Everyone wants a safe work environment. One of the workplace hazards are explosions and fires due to static discharge, but these can be mitigated by grounding equipment. Proper grounding is the only way to ensure true static protection if you are in any environment where the potential for static discharge exists.

Many places ground with heavy duty cast clips, solid copper clips and clamps of all shapes and sizes connected to a wire and attached to drums and pipes throughout a storeroom, plant floor or pumping stations.  These are referred to as grounding assemblies or “straps.”

These areas may or may not be perfectly grounded. Even though they may look grounded, it’s hard to tell if it’s done properly. An improper ground could mean safety hazards that can lead to fire or explosions.

First and foremost, it must be determined that access to a fully grounded grounding pin or buss bar is readily available. This will be necessary for a solid true ground and will act as the backbone of the grounding system. Keep in mind, however, that the grounding pin and buss bar must be kept clean so solid metal-to-metal connections are made.

The next step in ensuring that something is properly grounded is to make sure the correct connection device is utilized.

Many times a C-clamp or center spring clip will be used for this connection. This would certainly result in a good connection as the C-clamp can bite into the metal pin or buss bar and the clamp pressure on the center spring clamp is strong enough to drive the teeth into the metal pin or bar. It’s important that the clamp or clip is able to pierce any paint that might be on the surface. The connections on the grounding pin and buss bar must be solid tight connections as maintaining continual connectivity is critical for the integrity of the entire grounding system.

The type of cabling used from connection to connection (grounding pin / buss bar to clamp or clip) will depend on the environment being grounded. If the environment is clean such as a paint mixing room, uninsulated stainless steel wire rope or braided copper can be utilized. In other applications where the environment may contain more contaminants, an insulated wire may and should be considered such as THHN (oil and gas resistant).

Now that the connection to the ground source and wire are complete, focus can be placed on the connection to the can, drum, or tank. This connection can be made with a cast clamp with points, C-clamp containing a point or center spring clip with strong clamp pressure and teeth. The type of connection depends on the type of surface in which it is being attached. If the surface is clean and free of dirt and paint, a center spring clip can work fine. The size of the clip will be determined by the size or thickness of the object being grounded. If the container is dirty or painted the connection will need to be made with a connector which will break through those layers to make a solid metal-to-metal connection. Cast clips with points and the C-clamp with a point are perfect for this application.

Once a connection is made to the first container a “daisy chain” method of connecting the remaining containers in the area can be used. This means that a grounding cable can be attached from container to container to maintain a good ground as long as the series of containers is attached to the one connected to the grounding source. Keep in mind that each grounded container must have a solid metal-to-metal connection with the grounding device. It may be necessary in more caustic environments to wire each container directly to the grounding source. This same approach can be applied to grounding pipes for fluid flow, and even grounding work stations.

Following the above steps for creating a solid grounding system should produce good results and create a safe environment.  To confirm that there is good connectivity, take resistance measurements with a multi-meter, ohm-meter or ground analyzer. To ensure entire system integrity, a lead should be placed on the connection on the grounding source (grounding pin or buss bar) and the other on the very last connection in the system. This will incorporate a resistance measurement from point-to-point for the entire grounding system. If the reading taken is zero or approaching zero, the system is well grounded and a safe environment exists. If the reading approaches 1M Ohm then check the connections throughout the system to ensure that there are solid metal-to-metal connections. Once the appropriate measurement is received (zero or approaching zero), you have a good and well-grounded system in place ensuring static protection.         

When you think of plant safety it is common to think about the things you can see or do. This can be rules and regulations on how to navigate throughout the plant as well as wearing the appropriate safety attire such as hard hats, safety glasses, ear plugs, in addition to fire suits or Kevlar gloves to name a few. So, if the plant has all these things, isn’t it safe? Well, maybe, or maybe not? What about the things you can’t see such as static electricity? Have you considered the need for grounding and bonding?

