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56-530: The WLBT Tower was a 610-metre-high (2,000 ft) guy-wired aerial mast for the transmission of FM radio and TV-programs in Raymond, Mississippi , United States , for the Jackson metro area. The mast was constructed in 1966. On October 23, 1997, the mast, which was property of Cosmos Broadcasting ( WLBT a local NBC affiliate), collapsed during the renovation of its guy wires . Three workers were killed. The tower

112-636: A balloon rubbed against the hair becomes negatively charged; when near a wall, the charged balloon is attracted to positively charged particles in the wall, and can "cling" to it, suspended against gravity). Applied mechanical stress generates a separation of charge in many types of crystals and ceramics molecules. Heating generates a separation of charge in the atoms or molecules of certain materials. All pyroelectric materials are also piezoelectric. The atomic or molecular properties of heat and pressure response are closely related. A charged object brought close to an electrically neutral conductive object causes

168-460: A conductive antistatic strap . In the industrial settings such as paint or flour plants as well as in hospitals, antistatic safety boots are sometimes used to prevent a buildup of static charge due to contact with the floor. These shoes have soles with good conductivity. Anti-static shoes should not be confused with insulating shoes, which provide exactly the opposite benefit  – some protection against serious electric shocks from

224-402: A dead man. This type consists of a rod with wide screw blades on the end and an eyelet on the other for the guy wire. It is screwed deep into the ground, at the same angle as the guy, by a truck-mounted drill machine. These are commonly used as guy anchors for utility poles since they are quick to install with a truck mounted hydraulic powered auger drive. A rod with a pivoted blade on the end

280-531: A fluid to retain an electrostatic charge depends on its electrical conductivity. When low conductivity fluids flow through pipelines or are mechanically agitated, contact-induced charge separation called flow electrification occurs. Fluids that have low electrical conductivity (below 50 picosiemens per meter), are called accumulators. Fluids having conductivity above 50 pS/m are called non-accumulators. In non-accumulators, charges recombine as fast as they are separated and hence electrostatic charge accumulation

336-402: A guy cable would attach. Electromagnetic fields from the antennas complicate the design of guys that support mast antennas . Conductive metal guy-wires whose lengths are near to quarter wavelength multiples of the transmitted frequency can distort the radiation pattern of the antenna. This also applies to guy wires of neighboring masts or nearby metal structures. To prevent this, each guy wire

392-493: A mast collapse. Egg insulators have the porcelain in compression and if it fails, the end loops of the guy wires are still intertwined. AM radio broadcast towers are often fitted with insulators at the mast base and the RF energy is fed at that point. Some are also insulated at the center for feeding the RF energy at that point. Wire rope guys are frequently used and segmented with insulators at several points. Extensive lightning protection

448-631: A maximum energy of 60 mJ. IEC 479 -2:1987 states that a discharge with energy greater than 5000 mJ is a direct serious risk to human health. IEC 60065 states that consumer products cannot discharge more than 350 mJ into a person. The maximal potential is limited to about 35–40 kV, due to corona discharge dissipating the charge at higher potentials. Potentials below 3000 volts are not typically detectable by humans. Maximal potential commonly achieved on human body range between 1 and 10 kV, though in optimal conditions as high as 20–25 kV can be reached. Low relative humidity increases

504-405: A problem. For example, the noise in an ECG or another medical signal may make accurate diagnosis difficult or even impossible. Keeping triboelectric noise at acceptable levels requires careful material selection, design, and processing as cable material is manufactured. The spark associated with static electricity is caused by electrostatic discharge, or simply static discharge, as excess charge

560-405: A separation of charge within the neutral object. This is called electrostatic induction . Charges of the same polarity are repelled and move to the side of the object away from the external charge, and charges of the opposite polarity are attracted and move to the side facing the charge. As the force due to the interaction of electric charges falls off rapidly with increasing distance, the effect of

616-542: A small electrical spark might ignite explosive mixtures. The flowing movement of finely powdered substances or low conductivity fluids in pipes or through mechanical agitation can build up static electricity. The flow of granules of material such as sand down a plastic chute can transfer charge, which can be measured using a multimeter connected to metal foil lining the chute at intervals, and can be roughly proportional to particulate flow. Dust clouds of finely powdered substances can become combustible or explosive. When there

