Precautions for disassembly and assembly of pharmaceutical mechanical equipment


I. mechanical disassembly

Preparation before disassembly

A. the working area should be spacious, bright, smooth and clean.

B. The disassembly tools are fully prepared with appropriate specifications.

C. Prepare the stand, dividing basin and oil drum for different purposes

Basic principles of mechanical disassembly

A. According to the model and relevant data, the structural characteristics and assembly relationship of the model can be clearly understood, and then the method and steps of decomposition and disassembly can be determined.

B. Choose tools and equipment correctly. When the decomposition is difficult, find out the cause first and take appropriate measures to solve the problem.

C. When disassembling parts or assemblies with specified directions and marks, the directions and marks should be kept in mind. If the marks are lost, they should be re-marked.

D. In order to avoid damage or loss of dismantled parts, it shall be stored separately according to the size and accuracy of the parts, and shall be placed in the order of disassembly. Precise and important parts shall be specially stored and kept.

E. The removed bolts and nuts shall be put back in place without affecting the repair, so as to avoid loss and facilitate assembly.

F. Disassemble as needed. For those who do not disassemble, they can be judged to be in good condition. But the need to remove the parts must be removed, not to save trouble and careless, resulting in repair quality can not be guaranteed.

(1) for the connection that is difficult to disassemble or will reduce the quality of the connection and damage part of the connection parts after disassembly, disassembly shall be avoided as far as possible, such as sealing connection, interference connection, riveting and welding connection, etc.

(2) when impinging on the part with the batting method, the soft liner or hammer or punch made of soft material (such as pure copper) must be well padded to prevent damage to the surface of the part.

(3) proper force should be applied during disassembly, and special attention should be paid to protecting the main components from any damage. For the two parts of the match, if it is necessary to damage a part, it is necessary to preserve the parts of higher value, manufacturing difficulties or better quality.

(4) parts with large length and diameter, such as precision slender shaft, screw, etc., are cleaned, greased and hung vertically after being removed. Heavy parts can be supported by multiple fulcrum to avoid deformation.

(5) removed parts should be cleaned as soon as possible and coated with anti-rust oil. For precision parts, but also oil paper wrapped, to prevent rust corrosion or collision surface. More parts should be sorted by parts, and then placed after marking.

(6) remove small and easily lost parts, such as set screws, nuts, washers and pins, etc., and then install them on the main parts as far as possible after cleaning to prevent loss. After the parts on the shaft are removed, it is best to temporarily install them back to the shaft in the original order or place them on the string with steel wire, which will bring great convenience to the assembly work in the future.     

(7) remove the conduit, oil cup and other lubricating or cooling oil, water and gas channels, all kinds of hydraulic parts, after cleaning should be the import and export seal, so as to avoid dust and impurities immersed.

(8) when disassembling the rotating part, the original balance state shall not be disturbed as far as possible.

(9) for phase accessories that are prone to displacement and have no positioning device or directional features, they shall be marked after disassembly so as to be easily identified during assembly

Ii. Mechanical assembly

Mechanical assembly process is an important link to determine the quality of mechanical repair, so it must be:

(1) the assembled parts must meet the specified technical requirements, and any unqualified parts cannot be assembled. This part must pass strict inspection before assembly.

(2) the correct matching method must be selected to meet the requirements of matching accuracy. Mechanical repair of a large number of work is to restore the matching precision of the mutual fitting, can be adopted to meet the requirements of the selection, repair, adjustment and other methods. The effect of thermal expansion should be taken into account for the fit gap. For the fit parts made up of materials with different expansion coefficients, when the ambient temperature during assembly differs greatly from the temperature during operation, the gap change caused by this should be compensated.

(3) analyze and check the accuracy of the assembly dimension chain, and meet the accuracy requirements through selection and adjustment.

(4) to deal with the assembly order of machine parts, the principle is: first inside and then outside, first difficult and then easy, first precision and then general.

(5) select appropriate assembly methods and assembly equipment and tools.

(6) pay attention to parts cleaning and lubrication. The assembled parts must be thoroughly cleaned first, and the moving parts should be coated with a clean lubricant on the relative moving surface.

(7) pay attention to the sealing in the assembly to prevent “three leakage”. To use the specified sealing structure and sealing materials, can not use arbitrary substitutes. Pay attention to the quality and cleanliness of the sealing surface. Pay attention to the assembly method of seals and assembly tightness, for static seals can use appropriate sealant seal.

(8) pay attention to the assembly requirements of locking device and comply with safety regulations.

Iii. Matters needing attention in mechanical seal disassembly and assembly

Mechanical seal is one of the most effective ways to turn the mechanical body seal, its own processing accuracy is relatively high, especially the dynamic, static ring, if the disassembly method is not suitable or improper use, the mechanical seal assembly will not only fail to achieve the purpose of sealing, and will damage the assembled sealing components.

1. Precautions during disassembly

1) when removing the mechanical seal, it is strictly forbidden to use hammer and flat shovel to avoid damaging the sealing element.

2) if there are mechanical seals at both ends of the pump, you must be careful in the process of disassembly to prevent one from losing the other.

3) for the mechanical seal that has been worked, if the sealing surface moves when the gland loosens, the rotor and stator ring parts should be replaced, and it should not be used again after tightening. Because after loosening, the original running track of the friction pair will change, the sealing of the contact surface will be easily destroyed.  

4) if the sealing element is bound by dirt or condensate, remove the condensate before removing the mechanical seal.

2. Precautions during installation

1) before installation, it is necessary to carefully check whether the number of assembly sealing parts is enough and whether the components are damaged, especially whether there are any defects such as collision, crack and deformation in the dynamic and static rings. If there is any problem, repair or replace with new spare parts.

2) check whether the chamfering Angle of the sleeve or gland is appropriate, and if it does not meet the requirements, it must be trimmed.

3) all components of the mechanical seal and their associated assembly contact surfaces must be cleaned with acetone or anhydrous alcohol before installation. Keep it clean during installation, especially the movable and static rings and auxiliary sealing elements should be free of impurities and dust. Apply a clean layer of oil or turbine oil to the surface of moving and stationary rings.

4) the upper gland should be tightened after the coupling alignment. The bolts should be evenly tightened to prevent deflection of the gland section. Check each point with a feeler or special tool. The error should not be greater than 0.05mm.

5) check the matching clearance (and concentricity) between the gland and the outer diameter of the shaft or shaft sleeve, and ensure the uniformity around, and check the tolerance of each point with a plug not more than 0.10mm.

6) the spring compression quantity shall be carried out in accordance with the provisions. It is not allowed to be too large or too small. The error is ± 2.00mm. Too small will cause insufficient specific pressure and can not play a sealing role, after the spring installed in the spring seat to move flexibly. When using a single spring, pay attention to the rotation direction of the spring. The rotation direction of the spring should be opposite to the rotation direction of the shaft.

7) the movable ring shall be kept flexible after installation. It shall be able to automatically bounce back after pressing the movable ring to the spring.

8) first place the static ring sealing ring on the back of the static ring, and then put it into the sealing end cover. Pay attention to the protection of the static ring section, to ensure the vertical of the static ring section and the center line of the end cover, and the back of the static ring anti-swivel groove aligned with the anti-transfer pin, but do not make them contact with each other.

9) in the installation process, it is never allowed to directly knock the sealing element with tools. When it is necessary to knock, special tools must be used to knock the sealing element in case of damage.

Post time: Feb-28-2020