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Case Study: Static Discharge during Pneumatic Powder Processing

ems m13 19 4Pneumatic conveying systems have the ability to generate vast quantities of electrostatic charge via the movement of product through the plant equipment. The most common method of electrostatic charging on such process operations is due to tribo-electrification, which is simply the contact and separation of the powder with the walls of the processing equipment, the powder molecules itself or other factors that can cause charging, like surface contaminants.

In this incident a process operator working on a pneumatic conveying system heard a crackling noise when powdered material was being transported between the classifier and the loading hopper. During investigation, the operator came into contact with a section of the duct and received a significant static shock. Although the operator was unharmed, the severity of the incident warranted a full system shutdown and investigation.

Fortunately in this particular scenario, a larger scale incident was avoided by the luck of an operator. If the isolated ducting had not been found the outcome could have been very different. A static discharge in the right place through a combustible atmosphere along any section of ducting could have resulted in a significant ignition incident, putting the lives of employees and plant assets at risk.

The most effective way of ensuring complex equipment used in powder processing operations cannot accumulate static electricity is to provide a dedicated static grounding solution that is capable of monitoring the ground connection to components at risk of isolation. Such a solution should also be able to prevent the flow of product and alert personnel to a potential hazard should a component lose its connection to ground. This is especially important if the ground connection point to the equipment is not readily visible or isn’t easily accessible for example, the grounding clips mentioned in this scenario.

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