Downloads & Free Reading Options - Results

An electrostatic hazards assessment of procedures and service clothing used during flightline operations that involve electro-explosive devices (EEDs) has been completed. The assessment includes measurements of the body-to-ground resistance, capacitance and body potential for personnel in service clothing. Activities involved in the loading of 20 mm ammunition into an F/A-18 aircraft provide a focus for the investigation.

An electrostatic hazards assessment of procedures and service clothing used during flightline operations that involve electro-explosive devices (EEDs) has been completed. The assessment includes measurements of the body-to-ground resistance, capacitance and body potential for personnel in service clothing. Activities involved in the loading of 20 mm ammunition into an F/A-18 aircraft provide a focus for the investigation.

An electrostatic hazards assessment of procedures and service clothing used during flightline operations that involve electro-explosive devices (EEDs) has been completed. The assessment includes measurements of the body-to-ground resistance, capacitance and body potential for personnel in service clothing. Activities involved in the loading of 20 mm ammunition into an F/A-18 aircraft provide a focus for the investigation.

This article is from Sensors (Basel, Switzerland) , volume 12 . Abstract At a solid/liquid interface, physico-chemical phenomena occur that lead to the separation of electrical charges, establishing a zone called electrical double layer. The convection of one part of these charges by the liquid flow is the cause of the flow electrification phenomenon which is suspected of being responsible of incidents in the industry. The P' Institute of Poitiers University and CNRS has developed an original sensor called “capacitive sensor” that allows the characterization of the mechanisms involved in the generation, accumulation and transfer of charges. As an example, this sensor included in the design of high power transformers, could easily show the evolution of electrostatic charge generation developed during the operating time of the transformer and, therefore, point out the operations leading to electrostatic hazards and, then, monitor the transformer to prevent such risks.

This report is a review of the various electrostatic discharge (ESD) threats to EEDs and electronics. Methods of overcoming these hazards are outlined. A description is also presented of the methods and standards used for vulnerability testing.

Conductivity additives ASA-3 and Stadis 450 have been found to significantly reduce static electricity in JP-4 containing approved additives when fuel conductivity is at least 100 CU at use temperatures. In the absence of conductivity additives, some additives caused increased charge accumulation which may have contributed to previous static ignited aircraft fires. Tests were performed in a Mobil Research small-scale electrification unit modified to simulate USAF fueling velocities and aircraft fuel tank configurations. (Author)

The electrical capacitances of a number of subjects wearing insulating or conductive types of footwear on various insulating or conductive floors have been measured. The values range from 150 - 300 micromicrofarads for insulated conditions to 700 - 1500 micromicrofarads for conducting conditions. The effective skin resistances during electrostatic discharges from the hands and finger tips have been determined; also several measurements have been made under low-voltage continuous-current conditions. The values of resistance determined by the dynamic method are considerably smaller than those given by the low-voltage method. The results of the capacitance and resistance measurements are discussed in relation to the electrostatic hazard of handling primary explosives, and to a possible circuit equivalent to a discharging person.

Assistance has been sought to assess the safety from electrostatic hazards of personnel cleaning the 45,000 L tank fabric collapsible (TFC) that is used by the Australian Army for fuel storage. Concerns centre on the level of electrostatic charge that may be generated on personnel while wearing protective suits and working inside the TFCs. If inappropriate attire is worn the energy of an electrostatic discharge from personnel can exceed the ignition energy of the most sensitive concentration fuel air mixture. Electrostatic tests were carried out on suits supplied and several conclusions regarding safe working conditions are listed. Although not directly related to electrostatics, other occupational health and safety aspects are raised in the report.

Assistance has been sought to assess the safety from electrostatic hazards of personnel cleaning the 45,000 L tank fabric collapsible (TFC) that is used by the Australian Army for fuel storage. Concerns centre on the level of electrostatic charge that may be generated on personnel while wearing protective suits and working inside the TFCs. If inappropriate attire is worn the energy of an electrostatic discharge from personnel can exceed the ignition energy of the most sensitive concentration fuel air mixture. Electrostatic tests were carried out on suits supplied and several conclusions regarding safe working conditions are listed. Although not directly related to electrostatics, other occupational health and safety aspects are raised in the report.

The report describes the results of an experimental evaluation of the Static Charge Reducer. The Static Charge Reducer is a device which automatically neutralizes an electrically charged fuel as the fuel flows through it. The tests conducted confirmed the claims that the Static Charge Reducer would reduce the charge density of a flowing hydrocarbon fuel to below 30 microcoulombs per cubic meter. The tests also indicate that two corrosion inhibitor fuel additives significantly affect the electrical conductivity of fuel containing the ASA-3 antistatic additive.

A study of electrostatic discharge hazards was conducted to determine the worse case situation in handling and producing propellants, pyrotechnics and explosives (PEP). Electrostatic charge generation, storage and mechanisms of discharge were studied. External versus internal generated discharges were studied. A set of guidelines were established to evaluate electrostatic charging, charge transfer, storage and discharges. Impedance matching is essential for ignition of a wide variety of materials in processing and handling.

An experiment investigation has been been carried out to determine the primary factors that have contributed to recent aircraft electrostatically induced ground refueling fire incidents. It was found that the explosion suppression open pore polyurethane fuel tank foams along with the charging characteristics of the JP-4 fuel resulted in charge accumulation and electrostatic spark discharging. The polyurethane foams accumulated charge due to their highly resistive nature (blue, 10 to the 15th power ohm-cm; red, 10 to the 14th power ohm-cm; yellow, to to the 14th opwer ohm-cm; and orange, 10 to the 13th power ohm-cm). The fuel flow rate and velocity entering the tank and impinging on the open pore polyurethane foam directly affected te magnitude of the charge separation which was occurring. The number of refuelings that had taken place also was a critical factor due to its effect on charge accumulation/discharge frequency levels. The last major variable investigated was pro-static (Gulf-178) and conductivity improving (shell ASA-3) fuel additives. The Gulf-178 additive dramatically increased the levels of charge separation and accumulation taking place along with a reversal in the polarity of charge. The Shell ASA-3 fuel additive eliminated the aircraft ground refueling electrostatic discharge hazard decreasing the level of charge accumulation.

RJ-1 fuel surface potential is measured with a probe to determine the degree of hazard originating from static electricity buildup in the hydraulic fluid. The probe is mounted in contact with the fluid surface and connected to an electrostatic voltmeter.

The experience is described of NASA and DOD with electrostatic problems, generation mechanisms, and type of electrostatic hazards. Guidelines for judging possible effects of electrostatic charges on space missions are presented along with mathematical formulas and definitions.

An investigation into the electrostatic phenomena associated with the manufacturing and handling of explosives is discussed. The testing includes measurement of the severity of the primary charge generation mechanism, triboelectric effects between dissimilar surfaces; refinement of equivalent circuits of the XM15/XM165 and E8 fuse trains; evaluation of the electrostatic spark discharge characteristics predicted by an equivalent circuit analysis; and determination of the spark ignition sensitivity of materials, components, junctions, and subassemblies which compose the XM15/XM165 and E8 units. Special studies were also performed. These special tests included ignition sensitivity of the complete XM15 fuse train when subjected to discharges through its entire length, measurement of electrostatic potentials which occur during the E8 foaming operation during fabrication, and investigation of the inadvertent functioning of an XM15 cluster during manufacturing. The test results are discussed and related to the effectiveness of suggested modification to reduce the electrostatic ignition sensitivity.