The number of static electricity incidents reported in the U.S. exceeds more the 250 a year. The reports of these incidents are way more common that you would like to think. Certainly, when electrostatic charge build-up exists in a flammable or explosive environment a very hazardous situation has been created.

Typically these situations can be avoided by installing high quality low resistance grounding/ bonding cables containing clips and clamps. The clips are required to maintain high clamp pressure and the clamps will need to have a paint piercing point to be effective in garnering a solid metal on metal connection to reduce resistance and reduce static. The clips and clamps can be connected to a braided copper cable or better yet, a stainless steel wire rope which tends to hold up better in industrial applications. Make sure the connections to the cables are tight and always test the assembly for low resistance, the closer you get to 1 OHM the better.

Grounding / bonding cables don’t always guarantee static dissipation. Many times a grounding or bonding cable is attached to an object (tank or pump) which has been coated for protection. These types of coatings can impede the clip or clamp’s ability to make a solid metal to metal connection, which in turn, increases the resistance within the grounding structure. With increased resistance comes the possibility of electrostatic discharge failure. Rust build up on the clip or clamp can also create a coating which will disrupt a solid metal to metal connection. As a result, this too will create an unsafe environment. To avoid these situations, always test your grounding / bonding cable’s connections for resistance at the time of employment. If the resistance is low, great! Move on. If the resistance is high, make the necessary adjustments to insure a solid connection and low resistance. Don’t take a chance, make sure a solid connection is evident before giving it your seal of approval.

Proper maintenance is also critical to insure that your grounding / bonding equipment is in proper condition to effectively reduce static. Regular inspections of your grounding / bonding equipment are a necessity in any industrial setting. As you know, industrial environments can and will severely test the structural integrity of any device, including grounding / bonding cables and assemblies. Remember, inspect what you expect!

In conclusion, plant safety goes well beyond the need for appropriate attire and traffic flow logistics throughout the plant. Electrostatic discharge, the invisible threat, will need to be addressed as well. High quality, low resistance affordable grounding / bonding equipment is readily available to provide the required protection. Appropriately placed grounding / bonding cables and assemblies along with consistent resistance testing will provide a safe work environment for everyone.         

To read more about grounding and bonding, check out our whitepaper 

It may seem like common sense, but it’s important to make sure your grounding and bonding straps are working properly. It is essential that your clips are making a good connection. 

• Ensure your clips are clean and clear of debris.
• Check to see that you are getting a solid metal-on-metal connection. If there is paint on the surface the clips connect to, make sure the clips are breaking through that paint.
• Inspect your grounding equipment regularly and take measurements with a multimeter to ensure there is a low resistance.
• Replace any clips or straps that are too rusted to perform properly

Remember that bonding and grounding serves an important safety purpose, and regularly checking up on the grounding and bonding straps can prevent sparks and explosions.

To read more on static electricity in industry, check out our whitepaper here

If you are interested in custom-made grounding or bonding equipment, you can see our capabilities here

Static Electricity and Fluids

Some fluids that are flammable and combustible (like fuel and other chemicals) can be a static electricity hazard depending on how conductive they are.

As fluids move through pipes or a hose they can build up a static charge because they cannot conduct electricity unless the pipe is grounded. A spark can result if enough of a charge has built up, and an explosion can occur. Solvents that are water soluble like alcohol generally do not build up static electricity because the water is conductive. However when the liquids are transferred into a non-conductive container like glass or plastic, a charge can build up because the plastic or glass does not adequately dissipate the charge in the solvent.  Other factors are the flash point of the liquid, vapor pressure, air humidity, elevation, and temperature. For example, vapor levels in the air around the container will be higher in a hot room or on a hot day rather than on a cold day.

At high elevations the air pressure is lower and a solvent can boil and spark at a lower temperature

Some fluids that are flammable and combustible (like fuel and other chemicals) can be a static electricity hazard depending on how conductive they are.

