckboost transformer.

Buck-boost transformers are standard distribution transformers with ratings ranging from 50 VA to 10 kVA. Commercial units are made with primary voltages of 120, 240, or 480 V AC.

They can also power low-voltage circuits for control or lighting applications requiring 12, 16, 24, 32, or 48 V AC. Schematics of buck-boost transformers that can transform 120 and 240 V AC to 12 and 24 V AC are shown in the figure below.

When the primary and secondary lead wires of buck-boost transformers are connected together electrically in a recommended bucking or boosting connection, they become autotransformers. Some typical connection diagrams for these transformers in autotransformer arrangements for single-phase systems are shown below.

Buck-boost transformers have four windings for versatility. Their two primary and two secondary windings can be connected eight different ways to provide many different voltage and kVA outputs.

Because their output voltage is a function of input voltage, they cannot be used as voltage stabilizers. Output voltage will vary by the same percentage as the input voltage.

These transformers can also function in three-phase systems. Two or three units can be used to buck or boost three-phase voltage. The number of units needed in a three-phase installation depends on the number of wires in the supply line.

OVER CURRENT PROTECTIVE DEVICES FOR GENERATORS BASIC INFORMATION AND TUTORIALS

What are the basic overcurrent protection devices for generators?

As with other motors, NEC 445.11 requires a generator to have a nameplate giving the manufacturer’s name, the rated frequency, power factor, number of AC phases, the subtransient and transient impedances, the rating in kilowatts or kilovolt amperes, a rating for the normal volts and amps, rated revolutions per minute, insulation system class, any rated ambient temperature or temperature rise, and a time rating.

The size and type of OCPD will be based on this critical data. NEC 445.12 defines the basic overcurrent protection standards for various types of generators. A constant-voltage generator must be protected from overloads by either the generator’s inherent design or circuit breakers, fuses, or other forms of overcurrent protection that are considered suitable for the conditions of use.

This is true except for AC generator exciters.

Two-wire, DC generators are allowed to have overcurrent protection in only one conductor if the overcurrent device is triggered by the entire current that is generated other than the current in the shunt field. For this reason, the overcurrent device cannot open the shunt field.

If the two-wire generator operates at 65 V or less and is driven by an individual motor then the overcurrent device protection device needs to kick-in if the generator is delivering up to 150% of its full-load rated current.

When a two-wire DC generator is used in conjunction with balancer sets it accomplishes the neutral points for the three-wire system. This means it requires an overcurrent device that is sized to disconnect the three-wire system if an extreme unbalance occurs in the voltage or current.

For three-wire DC generators, regardless of whether they are compound or shunt wound, one overcurrent device must be installed in each armature lead, and must be connected so that it is activated by the entire current from the armature.

These overcurrent devices need to have either a double-pole, double-coil circuit breaker or a four-pole circuit breaker connected in both the main and equalizer leads, plus two more overcurrent devices, one in each armature lead.

The OCPD must be interlocked so that no single pole can be opened without simultaneously disconnecting both leads of the armature from the system.

The ampacity of the conductors that run from the generator terminals to the first distribution device that contains overcurrent protection cannot be less than 115% of the nameplate current rating for the generator per NEC 445.13.

All generators must be equipped with at least one disconnect that is lockable in the open position that will allow the generator and all of its associated protective devices and controls to be disconnected entirely from the circuits that are supplied by the generator.

ARC FLASH BOUNDARY SAFE DISTANCE BASIC INFORMATION AND TUTORIALS

Arc-flash boundaries need to be established around electrical equipment such as switchboards, panelboards, industrial control panels, motor control centers, and similar equipment if you plan to work on or in the proximity of exposed energized components.

Parts are considered exposed if they are energized and not enclosed, shielded, covered, or otherwise protected from contact. Work on these parts includes activities such as examinations, adjustment, servicing, maintenance, or troubleshooting.

Equipment energized below 240 V does not require arc-flash boundary calculation unless it is powered by a 112.5 KVA transformer or larger.

