Side-channel pumps solve many pumping problems
Featured Product from Dickow Pump Company, Inc.
The SCM-pumps are single or multistage, horizontal side-channel pumps in heavy duty design with end suction and vertical discharge flange. The pump shaft is driven via a permanent magnetic coupling. The static containment shell forms a closed system with hermetically sealed liquid end.
Suction- and pressure disks
The suction and pressure disks are sealed to the atmosphere by confined 0-rings, metal-to-metal fit, to prevent blowouts. In the shaft area, floating graphite impregnated PTFE-inserts are located for prevention of shaft deflection and seizing. The differential head is generated in the side-channel of the pressure disk.
The large diameter shaft is carried in slide bearings and has no deflection and only minimum torsional load. Thus, wear-free running of the impellers is ensured.
Since these pumps can handle relatively large amounts of gas, they are inherently self-priming as long as sufficient liquid remains in the pump. Therefore, the diffuser is also designed as a retaining stage. That means that the pump will still be filled with liquid after switch off and can be restarted without problem also in self-priming service.
The NPSH-conditions displayed on the next page are based on water at 20°C. When handling boiling liquids or hydrocarbons, the liquid level on suction side can be reduced to 50% o the published NPSH value.
Flameproof area features
Unlike "Canned motor" designs, the magnetic driven pump does not have electric windings adjacent to the fluid in the shroud and the magnet flux power transfer is non-sparking. Standard certified electric motors completely external from the pump housing are used, hence the possibility of flammable liquids contacting electrical windings is negligible.
The single elements of the multipolar magnetic coupling are manufactured of "Cobalt-Samarium Rare Earth", a permanent magnet material with unlimited life. The internal magnets are completely encapsulated; no contact with the liquid. Energy is transmitted to the hermetically sealed liquid end by a bank of external magnets passing motive force through the containment shell to a bank of internal magnets. Inner and outer magnet rings are locked together by magnetic power and work as a synchronous coupling. The inner magnet ring transmits the required torque directly to the impeller. Overload of the magnetic coupling and slipping will not affect demagnetization. The magnetic drives are designed for electric motors, direct on line starting. Should a subsequent increase of motor power be required, the nominal power of the magnetic coupling can be increased accordingly by an additional series of magnets. The maximum transmissible power for SCM-couplings is 45 kW at 1450 rpm (60 HP at 1750 rpm).
When pump is in operation it generates eddy currents which heat up the conatinment shell and the product in the magnet area. This heat is dissipated by internal circulation. The circulation flow is led from discharge through the magnet area and the pump shaft to the suction disk of the last stage. Pressurizing of the containment shell prevents flashing of the liquid in the magnet end.
The major heat source of magnetic driven pumps is in the containment shell area which is cooled at normal running by the handled liquid. Nearly all malfunctions can be detected by monitoring the liquid temperature in the containment shell area. Installation of a temperature sensor therefore provides an optimum inexpensive form of continuous process protection. All pumps are provided with the required connections for RTD-elements.
The DICKOW-pump, type SCM, is a one or multistage, self-priming horizontal side-channel pump with magnet coupling. The side-channel pump with its high differential head has the advantage of operating more economically than normal centrifugal pumps applied for low capacity and high heads. Due to these facts, the side-channel pumps are appropriate to solve many pumping problems in the chemical and petrochemical process. The SCM-pump is a heavy duty unit for handling clean pumpage withoutmore solids. Sealless magnetic driven pumps are designed to improve plant's and personnel safety, especially when handling toxic, explosive or other dangerous liquids which react on contact with the atmosphere. For all such services, the static shroud replaces double acting mechanical seals, along with external fluid reservoirs or barrier fluid circulating systems. Due to the fact that 90% o pump failures and required service base on leaking mechanical seals, the sealless design will save maintenance and spare parts costs remarkably. Considerable are the total cost savings of ownership.
Why Use Dickow Magnet Drive Pumps?
Since the 1970s concern for the environment has become increasingly important in the design of industrial plants. Today this issue is a vital concern in any discussion involving new plants and updating of facilities. Equipment designers, engineers, and suppliers must offer solutions which will eliminate any adverse environmental impact, or at a minimum reduce it to sustainable or regulated levels.
The weakest link with respect to centrifugal pumps is the shaft seal, when considering release of fluids to the environment. This is because there is always some inherent emissions from mechanical seals. The average emission rate of a mechanical seal is 0.13 GPM to 0.35 GPM, and although this appears to be quite small, the actual atmospheric penetration is quite large when one considers that large chemical plants have thousands of pumps in operation. In 1989 the Environmental Protection Agency (EPA) published its first report on environmental pollution. The report documents that American chemical and petrochemical industries, in 1987, emitted 390 tons of toxic materials into the atmosphere, in part attributable to pump leakage.
Potential problems occur by the formation of dangerous explosive mixtures, which become worse when toxic or malodorous gasses and vapors endanger plant personnel. In order to prevent the vaporization of liquids between seal faces additional cooling is required when the media has vapor pressure greater than atmospheric pressure at operating temperatures. Additionally, when handling fluids that crystallize in the atmosphere, an appropriate quench connection or barrier fluid must be provided.
Various attempts have been made to improve the performance of mechanical seals in order to meet regulations pertaining to emissions. Examples include double acting mechanical seals of "tandem design", "back-to-back design", and various gas seal types. All of these require auxiliary equipment, systems, and controls. For many applications the costs of this equipment is not justifiable in light of the gains attained.
It would appear that the outer limits have been reached for improvements in mechanical seals with regard to reliability and emissions control. The only realistic solution is a sealless pump with zero leakage, i.e. without the connection of the media to the environment due to the absence of a seal. Many of our earliest customers installed Dickow sealless magnet drive pumps for their zero leakage feature, but quickly realized that their mean times between failures was greatly improved as down time due to seal replacement was eliminated completely.
Dickow Pump Company has produced pumps for over 100 years. Our pumps are working steadily and dependably in all corners of the globe.
As the technical world leader in magnetic drive pumps, Dickow holds many patents, is ISO 9001 certified, and is a supplier-partner of major chemical companies.