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672-423: A spark that can ignite flammable gas or dust. Lightning is a dramatic natural example of static discharge. While the details are unclear and remain a subject of debate, the initial charge separation is thought to be associated with contact between ice particles within storm clouds. In general, significant charge accumulations can only persist in regions of low electrical conductivity (very few charges free to move in

728-484: A structural epoxy. When the grout hardens or expands, the anchor is secure. Historically, guyed structures have been some of the tallest man-made structures in the world . There are also many structures which consist of a freestanding bottom and a guyed top. These are either partially guyed towers or additionally guyed towers , the latter of which may be used temporarily to support tall buildings during their construction. Static electricity Static electricity

784-680: Is a static discharge in a dust or vapor cloud, explosions have occurred. Among the major industrial incidents that have occurred due to static discharge are the explosion of a grain silo in southwest France, a paint plant in Thailand, a factory making fiberglass moldings in Canada, a storage tank explosion in Glenpool , Oklahoma in 2003, and a portable tank filling operation and a tank farm in Des Moines , Iowa and Valley Center, Kansas in 2007. The ability of

840-549: Is an imbalance of electric charges within or on the surface of a material. The charge remains until it can move away by an electric current or electrical discharge . The word "static" is used to differentiate it from current electricity , where an electric charge flows through an electrical conductor . A static electric charge can be created whenever two surfaces contact and or slide against each other and then separate. The effects of static electricity are familiar to most people because they can feel, hear, and even see sparks if

896-427: Is best controlled by limiting fluid velocity. The British standard BS PD CLC/TR 50404:2003 (formerly BS-5958-Part 2) Code of Practice for Control of Undesirable Static Electricity prescribes pipe flow velocity limits. Because water content has a large impact on the fluids dielectric constant, the recommended velocity for hydrocarbon fluids containing water should be limited to 1 meter per second. Bonding and earthing are

952-450: Is between 2 and 1000 nanojoules. A relatively small energy, often as little as 0.2–2 millijoules, is needed to ignite a flammable mixture of a fuel and air. For the common industrial hydrocarbon gases and solvents, the minimum ignition energy required for ignition of vapor–air mixture is lowest for the vapor concentration roughly in the middle between the lower explosive limit and the upper explosive limit , and rapidly increases as

1008-473: Is divided by strain insulators into multiple sections, each segment non-resonant at the transmitted wavelength. Cylindrical or egg-shaped porcelain "Johnny ball" insulators (also called "egg insulators") are usually used. Non-conductive guys of Kevlar fiber (Phillystran) or extruded fiberglass rod are frequently used to not disturb the radiation pattern of the antennas. The strength and low stretch properties of Kevlar fiber approaches that of steel. However, Kevlar

1064-435: Is driven into the earth. When the guy wire is attached and tensioned, its force pulls the blade open, "setting" it into the soil. These are often used by the military for rapid mast installations. These are used in both soil and rock. A hole is drilled at the angle of the guy. A steel anchor rod with an eye is inserted, and the hole around it is filled with a liquid grout consisting of concrete and an expansion agent or

1120-425: Is envisaged that a charge generation mechanism only occurs when solid particles or liquid droplets are carried in the gas stream. Due to the extremely low humidity in extraterrestrial environments, very large static charges can accumulate, causing a major hazard for the complex electronics used in space exploration vehicles. Static electricity is thought to be a particular hazard for astronauts on planned missions to

1176-461: Is known as the triboelectric effect and results in one material becoming positively charged and the other negatively charged. The triboelectric effect is the main cause of static electricity as observed in everyday life, and in common high-school science demonstrations involving rubbing different materials together (e.g., fur against an acrylic rod). Contact-induced charge separation causes one's hair to stand up and causes " static cling " (for example,

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1232-409: Is neutralized by a flow of charges from or to the surroundings. The feeling of an electric shock is caused by the stimulation of nerves as the current flows through the human body. The energy stored as static electricity on an object varies depending on the size of the object and its capacitance , the voltage to which it is charged, and the dielectric constant of the surrounding medium. For modelling