The arc-flash boundary is the limit at which a person working on energized parts can be standing at the time of an arc-flash without risking permanent injury unless they are wearing flame-resistant clothing. Permanent injury results from an arc-flash that causes an incident energy of 1.2 calories/centimeter2 (cal/cm2) or greater and causes a minimum of second-degree burns.

This distance can only be effectively determined by calculating the destructive potential of an arc.

First you must determine the magnitude of the arc based on the available short circuit current, then estimate how long the arc will last based on the interrupting time of the fuse or circuit breaker.

Finally, you will need to calculate how far away an individual must be to avoid being exposed to an incident energy of 1.2 cal/cm2. It may sound like a lot of math and factoring in of potentials, but believe me the extra time you take to determine the arc flash boundary is well worth your safety and well-being.

Calculating flash protection boundaries for systems over 600 V requires performing a flash hazard analysis coupled with either the NFPA 70E Hazard Risk Category/PPE tables or the Incident Energy Formula.

Additionally, Section 4 of IEEE 1584 Guide for Arc Flash Hazard Calculations states that the results of the arc flash hazard analysis are used to identify the flash-protection boundary and the incident energy at assigned working distances throughout any position or level in the overall electrical system.

The purpose is to establish safe work distances and the PPE required to protect workers from injury. A flash-hazard analysis is comprised of the following three different electrical system studies:

1. A short circuit study
2. A protective device time-current coordination study
3. The flash-hazard analysis and application of the data

ELECTRICAL PROTECTIVE HIGH TENSION GLOVES BASIC INFORMATION AND TUTORIALS

What are high tension gloves?

High voltage gloves are a form of PPE that is required for employees who work in close proximity to live electrical current. OSHAs Electrical Protective Equipment Standard (29 CFR 1910.137) provides the design guidelines and in-service care and use requirements for electrical insulating gloves and sleeves as well as insulating blankets, matting, covers, and line hoses.

Electrical protective gloves are categorized by the level of voltage protection they provide. Voltage protection is broken down into the following classes:

n Class 0—Maximum use voltage of 1000 V AC/proof tested to 5000 V AC.

n Class 1—Maximum use voltage of 7500 V AC/proof tested to 10,000 V AC.

n Class 2—Maximum use voltage of 17,000 V AC/proof tested to 20,000 V AC.

n Class 3—Maximum use voltage of 26,500 V AC/proof tested to 30,000 V AC.

n Class 4—Maximum use voltage of 36,000 V AC/proof tested to 40,000 V AC.

Once the gloves are issued, OSHA requires that they be maintained in a safe, reliable condition. This means that high voltage gloves must be inspected for any damage before each day’s use, and immediately following any incident that may have caused them to be damaged.

This test method is described in the ASTM section F 496, Specification for In-Service Care of Insulating Gloves and Sleeves. Basically, the glove is filled with air, manually or by an inflator, and then checked for leakage.

The easiest way to detect leakage is by listening for air escaping or holding the glove against your cheek to feel air releasing.

OSHA recognizes that gloves meeting ASTM D 120-87, Specification for Rubber Insulating Gloves, and ASTM F 496, Specification for In- Service Care of Insulating Gloves and Sleeves, meet its requirements.

In addition to daily testing, OSHA requires periodic electrical tests for electrical protective equipment and ASTM F 496 specifies that gloves must be electrically retested every 6 months. Many power utility companies will test gloves and hot sticks for a reasonable fee.

RECOGNIZING HAZARDS IN ELECTRICAL WORKS BASIC INFORMATION AND TUTORIALS

The first step is to recognize and identify the existing and potential hazards associated with the work you need to perform. A task and hazard analysis and pre-job briefing are two of the tools you can utilize to ascertain the risks involved in your work for the day.

It’s a good idea to include everyone who will be involved in the task or associated work to discuss and plan for the hazards. Sometimes a coworker will think of hazards that you have overlooked, and it will ensure that everyone involved will be on the same page.

