Electrostatic Hazards Research Articles

Graphene nanoplatelets/lead azide composites for the depressed electrostatic hazards

Graphene nanoplatelets/lead azide composites (GLA) were prepared by adding graphene nanoplatelets (GNP) to the reaction solution or coating the normal lead azide (LA) with GNP. Scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD) were used to characterize the morphology and the composition of the products. The electrostatic spark sensitivity and static electricity accumulation of the obtained samples were investigated in detail. Results exhibit excellent anti-electrostatic performance.

Progress in the Study of Antistatic Fibers

Functional textiles are the fashionable concept,not only conform to the present society fashionable tide but also promote environmental development and it has very wide development space. Antistatic fibers play a vital role in ensuring the safety of people. The paper discusses the electrostatic hazards of textile materials and antistatic principle of textiles.

Electrostatic Hazard in High-Power Transformers: Results of Ten Years of Experience With ${P}^{\prime}$ Capacitive Sensor

In a high-power transformer, oil flowing on pressboard surface is suspected to be responsible of electrostatic hazards and failures. Different methods of risk assessment have been proposed to understand and prevent it: ministatic tester in the Westinghouse protocol, ministatic tester in the spinning disk measurement, monitoring of tangent delta, dissolved gas measurement, etc. At P' Institute of Poitiers, an original sensor was developed and used for quantification of the electric charge generated and of accumulated charge for an oil flow onto the surface of a transformer pressboard insulated from ground. Operational for ten years, this bench has been used to study over a hundred couples of oil/pressboard, pairs of new oil and pressboard, pairs of aged oil and pressboard, pairs of suspicious oil and pressboards, etc. This paper presents a comparative analysis of these ten years of experience. This analysis provides, among other results, a critical electrostatic hazard assessment in transformers and an attempt of discrimination tentative of a suspected transformer.

Distribution of Electric Potential at the Surface of Corona-Charged Polypropylene Nonwoven Fabrics After Neutralization

Accumulation of electric charges on insulating surfaces is frequently at the origin of severe electrostatic hazards. The best solution to this problem is to neutralize these charges by the use of ac corona discharges. The aim of this work is to evaluate the efficiency of this process in the specific case of fibrous electrets, by measuring the repartition of the electric potential at the surface of nonwoven polypropylene fabrics before and after neutralization. The samples were charged for 10 s,in ambient air, using a triode-type corona electrode system of positive polarity. In all the experiments, the neutralization was performed 180 s after the charging process. In some of them, the neutralization electrode (tungsten wire with a diameter of 0.3 mm) was fixed at a given distance (50 mm) above the samples and energized from an ac voltage amplifier (model 30/20A, Trek, Inc., Medina, NY, USA). In other experiments, the samples moved at constant speed (3 cm/s) in the ac corona discharge zone generated by the neutralization electrode. The experimental results show that the efficiency of neutralization (expressed as the relative reduction of the average potential measured at the surface of the sample) depends on the amplitude and the frequency of the sinusoidal high voltage, as well as on the charging time and the neutralization duration. Better effects were recorded in the case of the samples that moved through the corona discharge zone.

Improvements for electrostatic discharge immunity in thermal printing head

Electrostatic discharge (ESD) is one of the important sources of electromagnetic interference which would cause a reversible or permanent damage in modem electronic equipment. ESD may be introduced by the human body operating the electronic equipment or accumulated by friction, heating or other reasons when the electronic equipment is working. In this paper we use the print head of the thermal printer (TPH) suffered from electrostatic hazard as an example to analyze the reasons of the ESD happening, and some necessary improvements measures for protection of the TPH are also suggested.

Artificial intelligence in electrostatic risk management

In the last two decades protection against electrostatic hazards became a very important topic. The increase in the range of possible faults fast automated systems and complex fault analysis is required. The tools of artificial intelligence and expert systems have been applied successfully on this field and this paper aims to take a step further. While giving some insight to the currently used tools, another AI method, the 'support vector machines' are introduced in this paper. Besides a brief review on SVMs they are introduced to the SCOUT system, a novel approach to electrostatic hazard management.

