How to Standardize the Installation Steps of Mechanical Seals?

Mechanical seals are the oil sealing devices, commonly used in rotating machinery. During installation and operation, the mechanical seal must maintain the fit and relative sliding of the end face and auxiliary components to prevent fluid leakage. Therefore, the quality requirements for the installation of the mechanical seals are higher, and it needs to be gradually carried out and timely inspected in accordance with established norms. Let’s take a detailed look at it.

Overview of the principle of mechanical seals

Mechanical seal spare parts rely on a pair or several pairs of end faces that slide relative to the axis vertically and are equipped with auxiliary seals to prevent leakage of the shaft seal device under the action of fluid pressure and compensating mechanisms such as spring seats and fixing screws. Common mechanical seal structures consists of stationary rings (static rings), rotating rings (moving rings), elastic element spring seats, fixing screws, rotating ring auxiliary sealing rings, and stationary ring auxiliary sealing rings. The anti-rotation pin is fixed on the gland to prevent the stationary ring from rotating. The rotating ring and the stationary ring are often referred to as compensating rings or non-compensating rings depending on whether they have axial compensation capability.

Correct installation specifications for mechanical seals

Before installing mechanical seals, we need to ensure the cleanliness of the sealing parts, and they can be cleaned. Ensure that the sealing end face is not damaged to prevent impurities and dust from entering the sealing part. The radial runout of the shaft of the mechanical seal device should be ≤0.04mm, and the axial movement is not allowed to be larger than 0.1mm.

During the installation process, any collision or knocking will cause damage and failure of the mechanical seal. A layer of clean mechanical oil should be applied to the surface in contact with the seal, so that it can be installed smoothly. When installing the stationary ring gland, the screws must be tightened evenly to ensure the perpendicular requirements between the end face of the stationary ring and the axis line. After the mechanical seal is installed, the moving ring can be pushed by hand to move flexibly on the shaft, and has some elasticity. After installation and rotation by hand, there should be no sense of weight on the rotating shaft. The equipment must be filled with medium before operation to prevent dry friction and failure of the mechanical seal.

Mechanical seals are developing towards high parameters, high temperature, high pressure, high speed, and large shaft diameters. High temperature is one of the directions. Most liquid media will have reduced viscosity and lubricity and increased corrosion at high temperatures. At the same time, the conventional auxiliary sealing ring, end face sealing pair, and pump seal spring material used will become unstable when the temperature is higher than 250°C. For example, rubber parts will lose elasticity, PTFE sealing parts (the use temperature cannot exceed 220°C) will lose their original size accuracy, and hard sealing end faces will produce thermal deformation or cracking, while the carbon graphite soft ring end faces will produce pitting, and at the sliding end face temperature rise, it will cause coking and solidification, severely affecting the normal operation of the seal.