Tank cleaning

Available pressure and flow?

Once you have determined which type of tank cleaning nozzle is most suitable for your cleaning process, the next step is to determine the desired flow rate and nozzle size.

Pressure gauges mounted on the pipeline. Measuring instruments for pressure control.

Pressure and flow

Desired pressure and flow rate have often already been limited by the plants existing tank cleaning setup. If this is the case, flow rate and pressure at the cleaning head need to be specified. This should not be based on the pump, or the theoretical flows and pressures. It should be physically measured at the head. Unfortunately, in some cases it is not possible, and it may need to be “Guestimated”. This means that pump output has to be specified, along with the pipe lengths, diameters etc. This will give a good indication of what is reaching the head, but is no substitute for real measurements at the cleaning head.

If there is insufficient flow and pressure to use the optimum cleaning head or heads, then alternative solutions will be required. It may be possible to simple change the delivery pump, or add in a buffer tank for increased delivery, or it may be that a different tank cleaning nozzle or multiple units can solve the problem.

However, changing the tank washers in an existing set up, or changing the delivery pump for inlet flow may also have consequences on the outgoing flow. If a scavenge pump is used to remove liquid from the tank, then the settings on this pump need to be changed in accordance with the inlet flow. If not, excess pooling may occur in the tank and inhibit the cleaning action of the tank washer.

Recommended flow rate

In general, tank cleaning nozzle rotating speed is affected by pressure. The higher the rotation speed, the more likely it is that the rotating nozzle will atomise the droplets so that they become much smaller. This leads to reduced cleaning impact. It is therefore important that a tank cleaning nozzle or machine is used within the recommended flow rate range.

Cleaning fluid chemical properties

Changing the cleaning liquid can affect pressure and flow rate due to a different liquid viscosity.

Cleaning fluid particles

If cleaning fluids are being reused filtration might be required, which in turn could affect pressure and flow rate.