1、 Selection method

Mechanical seals are different from non-standard mechanical seals based on operating conditions and medium properties, including high-temperature and low-temperature resistant mechanical seals, high-pressure and corrosion-resistant mechanical seals, particle resistant mechanical seals, and mechanical seals for light hydrocarbon media that are prone to vaporization. Different types of mechanical seals with different shapes and materials should be selected for different applications.

The main parameters for selection include: sealed chamber pressure (MPA), fluid temperature (℃), operating speed (M/S), fluid characteristics, and effective space for device sealing.

The basic principles for selection are:

1: Based on the pressure of the sealed chamber, it is determined whether the sealing structure should be balanced or unbalanced, with single or double end faces.

2: Based on the homework speed, determine whether to choose rotary or stop type, fluid dynamic pressure or non touch type.

3: Based on temperature and fluid properties, determine conflict pairs and auxiliary sealing data, and accurately select mechanical seal circulation protection systems such as smooth, flushing, insulation, and cooling.

4: Based on the effective space sealed by the device, it is determined whether to use multi tension springs, single tension springs, or waveform tension springs, as well as internal or external installation types.

2、 Mechanical seal device and application request

1: Request for machine accuracy for mechanical seals (taking pump mechanical seals as an example)

(1) The maximum radial runout of the shaft (or sleeve) of the mechanical seal part of the device shall not exceed 0:04 to 0:06 mm.

(2) The axial displacement of the rotor shall not exceed 0.3MM.

(3) The maximum runout of the positioning end face of the sealed cavity combined with the sealed end cover on the outer surface of the shaft (or shaft sleeve) shall not exceed 0:04 to 0:06 mm.

2: Recognition of seals

(1) Admit whether the seal installed is consistent with the requested type.

(2) Before installation, carefully compare with the final assembly drawing to ensure that the number of parts is complete.

(3) The mechanical seal that uses a coil tension spring transmission has left and right tension springs, which must be selected according to the rotation direction of the shaft.

3: Device

The installation method varies depending on the type of mechanical seal and the variety of machine, but the installation method is almost the same. The installation process and precautions are as follows:

(1) Determination of device scale

When installing, the size of the mechanical seal device should be ensured according to the product manual or sample.

(2) Before installation, the shaft (sleeve) and cover should be free of burrs, and the bearing condition should be good; Seals, shafts, sealing chambers, and glands should all be clean and tidy. To reduce conflict resistance, a thin layer of oil should be applied to the mechanical seal on the shaft for smoothness. Considering the compatibility of rubber O-rings, if oil is not suitable, soapy water can be applied. Floating static rings without anti rotation pins should not be coated with oil and should be installed in a dry manner under the cover.

(3) First, install the static ring and the cover on the shaft together, being careful not to touch the shaft, and then install the dynamic ring assembly. The fastening screws of the spring seat or transmission seat should be tightened evenly in several rounds.

Before fixing the cover, manually push the compensating ring for axial compression. After releasing, the compensating ring can automatically bounce back without any jamming, and then evenly lock the cover bolts.

4: Application

(1) When the temperature of the transport medium is too high, too low, or rich in impurity particles, flammable, explosive, or toxic, it is necessary to take corresponding measures such as blocking, flushing, cooling, and filtering.

(2) Before starting the homework, use a hand crank to check if the torque is too high, if there are any scratches or abnormal noises.

(3) Pay attention to the rotation direction, whether the coupling is aligned, whether the smooth oil addition method at the bearing part is appropriate, and whether the piping is accurate.

(4) Before starting the task, first open the medium and cooling water valves to check if all the gas in the sealed chamber has been completely discharged, in order to avoid leakage caused by static pressure, and then turn on the machine for operation.

(5) Is the homework normal and stable after driving, is there any abnormal torque caused by axle rolling, as well as abnormal noise and overheating symptoms.