1288-578: Is not significant. In the petrochemical industry , 50 pS/m is the recommended minimum value of electrical conductivity for adequate removal of charge from a fluid. Kerosines may have conductivity ranging from less than 1 picosiemens per meter to 20 pS/m. For comparison, deionized water has a conductivity of about 10,000,000 pS/m or 10 μS/m. Transformer oil is part of the electrical insulation system of large power transformers and other electrical apparatus. Re-filling of large apparatus requires precautions against electrostatic charging of

1344-440: Is often possible to use a grounded mast. The power to the guys is fed via wires running from a tuning unit to the feed point on the guys. When operating a crane , guy wires, known as tag lines, may be connected to unwieldy payloads, allowing ground crew to control rotation and swaying while maintaining a safe distance. Guys can be used to raise an extension ladder in a technique called a church raise. In ground-anchored guys,

1400-408: Is required for insulated towers. On antennas for long-wave and VLF, the guys may serve an electrical function, either for capacitive lengthening of the mast or for feeding the mast with the radiation power. In these cases, the guys are fixed without an insulator on the mast, but there is at least one insulator in the guy if necessary. If guys are used for feeding the mast with high frequency power it

1456-400: Is very susceptible to ultraviolet degradation, so it is enclosed in a UV resistant plastic sheath. The individual sections of conductive guys can develop large charges of static electricity , especially on very tall masts. The voltage caused by this static electricity can be several times larger than that generated by the transmitter. In order to avoid dangerous and unpredictable discharges,

1512-415: The capacitance ( C ) of the object and the static potential V in volts (V) by the formula E  = ½ CV . One experimenter estimates the capacitance of the human body as high as 400  picofarads , and a charge of 50,000 volts, discharged e.g. during touching a charged car, creating a spark with energy of 500 millijoules. Another estimate is 100–300 pF and 20,000 volts, producing

1568-460: The mains voltage . Within medical cable assemblies and lead wires, random triboelectric noise is generated when the various conductors, insulation, and fillers rub against each other as the cable is flexed during movement. Noise generated within a cable is often called handling noise or cable noise, but this type of unwanted signal is more accurately described as triboelectric noise. When measuring low-level signals, noise in cable or wire may present

1624-601: The Moon and Mars . Walking over the extremely dry terrain could cause them to accumulate a significant amount of charge; reaching out to open the airlock on their return could cause a large static discharge, potentially damaging sensitive electronics. A static discharge in the presence of air or oxygen can create ozone . Ozone can degrade rubber parts. Many elastomers are sensitive to ozone cracking . Exposure to ozone creates deep penetrative cracks in critical components like gaskets and O-rings . Fuel lines are also susceptible to

1680-438: The charge buildup; walking 20 feet (6 m) on vinyl floor at 15% relative humidity causes buildup of voltage up to 12 kV, while at 80% humidity the voltage is only 1.5 kV. As little as 0.2 millijoules may present an ignition hazard; such low spark energy is often below the threshold of human visual and auditory perception. Typical ignition energies are: The energy needed to damage most electronic devices

1736-454: The closer (opposite polarity) charges is greater and the two objects feel a force of attraction. Careful grounding of part of an object can permanently add or remove electrons, leaving the object with a global, permanent charge. Removing or preventing a buildup of static charge can be as simple as opening a window or using a humidifier , to increase the moisture content of the air, making the atmosphere more conductive. Air ionizers can perform

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1792-422: The concentration deviates from this optimum to either side. Aerosols of flammable liquids may be ignited well below their flash point . Generally, liquid aerosols with particle sizes below 10 micrometers behave like vapors, particle sizes above 40 micrometers behave more like flammable dusts. Typical minimal flammable concentrations of aerosols lay between 15 and 50 g/m . Similarly, presence of foam on

1848-406: The design. Often the guy wire is divided by strain insulators into isolated sections whose lengths are not resonant with the transmission frequencies. The guys supporting a sailboat mast are called "standing rigging" and in modern boats are stainless steel wire rope. Guys are rigged to the bow and stern, usually as a single guy. Lateral guys attach to "chain plates" port and starboard attached to

