Hazards mechanical systems

Werley, B. M., ASTMSpec. Tech. Publ., 1983, (812), 108-125 The hazards arising from presence of oil films in oxygen-handling systems are reviewed, with consideration of cleanliness specifications, film flammability, film migration and hazard mechanisms. 

In most workplace and transport chemical hazard communication systems, training is also a component. In consumer settings, however, the container label is the only communication mechanism available to provide information on safe handling and use. 

One of the new creative ideas to promote employee involvement and the expression of their ideas is the targeted hazard identification system. This system provides an easy and cost-efficient method through which employees are trained to identify safety hazards in their workplace and provides a mechanism through which the hazard can be corrected. Additionally, this system provides a simple method by which employees can express their ideas and acquire feedback within a 24-hour time period (see Appendix C for program details). Important components of this program are the anployee involvement and the acquisition of their opinions to generate corrective action. 

The Safety Documents can be a Permit for Work , a Limited Work Certificate and/or a Sanction for Test . These SAPs are responsible for ensuring that the precautions laid down in the Safety Rules are taken before access or work is permitted. This includes making sure all appropriate electrical supplies, mechanical systems and other hazards are isolated, so that the work can proceed safely. The SAP must determine that the recipient of the Safety Documentation understands all aspects of the work or tests. 

Tuned Mass Damper (TMD) A mechanical system including amass block, spring, and a viscous damper able to absorb the entrance energy from the environmental hazards such as winds and earthquake excitations. 

Permit to work (P.T.W) is a formal written system to control certain types of work which are identified as potentially hazardous. This system may need to be used in high-risk jobs such as hot works, confined space entry, carrying hazardous substances, and electrical or mechanical isolation. In this system, responsible persons should assess the work and check safety at all stages. Moreover, permits are effectively a means of communication between site management, plant supervisors and operators, and those who carry out the work. The people doing the job sign the permit to show that they understand the risks and precautions necessary. 

As mentioned previously, ISO 26262 defines functional safety as freedom of unacceptable risks based on hazards, which are caused by malfunctional behavior of E/E-systems. However, interactions of systems with E/E-functions are included as well and therefore also mechatronic systems. Whether pure mechanical systems really show not any interactions with E/E is doubtful. Furthermore, the introduction chapter of ISO 26262, which describes the scope of the norm, excludes hazards such as electric shock, fire, smoke, heat, radiation, poisoning, inflammation, (chemical) reactions, corrosion, release of energy or comparable hazards, as long as the failure was not caused by electrical components. Such hazards are caused more by the battery as well as the poisonous electrolytes in the capacitors. Whether a motor winding is an electrical device or a mechanical component is also questionable. 

Automated or mechanized systems must be chosen in certain situations, particularly where operator safety is paramount, for example, hazardous or toxic environments, heavy component parts or a high repeatability requirement causing operator fatigue. 

Lloyd and Tye (1995) recall that the airworthiness requirements (e.g. BCAR and FAR) of the mid-20th century were devised to suit the circumstances. Separate sets of requirements were stated for each type of system and they dealt with the engineering detail intended to secure sufficient reliability . Where the system was such that its failure could result in a serious hazard, the degree of redundancy (i.e. multiplication of the primary systems or provision of emergency systems) was stipulated. Compliance was generally shown by some sort of an FMEA. For simple, self-contained systems this approach had its merits. However, systems rapidly became more complex. Complex systems have a considerable amount of interfaces and cross/interconnections between the electrical, avionic, hydraulic and mechanical systems. In addition, there are essential interfaces with the pilot, maintenance personnel and flight performance of the aircraft. The aircraft designer is thus faced not only with the analysis of each individual system independently, but also needs to consider how these systems act in concert with other systems. 

Fault Tree Analysis Faiilt tree analysis permits the hazardous incident (called the top event) frequency to be estimated from a logic model of the failure mechanisms of a system. The top event is traced downward to more basic failures using logic gates to determine its causes and hkelihood. The model is based on the combinations of fail-... 

Loss of containment due to mechanical failure or misoperation is a major cause of chemical process accidents. The design or storage systems should be based on minimizing the hkelihood of loss of containment, with the accompanying release of hazardous materials, and on limiting the amount or the release. An effective emergency response program that can reduce the impacts of a release should be available. 

Low power usage Very long life No Oil required Low system weight Reduced fire hazard Vibration sensors built-in Small load capacity Large size Higher investment Requires mechanical backup for power interruptions New technology Possible rotor-d3ntiamic problems... 

Examining a candidate toller s records of formal reporting and follow-up on mechanical deficiencies or hazardous conditions is imperative. The assessor should verify whether such a system is in place and is effective. 

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