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.

RELIABILITY CENTERED MAINTENANCE (RCM)

What is Reliability Centered Maintenance?
Reliability-Centered Maintenance (RCM) is the process of determining the most effective maintenance approach. The RCM philosophy employs Preventive Maintenance (PM), Predictive Maintenance (PdM), Real-time Monitoring (RTM), Run-to-Failure (RTF- also called reactive maintenance) and Proactive Maintenance techniques in an integrated manner to increase the probability that a machine or component will function in the required manner over its design life cycle with a minimum of maintenance.

The goal of the philosophy is to provide the stated function of the facility, with the required reliability and availability at the lowest cost. RCM requires that maintenance decisions be based on maintenance requirements supported by sound, technical, and economic justification.

A Brief History of RCM
RCM originated in the Airline industry in the 1960s. By the late 1950s, the cost of maintenance activities in this industry had become high enough to warrant a special investigation into the effectiveness of those activities. Accordingly, in 1960, a task force was formed consisting of representatives of both the airlines and the Federal Aviation Administration (FAA) to investigate the capabilities of preventive maintenance.

The establishment of this task force subsequently led to the development of a series of guidelines for airlines and aircraft manufacturers to use, when establishing maintenance schedules for their aircraft.

This led to the 747 Maintenance Steering Group (MSG) document MSG-1; Handbook: Maintenance Evaluation and Program Development from the Air Transport Association in 1968. MSG-1 was used to develop the maintenance program for the Boeing 747 aircraft, the first maintenance program to apply RCM concepts. MSG-2, the next revision, was used to develop the maintenance programs for the Lockheed L 1011 and the Douglas DC-10.

The success of this program is demonstrated by comparing maintenance requirements of a DC-8 aircraft, maintained using standard maintenance techniques, and the DC-10 aircraft, maintained using MSG-2 guidelines. The DC-8 aircraft has 339 items that require an overhaul, verses only seven items on a DC-10.

Using another example, the original Boeing 747 required 66,000 labor hours on major structural inspections before a major heavy inspection at 20,000 operating hours. In comparison, the DC-8 - a smaller and less sophisticated aircraft using standard maintenance programs of the day required more than 4 million labor hours before reaching 20,000 operating hours.

In 1974 the U.S. Department of Defense commissioned United Airlines to write a report on the processes used in the civil aviation industry for the development of maintenance programs for aircraft. This report, written by Stan Nowlan and Howard Heap and published in 1978, was entitled Reliability Centered Maintenance,5 and has become the report upon which all subsequent Reliability Centered Maintenance approaches have been based.

What Nowlan and Heap found was that many types of failures could not be prevented no matter how intensive the maintenance activities were. Additionally it was discovered that for many items the probability of failure did not increase with age. Consequently, a maintenance program based on age will have little, if any effect on the failure rate.

THE SAFETY-RELATED CASE FOR ELECTRICAL MAINTENANCE

The relationship between safety and preventive maintenance is not a difficult one to establish. Properly designed equipment that is properly installed is well capable of doing its job when it is new.

As equipment ages however, several factors begin to take their toll on electrical equipment.

● Dust, dirt, and other contaminants collect on equipment causing the equipment to overheat and bearings and other moving parts to bind.

● Vibration causes hardware to loosen. Subsequent operations of equipment can cause joints and equipment to fail explosively.

● Heat and age can cause insulation to fail, resulting in shock hazards to personnel.

● Increased loads, motor starting surges, and power quality issues such as harmonics combine to increase the aging process and set the stage for equipment failure.

Unfortunately, the ultimate failure of unmaintained equipment usually occurs when the equipment is needed the most—during electrical faults. Such failures result in arc and blast events that can and do harm workers in the area.

They also result in significant downtime, loss of equipment, and construction cost incurred in rebuilding the equipment. The only way to ensure that electrical equipment continues to operate in an optimal manner is to maintain it so that it stays in factory-new-operating condition.

Regulatory
As discussed above and in previous chapters, the catastrophic failure of electrical equipment creates severe hazards for personnel working in the area. Recognizing this the

Standard for Electrical Safety in the Workplace (NFPA 70E)3 requires that electrical equipment be properly maintained to minimize the possibility of failure.

Relationship of Improperly Maintained Electrical Equipment to the Hazards of Electricity

Improperly maintained equipment may expose workers to any of the three electrical hazards. For example:

1. Improperly maintained tools or flexible cord sets (extension cords) can have frayed insulation which exposes the energized conductors and allows them to contact the worker or the metallic tool the worker is using. The result is an electric shock.

2. Improperly maintained protective devices, such as circuit breakers or fuses, can fail when interrupting an overcurrent. Such a failure is likely to be explosive; consequently, the worker is exposed to electrical arc and electrical blast.

3. Improperly maintained connections can overheat resulting in any of the following:
a. melted insulation, exposed conductors, and the attendant electrical shock hazard
b. fire
c. failed connections resulting in electrical arc and blast

4. Improperly maintained switchgear, motor control centers, or panelboards can fail explosively when an arc occurs internally. This exposes workers to the effects of electrical blast and possibly electrical arc.