1904-476: The effect of static discharge on sensitive electronic devices, a human being is represented as a capacitor of 100 picofarads , charged to a voltage of 4,000 to 35,000 volts. When touching an object this energy is discharged in less than a microsecond. While the total energy is small, on the order of millijoules , it can still damage sensitive electronic devices. Larger objects will store more energy, which may be directly hazardous to human contact or which may give

1960-579: The excess charge is neutralized when brought close to an electrical conductor (for example, a path to ground), or a region with an excess charge of the opposite polarity (positive or negative). The familiar phenomenon of a static shock – more specifically, an electrostatic discharge  – is caused by the neutralization of a charge. Materials are made of atoms that are normally electrically neutral because they contain equal numbers of positive charges ( protons in their nuclei ) and negative charges ( electrons in " shells " surrounding

2016-403: The fluid, which may damage sensitive transformer insulation. An important concept for insulating fluids is the static relaxation time. This is similar to the time constant τ (tau) of an RC circuit . For insulating materials, it is the ratio of the static dielectric constant divided by the electrical conductivity of the material. For hydrocarbon fluids, this is sometimes approximated by dividing

2072-445: The fuel vapor. When the electrostatic discharge energy is high enough, it can ignite a fuel vapor and air mixture. Different fuels have different flammable limits and require different levels of electrostatic discharge energy to ignite. Electrostatic discharge while fueling with gasoline is a present danger at gas stations . Fires have also been started at airports while refueling aircraft with kerosene. New grounding technologies,

2128-524: The hull. Multiple guys are usually installed with spreaders to help keep the mast straight ("in column"). Temporary guys are also used. A fore-guy is a line ( rope ) pulling on the free end of a spar . On a modern sloop -rigged sailboat with a symmetric spinnaker , the spinnaker pole is the spar most commonly controlled by one or more guys. Utility poles are buried in the ground and have sufficient strength to stand on their own; guys are needed on some poles only to support unbalanced lateral loads from

2184-401: The insulators must be designed to withstand this high voltage, which on tall masts results in over-dimensioned backstage insulators. At each backstage insulator, a lightning arrestor in the form of an arc gap is required for the purpose of over-voltage protection in case of lightning strikes. The insulators and arrestors must be maintained carefully, because an insulator failure can result in

2240-407: The middle of the pole, then continues vertically to the ground. Thus, the bottom length of the guy is vertical and does not obstruct headroom, so a sidewalk can pass between the pole and the guy. An alternative to guy-wires sometimes used on dead-end utility poles is a push-brace pole , a diagonal pole with one end set in the ground and the other butting up against the vertica pole, opposite to where

2296-523: The nucleus). The phenomenon of static electricity requires a separation of positive and negative charges. When two materials are in contact, electrons may move from one material to the other, which leaves an excess of positive charge on one material, and an equal negative charge on the other. When the materials are separated they retain this charge imbalance. It is also possible for ions to be transferred. Electrons or ions can be exchanged between materials on contact or when they slide against each other, which

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2352-531: The number 18 by the electrical conductivity of the fluid. Thus a fluid that has an electrical conductivity of 1 pS/m has an estimated relaxation time of about 18 seconds. The excess charge in a fluid dissipates almost completely after four to five times the relaxation time, or 90 seconds for the fluid in the above example. Charge generation increases at higher fluid velocities and larger pipe diameters, becoming quite significant in pipes 8 inches (200 mm) or larger. Static charge generation in these systems

2408-408: The plate anchor, in which the guy is attached to a rod with an eyelet extending from the center of a steel plate buried diagonally, perpendicular to the angle of the guy. In the concrete anchor, a diagonal rod with an eyelet extending in the guy direction is cemented into a hole filled with steel reinforced concrete. A sufficiently massive concrete block on the surface of the ground can also be used as

2464-435: The problem unless preventive action is taken. Preventive measures include adding anti-ozonants to the rubber mix, or using an ozone-resistant elastomer. Fires from cracked fuel lines have been a problem on vehicles, especially in the engine compartments where ozone can be produced by electrical equipment. The energy released in a static electricity discharge may vary over a wide range. The energy in joules can be calculated from

2520-655: The same task. Items that are particularly sensitive to static discharge may be treated with the application of an antistatic agent , which adds a conducting surface layer that ensures any excess charge is evenly distributed. Fabric softeners and dryer sheets used in washing machines and clothes dryers are an example of an antistatic agent used to prevent and remove static cling . Many semiconductor devices used in electronics are particularly sensitive to static discharge. Conductive antistatic bags are commonly used to protect such components. People who work on circuits that contain these devices often ground themselves with