Careful planning of safety procedures reduces the risk of injury. Determine whether everyone has been trained for the job they need to do that day. Do you need to present a safety training focused on specific risks that are present today?

Decisions to lockout and tagout circuits and equipment and any other action plans should be made part of recognizing hazards. Here are some other topics to address:

n Is the existing wiring inadequate?
n Is there any potential for overloading circuits?
n Are there any exposed electrical parts?
n Will you be working around overhead power lines?
n Does any of the wiring have damaged insulation that will produce a shock?
n Are there any electrical systems or tools on the site that are not grounded or double insulated?
n Have you checked the condition of any power tools that will be used to confirm that they are not damaged and that all guards are in place?
n What PPE is required for the tasks to be performed?
n Have you reviewed the MSDS for any chemicals present on the site or that will be used that could be harmful?
n Will any work need to be performed from ladders or scaffolding and are these in good condition and set-up properly? Is there any chance of ladders coming in contact with energized circuits?
n Are the working conditions or equipment likely to be damp or wet or affected by humidity?

AMERICAN NATIONAL STANDARD INSTITUTE (ANSI) AND ITS RELATION TO SAFETY

American national standards institute

The ANSI is a nonprofit organization that oversees the development of voluntary standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international standards so that American products can be used worldwide.

For example, standards make sure that people who own cameras can find the film they need for them anywhere around the globe.

The ANSI mission is to enhance the global competitiveness of U.S. business and the U.S. quality of life by promoting and facilitating conformity and voluntary consensus standards and maintaining their integrity.

ANSI accredits standards that ensure consistency among the characteristics and performance of products, that people use the same definitions and terms regarding materials, and that products are tested the same way.

ANSI also accredits organizations that certify products or personnel in accordance with requirements that are defined in international standards. The institute is like the umbrella that covers thousands of guidelines that directly impact businesses in almost every sector.

Everything from construction equipment, to dairy standards, to energy distribution, and electrical materials is affected. ANSI is also actively engaged in accrediting programs that assess conformance to standards, including globally recognized programs such as the ISO 9000 Quality Management and ISO 14,000 Environmental Systems.

The ANSI has served as administrator and coordinator of the United States private sector voluntary standardization system since 1918. It was founded by five engineering societies and three government agencies.

Today, the Institute represents the interests of its nearly 1000 company, organization, government agency, institutional, and international members through its headquarters in Washington, D.C. Accreditation by ANSI signifies that a procedure meets the Institute’s essential requirements for openness, balance, consensus, and due process safeguards.

For this reason, American National Standards are referred to as “open” standards. In this context, open refers to a process that is used by a recognized organization for developing and approving a standard. The Institute’s definition of “open” basically refers to a collaborative, balanced, and consensus-based approval process.

The criteria used to develop these open standards balance the interests of those who will implement the standard with the interests and voluntary cooperation of those who own property or use rights that are essential to or affected by the standard.

For this reason, ANSI standards are required to undergo public reviews. In addition to facilitating the creation of standards in our country, ANSI promotes the use of U.S. standards internationally and advocates U.S. policy and technical positions in international and regional standards organizations.

OHSA FREQUENT VIOLATION CATEGORIES BASIC INFORMATION

OSHA relies heavily on data and statistics to formulate its regulations and focus its attention on workplace safety. The most frequently violated OSHA construction industry standards include the following categories:

Aerial lifts (OSHA 1926.453)
Electrical general requirements (OSHA 1926.403)
Electrical wiring design and protection (OSHA 1926.404)
Electrical wiring methods, components, and equipment for general use (OSHA 1926.105)
Eye and face protection (OSHA 1926.102)
Fall protection practices (OSHA 1926.502) and fall protection training requirements (OSHA 1926.503)
General duty requirements (OSHA 5 A 1)
General safety and health regulations (OSHA 1926.20)
Head protection (OSHA 1926.100)
Ladder safety (OSHA 1926.1053)
Recordkeeping requirements (OSHA 1926.1101)
Scaffolding safety practices (OSHA 1926.451) and scaffolding training requirements (OSHA 1926.21)

There are many safety compliance issues for the average small company to digest. But OSHA is not some big, bad wolf that lurks in the shadows waiting to pounce on unsuspecting employers.