As fluids move through pipes or a hose they can build up a static charge because they cannot conduct electricity unless the pipe is grounded. A spark can result if enough of a charge has built up, and an explosion can occur. Solvents that are water soluble like alcohol generally do not build up static electricity because the water is conductive. However when the liquids are transferred into a non-conductive container like glass or plastic, a charge can build up because the plastic or glass does not adequately dissipate the charge in the solvent.  Other factors are the flash point of the liquid, vapor pressure, air humidity, elevation, and temperature. For example, vapor levels in the air around the container will be higher in a hot room or on a hot day rather than on a cold day.

At high elevations the air pressure is lower and a solvent can boil and spark at a lower temperature.

Grounding and Bonding

Electric sparks can result from transferring a liquid from one metal container to another as a result of static electricity buildup.  To prevent sparks and electrostatic buildup, it is necessary to bond or ground the containers before pouring. Bonding is making an electrical connection with metal clamps and a wire between all the containers which will equalize the electrical potential between the containers. Bonding containers establishes a metal-on-metal connection between two or more containers.

Grounding is attaching a wire from the container to an already grounded object which will cause the static electricity to run into the ground. 

Both methods will guarantee that there will be no difference in electrical potential between the containers pouring and receiving the liquid. Bonding the containers and then grounding one of them will drain off the static charges from everything and will prevent static discharge and sparks.

For more information on static electricity and grounding, read our whitepaper. 

If you are in need of a wire or cable assembly that is custom made for your specific requirements, there are a number of options to consider. On the surface it's pretty simple - You have a wire, and then something on the ends of the wire (or not). But there are tons of options to customize and get it just right for what you need. 

If you are not 100% sure of your needs, we are here to help. Click the button below and fill out the form on the page to consult with our team or get a quote. 

From electrical design to maintenance, engineers must determine what electrical clips (also called alligator or crocodile clips) are best suited for their project.

These clips can range from small to large, be made of a wide range of materials, come in various jaw types, handle wide ranges of electrical current and can be certified for safety by being UL-listed.

With such a wide range of options, there are many factors to come into play when selecting clips

Amperage

Typically, electrical and electronic clips are rated by their ability to handle varying levels of current which is measured in amps so you will need to know the amount of current that you will be dealing with.

Once you know the level of current, you can calculate the amperage rating required for the clip.

The formula for Amps is Watts divided by Volts.

The amperage capacity of a clip is typically listed right on the clip itself.

Generally speaking, larger clips are able to handle more current, however, that doesn’t always mean a larger clip is always necessary. Solid copper clips are able to handle higher levels of current and carry a higher amperage rating than its zinc plated steel counterpart. For example, a heavy duty clip for battery and test work applications may be rated at 50 AMPS for the zinc-plated steel version while the same sized clip made in solid copper is rated at 100 AMPS. 

Clip Jaw Types

Another factor to be considered is how the clip needs to connect to its point of contact. Clips come in all shapes and sizes with different types of jaws and teeth. Clip jaws can come flat nosed, with teeth, or wrap around a terminal or pipe. Some clips have flat wide noses with teeth and others may be rounded to grab round objects. Deciding which clip to use is dependent of what the clip is grabbing on to and will vary per application.

Flat nosed clips are typically used in paint grounding.

Smaller clips with teeth are used for test and measurement.

Larger clips that wrap around will provide a strong grip and may penetrate a layer of paint. These are often used for battery charging and grounding.

Flat wide jaws with teeth are perfect for grounding and work holding uses.

There are, however, a tremendous number of applications for all types of jaw styles. As technology progresses, so do clips, with new types being invented all the time.

For more on different types of clips and what they are used for, check out our guide to clips. 

Clamp Pressure

Clip grabbing strength, or clamp pressure, is another factor to take into consideration when selecting the right clip. Clamp pressure usually increases as clip and spring size increase. Larger clips will have a stronger grip than smaller clips. In some cases clips can be made to have less clamp pressure which can be helpful for delicate or detailed situations.

Clip Size

There are many different sizes of clips and size can sometimes be important to consider. One determining factor is if there is a space requirement. Another factor is the amount of clamp pressure required, as well as the amperage rating needed.

