Troubleshooting: Air Header got no air for the pulse jet cleaning system

 

One customer told us that their dust collection system had a very weak suction on the grinding process line, and we went to their workshop on-schedule to do troubleshooting. 

Introduction of the dust collection system

The dusty air from the plastic grinder first ran through a cyclone and the separated dust from the cyclone directly went back to the process; the airflow with fine particles from the cyclone went to a cartridge dust collector, and then the filtered air was released to outside of the building.

Since the plastic dust is combustible, an explosion panel and a vent duct were installed on the dust collector, and a non-return valve on the ductwork just in front of the dust collector inlet.

The cartridge dust collector was equipped with a pulse jet cleaning system controlled by a Photohelic pressure gauge. The Photohelic Gauge measures the Differential Pressure and provides the capability for “on-demand” cleaning in conjunction with a Timer Board.

Troubleshooting process

When we walked around the cartridge dust collector doing a visual inspection, we saw that the pointer of the pressure gauge on the air header pointed to 0 (zero) psi, then we tracked down the supply line of the compressed air and found that the shutoff valve on the compressed air branch line to the air header was turned off (Figure 1). Apparently, the customer forgot to turn it back on. 

Figure 1 the shutoff valve was turned off and forgotten

Before opening the shutoff valve, we used this chance to empty any condensed water in the air header. On the drainpipe of the air header, no drain valve was installed, only a blind cap. The filter and water trap bowl of the air filter and pressure regulator piggyback in front of the air header were inspected as well.

The shutoff valve was cautiously opened, and the air header pressure roared to about 83 psi (Figure 2). Then the manual drain of the piggyback was tested. 

No abnormal sounds around the air header, solenoid valve manifold, diaphragm valves, and blowpipes indicated air leaks.

 

Figure 2 air header pressure, 83 psi

After tagout/lockout, we opened the access cover and inspected the inside of the dust collector and took out cartridges for cleaning with compressed air on the floor. From the look of the cartridge body and inside of the collector, pulse jet cleaning had not functioned for some time (Figure 3&4). 

The collected dust was discharged from the hopper directly to a barrel below on the ground through a flex hose. The barrel was almost empty.

Figure 3 inside of the dust collector without pulse cleaning

Figure 4 cartridges without pulse cleaning

 The cyclone and the ductwork were also inspected to make sure they were not clogged. They were fine too.

The differential pressure hoses connected to the Photohelic pressure gauge were inspected. They were not clogged.

We manually triggered the diaphragm valves to make sure they were functioning properly. They were fine.

After the system was turned on, it ran normally.

The high set point and the low set point of the differential pressure on the Photohelic pressure gauge were lowered by hand to turn on the pulse cleaning in a shorter time; the solenoid valves were then inspected, and they all functioned properly, and then both set points were turned back to its old settings.

The integrated fan and motor were on top of the dust collector. We checked the vibration of the compact combo, and they were fine; we also checked the outlet damper, and it was fine too.

At last the vent ducting was visually checked from the outside of the building, and it was clean with no dust accumulated inside the ducting and no other debris. 

Problem solved; the customer was happy.

A piece of advice 

In fact, we found that customers often forgot to turn back on the valves to air headers after they were turned off, especially when the valves were within easy reach, and consequently they got weak suction at hoods. 

So, please check the openness of the valve to the air header of your pulse jet cleaning system before calling in a service contractor, as this will save your money and reduce your downtime.

Leak Test, Air Balancing, Trouble-shooting, and System Evaluation services by Airvate

• Dye test for bag/cartridge leak 
• Dust collection system and industrial ventilation system Testing and Air Balancing
• Technical services: field survey and dust collection system audit / evaluation and trouble-shooting
• New system start-up
• Dust sample analysis
• Dust collector selection and sizing: baghouse, wet scrubber, cyclone, settling chamber, drop-out box, etc.