Effectively Clean Tanks and Reactors

Choose the right equipment to avoid costly contamination problems.

By Anthony Wood, Spraying Systems Co.

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If you're not certain how much impact is needed, a cleaning equipment vendor should be able to provide guidance and impact data. Some manufacturers will conduct tests in their spray labs with your specific residue to optimize cleaning performance. Another option is a short-term lease on a pumping system and vessel cleaner, so you can evaluate the equipment in your production environment. Some vendors also offer no-obligation equipment trials.

Safety. Is the residue, cleaning solvent or environment toxic or flammable? The answer will significantly influence the type of equipment you choose.

Once you understand your cleaning requirements, the next step is to evaluate the cleaning equipment. So, let's look at what's available and the pros and cons of each option.

THE TYPE OF POWER FOR CLEANING TANKS
The first decision is whether to use a machine powered by fluid or a motor.

• Fluid-driven cleaning machines use fluid to spin a turbine that powers a gear set (Figure 2). The nozzle assembly rotates as the hub revolves around its central axis. The higher the liquid pressure and flow, the faster the rotation.

• Motor-driven cleaning machines rely on an external electric or air motor to drive the nozzle assembly (Figure 3). The nozzles revolve around the central axis of the nozzle assembly.

[Avoid Costly Fabrication Mistakes]

Both machines operate at high pressures, provide 360° cleaning coverage and suit large vessels (up to 100 ft. dia.). They often offer comparable cleaning performance. However, there are several operational differences.

Clogging. A fluid-driven machine is more prone to clogging. As fluid passes through the device, debris can accumulate in the internal flow passages or get caught in the gears. When this happens, the machine stops working because the gears no longer can rotate. Verifying operation is crucial but can be challenging -- it's difficult to visually observe the inside of a large vessel.

A motor-driven machine will continue to operate even with debris in the nozzles. The external motor ensures continued rotation and cleaning. Plus, you easily can hear the sound from the motor and verify operation without having to inspect the vessel.

If you're using less than pristine water and it's difficult to see inside your vessel, a motor-driven machine is a better choice.

Cleaning cycle time. If short cleaning cycles are a priority, consider a motor-driven unit. Using an electric motor, cycle times remain constant regardless of operating pressure and flow rate. With an air motor, you can increase air pressure to make the nozzle hub rotate more quickly.

Fluid-driven machines can achieve comparable cycle times to motor-driven machines by raising pressure. However, operating at higher pressures increases wear of internal parts and results in more frequent maintenance.

Sparking or explosion risks. Explosion-proof electric motors are available or you can use an air motor. Or you may be able to change cleaning solvents to eliminate the explosion hazard without negatively impacting cleaning. Other options include increasing humidity in the vessel to minimize the risk of static electricity, prevent complete drying of the residue and ease residue removal.

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