Several causes of mechanical seal leakage in petrochemical gear oil pumps and exploration of pipeline quality control

{1} Several reasons for mechanical seal leakage in gear oil pumps

The main reasons for mechanical seal leakage in stainless steel pumps are as follows:

Firstly, the dynamic or static ring of the mechanical seal in gear pumps or gear oil pumps is broken.

Secondly, the medium conveyed by the gear pump or gear oil pump contains impurities, causing wear on the sealing surface of the mechanical seal

3. The spring of the mechanical seal of the gear pump or gear oil pump is damaged or stuck, and the compression is not flexible

4. The compression ratio of the dynamic and static rings of the mechanical seal of the gear pump or gear oil pump is not appropriate

5. When transporting corrosive media, replace the sealed O-ring of the gear pump or gear oil pump with a corroded one, otherwise it will cause leakage of the gear pump

6. When transporting solvents such as phenol, the O-ring of the mechanical seal of the gear pump or gear oil pump cannot be made of rubber material, otherwise it will cause seal leakage

7. The surface accuracy of the main and main shaft sealing positions of the gear pump or gear oil pump is not sufficient or has not been processed to the 0-line standard, which prevents the sealing O-ring from coming into close contact with the shaft wall, resulting in leakage of the gear pump and gear oil pump

8. The machining size of the static ring sealing cover of the gear pump or gear oil pump is slightly larger than the outer diameter of the mechanical seal static ring, resulting in mechanical seal leakage

9. Excessive pressure during the use of gear pumps or gear oil pumps can cause pump seal leakage

10. The assembly of the dynamic and static rings of the mechanical seal of the gear pump or gear oil pump is not concentric, resulting in leakage of the gear pump

{2} Discussion on Quality Control of Petroleum Pipelines

Strengthen Material Control.

. Material control is an important link in the quality control of gear pump oil pipeline installation. Pipelines, fittings, valves, materials, and their standard components need to be re inspected upon entry, and there must be no defects that affect strength and pipeline sealing. The parts used for pipeline construction must comply with the design drawings and standard specifications. To verify the consistency between the model, specifications, production date, batch number, and quality certification documents of standard components and auxiliary materials such as valves, screws, nuts, and welding materials, hardness and other mechanical performance tests are required. The on-site raw materials are arranged in an orderly manner, and welding equipment, lifting equipment, etc. are all within the equipment calibration period

Strictly follow the process specifications. Serious process discipline is the key to the installation quality of gear oil pumps and oil pipelines. After the pressure test of the valve, the internal water should be drained and oil and rust proof grease should be applied. However, when conveying compressed oxygen with pressure, if the flowing oxygen is prone to collision and friction with grease, iron filings or objects in the pipeline, resulting in explosion, oil should not be applied; When conducting a hydrostatic test on stainless steel valves, in order to avoid stress corrosion caused by chloride ions operating together with austenitic stainless steel, the chloride ion content in the water should not exceed 100ppm; Conduct a full inspection of the installed pipes; For alloy steel and stainless steel pipes, mechanical methods such as sawing and grinding wheels should be used during cutting, and gas cutting or welding cutting should not be used; When bending pipes, cold bending should be used as much as possible due to changes in the mechanical properties of the pipes caused by heating during hot bending

Welding quality control. The quality of welding is directly related to the quality of pipelines. Before welding, component determination should be carried out, and welding personnel should strictly follow the welding sequence and quality regulations according to the welding process, welding operation manual, and welding process card. After welding, a detailed inspection of the weld seam should be carried out, and sampling should be used to inspect the welding quality. For welds that require heat treatment, the principle of testing before treatment should be strictly followed, and they should be tested after passing non-destructive testing

Installation of valves, engineering. Valves should be installed in convenient positions for operation. To reduce the spacing between pipelines, valves should be staggered during pipeline installation. Valves on horizontal pipelines should not be installed vertically downwards, and heavier valves should be lifted and installed using appropriate tools; Qualified pressure testing of valves used on oil pipelines; During the installation of oil pipelines, it is strictly prohibited to use low-pressure valves on high-pressure pipelines or install one-way valves in reverse on pipelines

Pay attention to the process. Adopting new technologies to solve the problem of oil pump pipelines is also an important measure to improve the installation quality and service life of pipelines. At present, the commonly used method in China is to apply cheap asphalt to oil pipelines

Engineering construction is a common problem in petroleum pipeline installation engineering. Engineering management personnel should actively coordinate design, production, supervision, construction and other units to make adjustments and avoid disorderly pipeline installation operations

Inspection and verification. After the installation of the gear oil pump pipeline is completed, visual inspection and other inspections are also carried out. The quality of the internal welds is inspected through non-destructive testing; The quality of the pipeline system is verified through pressure testing

In summary, oil pipeline installation is a complex system engineering. Only by starting from the five quality factors of "human, machine, material, method, and environment", analyzing and researching common problems in the construction process, strengthening process control and inspection, can the quality level of oil pipeline installation be effectively improved