Engineering in Kenya

Mechanical Shaft Seal

Posted by on May 5, 2018 in Mechanical Engineering | 0 comments

insp 2 300x250 Mechanical Shaft Seal

A mechanical shaft seal is one of the main components in the design of filter pumps like the ones used in a swimming pool known as the spa. The basic function of a mechanical shaft seal is to prevent the water from leaking along the pump’s motor shaft.

Today, with rapid evolution of sealing technology that has taken place over a short period of the past decades, it is now possible to use mechanical shaft seals on just about all applications that involve the use of fluids. However, when thinking of designing this mechanical shaft seal there are a number of factors that should be given the main concern:

Mechanical Shaft Seal Designing Tips

Mechanical Shaft Seal Mechanical Shaft SealThere are many factors to be considered but there are some which are of most importance. To begin with, the nature of the fluids that the mechanical shaft seal will encounter should be taken into account for the mechanical shaft seal design and the elastomer choices.

The mechanical shaft seal will require lubrication and cooing because of the movement of the rotary seal as well as the hydraulic pressure on the seal faces that will generate heat.  The mechanical shaft seals which are not balanced will generate heat, and then wear the faces quickly and therefore it will fail quickly.

If the pusher seals are handling fluids that crystallize or coke they will be forced to hang up on the pump shaft. This usually takes place because the secondary sealing members that needs compensate for the travel given that the seal faces wear will not be able to.

The rotary part of the mechanical shaft seal will be either a positive or even fiction drive. Therefore, if the wrong device might be used for your application, then the seal will fail quickly.

The best design for the sealing pumps is to use the inside mechanical shaft seals but the outside seals may be installed if the pump contains a stuffing box that is very small for the seals. Double mechanical shaft seals may also be used given that it is needed for the performance optimization and also cost effectiveness.

Given that it is really important for your application to have absolutely no leakage, like seen with hazardous materials, the tandem seals will allow you to set a design that won’t fail with the use of the alarms, shut-down devices, e.t.c

In other applications where you do not have much downtime for replacing the mechanical shaft seals, cartridge seals may be pre-set and readied so as to be available for quick installation.

In the past, mechanical shaft seals were designed in a way to overcome some of the problems experienced with packed stuffing boxes. The stuffing boxes then would leak fluids and the mechanical shaft seals solved the problem. In addition, packed stuffing boxes required to have the packing materials to be frequently and the new seals could eliminate the problem; then they would function until the seal faces would be worn out.

How to Transport Certain Types of Mechanical Shaft Seals

Carbon and Graphite Corporation is engaged in the manufacture and exportation of a wide range of the mechanical shaft seals. These include; balanced seals, rubber bellow seals, unbalanced, Teflon below seals, seals with pumping screw, brazed face seals, multiple spring in sleeves, etc.

These types are highly effective in the use and are available in various shapes, designs and sizes.

Tips to Successfully Replace your Pump Mechanical Shaft Seal

The first thumb rule is to read, understand and abide by all the safety instructions at any given time while servicing any type of electrical equipment.  Otherwise, the repercussions are serious injuries or even death.

Before setting out to start the repairs of you spa ensure that all the electrical power sources are completely disconnected. Make sure that you tag and lock out the main circuit breaker.  Close the valves on both the discharge and suction sides of the pump.

Remove the four hex head bolts, the four that connect the impeller and the motor assembly to the pump housing, in order to access the bad mechanical shaft seal on your pool pump.

Hold the motor firmly using both your hands and wiggle it from one side to the other slightly. Using your pliers or a crescent wrench, hold the end that is extended.  Now take the impeller wrench and unscrew the impeller away from the pump shaft.

Now the seal plate has to be removed from the pump motor. Take a careful notice of how the mechanical shaft seal was installed, to aid you while installing the new pump shaft seal.

The seals’ stationary portion is in the recess on the seal plate that is located on the motor bracket. Make sure to use the emery cloth and a little water to clean the sleeve/shaft of the motor. Then place a small amount of silicone lubricant in the mechanical seal recess and the motor shaft.

The other part of the mechanical shaft seal will go onto the motor shaft which should be after the motor bracket had been bolted back in place. Make sure to check the pump gasket and replace it if it is damaged in any way.

In case you are needed to replace the pump head gasket, you should insert the new one between the two the halves of your pump. Finally, re-assemble the swimming pool pump in a reverse form that you disassembled it.

Then open the valves on your pump’s suction and then discharge the lines. Restore the electrical power supply and stat it up and cheek any signs of leakage.

A mechanical shaft seal is very sophisticated today. It can withstand much higher pressure and temperature than it was in the past. Mechanical shaft seals can be set up to avoid any chances of leakage. And they can now be used with almost any given application that uses a centrifugal or positive displacement of the pump. Therefore, you have no excuse for allowing water to leak along the pump motor shaft, you only need to use a mechanical shaft seal and let it perform its function and thus Mechanical Shaft Seal.

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