Benefits of using Sealless Magnetic Drive Pumps

Sealless Magnetic Drive Pumps vs. Mechanical Seal Pumps

 

How does a positive displacement pump work?

Positive displacement pumps move liquids by repeatedly encapsulating a fixed volume using seals or valves to mechanically move it through the system. The action (or motion) of a pump is driven by pistons, screws, gears, or vanes (impeller), to name a few. Applications for these pumps are typically found in situations where highly viscous liquids such as viscous oils and slurries are transported. When choosing the right pump for an application, there are many considerations that must be made. Among these considerations are required flow rates, what fluid is being pumped, the heat load surrounding the pump, and the style of pump that completes the required task most effectively.

The pump comes with various seals that can be used. Pumps are a piece of equipment that must be fine-tuned to ensure they operate as they are intended to in a multitude of service fields. Prevention of effects such as cavitation is also important to promote the proper operation of pump systems. Seemingly minor issues within the pump may cause it not to work correctly and result in a longer period of downtime. For simplicity, we will discuss two of the main types of seals: mechanical seals and magnetic seals.

 

Types of Pump Seals:

1. Mechanical Pump Seal 

The purpose of a mechanical seal is to act as both a check valve and slider bearing. By acting as a check valve, the pressurized fluid is prevented from seeping out or allowing air into the pump when under vacuum. Seal life often is unpredictable, as they must act as slide bearings for the pump. Mechanical pump seals are typically replaced very often during the working life of the pump. The fluid pumping through the mechanical pump lubricates the bearings. The fluid is responsible for filling an air gap between the mating surfaces. Though some of this liquid is released into the atmosphere, it is so small that it will only be recognized only as slight corrosion on where the pump connects to the system.

A factor that greatly influences seal life most commonly is fluid condition. One of the largest opponents of mechanical seals is the presence of abrasive substances in the working fluid. Examples of these abrasives range from dirt to dissolved impurities in liquids that precipitate out of the solution. The working fluid, along with these abrasive materials, finds its way between the sliding surfaces and polishes the pump primary ring.

Excessive heat can also be detrimental to pump performance. This excess heat will damage the face seals and elastomeric components. It should also be noted that running a pump without liquid will adversely affect the condition of the pump. The surfaces of the primary ring and mating ring will be at risk of becoming either under-lubricated or completely unlubricated. If the pump becomes overheated, membranes and O-rings are at risk of becoming brittle and cracking. This will then cause the seal to leak and require replacement.

The seal material is chosen to complement the temperature limits and type of fluid being pumped. In standard operating conditions, seals wear out much faster than other pump parts. A large number of abrasives, as well as overheating, will increase the amount of wear and shorten the lifespan of the seal. A mechanical seal comprises two parts: a stationary component and a rotating component. The stationary component is attached to the pump housing, whereas the rotating component is mated to the pump shaft. The contacting faces of the components are precisely machined to be smooth and are pressed together by bolts and springs.

In this application, this is the best solution for reducing leaks, but it can be expensive and difficult to set up. Complete elimination of leaking is not attainable with this solution. It is important to allow some leakage to lubricate and cool the seal as well as the pump shaft. Pump seals require monitoring and frequent maintenance to prevent excessive leaking, especially when the pumped fluid is known to contain abrasives. Leaking fluids must be contained and properly disposed of. In cases where the fluid is toxic, flammable, radioactive, or environmentally damaging, even minor leaks can be a major risk. One of the leading causes of pump failures or shutdowns is fluid leaks.

2. Sealless Magnetic Drive Pump

When leak prevention is necessary, or liquids are challenging to seal, magnetically sealed pumps are required. Magnetic drive pumps are sometimes referred to as magnetically coupled pumps. The difference between magnetic drive pumps and conventional pumps is the pairing of the pump to a motor. In this case, the motor drives the pump by way of a magnetic field created by magnets in the pump housing rather than a mechanical shaft. The pump operates using a driving magnet, which avoids the need for any shaft sealing. This is a significant benefit.

By removing the factor of mechanical seals, friction loss, wear, maintenance costs, and noise are also positively affected. This allows for the isolation of the pumped fluid from the drive of the pump. A large air gap separates the pump chamber from the drive motor. This results in a minimal amount of convective heat transfer, reducing how hot the pump will become. Since the coupling is magnetic, it is good for preventing torque spikes that would damage a mechanical coupling. In the most demanding situations, the magnetic coupling will act as a fuse. In the event of an excessive pump load, magnetic bonds will be broken temporarily. This effectively means that the pump will not be allowed to overload, preventing damage.

Since a magnetic drive pump is an isolated piece of equipment, the bearings are unable to be lubricated by normal means. Because of this, the working fluid is responsible for the lubrication of the bearings as well as for cooling the pump. 

For viability as a lubricant, the working fluid should maintain a proper film thickness at the operating temperature and load. If this condition is not met, the bearings will become subject to extreme wear. Many fluids, such as water and most solvents, do not meet this criterion and thus are unable to act as lubricants.

