In the petrochemical or flammable chemical world, this a huge issue, regardless if it is a drilling rig or processing plant or chemical site producing flammable liquids.
Before you even think about grounding or bonding are you TRAINED TO USE an OHM meter and is it working properly never assume this has been done or done properly on site!
And yes without proper grounding a single person can produce, static discharge on sensitive electronic devices, a human being is represented as a capacitor of 100 picofarads, charged to a voltage of 4000 to 35000 volts. When touching an object this energy is discharged in less than a microsecond, but it only take that second to create the spark!
Your ground rods
Note that whatever the rod steel core coating is (copper-plating, zinc-coating and stainless in the case of cladding) is there to protect deterioration of the steel core, not for strength or conductive purposes.
Yet how often is soil analysis of the specific site actually employed? The cost is often prohibitive and, instead, general conclusions are made for overall economic purposes. The most common statement is, “We have used this type of rod coating for decades, and it seems to work and we are not changing it under my watch.” While not always the most technically sound way to arrive at an engineering conclusion, it more often than not is the justification and probably is not too far off target. Moreover, a single soil analysis can often result in opposing views based upon the engineer conducting the analysis.
Ground resistance is only one measurement criteria to be used in the selection of a coating, but it is generally considered one of the prime factors. Soil pH is another critical factor to be considered. Ground soil resistivity and pH alone does provide a basic guideline; however, other factors that should be considered in a thorough evaluation include
· Soil resistivity
· Soil pH
· Moisture and drainage
· Stray current (ac and/or dc)
· Soil bacteria and/or acids
· Dissimilar metals buried nearby
· Soil make-up characteristics (rock, gravel, etcwhere the rod electrode is being driven inflicting potential damage to the coating resulting in premature degradation of electrode life due to surface degradation
· Certain soil enhancement materials
· Degradation of rod coating to rod steel core
Ground. A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth.
Grounding conductor. A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes.
Also review the requirement that note in part:
Grounding of electrical equipment. Conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.
This concept seems simple:
Connect metal parts of an electrical system to the earth to limit the voltage-to-ground on the metal parts. But where did the voltage come from and how are you limiting it?
As you bond metal parts of an electrical system together and then ground the bonding system to earth to limit the voltage-to-ground — thus preventing destruction of electrical components as well as electric shock that can occur from superimposed voltage from lightning and voltage transients.
The resistance of the ground determines how effectively your grounding system can dissipate high-voltage surges into the earth. The impedance of the earth ground depends on the resistance of the electrodes, termination resistance, contact resistance of the electrodes to the adjacent earth, and the resistance of the body of earth surrounding the electrodes (soil resistivity).
Based upon the recognized standards:
When you use two or more ground rods, the measured ground resistance can exceed 25 ohms. To achieve and maintain a low-resistive ground, you must use special grounding configurations, design, and equipment and measuring devices. Failure to properly ground the metal parts of an electrical system to the earth can result in electric shock and fire. Electronic equipment can be destroyed by lightning, line surges, or other high-voltage transients.
The discharge of electricity between your finger and the doorknob is in principle the same as the discharge from a cloud to a tree during a storm. It occurs because of the general diffusive principle in nature (entropy) — that is, things try to balance out to equal distribution.
If you have a lot of negative charge in one place and a lack of negative charge in another (a positive charge), it will eventually “discharge” or equalize the charges. This is a “lightning bolt” or a “static bolt” depending on how much charge we’re talking about. In a cloud, lots of dust in the cloud is churning around, or in a tank with the fluid sloshing around the negative charges accumulate.
The earth is the ultimate “equalizer” in nature, so enough negative charge build up will jump to the ground. In the same way, when you rub your feet on the carpet, you push negative charges on or off of you; by building up this charge in your body, you cause a static jump the next time you touch something “grounded” (i.e., in contact with the earth).
Knowing the Fire Triangle
Three elements are required in which to have a fire or an explosion. Fuel, Oxygen, and Heat or Ignition. Eliminate any one of these elements and there is no possibility of a fire
-Oxygen: It’s in the air all around us. This is pretty hard to control in most situations.
– Fuel: In the oil and gas industry we are working with hydrocarbons and other fuel sources at almost every area of every location. In most cases these fuel sources are contained in wellheads, piping, and vessels, but occasionally these gasses are released either controlled or uncontrolled.
– Heat or ignition: With the rules and regulations that are in place presently in the oil and gas industry we are trying our utmost to eliminate all sources of ignition where ever possible. ( ie: hot work permits, no smoking or open lights, explosion proof equipment, engine shutdowns, and bonding/grounding)
There is a big difference between grounding and bonding.
Grounding – running permanent cable from a permanent facility to a permanent ground.
Bonding – running a temporary cable from a mobile unit to a permanent ground.
The grounded circuits of machines need to have an effective return path from the machines to the power source in order to function properly. In addition, non-current-carrying metallic components in a facility, such as equipment cabinets, enclosures, and structural steel, need to be electrically interconnected so voltage potential cannot exist between them. And yes troubles can arise when terms like “bonding,” “grounding,” and “earthing” are interchanged or confused in certain situations.
Grounding metal parts to the earth does not assist in removing dangerous voltage from line-to-ground faults by opening the circuit overcurrent protection device for the systems that operate at less than 600V!
MOST COMMON PLACES TO BOND ON A WELLHEAD sites for instance are but not limited to:
Wellhead Flange Nuts– Probably one of the best spots. made out of steel. Paint and rust problems. Not Testable.
Surface Casing Vent– Very poor. May be venting. Explosion hazard. Not Testable
Valve Handle– Very poor. Valve stem is held in place by rubber seals. Isolated from the wellhead. Not Testable.
Ratigan Pins– Very poor. Stem is held in place by rubber seals. Isolated from the wellhead. Not Testable.
Flange Nuts– May have cathotic protection in place. Flange may have an insulator package. Not Testable.
Piling– Probably one of the best spots. made out of steel. Paint and rust problems. Not Testable.
Ground Lug– Good spot if you can find one. May loosen off if used too many times, leaving what it was supposed to ground, ungrounded. Not Testable.
“I’ve seen equipment bonded to the orange fence that surrounds some wellheads. I’ve seen equipment connected to the rubber 1 inch valve handles on the highline and I’ve seen a ground cable connected to one of the clamps used to start a catalytic heater; but by far the worst, and I have seen this dozens of times, are ground clamps connected to the opening of the surface casing vent. What would happen if this vent was actually venting? None of these locations are a proper bonding issues”.