OSHA seeks to identify clear and realistic priorities and to provide employers with the tools and opportunity to protect their workers by emphasizing safety and health. OSHA’s purpose is to save lives, prevent workplace injuries and illnesses, and protect the health of all American workers.

Whenever possible, OSHA’s primary emphasis is on the implementation of hazard control strategies that are based on prevention, and reducing hazardous exposures at their source. For these reasons, OSHA focuses the majority of its field activities on workplaces and job sites where the greatest potential exists for injuries and illnesses.

OZONE METER BASIC INFORMATION AND TUTORIALS

What is an ozone meter?


Description and Application.
The detector uses a thin-film semiconductor sensor. A thin-film platinum heater is formed on one side of an alumina substrate.

A thin-film platinum electrode is formed on the other side, and a thin-film semiconductor is formed over the platinum electrode by vapor deposition. The semiconductor film, when kept at a high temperature by the heater, will vary in resistance due to the absorption and decomposition of ozone. The change in resistance is converted to a change of voltage by the constant-current circuit.

The measuring range of the instrument is 0.01 ppm to 9.5 ppm ozone in air. The readings are displayed on a liquid crystal display that reads ozone concentrations directly. The temperature range is 0°-40° C, and the relative humidity range is 10%-80% RH.

Calibration.
Calibrate instrument before and after each use. Be sure to use a well-ventilated area since ozone levels may exceed the PEL for short periods. Calibration requires a source of ozone.

Controlled ozone concentrations are difficult to generate in the field, and this calibration is normally performed at SLTC. Gas that is either specially desiccated or humidified must not be used for preparing calibration standards, as readings will be inaccurate.

Special Considerations.
• The instrument is not intrinsically safe.
• The instrument must not be exposed to water, rain, high humidity, high temperature, or extreme temperature fluctuation.
• The instrument must not be used or stored in an atmosphere containing silicon compounds, or the sensor
will be poisoned.
• The instrument is not to be used for detecting gases other than ozone. Measurements must not be performed when the presence of organic solvents, reducing gases (such as nitrogen monoxide, etc.), or smoke is suspected; readings may be low.

Maintenance. 
The intake-filter unit-Teflon sampling tube should be clean and connected firmly. These should be checked before each operation. Check the pump aspiration and sensitivity before each operation.

TOXIC GAS METERS BASIC INFORMATION AND TUTORIALS

What is a toxic gas meter?


Description and Application.
This analyzer uses an electrochemical voltametric sensor or polarographic cell to provide continuous analyses and electronic recording. In operation, sample gas is drawn through the sensor and absorbed on an electrocatalytic sensing electrode, after passing through a diffusion medium.

An electrochemical reaction generates an electric current directly proportional to the gas concentration. The sample concentration is displayed directly in parts per million. Since the method of analysis is not absolute, prior calibration against a known standard is required.

Exhaustive tests have shown the method to be linear; thus, calibration at a single concentration, along with checking the zero point, is sufficient.

Types: Sulfur dioxide, hydrogen cyanide, hydrogen chloride, hydrazine, carbon monoxide, hydrogen sulfide, nitrogen oxides, chlorine, and ethylene oxide. These can be combined with combustible gas and oxygen meters.

Calibration. 
Calibrate the direct-reading gas monitor before and after each use in accordance with the manufacturers instructions and with the appropriate calibration gases.

Special Considerations.

• Interference from other gases can be a problem. See manufacturers literature.

• When calibrating under external pressure, the pump must be disconnected from the sensor to avoid sensor damage. If the span gas is directly fed into the instrument from a regulated pressurized cylinder, the flow rate should be set to match the normal sampling rate.

