THE LOWEST cost components often have the largest influence on the reliable operation of dust collectors and knowing what makes a reverse pulse jet dust collector operate reliably is essential to preventing system failure.
Reverse pulse jet dust collectors are available in a vast array of formats and sizes to suit a wide range of applications.
In order to operate reliably, all reverse pulse jet dust collectors require a well specified and suitably sized filter cleaning system. Without such a system, any reverse pulse jet dust collector will fail.
Recognising the signs
At the extreme, a dust collector has failed when the gas stream is unable to pass through it at the flow rates required to capture particulate, or when the dust collector unsuccessfully separates the particulate from the gas stream leading to emissions.
Other significant failure indicators include high differential pressures across the filters caused by insufficient filter cleaning pressure, resulting in poor particulate capture and/or excessive power consumption to draw the required flow rate through the filters.
Another sign of malfunction is very low differential pressures across the filters, indicating insufficient dust cake on the filter media. This is usually caused by excessive filter cleaning and results in poor separation of particulate from the dust stream.
Torn or broken filter media and short filter lives, often caused by too frequent pulsing and excessively high pulse cleaning pressures, is another major indication that a filter system is not working at its optimum level.
The financial costs of these failures can be very significant and may impact not only the equipment manufacturer through delayed commissioning, system rectification and liquidated damages, but also dust collection operators can be affected, at worst with EPA fines, at best with premature filter media changeovers.
Costs incurred can range from a few thousand dollars for a small collector to over $100,000 for larger systems.
Reversing the trend
A reverse pulse jet filter cleaning system is a combination of components designed to deliver a pulse of air into a series of filters.
These components include the diaphragm valves, pilot solenoid valves and enclosures, header tanks, blow tubes and nozzles, venturis, pulse cleaning system controllers, and emissions monitoring equipment.
To maintain the differential pressure across the dust collector within an appropriate range, the cleaning system will briefly pulse through each diaphragm valve.
As the pulse is discharged through the blow tube, air is entrained into the jet from the clean air side plenum and enters the filter element.
The cleaning pulse must first stop, and then reverse the normal forward flow through the filter.
This develops a positive pressure inside the filter element, which is known as the developed cleaning pressure, the filter over pressure, or the filter cleaning pressure, and has typically developed cleaning pressures ranging between 6” and 20” water column.
After the pulse has concluded, the forward flow re-establishes across the filter elements and another row of filters is pulsed clean.
All these components comprise the reverse pulse jet filter cleaning system.
The correct selection, operation and maintenance of these components are vital to reliable dust collector operation, and it is recommended that filter cleaning system experts are consulted during the specification and operation of a dust collector’s filter cleaning system.