How to install the mechanical seal the most appropriate

Introduction: Mechanical seal components are very strict in terms of both manufacturing precision and installation accuracy. If they are improperly installed, they will affect the life and sealing performance of the seal. In severe cases, the seal will quickly fail. Mechanical seals are widely used for various types of pumps. The mechanical seal is a high precision sealing device, which has certain requirements for the installation and use conditions.

How to install the mechanical seal the most appropriate

First, the installation of mechanical seals

In order to make the mechanical seal have a good sealing performance, the installation of sealed equipment should meet the following requirements:

1. The tolerance of the outer diameter of the shaft (or sleeve) installed and installed on the mechanical seal is h7, and the surface roughness Ra is not greater than 1.6um. When the outer diameter of the shaft (or shaft sleeve) where the mechanical seal is installed is ≤ 50mm, the radial runout tolerance is ≤ 0.04mm; when the outer diameter is greater than 50mm, the radial runout tolerance is ≤ 0.06mm, and the axial turbulence of the rotor of the installation equipment is mechanically sealed. ≤0.3mm. When installing, the shaft, seal chamber (pump cover), and mechanical seal must be cleaned to prevent impurities from entering the sealed installation area.

2. The installation of the sealing mechanical seal is performed during the assembly of the pump. After the pump shaft is mounted on the bearing housing and the sealing element of the bearing housing is installed, follow the steps below to install the mechanical seal:

First of all, before installation, make sure that the product model and specifications are consistent with the equipment requirements. In the installation of the sealed shaft, the cavity and the gland are evenly oiled at the contact with the auxiliary seal (NOTE: It is not allowed to inject ethylene propylene rubber or medium. In the case of lubricating oil, vegetable oil or soapy water can be applied, and then the mechanical seal is put on the shaft and installed in place according to the designed working height.The over-pressure cover through hole adopts diagonal cross-tightening method and bolts the entire seal and seal. The cavity (pump cover) is screwed tightly, and when the mechanical seal is equipped with an auxiliary system, the pipe is correctly connected according to the label and the final test is performed.

3. After observing the above steps, manually turn the car, pay attention to observe the change of torque, and whether or not there is abnormal noise, etc., to determine whether to re-install and adjust. Open the valve, seal the cavity into the sealing medium, all the air out of the sealed chamber, so that the sealed cavity is full of media, and observe the seal with or without leakage, confirm that the above two items are correct after the test run.

Second, the general principle of the installation of mechanical seals

1, to understand the equipment, to understand the equipment shaft speed, shaft diameter; equipment manufacturing precision and the size of the sealed cavity, the life of the equipment itself and equipment in the production process to do a comprehensive and balanced consideration.

2, estimate the medium pressure. The pressure in the seal chamber of the pump is generally not the outlet pressure of the pump but is lower than the outlet pressure of the pump.

3, understand the situation of the sealed media. To understand the state of the sealed medium, whether it is gaseous or liquid, whether the medium contains particles and particles; understand the nature of the medium, temperature, in order to properly select the type and take the necessary cooling, flushing, lubrication measures.

Three, mechanical seal installation precautions

1, the assembly should be clean and smooth. Mechanical seal parts, related machinery and equipment parts, tools, lubricants (grease), wipes (cotton yarn, white cloth, silk, etc.) should be very clean. The sealing surface of the ring should be wiped with white silk or soft gauze. Trimming chamfer rounding, shaft, sealing caps and other chamfers should be smooth, and the relevant roundness of shafts and end caps should be sanded. During installation, apply smooth oil or No. 10 engine oil to the auxiliary ring, shaft, and end cap on the moving ring and stationary ring (especially the sealed end face) to reduce the friction so as not to damage the sealing end face of the stationary ring and auxiliary Sealing ring.

