Relationship between static electricity and fluid velocity

relationship between static electricity and fluid velocity

Discharging of static electricity between two conductors. there is a transfer of electrons from one surface to another as they flow past each other. . This relationship is used to determine the charge developing in the tank as a function of time. Static electricity is one of the prime ignition sources in flammable liquid dispensing operations. Similar to rubbing things together, liquid flow can cause electrons to move Bonding is an electrical connection between conducting objects with a. Static electricity is an imbalance of electric charges within or on the surface of a material. . The ability of a fluid to retain an electrostatic charge depends on its electrical conductivity. (formerly BSPart 2) Code of Practice for Control of Undesirable Static Electricity prescribes pipe flow velocity limits.

In addition, to further ensure that accidents are prevented, it is important to implement multiple prevention measures simultaneously. In particular, the following measures should be taken if large amounts of flammable solvents are used. Measure 1 Use a metal liquid waste container with a conductive interior surface, such as a plated metal can and connect the container to ground. Properly ground liquid waste containers.

There is no point in using a metal container if it is not grounded or the ground wire becomes disconnected.

Static electricity - Wikipedia

This ensures that static charge does not accumulate in the waste liquid or the container. Even some metal containers have surfaces that are oxide-coated or laminated and, therefore, may not be conductive.

Use an electrical tester to confirm that the container is grounded. Configuration with Measures to Prevent Static Electricity Implemented Measure 2 To prevent sparks from entering the waste container, keep the size of any gaps at inlet and outlet openings as small as possible.

Measure 3 Keep electrostatically charged objects, including human bodies, away from the waste container. If you have not taken any anti-static measures, touch a grounded metal object before approaching the waste container in order to ground any electrostatic charge from your body.

Measure 4 Use tubing with a larger inner diameter at least 2 mm, for example for drain lines through which large amounts of liquid flow. Air bubbles in the liquid can increase electrostatic charge by a factor of several tens. Check the tubing connections for air leaks. Measure 5 If the liquid waste container cannot be made conductive, make sure the end of the drain tube remains below the surface of the liquid in the waste container.

Alternatively, place grounded metal in the liquid. Measure 6 Use a liquid waste container that is as small as possible to minimize the damage in the event of a fire.

Therefore, do not let the room become dry. Static electricity accidents can be prevented by observing the measures indicated above. These measures may seem like an unnecessary bother, but being prepared for such possibilities is also important. As a manufacturer of HPLC systems, we hope to supply easy-to-use peripheral products that are carefully designed for safety as well.

Liquid Chromatograph-Mass Spectrometry Additional Remarks There are many other areas of the laboratory, besides the HPLC system, that require particular caution regarding static electricity. Laboratories contain many flammable substances, such as organic solvents. Keep flammable substances covered to prevent exposure. Provide ventilation for flammable vapors. Select the height of ventilation fans based on most solvents being heavier than air, but hydrogen being lighter than air.

Circuit boards are especially vulnerable to static electricity. In particular, if a statically charged person touches an electrical device with a metal tool, it can cause a malfunction or an instantaneous power interruption. Form a habit of touching the building or water pipes to eliminate any static charge before touching an electrical device.

Generation and Control of Static Electricity

For hydrocarbon fluids, this is sometimes approximated by dividing the number 18 by the electrical conductivity of the fluid.

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. Static charge generation in these systems is best controlled by limiting fluid velocity. 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.

relationship between static electricity and fluid velocity

Bonding and earthing are the usual ways charge buildup can be prevented. Non-polar liquids such as gasolinetoluenexylenedieselkerosene and light crude oils exhibit significant ability for charge accumulation and charge retention during high velocity flow.

Static Electricity part two Conduction-Induction // Homemade Science with Bruce Yeany

Electrostatic discharges can ignite the fuel vapor. 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. New grounding technologies, the use of conducting materials, and the addition of anti-static additives help to prevent or safely dissipate the buildup of static electricity.

The flowing movement of gases in pipes alone creates little, if any, static electricity. In space exploration 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 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.

Ozone can degrade rubber parts.

Beware of Static Electricity Generated by Flowing Liquids

Many elastomers are sensitive to ozone cracking. Exposure to ozone creates deep penetrative cracks in critical components like gaskets and O-rings.

relationship between static electricity and fluid velocity

Fuel lines are also susceptible to 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.

Energies involved The energy released in a static electricity discharge may vary over a wide range. Typical ignition energies are: The energy needed to damage most electronic devices[ specify ] is between 2 and nanojoules.

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 limitand rapidly increases as the concentration deviates from this optimum to either side. Aerosols of flammable liquids may be ignited well below their flash point.

Similarly, presence of foam on the surface of a flammable liquid significantly increases ignitability. Simultaneous presence of flammable vapors and flammable dust can significantly decrease the ignition energy; a mere 1 vol. Higher than normal oxygen content in atmosphere also significantly lowers the ignition energy. Spark, responsible for the majority of industrial fires and explosions where static electricity is involved.

Sparks occur between objects at different electric potentials. Good grounding of all parts of the equipment and precautions against charge buildups on equipment and personnel are used as prevention measures.

relationship between static electricity and fluid velocity

Brush discharge occurs from a nonconductive charged surface or highly charged nonconductive liquids. This is not considered to be a hazard for dust clouds. Propagating brush discharge is high in energy and dangerous. Larger dust volumes produce higher energies.