The facile synthesis of graphene nanoplatelet–lead styphnate composites and their depressed electrostatic hazards

Graphene nanoplatelet–lead styphnate composites (GLS) were prepared either by adding graphene nanoplatelets (GNP) to the reaction solution or by coating normal lead styphnate (LS) with GNP. The composites exhibited excellent anti-electrostatic performance with depressed electrostatic spark sensitivity and static electricity accumulation.

“Capacitive Sensor” to Measure Flow Electrification and Prevent Electrostatic Hazards

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.

Helmut Krämer memorial lecture: Electrostatic assessment of products and processes – A view backwards and forwards

Abstract In the last few decades, electrostatic knowledge as laid down in standards and regulations has developed from lean national documents to two comprehensive international IEC documents with more than 200 pages together. In this paper, the development of the knowledge on the electrostatic assessment of products and processes is given as well as expected future trends. As the work of Helmut Kramer was focused on electrostatic hazards of solids and liquids, the emphasis of this paper is placed on this topic too. Additionally, a curriculum vitae of Helmut Kramer and his contribution to this development is given in an annex .

Ester oils and flow electrification hazards in power transformers

In large power transformers where forced convection of the insulating liquid is the predominant heat transfer mean, the electrification risk can appear. This phenomenon has been suspected to be responsible for several failures. Studies have shown, in addition to the transformer design (shell or core type), that the type of liquid used is quite important in limiting these hazards. The goal of this paper is to present an analysis of ester oil behavior versus electrostatic hazard due to flow electrification. Two experimental studies were conducted on different ester oils: the first one is for measuring the Electrostatic Charging Tendency (ECT) by using ministatic charge tester, and the second one is made by mean of a test loop simulating the oil flow as in a real transformer and equipped with a capacitive sensor. This sensor is able to measure both the charge accumulation at the pressboard surface and the generating current. All these results are compared with those of mineral oils which are actually used for large power transformers. It was shown that even if ester oils increase the charge generation in comparison with mineral oil, the charge accumulation on the solid surface is not excessive thus limiting the potential at the solid/liquid interface and associated electrification hazards. One can assume that the higher conductivity of esters would enable a better evacuation of generated charges.

Static electricity: New guidance for storage tank loading rates

This article describes how the IEC TC31/101 JWG29 committee adapted a new theoretical model for practical use in the forthcoming IEC Technical Specification 60079-32-1, “Explosive Atmospheres - Part 32-1: Electrostatic hazards, Guidance”. The model, by Britton and Smith, addressed flow rate limits for the transfer of single-phase, static-accumulating flammable liquids into vertical cylindrical tanks containing no significant sediment or water bottom. Practical adaptation involved a technical evaluation of the model, optimization of variables in the empirical expression relating charging to flow velocity, plus selection of applicability limits in terms of tank size. From the results we present easy-to-use expressions for calculating the flow velocity and flow rate limits, plus tables of example solutions. We also show how to apply the flow velocity limits to piping systems that involve a multiplicity of flow velocities in different pipe segments. During the adaptation process, the model was extended to liquids such as simple ethers, whose dielectric constants exceed those of the hydrocarbons previously considered and, by introducing the concept of “effective diameter”, to square and nearly-square vertical tanks. Mathematical details are provided in an appendix. The information in this article is subject to a broad, comprehensive disclaimer of liability as expressed in Section 8. Tank loading system designs should be based on a recognized Code of Practice with consideration of all relevant requirements and limitations. The purpose of this article is to provide a detailed description of the theoretical considerations behind the new methodology. The article is of general interest since this is the first practical application of a technically-based “electrostatic” model to the tank loading problem. Of particular interest is how electrostatic theory plus empirical data have been reduced to yield a very simple flow velocity expression. The flow rate solutions and tables are the same as those given in the forthcoming IEC 60079-32-1 Technical Specification and are provided to assist other standards-setting agencies wishing to adopt the same guidance. © 2012 American Institute of Chemical Engineers Process Saf Prog, 2012

Sinusoidal and Triangular High-Voltage Neutralizers for Accelerated Discharge of Nonwoven Fibrous Dielectrics

