During pump operation, fluid loss occurs. 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. This device will be discussed.
Stuffing box packing
On modern centrifugal sediments, various structural elements and parts are installed.
In this case, it is necessary to ensure the normal functioning of not only individual elements, but also of all equipment. Gland packing is used more often than other methods. The reason for this is the simplicity of design, as well as easy installation.
Seal requirements
Household pumps work thanks to the impeller, which is powered by an engine.
It is usually electric. The rotation of the impeller is 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, large amounts of fluid leak. By using a stuffing box seal, problems can be avoided. Today, various methods are used:
- Stuffed seal. This is a round structure consisting of fibrous material.
- Lip seal. As this sealant, materials that work well in tension are used. To increase the rigidity of the structure, reinforcement is used. This type is installed on household pumps, where the shaft rotation speed has a low rate.
- Crevice seal. It has another name - labyrinth. This is the most reliable type of seal. It is a round structure made of soft material. This type is mounted on multi-stage pumps. If other seals are installed on them, this will lead to a loss in unit performance.
- Mechanical seal. This type is presented in the form of two rings which are densely 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 seal is not required. These are devices containing a magnetic coupling.
Seal Operation
The pump shaft seal is used to ensure tightness.
As a rule, they are used for submersible types, since they do not have special requirements for fluid leakage. In this case, a longer life is more important.
Stuffing box seals appeared on the market along with fluid transfer devices. Why are they called that? The sealant has a round shape consisting of a fibrous material. This form is made on an omental basis. The fibrous material must be constantly wetted with the pumped liquid. It acts not only as a lubricant, but also as a cooling material. Therefore, fluid loss still cannot be avoided. In one hour of work, up to 15 liters of water is 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 packing gland is replaced indiscriminately at the pump and motor. This is a significant advantage. You do not need to call a specialist. Cuff pulling is done independently.
Stuffing box design
Today, the market has a wide selection of stuffing boxes.
The main types are:
- Reinforced material with one edge. Serves to prevent leaks.
- Reinforced cuffs with one edge. 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 made in several versions:
Seals are also divided by type of material for rubber used in cuffs.
Among them are the following materials:
- Rubber. Different classes of rubber are made from this material. Their main advantage is the ability to withstand low temperatures.
- Fluoroelastomer. Used only for rubber grades 1 and 2. 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 up to -60 ° C.
Modern cuffs are produced together with a spring, which is needed to seal shafts of various diameters.
Characteristics of the sealing material
Compared to other gaskets, the cuffs are flexible and ductile. Operational features depend on the type of sealing material. Depending on the structure, they can have diagonal weaving 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 unreinforced.
Gland seals for centrifugal pumps and hydraulic presses are also used . During installation, it should be borne in mind that a certain amount of pumped liquid will be used to wet the seal.
Advantages of stuffing box seal
So, the cuff used to pump fluid has the appearance of a braided rope. The threads are made of asbestos or cotton. Sometimes a copper wire is inserted into them. The middle consists of lead. When weaving, from 4 threads can be used.
The seals are installed on the suction side. However, they can be mounted in other places. The amount of packing depends on the diameter of the shaft.
How the oil seal is selected
Before you buy a seal, you need to consider a number of characteristics.
The first and most important issue is the indicator of reliability. Another important factor is cost. Among other criteria, consider:
- operating time;
- specific indicator of fluid loss;
- life time;
- repair or replacement costs.
It is necessary to choose a stuffing box seal, proceeding from standard sizes. Here they look at the outer and inner diameters, as well as the wall thickness.
Reviews
Many users are happy with the stuffing box. Using it for mounting a single-stage pump, they noticed that the seal is suitable for any shaft speed. The most popular models are silicone grease 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 consists of a woven asbestos thread.
In its manufacture also use
copper wire. This combination makes it strong enough, and it is not exposed to the effects of the pumped liquid.
Cost
As mentioned earlier, when choosing a sealant, some characteristics should be taken into account.
They affect the cost of the device. Their price ranges from 100 to 500 rubles.
Conclusion
In order not to cause large fluid leaks, stuffing boxes are used. They are performed in various ways. Of course, there will be fluid loss, but it is small. The volume will be spent on wetting the sealing material. Many users are happy with this device. As a rule, it is placed on submersible pumps used for pumping dirty water. Their service life is quite long, and the reliability is high. For a fairly small price, you can purchase high-quality material that will last a long time.
So, we examined what the packing of centrifugal pumps are for and what types they are divided into.