2. Assemble the auxiliary seal ring. Rubber-assisted seals must not be soaked with gasoline or kerosene to avoid large deformation and premature aging. After the O-ring is mounted on the moving ring assembly or the stationary ring assembly, it must be straightened out so that it is not twisted, so that the burrs are in the cross section of the free state. For O-rings with a slightly rough edge, if the burr is 45o, it can still be used. When advancing the assembly, prevent the O-ring from being damaged. According to the technical requirements, adjust the compression amount of the machine seal. Refer to the product manual for the value. Otherwise, the amount of compression is too large, increase the end face specific pressure, accelerate the wear of the end face; too small, the relative pressure of the static and dynamic ring end face is insufficient, the seal fails, and the press ring or the drill press should be used to insert the static ring assembly into the gland (or seal chamber) ). Under no circumstances should mechanical seal parts or components apply impact forces. The pressed surface should be covered with clean paper or cloth so as not to damage the sealed end surface. After assembly into the ring or static ring assembly, press the compensation ring by hand to check whether it is installed in place; whether it is flexible; whether the elastic opening ring (in some structural mechanical seals, the elastic opening ring is used for axial positioning of the compensation ring) is positioned reliably . The anti-rotation pin of the static ring assembly must be accurate. When the static ring assembly is pushed in, the pin groove of the assembly must be aligned with the pin. After pushing it into place, measure the distance between the end face of the assembly and the end of the seal chamber and determine whether it is installed in place. When tightening the bolts to compress the end cap, use force evenly, symmetrically, and carefully, and close it several times. Do not set it tightly once to avoid skewing or even crushing the static ring. After the ring is installed, it must be ensured that it moves axially and flexibly on the shaft (the ring is pressed against the spring and then it can bounce back freely).

Fourth, the technical requirements of mechanical seal installation

1. The radial runout of the shaft or bushing installed in the mechanical seal part shall not exceed 0.1mm, the axial runout shall not be greater than 0.15mm, and the surface roughness of the shaft or bushing shall not be greater than 1.6 microns. The dimensional tolerance of the outer diameter shall be H7.

2, the surface of the sealed cavity facing the surface of the shaft runout every 3cm should not be greater than 0.015mm

3. The end face of the shaft or bushing and the end face of the sealing cavity should have a smooth and excessive chamfer. The shoulder chamfer angle is 3×10° and the end cover chamfer is 2~2.5×20°.

4, when the transmission medium temperature is too high, too low or contain particles, flammable, explosive, toxic, should take the appropriate sealing, washing, cooling, filtration and other measures.

5. For some mechanical seals driven by springs, attention must be paid to the direction of rotation of the springs. That is, the direction of rotation of the shaft should make the springs more and more tight. Otherwise, the sealing failure may be caused. The selection of the spring rotation direction is determined by the following method: Looking at the moving ring, the shaft rotates clockwise with a right-handed spring, and vice versa, a left-handed spring is used.

Fifth, start

Must be checked before starting

1. Whether all sealing system fittings are connected and whether the system is in working condition.

2. The cooling water chamber is full of liquid.

3, check the car should feel resistance, but there should be no heavy or stagnant phenomenon.

Six, run

1. Observe the operation of the sealed cooling water system.

2. Observe the leakage of the seal.

3. During operation observation, attention must be paid to safety protection to avoid injury to personnel due to unexpected accidents.

Seventh, stop

When shutting down, the cooling water must be kept open to reduce the temperature.

Eight, maintenance

No need for maintenance during seal operation

9. Demolition

1. Check if the pump or equipment is in a state of no pressure.

2. Check if the pump or equipment has reached the temperature that personnel can fully contact.

3, check the pump or equipment has been drained of liquid.

4. Understand the degree of injury to people during the night in the pump or equipment and take necessary safety measures.

5, do a good job site environment pollution prevention measures.

Ten, storage

1, the seal must be stored in a clean, normal temperature environment.

a. There is no direct sunlight in the storage area.

b. There is no ash, dust in the storage.

c. There is no ozone, radioactive material and corrosive gas in the storage.

d. The relative humidity of storage is ≤ 65%.

e. Storage temperature should not be too high, keep room temperature and ventilation.

2. The storage period of the "O" ring is ≤ 2 years, and the expired "O" ring must be replaced

3. Sealing period of storage for two years. Please check the sealing surface. If there is any deformation, it must be repaired before use.

In short, when installing, it is necessary to check whether the type, size, and quantity of the mechanical seal meet the requirements of the design drawings. All parts (especially the sealing surface and auxiliary sealing ring) have no damage, deformation, cracks, etc. If there is any defect, they must be replaced or repair. Seal the seal between the end cap and the pump body. In general, leaks between shafts, seal caps, and pump bodies are more easily found and resolved, but they must be carefully observed. The remaining leaks are intuitively difficult to discern and judge, and on the basis of long-term management and maintenance practices, leakage symptoms must be observed, analyzed, and judged in order to draw correct conclusions.

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