Seal less mag drives to attack steel centrifugal pumps

Non metallic mag drive pumps and operating temperature

Non-metallic synchronous magnet drive pumps have shown tremendous growth last years in finding their way to end-users.
Nevertheless, many companies in the steel industry, which are very demanding due to the “high” temperatures of chemicals in combination with solids (like FeCl2 and FeCl3) do not see environmental compliance as a way to reduce costs. We will prove that the opposite is true with our Verdermag TB series mag drive pumps.
Reduced stocks, lengthening MTBM (longer operation), elimination of Eddy Current lossess (no heat, lesser power consumption) and total product containment (no spoil of hazardous liquid).

Improved manufacturing methods in combination with a wide availability of necessary materials for construction have made these seal less mag drive pumps more beneficial as initial investment and worthwhile in terms of total cost of ownership. Reducing the required spares by introducing modular, simple by design construction and lengthening of the M(ean) T(ime) B(etween) M(aintenance) are the main important factors for the growing popularity of the Verdermag non-metallic mag-drive pumps either in E-TFE or PFA construction.

Steel manufacturing

An important part of steel manufacturing is the finishing area, where the steel will be pickled with help of chemicals. The mill scale and other surface films are removed by immersing the unfinished steel in various concentrations of acids.
This is called pickling. Commonly used are Hydrochloric acid and Sulfuric acid for steel manufacturing.

Continuous pickling

The continuous method is employed for pickling coiled steel sheet and runs a continuous roll of steel through a series of vats (basins) with re-circulating concentrations of acid help at prescribed temperatures.
The steel enters the process in the hottest and least concentrated acid solution. As it moves through, it progressively passes through cooler and more concentrated acid. The maximum temperature for an optimum pickling process is 96 °C. 

In most cases non-metallic (plastic or carbon) mag drive pumps are used to cover the chemical resistance against the acids in five areas:

  1. Pumping the acids from storage to the tank farm
  2. Re-circulating the pickling acid over the vats
  3. Re-generating the used pickling acid
  4. Circulating the rinsing liquid over the cascade tanks
  5. Pumping the neutralization liquids for the water treatment

1. Pumping the acids from storage to the tank farm

Mag drive pumps used in this process, will run intermittent (batch-wise) to fill up the storage tanks in the tank farm and upgrade the re-generated acid. To empty the trucks or rail cars the TB or GPSP-version will be preferable, utilizing common parts with the normal priming horizontal pumps. The TB pump a mag drive seal less centrifugal pump with integrated suction chamber.

2. Re-circulating the pickling acid over the vats

Re-circulating applications are the most demanding processes, as the centrifugal pumps have to operate continuously with low available NPSH values.
Required flows depend upon the size of the pickling section, but the majority of applications are operated between 80 and 120 m³/h.The magnet drive construction prevents the Verdermag pump from leaking, also in cases of power supply interruption, maintenance checks etc. The pickling acid will be de-valued as part of the process and transferred to the next vat, where it’s temperature will be elevated.
The Verdermag mag drive TB series pumps combine a stationary shaft, trust balancing and secondary bearing design to reduce radial loads in the pump and make them capable to pump solids together with the acid without damaging the pump. 

3. Re-generating the used pickling acid

The concentrated waste pickling acid will be generated in a furnace under “high” pressure. The nozzle demand a differential pressure of at least 6 bar, and depending upon the customers’ plant lay out, the total differential pressure will be around 11 bar. Again the liquid temperatures are around 96 °C.

4. Circulating the rinsing liquid over the cascade tanks

Rinsing is done with de-mineralized water, but the steel sheet will be contaminated with the pickling acid. Again conventional centrifugal pumps are not appropriate for these applications due to chemical resistance. In case of this application Verder has the seal less advantage over conventional pumps.

5. Pumping the neutralization liquids for the water treatment

Due to the 'acid' environment the neutralization is done with mainly caustics. Verder has a wide experience with the handling of Caustic Soda.
The Verdermag pumps have optimum torque transmission; even when viscosity increases at lower ambient temperatures. These fully hermetic closed pumps will not show any cristallization, which is usual in the sealing area of conventional pumps.

Advantages and Benefits of Verdermag non metallic pumps

Many (Steel) companies have set themselves targets in reducing energy costs, Verdermag non-metallic mag drive centrifugal pumps will help to achieve these goals:

  • No Eddy Current losses, nor mechanical seal friction losses; lower installed power 
  • No (seal) flushing equipment required

If you have interest in the Verdermag drive pump please contact us.

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