During the operation of the pump, liquid losses occur. As a rule, this occurs at the point of its connection to the pipeline. To avoid it, it is necessary to use a stuffing box seal of the pump. It is this device that will be discussed.
Pump packing
Modern centrifugal pumps are equipped with various structural elements and parts.
In this case, it is necessary to ensure the normal functioning of not only individual elements, but the entire equipment. The stuffing box seal of the pump is used more often than other methods. The reason for this is the simplicity of the design as well as the easy installation.
Seal requirements
Household pumps work thanks to the impeller, which is driven by the engine.
It is usually electric. The rotation of the impeller occurs due to the energy coming from the motor through a mechanical clutch. The motor shaft is not in the housing. Therefore, its tightness is broken. Because of this, a large amount of fluid leaks. If you use a stuffing box seal on the pump, then the problem can be avoided. Various methods are used today:
- Packed seal. It is a round structure made of fibrous material.
- Lip seal. As this sealant, materials are used that work well in tension. Reinforcement is used to increase the rigidity of the structure. This type is installed on household pumps, where the shaft rotation speed is low.
- Groove seal. It has another name - labyrinth. This is the most reliable type of seal. It is a round design made of soft material. This type is mounted on multistage pumps. If other seals are installed on them, this will lead to a loss in unit performance.
- Face seal. This type is presented in the form of two rings, which are tightly located to each other. The first performs rotational movements together with the working shaft, and the second is static.
There is such pumping equipment where the use of a sealant is not required. These are devices containing a magnetic coupling.
Operation of seals
Stuffing box seal of the pump shaft is used to ensure tightness.
They are generally used for submersible types as they are not subject to special liquid leakage requirements. In this case, the long term is more important.service life.
Stuffing box seals appeared on the market along with liquid pumping devices. Why are they called that? The seal has a round shape, consisting of a fibrous material. This form is made on a stuffing box basis. The fibrous material must be constantly wetted by the pumped liquid. It acts not only as a lubricant, but also as a cooling material. Therefore, fluid loss is still unavoidable. For one hour of work, up to 15 liters of water are consumed. If you do not wet the fibrous material, it will quickly burn out and you will have to install a new one.
It is worth noting that the elements need constant maintenance. The gland seal is replaced without dismantling the pump and motor. This is a significant advantage. There is no need to call a specialist. Pulling up the cuffs is done by yourself.
Stuffing box design
There is a wide range of gland seals on the market today.
The main types are:
- Reinforced material with one edge. Serves to prevent leaks.
- Reinforced cuffs with one lip. This device is used to protect the seals from dirt, as well as from loss of fluid during pumping.
In addition, the edge can be produced in several versions:
- standard;
- Machined.
Seals are also divided by the type of rubber material used in the cuffs.
Among them are the following materials:
- Rubber. Various grades of rubber are made from this material. Their main advantage is their ability to withstand low temperatures.
- Fluoro rubber. It is used only for rubber of 1 and 2 classes. Able to withstand temperatures up to 170°C, which is achieved when pumping viscous oil.
- Silicone. It is applied only to rubber of 1 class. Able to withstand temperatures down to -60°C.
Modern cuffs are produced together with a spring, which is needed to seal shafts of various diameters.
Sealing material specifications
Compared to other seals, cuffs are flexible and plastic properties. Operational features depend on the type of sealing material. Depending on the structure, they can have diagonal weaves and in the form of a heart. Their composition is also different, and may be as follows:
- may contain asbestos;
- be dry or soaked;
- reinforced and non-reinforced.
Gland seals of centrifugal pumps and hydraulic presses are also used. During installation, please note that some of the pumped liquid will be used to wet the seal.
Gland packing benefits
So, the cuff used to pump fluid looks like a braided rope. Threads are made of asbestos or cotton. Sometimes copper wire is inserted into them. The middle is lead. When weaving,used from 4 threads.
Install the glands on the suction side. However, they can be mounted in other places. The amount of packing depends on the diameter of the shaft.
How to choose an oil seal
There are a number of characteristics to consider before purchasing a seal.
The first and most important issue is the reliability indicator. Another important factor is cost. Among other criteria consider:
- operation time;
- specific fluid loss;
- service life;
- repair or replacement costs.
It is necessary to choose a stuffing box seal based on the standard sizes. Here they look at the outer and inner diameters, as well as the wall thickness.
Reviews
Many users are satisfied with the gland seal. Using it to mount a single-stage pump, they noticed that the seal was suitable for any shaft speed. The most popular model is silicone lubricated seals. They are able to withstand high temperatures. Some fibers are treated with a special liquid, which allows the use of a sealant for pumping aggressive media.
Users pay attention to the design of the seal. The cuff is made of woven asbestos thread.
Copper wire is also used in its manufacture. This combination makes it strong enough that it is not affected by the pumpedliquid.
Cost
As mentioned earlier, there are several characteristics to consider when choosing a seal.
They affect the cost of the device. Their price ranges from 100 to 500 rubles.
Conclusion
To prevent large fluid leaks, stuffing box seals are used. They are available in various versions. Of course, there will be fluid loss, but it is small. The volume will be spent on wetting the sealing material. Many users are satisfied with this device. As a rule, it is placed on submersible pumps used for pumping dirty water. Their service life is quite long, and reliability is high. For a fairly small price, you can buy quality material that will last a long time.
So, we have considered what the gland seals of centrifugal pumps are used for, and what types they are divided into.