Some clip sizes are determined by the application itself as there may be limited space where the clip can fit.  Naturally if you have a small space then you probably will pick a smaller clip.

Higher amp rated clips tend to lend themselves to uses where a tight space is not a concern. The environment may dictate what a clip size may need to be as the larger clips tend to hold up better in harsh environments such as electroplating.

There is no real guideline on determining what clip size to use. Some engineers try to make sure they have the right amperage rating, clamp pressure and jaw type in the smallest package possible to reduce the possibility of “overkill” and inflating costs unnecessarily. Other engineers go one step up in size to ensure all bases are covered. In most cases, several different sizes of clips are used in various prototypes to test first hand which clip size is best.

Material

Clips are made with zinc or nickel plated steel, stainless steel, solid copper, gold plating and even nickel-silver.

Generally speaking, zinc or nickel plated steel is the most cost effective material used in clips.

Solid copper clips can handle higher levels of current better than similarly sized clips made of other materials.

The environment where the clip will be used can determine what material should be used for a clip. For example, stainless steel clips can withstand marine, caustic or corrosive environment better than other materials. Other clips that can be used in marine environments are marine rated clips which are made of solid copper for greater connectivity but with moisture resistant springs which significantly extend the life of a clip used in the vicinity of water and salt.

We did an experiment to show how marine and stainless steel clips hold up compared to other clips. Read about it here. 

Read about different metal finishes for clips here.  

Safety

Safety is always a consideration when working with electrical components, but some more than others.

For instance, when using clips and cables for grounding and bonding, an exposed clip works just fine, while other applications it may call for an insulated clip.

UL Listed products are certified for safety. UL Listed clips and connectors are certified to insure that human hands cannot come in contact with the conductors while in use and energized.

Other applications may call for clips to be utilized in a “hands free” environment which means that the clips are not manipulated or touched while a circuit is energized. The clips still need protection from touching each other or other parts which could interfere with the electrical signal or cause a short, so insulators or “boots” are placed over the clips to protect them.

For help in selecting clips with different features, try our clip selector.

When trying to determine the cause of problems encountered with electrostatic painting, it can be confusing. The problem is often solved by updating the grounding process, however this simple solution is often overlooked. 

1. There is a drop in transfer efficiency

Your measurements and output are lower than they should be. 

2. Paint thickness is not what it should be

You may see a reduced paint thickness, uneven paint thickness, or both.  

3. There is a lot of scrap/rework

Lack of a good ground can result in much higher  amounts of scrap and rework than there should be. 

4. There's more paint on the surrounding surface than on the substrate

This can indicate you had a bad ground or no ground at all. 

5. Your cost of paint has gone up

You are going through more paint to coat the same number of items. 

6. Servicing the robots doesn't help

You may have thought there was something wrong with the paint robots, but they are in working order

7. There's a drop in weight

If your substrates come out weighing less than they normally do, this can indicate that less paint is making it to the surface which usually indicates there're something wrong with the ground.

If you think updating your grounding process will help, you can head over to this handy page which addresses the most common considerations and questions for updating your grounding process. 

For more information on grounding, read our whitepaper Static Electricity and Grounding in Industry. 

You can also take a look at our free guides for grounding plastic and metal for painting.

Static electricity is all around us in everyday life and generally refers to an imbalance between positive and negative charges in objects. Most people have experienced it in some form or another whether it be with their laundry being particularly “clingy,” making a balloon stick to a wall after rubbing it on your clothes, or when walking around wearing socks on a carpet and getting a small shock when touching another object or person.

The Science of Static

To understand static, it helps to understand some basic physics with atoms and magnetism.

All objects are made up of atoms which have positive and negative charges, like a magnet. Also like magnets, like charges repel each other (positive-positive, or negative-negative), while different charges attract each other (positive-negative).

