When this is a problem, appropriate storage and piping can be a very effective correction when properly implemented (Table 1 and Table 2). For example, pictured below is a dust collector system which has six pulsing valves that use 3.5 ft 3 over a half-second for each pulse. Sequence controllers can have a very significant impact on the required rate of flow. Dust collectors have this characteristic. Even relatively small air demands in ft 3 can have a very high rate of flow, if they occur over a very short time period. Rate of flow is the actual rate of flow of compressed air demand expressed in ft 3/min, regardless of duration. Rate of flowįlow rate is the average flow of compressed air in ft 3/min either required by a process or delivered to the system. Feed line sizing, regulator sizing, and air supply all require an identified rate of flow. They occur because, prior to the installation or prior to some operational change, the proper rate of flow wasn’t identified for the dust collector cleaning action.
One very common installation or system situation causes restricted air flow. Monitor inlet pressure and drop at pulse.Use of storage to supply air without pulling down feed to receiver/collector.
Use proper line size to handle rate of flow without high pressure loss.Improper compressed air delivery and supply may create an ineffective pulse. This will make it unable to handle the required rate of flow required by the dust collectors. This will have the same effect as lack of air supply. Too small of a feed line to the dust collector entry.With too low of an inlet pressure, the mass weight of the air pulse is too low, which then becomes ineffective in removing the cake. Lack of sufficient storage or compressed air supply near the inlet manifold to supply the required pulse air without collapsing the inlet pressure.These settings have to be set carefully to begin with and have to be monitored regularly. The actual requirement for the optimum timer setting may well change as various product runs change or even seasonally. Incorrect timer settings for the operating conditions.There are usually several basic causes for this. This causes not only short bag life, but very poor performance. Short bag life usually comes from the pulsers hitting the bag when the cake is not ready to flake off or the cake has gone too long between pulsing and grown too thick and heavy to clean effectively. Installation considerations for proper compressed air supply However, if this pressure varies, then performance will not be consistent or satisfactory. The operator may experiment to find the right timing sequence at a desired compressed air inlet pressure. The dust collector must receive the correct pressure, or close to it, and a steady repeatable pressure level for each pulse, particularly if timers are used to control the pulses.
The actual amount of weight of air is dependent upon the pulse nozzle being fed compressed air at a predetermined and steady pressure. The pulse valve sends a given volume or weight of air to the bag at a predetermined velocity to strike and clear the cake. When the cake is not removed efficiently, the dust collector doesn’t remove dust effectively from its assigned environment and the bag life can be significantly shortened.ĭust collection system designs specify the compressed air inlet pressure to the manifold and pulse valves necessary for effective dust removal. When the cake is removed correctly from the dust collector, the system removes dust from its assigned environment and has a normal bag life. This pulse may sometimes be accompanied by physical shaking and even reverse air flows, depending on design. In a pulse jet dust collector, the dust is collected on the bag or fingers, and, when the cake of dust is of appropriate thickness and structure, a pulse or pulses of compressed air hit or shock the bag and knock the cake off. The timers are generally set by the operators to what they believe is appropriate for proper cake removal and bag life. The pulse is usually controlled by a timer which might have an auxiliary demand control. There are many types, and sizes and many use a pulse of compressed air to clear the bag or filter. Proper operation of dust collectors is critical to minimizing cost and maximizing system effectiveness. Often, the compressed air feed lines are the same size as the connector opening. On at least half of the dust collectors, most have gauges at the entry some of the gauges are even operational. When they try to run on demand control, they often get extreme short cycling, which causes even more bag problems. Many have continuing problems with short bag life and low-pressure problems at the farthest points from the central air system. Many production facilities have a significant number of dust collectors.
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