• Due to the high reaction rate of the gas in the sensor, substantially lower flow rates result in lower readings. This high reaction rate makes rapid fall time possible simply by shutting off the pump. Calibration from a sample bag connected to the instrument is the preferred method.

INFRARED ANALYZERS BASIC INFORMATION AND TUTORIALS

What is an Infrared Analyzer?

Description and Applications.
The infrared analyzer is used as a screening tool for a number of gases and vapors and is presently the recommended screening method for substances with no feasible sampling and analytical method.

These analyzers are often factory-programmed to measure many gases and are also user-programmable to measure other gases. A microprocessor automatically controls the spectrometer, averages the measurement signal, and calculates absorbance values.

Analysis results can be displayed either in parts per million (ppm) or absorbance units (AU). The variable path-length gas cell gives the analyzer the capability of measuring concentration levels from below 1 ppm up to percent levels.

Some typical screening applications are:

• Carbon monoxide and carbon dioxide, especially useful for indoor air assessments;
• Anesthetic gases including, e.g., nitrous oxide, halothane, enflurane, penthrane, and isoflurane;
• Ethylene oxide; and
• Fumigants including e.g. ethylene dibromide, chloropicrin, and methyl bromide.

Calibration.
The analyzer and any strip-chart recorder should be calibrated before and after each use in accordance with the manufacturer's instructions.

Special Considerations. 
The infrared analyzer may be only semispecific for sampling some gases and vapors because of interference by other chemicals with similar absorption wavelengths.

Maintenance. 
No field maintenance of this device should be attempted except items specifically detailed in the instruction book such as filter replacements and battery charging.

NEW EMPLOYEE SAFETY ORIENTATION TUTORIALS AND TIPS

For employers with a safety manager, the manager can conduct the classroom part of orientation/training, prepare all the training materials (handouts, forms, checklists, lesson plan, etc.), conduct the employee evaluation, and maintain all documentation. The facility supervisor(s) can conduct the on-the-job training and observation, and determine when the employee is çéady for the evaluation.

For employers or departments without a safety manager, the company safety committee can share responsibilities for conducting the job hazard analyses and the training program. The safety committee can put together the orientation/training materials, conduct the "classroom" training, and keep records. The department where employees will work can conduct the hands-on training.

During the orientation period, introduce new workers to all the basic safety information that applies to their work areas, such as:

• General hazards in the work area;
• Specific hazards involved in each task the employee performs;
• Hazards associated with other areas of the facility;
• Company safety policies and work rules;
• Proper safety practices and procedures to prevent accidents;
• The location of emergency equipment such as fire extinguishers, eyewash stations, first-aid supplies, etc.;
• Smoking regulations and designated smoking areas;
• Emergency evacuation procedures and routes;
• Who to talk to about safety questions, problems, etc.;
• What to do if there is an accident or injury;
• How to report emergencies, accidents, and near misses;
• How to select, use, and care for personal protective equipment;
• Safe housekeeping rules;
• Facility security procedures and systems;
• How to use tools and equipment safely;
• Safe lifting techniques and materials-handling procedures; and
• Safe methods for handling, using, or storing hazardous materials and the location of material safety data sheets.

Orientation programs can be updated and refined by reviewing accident near-miss reports. Near-miss reports offered early warning signs of new or recurrent hazards in the workplace that must be corrected before someone gets hurt or equipment is damaged.

An evaluation of illness and injury reports are also a catalyst for changes in safety orientation and training programs. Orientation can involve several ley els of new employee involvement, from awareness information to formal training programs.

Awareness orientation/training informs employees about a potential hazard in the workplace and their role in responding to the hazard, even though they are not directly exposed to the hazard. For example, "affected" employees can be told about locks and tags for electrical systems without being trained how to implement the lockout/tagout program.

It is useful to rely on a checklist to ensure that appropriate safety orientation is provided to new workers. These checklists should be modified to fit the needs of the organization or site.