Static electricity is a result of an imbalance between positive and negative charges when two objects or materials come into contact. The surface electrons try to balance each other while the two surfaces are together. When two materials or surfaces are touching, one surface gives up electrons and becomes more positively charged while the other object surface collects extra electrons and becomes more negatively charged. When the two materials are separated, an imbalance occurs when the surfaces are left with either a surplus or shortage of electrons, and the surfaces become electrically charged. These charges build up when they don’t have a direct path to the ground, and can eventually build up enough to cause a spark to a nearby grounded or less charged object in an attempt to balance the charge.  

Examples of Static Electricity

When you take off a wool sweater and the hair on your head and arms stand up, the hair acts this way because your body got an extra charge from the friction of the sweater being removed and your hairs are moving away from each other because they all have the same charge.  

With your laundry, your clothes in the dryer are rubbing up against each other (particularly when you have different types of fabrics in there, like cotton and polyester), those charges will cause the fabrics to cling to your body.   

Lightning is another example of static discharge. You see it because electricity is being produced between two clouds or between a cloud and the earth as the static electricity is discharged.

Static in Industry

Static electricity is very important in many industries as can used to our benefit, or it is a problematic issue that needs to be mitigated, reduced, or removed.  

For example, some helpful uses in industry are in pollution control – like air purifiers. The air purifier applied a static charge to dirt particles in the air and then passes the air over an electrostatic plate of the opposite electrical charge. The dirt then clings to the plates and can be easily removed. Factories use this same principle on a larger scale for their smokestacks to keep pollution out of the environment.

Another use for static electricity is for spray painting car parts. This requires a specialized paint gun that applies an electrostaitc charge to the paint. The parts for painting need to be properly grounded using metal clips, clamps and wires. The charge causes the paint to be attracted to the car parts resulting in an even coat, less mess, and less wasted paint.

In other industries, static can cause a lot of problems. Sparks caused by static can cause fires and explosions. While hazards for fires may be obvious with flammable materials, this can also happen in industries where there is dust, like flour mills. Static electricity is also an issue where electronics are used and manufactured.

Static electricity in industry is caused by machinery where this is friction and contact and separation, as well as in instances where there are rapid heat changes. People can build up their own charges simply by the friction created when they walk, so when they move within proximity to a machine, they can receive a shock. Static sparks can be very serious in industry, not only can they cause an ignition or explosion but they can also cause a burn or stop someone’s heart.

Some other sources of static electricity production in industry can be liquid flowing through a pipe, hose or opening, blending or mixing, spraying or coating, filling drums, cans, pails, or tanks and conveyer belts.

Electrical charges can also build up in flammable liquids when they flow through pipe systems or when they splash due to being moved in their storage containers.

Humidity is a significant factor as moisture in the air helps to remove some charge. Dry environments are much more prone to static buildup. Different materials and production speeds also play a role in how much and how fast static is created.

Static Control

Static electricity in industry is controlled by several methods. We will focus on the most common of these methods, Bonding and Grounding. 

Bonding is when two or more conductive objects are connected with a conductor like a wire, which helps to equalize the charge between them. Bonding doesn’t eliminate static electricity but it does ensure that a spark will not happen between the objects. An example of a cable used for bonding is to the left. In this example, two copper clips are on either end of a wire and clip directly to the items being bonded. 

Grounding is when objects that can gain a charge are connected directly into the earth using metal like grounding rods, copper, and steel. Grounding drains the static charges away as they are produced. Grounding and bonding connections are made with connectors using metal clips, clamps and wires.

Grounding Assembly

A grounding/bonding assembly is a clamp or clip with a grounding cable or wire. One end attaches to the item being grounded or bonded. The other end attaches to the ground, whether it be a ground rod or a grounding "bus" mounted on a wall. Ground connectivity of all devices, cables and connections must be checked at installation and regularly afterwards for safety and to ensure the connection is maintained. Many grounding clips and clamps have a paint-piercing ability to ensure a metal-on-metal connection. Check out Mueller Electric's catalog for more examples of grounding and bonding equipment.  

Other Websites For More Reading: 

Uses of Electrostatics on BBC.co.uk

GCSC Science / Uses of Static Electricity