2576-431: The soil to resist the forces from all of the guys attached to it. Several types of anchor are used: In this type, a hole is excavated and an object with a large surface area is placed in it with the guy wire attached, and the hole is backfilled with earth or concrete. In the historical form of dead man anchor, a log is buried horizontally in a trench with the guy attached perpendicularly to its center. Modern forms are

2632-426: The structure which attaches the guy-wire to the ground is called an anchor . The anchor must be adequate to resist the maximum tensile load of the guy wires; both the dead load of the tension of the wire and the maximum possible live load due to wind. Since the guy wire exerts its force at an angle, the anchor has both vertical and lateral (horizontal) forces on it. The anchor relies on the lateral shear strength of

2688-512: The superheated air expands. Many semiconductor devices used in electronics are very sensitive to the presence of static electricity and can be damaged by a static discharge. The use of an antistatic strap is mandatory for researchers manipulating nanodevices. Further precautions can be taken by taking off shoes with thick rubber soles and permanently staying with a metallic ground. Discharge of static electricity can create severe hazards in those industries dealing with flammable substances, where

2744-415: The surface of a flammable liquid significantly increases ignitability. Aerosol of flammable dust can be ignited as well, resulting in a dust explosion ; the lower explosive limit usually lies between 50 and 1000 g/m ; finer dusts tend to be more explosive and requiring less spark energy to set off. Simultaneous presence of flammable vapors and flammable dust can significantly decrease the ignition energy;

2800-414: The surrounding air causing the bright flash, and produces a shock wave causing the booming sound. A lightning bolt is simply a scaled-up version of the sparks seen in more domestic occurrences of static discharge. The flash occurs because the air in the discharge channel is heated to such a high temperature that it emits light by incandescence . The clap of thunder is the result of the shock wave created as

2856-454: The surroundings), hence the flow of neutralizing charges often results from neutral atoms and molecules in the air being torn apart to form separate positive and negative charges, which travel in opposite directions as an electric current, neutralizing the original accumulation of charge. The static charge in air typically breaks down in this way at around 10,000 volts per centimeter (10 kV/cm) depending on humidity. The discharge superheats

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2912-407: The top, to keep dangerous voltages away from the lower end. The length near the ground is often encased in a yellow plastic reflector to make it more visible, so that people or vehicles do not run into it. In urban areas with pedestrian traffic around the pole, a variation called a sidewalk guy is often used: the guy line extends diagonally from the top of the pole to a spar brace extending out from

2968-415: The use of conducting materials, and the addition of anti-static additives help to prevent or safely dissipate the buildup of static electricity. Customers who need to fill containers at gas stations are advised to set them on the ground first so that any static buildup will dissipate without risk of fire or explosion. The flowing movement of gases in pipes alone creates little, if any, static electricity. It

3024-558: The usual ways charge buildup can be prevented. For fluids with electrical conductivity below 10 pS/m, bonding and earthing are not adequate for charge dissipation, and anti-static additives may be required. The flowing movement of flammable liquids like gasoline inside a pipe can build up static electricity. Non-polar liquids such as gasoline , toluene , xylene , diesel , kerosene and light crude oils exhibit significant ability for charge accumulation and charge retention during high velocity flow. Electrostatic discharges can ignite

3080-417: The utility wires attached to them, or to resist ground movement. Guys are particularly needed on dead-end ( anchor ) poles, where a long straight section of wire line ends, or angles off in another direction. To protect the public against faults that might allow utility guy cables to become electrified, they usually have a ceramic strain insulator ("Johnny ball") or a fiberglass strain insulator inserted near

3136-506: Was rebuilt in 1999. 32°12′50″N 90°22′57″W  /  32.21389°N 90.38250°W  / 32.21389; -90.38250 This article about a guyed mast or radio tower in the United States is a stub . You can help Misplaced Pages by expanding it . Guy-wire Conductive guy cables for radio antenna masts can catch and deflect radiation in unintended directions, so their electrical characteristics must be included in

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