Magnetic Driven Centrifugal Pumps Basics

Magnetic Driven Centrifugal Pumps Basics

Magnetic Driven Centrifugal Pumps Basics. Magnetic drive centrifugal pumps area unit utilized in each chemical and organic compound industries for pumping venturous liquids.

The need of  Magnetic Driven pump

Environmental issues and revenant mechanical seal issues have created a necessity for sealless pumps within the chemical and organic compound industries.

In some cases, additional rigorous laws by the Environmental Protection Agency, OSHA, and native agencies area unit mandating the utilization of sealless pumps.

One kind of sealless pump is that the magnetic drive pump that uses a permanent magnetic coupling to transmit torsion to the vane while not the necessity for a mechanical seal for packing.

Basics of Magnetic Driven Centrifugal Pumps

Magnetic driven pump operation is comparable to a typical pump except the shaft seal is eliminated. Magnetic driven pumps area unit designed to isolate the pump body from the motor driving associate vane and magnet assembly with a drive magnet hooked up to the motor shaft.

The homocentric synchronous torsion coupling consists of 2 rings of permanent magnets as shown in the below figure.

A magnetic attraction field is established between the north and pole magnets within the drive and driven assemblies. This provides the no-slip or synchronous capability of the torsion coupling. The force field is shown as broken lines and shaded areas. Refer below figure.

Motor torsion is transmitted to the vane assembly by mean of magnetic coupling.

Magnetic coupling consisting of a permanent outer magnet ring (in the image shown in RED color) associated with an inner torsion ring or inner magnetic ring(in the image shown in inexperienced color) containing a network of copper rods supported on a gentle steel core. The rotating outer magnet ring generates eddy currents within the copper rods that convert the core to associate magnet. The magnet follows the rotating outer magnet ring, however at a rather slower speed because of slip.

Contaminating shell

It is a pressure-containing half situated inside the drive finish that separates the inner and outer magnet rings of a magnetic drive pump.

It should contain the total operating pressure of the pump since it isolates the pumped-up liquid from the atmosphere. one-piece shaped shells supply the simplest dependability, eliminating welds used for two-piece shells.

Since the torsion coupling, magnetic attraction field should taste the shell, it should be fabricated from a non-magnetic material. Non-magnetic metals like Hastelloy and 316SS area unit typical decisions for the containment shell.

The motion of the magnets past associate electrically semiconducting containment shell produces eddy currents, that generate heat and should be removed by a method fluid recirculation circuit. The eddy currents additionally produce an HP loss, that reduces the potency of the pump.

Metals with low electrical physical phenomena have lower eddy current losses, providing superior pump potency. Hastelloy contains a comparatively low electrical physical phenomenon and sensible corrosion resistance so it is a superb alternative for metal containment shells.

Electrically non-conductive materials like plastic and ceramics {are also|also area unit|are} sensible decisions for containment shells since the eddy current losses are wholly eliminated.

This ends up in pump efficiencies capable of conventionally sealed pumps. Plastic containment shells area units usually restricted to lower pressures and temperatures because of the restricted strength of plastics.

Bearing

Magnetic drive pumps utilize method lubricated bearings to support the inner drive rotor. These bearings area unit subject to the corrosive nature of the liquids being pumped-up so got to be made up of corrosion-resistant materials.

Two ordinarily used materials area unit exhausting carbon and carbide (SIC). Pure mold assault is superior to

reaction secured assault since reaction secured assault has free semiconductor left within the matrix, leading to lower chemical resistance and lower strength.

Hard Carbon

Hard carbon against carbide offers wonderful service life for several chemical applications and additionally offers the advantage of short operation in marginal lubrication conditions.

Silicon Carbide

Silicon carbide against carbide offers wonderful service life for nearly all chemical applications. Its hardness, high thermal physical phenomenon, and strength build it a superb bearing material.

Carbide should be handled rigorously to stop breakage. carbide against carbide has terribly restricted capability in marginal lubrication conditions.

Like traditional centrifugal pumps, these pumps additionally include vane, wearing, throat bushings, auxiliary vane, and/or flushing-line arrangements. Also, maintain the rotor chamber pressure bigger than the suction pressure.

The pump style shall additionally make sure that the temperature and pressure within the rotor chamber forestall vaporization in the least operative conditions, as well as minimum flow whereas providing continuous flow through the rotor chamber for cooling and bearing lubrication.

More attention to relinquish whereas choosing this pump area unit

1. Vaporization within the bearing space of sealless pumps might occur at flows on top of minimum flow within the rotor space.

• To avoid this the temperature versus pressure profile throughout the pump should be on top of the pressure curve in the least locations within the flow path for all conditions. this is often to make sure that the fluid doesn’t flash.

2. We should take into account associate acceptable NPSH margin additionally to the NPSH needed specific by pump merchant. it’s fascinating to possess associate operative NPSH margin that’s ample in the least flows (from minimum continuous stable flow to a most expected operative flow) to guard the pump from harm caused by flow recirculation, separation, and cavitation. thought ought to lean to the results of heated fluid once recirculated back to the pump suction in establishing the NPSH margin.

DON’T INSTALL MAGNETIC DRIVEN CENTRIFUGAL PUMPS TO BEAT SYSTEM ISSUES

Magnetic drive pumps shouldn’t be put in to resolve a maintenance downside, like a difficult mechanical seal, while not 1st determinative the $64000 reason for the matter.

Once the matter has been known, make sure that the installation of Magnetic drive pumps won’t produce a ripple impact. Typical pump and system issues to look at for are:

1. Cavitation
2. Operating too off from best potency purpose (BEP)
3. Net positive suction head on the market (NPSHA) too low
4. Slurries
5. Pump operative while not liquid within the unit