As a result of insufficient pressure or flow rate of the working fluid through the bearings and other critical components, overheating will occur, which can pose a serious issue. If this happens, the liquid may reach a flash point, and the lubricating ability of the fluid will be reduced as the liquid increases in temperature and decreases in viscosity. The factor that determines the maximum torque these pumps produce is the gap between the magnets: the smaller the gap, the greater the torque. However, there is a limit to how small this can be designed as the gap needs to account for the containment shell as well as any protective coating on the magnets. To ensure the safe operation of the pump, there must be a reasonable gap between the rotating parts and the containment shell. This is highly important in cases where the pumped fluid is highly viscous or contains solids. In the creation of the parts, the tolerances they are machined to must be very tight for optimal efficiency.

 

Pump Maintenance Practices

Though there are a limited number of parts within a pump, proper maintenance is necessary to ensure that they continue working at their optimal efficiency. In the case of mechanically sealed pumps, the seals need to be replaced depending on the usage of the pump. However, with a magnetically sealed pump, the cost of replacing seals is removed as they are service free. This contributes to high initial investment, but the return on investment is seen when it comes time for pump maintenance. At a minimum, the pump should be disassembled and checked every 10,000 hours or two (2) years of operation to ensure no catastrophic damage or excessive wear has occurred. Though the previous statement gives a general idea of when a pump should be maintained, it is always best to consult the pump manufacturer’s guidelines. Be sure to consider how much downtime will be necessary to complete a pump service.

How many lines will have to be disabled? Is this pump critical for another operation of other equipment, or is it isolated? Choose a time when the system is not normally operating, if possible, and use your best judgment when deciding the time and frequency of maintenance. Eliminating the possibility of a seal failing decreases pump downtime as it is one less part to replace during the scheduled maintenance of equipment. Prior to performing your maintenance and/or systems check, it is advisable to ensure no power is supplied to the pump. Proper isolation is important not only for electrical systems but for hydraulic systems as well. Ensuring the internals of the pump stay as clean as possible by removing debris and cleaning the pump of sludge will also allow users to get the most bang for their buck out of this piece of equipment. The longer you can keep the same piece of equipment running, the easier it is to justify the cost of upgrading and making the switch to a sealless magnetic drive pump.

 

Why use sealless magnetic drive pumps?

Magnetically sealed pumps come with many added benefits of use. Removal of a critical failure point in a piece of equipment that finds use in many different industries allows for the possibility of improved processes and productivity for these industries. Though the initial investment is comparatively high, the resulting savings in maintenance costs will provide justification for making the switch if such a pump can be used in your particular application. As magnetically driven pumps don’t need to be lubricated by conventional means, this removes another maintenance item from the checklist, once again increasing the savings in that area. The elimination of seals in a pump system also decreases the risk of fuel/lube (mineral oil) leakage from the sealing points. Improper seals can also lead to a pump not being primed and losing suction, so this problem is removed at the pump level as well.

The next time you are searching for a pump for your application, be sure to consider a sealless magnetic drive pump.

As stated previously, the possibility of overloading and damaging the pump is reduced since it is not directly connected to the shaft of the electric motor. The usage of a magnetically sealed pump can provide proven reliability and lead to an increase in production as a result of shortened periods of downtime and longer periods of performance. With a magnetically sealed pump, operators and maintenance personnel have a reduced risk of exposure to leaking mineral oils. Reduction of exposure will have a clear positive effect on workplace safety. Maintaining a safer environment also improves morale since employees feel more comfortable in their surroundings. The next time you are searching for a pump for your application, be sure to consider a sealless magnetic drive pump.

 

IOW Group

IOW Group provides a full range of positive displacement triple screw pumps. All IOW pumps fit within the industry-standard footprint for easy installation. There is a choice of standard mechanically sealed pumps or, for a superior seal, IOW Group has a full range of sealless magnetic sealed pumps. The IOW triple screw pump is compact, powerful, efficient, and reliable. The IOW pumps are designed to endure a long, problem-free operation, even in the toughest environments. IOW Group pumps are utilized in the commercial, marine, navy, power generation, and general industries.

IOW Magnaline pumps are sealless magnetic drive pumps and are completely leak-free.

Magnaline sealless magnetic drive pumps (magnetically driven triple screw pumps) have no disposable seals; therefore, they require less service and maintenance than mechanical seal pumps. Magnetic seals eliminate any leaking, which is ideal for environments where the leaking liquid would pose a risk. The elimination of consumable spares improves the pump’s performance, reliability, and efficiency. Installation of an IOW Magnaline pump/magnetic coupling is easy, as there is no need for alignment of the pump and motor due to the strong magnetic force within the coupling.

To learn more about the IOW Magnaline sealless magnetic drive pumps, visit IOW Group’s Magnaline magnetic seal pump range webpage or visit our IOW Group triple screw pump webpage.

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