Sealing of stuffing boxes of pumps: description, varieties and reviews

In industrial production, when operating pipelines, various types of pumps , losses of pumped liquids inevitably arise. The prevention of these cases are numerous seals, one of which will be discussed in detail in this article.

Sealing of oil seals of pumps

Modern pumping equipment is completed with a large number of elements. At the same time, the specifics of the work require paying special attention to the normal and uninterrupted functioning of the products as a whole. Sealing of pump glands due to the simplicity of their design and ease of use is used much more often than other sealing devices.

Operational requirements

The impeller of all varieties of pumping equipment works thanks to the motor. Most often it is electric. The mechanical coupling transfers energy from the motor shaft to the impeller, which drives it. The shaft itself goes beyond the equipment housing, which makes the envelope leaky. Therefore, loss of working fluid is inevitable.

If you use the seal of the stuffing boxes of the pumps, leakage of the pumped liquid can be avoided. The following technologies are used:

1. Stuffing (stuffing box) seal. It is a ring of fibrous material.

2. Cufflings. For such a seal, elastic materials are used, which can be reinforced to increase rigidity. Used for mounting in pumping equipment with a low shaft speed.

3. Edge. It consists of two rings, densely located to each other on the shaft. One of them rotates together with the shaft, and the other remains completely immobile.

4. Slit. The second name is labyrinth. It is considered the most reliable modern type of compaction. Presented as a ring of soft alloy. It is used in multi-stage pumps, where the use of other technologies can significantly affect the efficiency.

In addition, there are devices that do not require seals, such as pumps with a magnetic clutch and a wet rotor.

Description of packing glands

Slit materials are most often used to ensure the integrity of submersible pumps. They do not have special requirements for leakage of liquids. Here the long duration of operation plays an important role.

Sealing of the stuffing boxes of pumps appeared almost at the same time with the equipment for pumping liquids. These are original rings of fibrous material, which are in a stuffing box, from where their name came. Packing must be wetted by liquid transported through pipelines. This is necessary for cooling and lubricating the stuffing box. The very wetting is fraught with losses of liquid. The hour of the pump operation involves the loss of 1-15 liters of water. If the packing is not wetted, then the material will lose the expediency of use, quickly "burn out".

It is necessary to constantly maintain the oil seals. Compressors and pumps can not be disassembled, which is one of the significant advantages of seals. Self-service is a periodic "pull-up" cuff.

Typical variations of seals for pumping equipment

The modern market offers various seals for pumps; Typical oil seals are represented by two main types:

1. Stuffing reinforced with one edge. The main purpose is to prevent losses of the pumped liquid.

2. Cuffs reinforced with anther and one edge. Used to protect the connection itself from dust and dirt. Also, liquids are not allowed to leave the transportation system.

If we consider the mode of production, then we can distinguish omentums:

• With molded edge;

• With an edge that has been machined.

Depending on the type of rubber used, there are such cuffs:

1. Based on butadiene-nitrile rubber. Products are made from 1, 2 and 3 classes of rubber. They are characterized by a relatively high threshold of negative operating temperature (-30, -45, and -60 ° C, respectively).

2. Based on fluorine rubber. Raw materials are rubber of groups 1 and 2. When pumping mineral or transmission oil, the temperature is maintained at 170 ° C.

3. Of silicone rubber. At manufacturing rubber of exclusively 1 group is used. The lower limit of the working temperature of the gasket is -55 ° C.

As a rule, modern cuffs come complete with springs. They are suitable for sealing on shafts of different diameters.

The spring can be supplied separately from the stuffing box if it is supposed to work with a shaft up to 20 mm or more than 120 mm.

Gland packing: performance properties, for which pumps it is better to use

As a rule, the cuffs differ from other seals by their flexibility, plasticity. High wear resistance is also a significant advantage of the products. Minor impact on the shaft extends the application segment.

The performance characteristics directly depend on the structure of the sealant and the composition used in the production. Depending on the weaving, there are diagonal (through and combined) seals and single-layered (referring to the structure of the core). The composition of the cuffs are:

• Asbestos and asbestos-free;

• Dry and impregnated (as an impregnation, fat, graphite and glue mixtures are used);

• Reinforced and unreinforced.

Used seals for sealing the connection of centrifugal, reciprocating pumps and hydraulic presses. The packing can also be used in plunger equipment for pumping liquid medium. When installing the product, it should be remembered that the pumps with packing glands will allow passage of a certain amount of the liquid mentioned above.

Graphite-ceramic seals

This is one of the types of cuffs for pumping equipment. The use of this type of seal completely eliminates the entry of working fluid into the equipment motor. Where are the graphite-ceramic packing seals applied? Water pumps, to which the mechanical seal is suitable , is not so much. Typically, the application segment is limited only to surface mechanisms.

The service life can reach 10 years. Thus it is necessary to adhere to the correct operation of the pumping station. The main requirements put forward at the time of operation of the equipment:

1. Absence of "dry running". It is strictly forbidden to keep the pump in "on" mode, if there is no liquid in the system.

2. It is best to pump the maximally purified substance. The presence of impurities shortens the life of the cuff.

3. It is necessary to adhere to the temperature regime.

The advantages of oil seals for pumps with water seal

The cuff of equipment for pumping water looks like a braided lacing square section. Asbestos (cotton or bast) thread can have inclusions of copper or brass wire. Seals of pumps with a water seal have a core made of lead. The size of the tape is 5 * 0.5. Weaving can be used instead of it of 4 lead wires.

Seals with a water seal, usually on the suction side, are used. But their use can not be excluded from the opposite side. The size of the packing is directly related to the diameter of the shaft. The maximum number of seal rings is 5.

How to choose an epiploon

Selection of seals is carried out for a number of characteristics. Without doubt, the most important question remains reliability. Among other important criteria, cost is considered. Additional parameters that are taken into account when selecting devices:

• Number of hours of operation;

• Loss of fluid;

• shelf life;

• Costs that arise in the event of a repair.

In addition, the selection of seals for pumps is carried out taking into account the sizes. These include the outer and inner diameters, the height and thickness of the substrate.

What consumers say

Many have already encountered installing a stuffing box for a single-stage pump. Often the universality of packing is noted. The use of gaskets is not limited to high speed shafts.

It is noted that the sealing of oil seals of pumps with lubricant based on silicone exhibits greater thermal stability.

Variations with a high carbon content significantly reduce the degree of expansion as the temperature of the pumped liquid increases. Aramid fibers with special PTFE impregnation allow the gland to work in an aggressive environment in chemical production, CHP and in the paper industry.