Chapter 2 - Clamp Placement Guidelines - Garnet SEELEVEL PosiGround 672-H Manual

CHAPTER 2 - CLAMP PLACEMENT GUIDELINES

Principle of grounding verification using the PosiGround:
A major hazard in pumping liquids or granular solids is that an electrical
charge can be built up on the truck due to the moving product being
pumped. If this charge is allowed to build up high enough, then an
electrical spark can result which can ignite a fire or cause an explosion. By
grounding the truck, this charge is being constantly bled off so that it can
never build up to dangerous levels.
The key to proper grounding is to ensure that the truck is electrically
connected to the source location of the product or material being pumped.
This could be a tank, or the ground itself if material is being vacuumed up
from the ground.
The PosiGround helps to verify that the truck is grounded by sending
out a small signal from one clamp to the other. If this signal is properly
conducted from one clamp to the other, then the PosiGround shows a
good ground. It is very important to properly connect the two clamps
so that the PosiGround can give accurate results. When properly used,
the PosiGround is very effective at verifying ground, much more so than
relying on a visual inspection of a single ground cable.
In order to verify that the truck is grounded, the PosiGround clamps must
be connected so that the PosiGround signal is forced to travel through the
ground to get from one clamp to the other. Alternatively, if a metal tank
is being pumped to or from, then the clamps must be connected so that
the PosiGround signal is forced to travel through the tank wall to get from
one clamp to the other. The other situation is when a designated (often
labelled as such) ground connection is provided, then the clamps must be
connected so that the PosiGround signal is forced to travel through the
metal of the ground terminal to get from one clamp to the other.
It is NEVER sufficient to just have conductivity between the clamps if the
PosiGround signal does not have to travel through the ground or the tank/
ground point in question to show conductivity.
To further illustrate this, what follows is a series of examples showing both
good and bad practices.
Page 8 672-H Manual