Electric charge accumulation on fibrous dielectric media during manufacturing processes can easily attain high levels of electrostatic hazard. In a previous paper, the authors addressed the problem of the accelerated discharge of such materials using a commercial ion generator. The aim of this paper is to evaluate the various factors that influence the efficiency of charge neutralization performed using a wire-type corona electrode energized from either a sinusoidal or a triangular ac high-voltage supply. The experiments were performed on 400-μm-thick nonwoven sheets of polypropylene and polyester, in ambient air. The samples were charged for 10 s using a triode-type corona electrode system of negative polarity. The surface potential on the charged medium, which was in contact with the grounded electrode, was then measured with an electrostatic voltmeter. After 10 min, the medium was moved beneath a neutralizing electrode, connected to a high-voltage amplifier. The efficiency of the neutralization was quantified by the ratio between the surface potential after and prior to the charged sample exposure to ac corona discharge. The experimental design methodology was employed for evaluating the effects of two factors, namely, amplitude (range: 16-24 kV) and frequency (range: 20-400 Hz), of the neutralizing voltage. The potential at the surface of the nonwoven fabrics after neutralization was found to vary insignificantly with thermal conditioning and signal waveform but was significantly lower for higher frequencies and amplitudes.

An assessment of electrostatic ignition hazards associated with fuel flow through plastic pipes at roadside filling stations

Abstract The use of electrically insulating synthetic materials, such as high-density polyethylene (HDPE), for fuel pipelines and other fuel handling components is now widespread. It is well reported however that the flow of fuel under certain conditions in plastic pipes can produce measurable levels of electrostatic charge. This paper describes in detail a full-scale experimental test rig simulating a filling station layout – in particular the conditions existing during road tanker delivery of high-charging fuels. It presents data from a series of electrostatic measurements, discusses results and draws conclusions with regard to existing safety margins and precautions for safe operation.

Static Hazards of the VAST

The vertical atmospheric storage tank (VAST) is a large, mechanically weak tank often used to store static accumulating flammable liquids. Explosion of a single VAST can destroy an entire tank farm via rocketing and domino effects. This article provides a new methodology for assessing electrostatic hazards. Appendix A describes flammability aspects, including a new analysis of flash point measurement errors. Appendix B discusses two recent VAST explosions. Recommendations are made for improving the safety of VAST operations. Electrostatic analysis starts with our previously published model expressing the surface potential at the center of the liquid surface “Vmax” in the form of an infinite series of Bessel and hyperbolic functions. A truncated one-term approximation with an improved scale factor “κ” is provided to facilitate spreadsheet calculation. Using at least the first three terms of the series expansion, thousands of individual calculations were made for a wide range of tank dimensions, filling rates and liquid relaxation times, to determine the maximum potential “V∗max” attained during filling, which occurs at some critical depth “Dcrit”. It’s shown there exists a critical width “wcrit”, typically 0.75-1.5 m, at which V∗max reaches a maximum for a given flow rate and relaxation time. At widths above the critical width, V∗max becomes independent of flow rate and, provided the aspect ratio (H/w) of the VAST exceeds 2/3, V∗max becomes independent of height (H) as well. The worst case for VAST filling is a width near “wcrit” plus an effective liquid relaxation time ∼30 s (measured conductivity ∼1 pS/m). We derived very simple expressions for the critical width “wcrit”, the critical liquid depth “Dcrit”, the V∗max yielded by a given charging current “IC”, and the charging current needed to yield a particular V∗max. Of particular interest were the conditions for V∗max = 25 kV, the recognized threshold for incendiary brush discharges. Assuming a worst case 30 s relaxation time and a maximum allowable V∗max of 25 kV, we examined three different expressions for the charging current “IC” and determined the minimum “vd” product (flow velocity x inlet pipe diameter) that could theoretically produce this potential. Equations and graphs are presented showing that the maximum allowable vd product increases with increased VAST width (beyond the critical width) and varies with the assumed charging equation. It’s shown that the classic “Schon” equation isn’t conservative and that charging currents are likely to be much higher than predicted, especially when the diameter of the inlet pipe is less than about 0.1 m (4-inch) and the liquid has a high charging tendency. The “vd” expressions and graphs should assist in the development of Codes of Practice. The uniform charge density assumption used in our model is most valid as conditions approach worst-case, since for widths near the critical width the jet mixing time constant at typical flow rates is small compared with the assumed “worst case” 30 s relaxation time constant. However, in practical cases, jetting from bottom side entry inlets may greatly increase charge densities at the liquid surface. This plus other non-idealities such as water and sediment in tank bottoms are discussed with reference to practical VAST operations.

Study and Application of ESD Generator Modele

Phenomenon of electrostatic hazards is becoming increasingly prominent with wide application of microelectronic elements. Electrostatic Discharge (ESD) is an extremely complex process, which is not only related to the materials, the object shape and the value of discharging circuit resistance, but also always involved in very complicated process of gas breakdown, so ESD is also a stochastic process which is difficult to repeat. According to the request of standard IEC61000-4-2, simulation circuit of the equivalent Human-Metal Model is established, discharging process is simulated and analyzed, and the influence laws of circuit parameters and distribution parameters for ESD current waveform are obtained. Thus the structure of discharging circuit and element parameters can be determined, test results can be verified to some extent, and the characteristics and influencing factors of ESD process can be known better. Simulation results show that waveform parameters are all within the range of standard errors, which proves that the design of model parameters is correct, the analysis of ESD process is reasonable.

Study on the test method of the electrostatic sensitivity of the non-initiating explosive devices

Abstract The application of the non-initiating explosive devices may cause the problems of the electrostatic hazard. With the support of the fitting test apparatuses, the anti-electrostatic ability and/or the electrostatic sensitivity of the tested samples can be accurately measured and assessed by adopting the test method of the initiating explosive devices. The related results could provide a scientific evidence for the establishment of safety standards and the adoption of preventive and protective measures.

Electrostatic hazards with underground plastic pipes at petrol stations

The paper analyses some ignition incidents that have been reported with insulating, (non-conductive) underground plastic pipes in retail petrol stations. The occurrence of the incidents is compared with voltage measurements, observations of the typical spread of streaming currents recorded in gasoline handling and theoretical estimates of the voltages on the pipes. The comparisons suggest that neither incendive sparks from unbonded conductors nor incendive brush discharges from insulating pipe surfaces can be ruled out although both are expected to be rare. The hazards can be prevented by using pipes with earthed conductive or dissipative inner linings.

Explosion safety in industrial electrostatics

Complicated industrial systems are often endangered by electrostatic hazards, both from atmospheric (lightning phenomenon, primary and secondary lightning protection) and industrial (technological problems caused by static charging and fire and explosion hazards.) According to the classical approach protective methods have to be used in order to remove electrostatic charging and to avoid damages, however no attempt to compute the risk before and after applying the protective method is made, relying instead on well-educated and practiced expertise. The Budapest School of Electrostatics – in close cooperation with industrial partners – develops new suitable solutions for probability based decision support (Static Control Up-to-date Technology, SCOUT) using soft computing methods. This new approach can be used to assess and audit existing systems and – using the predictive power of the models – to design and plan activities in industrial electrostatics.

Induced-charge errors in charge-transfer measurement: Calculations for sparks and additional brush-discharge geometries

We recently reported calculations of the influence of induced-charge errors on brush discharge charge-transfer measurement for electrostatic hazard assessment. We concluded, tentatively, that, provided concave charged systems were avoided, the use of a correction factor of ×2 to ×2.5 when interpreting charge-transfer measurements made with fast, unshielded probes would avoid the underestimation of hazards at a 60 nC threshold level. However, our calculations applied directly only to brush discharges with a restricted range of geometries and consequently, it was not certain that the factors were necessarily sufficient in all circumstances. This paper presents numerical calculations that extend our results to a wider variety of geometries and include sparks as well as brush discharges. For brush discharges, the results reinforce the conclusions of the original work. For sparks they suggest that a similar worst-case correction factor (×2.2) is applicable.

Behavioral Compliance to In-Manual and On-Product Warnings

Warnings have several purposes, including the communication of hazard information and promotion of safe behavior. The present study examined how compliance is affected by viewing duration of product manual warnings and the presence and content of on-product warnings for a computer memory installation task involving an electrostatic discharge hazard. Analyses showed that both the presence of an ANSI-style label and longer manual exposure increased behavioral compliance. The additive effect of exposure time and label presence and content suggest that both previous exposure to warning information and effective on-product warning design benefit compliance.