Sealing oil pressure difference.
Check the following temperatures: oil tank oil temperature, oil supply temperature, bearing oil temperature, off-cylinder oil temperature, return oil temperature, and inlet temperature of each section.
Check the following liquid levels: oil level in the tank, oil level in the seal oil collection cylinder, oil level in the separator, and oil level in the high level tank.
Control parameters of the sealing system: see Table 1. 5 System Shutdown In accordance with the principle of first reducing load and then stopping, the liquid level regulating valve is slowly closed.
Take anti-surge measures and fully open the anti-surge valve manually.
Close the liquid level adjustment valve and shut-off valve of each separator.
Turn off the main electric power supply, and the host machine stops.
Close all inlet valves.
Close the main valve.
Tao Changqing 407061 Vibration Analysis and Improvement of Piston Compressor Piping System of the Third Branch of Natural Gas Production and Marketing Plant of Liutun Zhongyuan Oilfield, Puyang City, Henan Province, and Improvement of the Pipeline Improvement of Zhang Ruilin Air Separation Oxygen Generator Unit at Liaoyang Petrochemical College
Piston compressors are widely used in petroleum, chemical, metallurgy, textile, power, and other sectors. They have complex structures, many parts, and various failures. The failure of pipeline vibration caused by the pulsation of the air pressure of the piston compressor is also very common. This article analyzes this with the air separation oxygen unit.
1 The operation of the air separation oxygen unit C103A / B of the Liaohua Polyester Plant Air Separation Oxygen Unit uses the domestic 4M8-52 / 32 four-row four-stage double-acting symmetrical piston compressor. The main performance parameters of the compressor are as follows: flow rate: 3200m3 / h medium: the pressure and temperature of all levels of the oxygen compressor during normal operation are shown in Table 1. Table 1 The pressure and temperature parts of the compressor 1 level U level 1 suction pressure (MPa) row Air pressure (MPa) Suction temperature T. (C) Exhaust temperature T (Table 2 Pipeline vibration monitoring data (mm) parts Two oxygen compressors at the exhaust end of the 1st U level m level V level suction end since the operation Although the performance parameters basically meet the design requirements, the pipelines between the compressor stages are severely vibrated and accompanied by a lot of noise, causing the pipeline support between the stages to be loose many times, and there is the possibility of pipeline fatigue fracture and oxygen leakage at any time and anywhere , Which poses a direct threat to the personal safety of the operator. The results of vibration monitoring are shown in Table 2. 2 Causes of compressor unit piping vibrations Due to different vibration mechanisms, piston compressor piping vibrations are mainly due to the following reasons: The pipeline system has its own natural frequency according to different piping conditions, support types, support positions and boundary conditions. Any kind of external vibration force such as unbalanced inertia when the compressor reciprocates , Pulsating air flow impact force, the shaft of the mechanical power pulse isochronous poor, the mechanical vibrations can cause the pipe. If the natural frequency of the main frequency of the excitation force conduit coincides provoke strong mechanical resonance.
2 During the operation of the air column resonance piston compressor, because the suction and discharge are alternating and intermittent, and the speed of the piston movement changes with time, this phenomenon will cause pressure pulsation. When the excitation frequency fx of the compressor enters the area of ​​the natural frequency of the air column, the air column of the pipeline will be in a resonance state11, and the pulsation of the air flow is very serious, causing strong vibration of the pipeline and even the compressor and the foundation.
The excitation frequency and the natural frequency of the gas column are calculated according to the following formula: the number of times the m crankshaft sucks or discharges into the pipeline every revolution of the crankshaft, single-acting compressor m = 1, double-acting compressor m = 2 K gas insulation index R gas constant T gas adiabatic temperature L The length of the pipeline can only avoid the resonance region of the gas column if the length L of the system pipeline is outside the following range: 3 The gas flow pressure pulse impacts and vibrates at the pipe fittings. The air flow pressure pulsation of the piston compressor can cause the gas column In addition to resonance, the pressure and speed fluctuations in the pipeline may also have an impact effect at the turning points of the pipeline, the changes in cross-section and various valves and blind plates, causing vibration and noise in the pipeline.
The analysis of the force at the right-angle elbow is as follows: the shown section of a constant-section pipe elbow, if the air flow in the pipe is pulsating, the unevenness of pressure pulsation is § The average pressure is P0, then the amplitude of pressure pulsation is AP: 3 The treatment method of pipeline vibration is based on the analysis of the vibration mechanism of the piston compressor piping system. The reasons for the vibration of the piping system of the oxygen compressor C103A / B of the air separation unit of the polyester plant are analyzed as follows: 1 Mechanical resonance To verify whether the piping vibration of the unit is Caused by mechanical resonance, the method of adding new support to the pipeline system and strengthening the original support changed the natural frequency of the pipeline. Through the above treatment, the vibration of the pipeline has not improved, thus eliminating the possibility of vibration caused by mechanical resonance.
Calculate the length of the air column resonance tube of each section of the pipeline to determine whether the air column resonance is formed in the pipeline system. The following only calculates the length of the air column resonance tube of the secondary cylinder inlet and outlet pipelines. The calculation method of the other levels is the same. The results are shown in Table 3. The magnitude of the impact force of the airflow on the elbow: the length of each pipeline measured on site is shown in Table 3. The length of each pipeline is not within the range of the first-order gas column resonance tube length, so the possibility that the vibration of the pipeline system is caused by the unreasonable design of the pipeline length is excluded.
Table 3 Measured lengths and lengths of gas column resonance tube lengths for all levels of pipelines Level 1 u-level 1 W-level inlet pipeline length outlet pipeline length inlet first-order resonance tube length Li outlet first-order resonance tube length L0 3.3 change in pipe bend radius Through the analysis, it can be seen that the air column pulsation formed by the suction and exhaust of the piston compressor will cause an impact force on the pipe system at the elbow. After the compressor is determined, if the pipe diameter of the system is not changed, the only parameter that affects the impact force AR is the smaller the pipe angle, that is, the smoother the pipe, the smaller the impact force on the pipe.
In the C103A / B oxygen compressor system, each pipe is of equal diameter, and the connection size of both ends of the pipe is determined. Therefore, without changing the pipe layout, only the radius of curvature at the large bend.
As shown, the angle 90 of the pipeline 1 and the pipeline 2 is also the same from the formula (5), the impact force of the two elbows is equal, because the curvature radius R2 of the pipeline 2 is greater than the curvature radius of the pipeline 1, so the pipeline 2 The impact load per unit length is less than that of pipeline 1, that is, the impact load per unit length of two elbows with the same angle is inversely proportional to the radius of curvature of the two elbows.
Table 4 Elbow size items of pipeline systems at various levels Grade 1 u grade 1 W grade Original elbow radius Elbow radius pipe diameter after modification DN 3.4 Unit operation status after modification After replacing 16 elbows of two unit piping systems, the unit starts Once successful, the vibration noise of the pipeline system is significantly reduced. The test results are shown in Table 5. The vibration values ​​of each section are within the standard range.
After 6 consecutive months of testing, the C103A / B piping system did not experience severe vibrations and operated smoothly, completely eliminating hidden dangers and providing a guarantee for the safe operation of the device.
Table 5 Vibration force data (mm) of the pipeline after modification. The radius of curvature of the elbows on each pipe section of the original system C103A / B at the suction end and exhaust end of the part level u level 1 is small. The load acts on the elbow, causing severe vibration of the piping system. To this end, the elbow with a larger radius of curvature is used instead of the original elbow. By measuring the relative position of the compressor's various cylinders and interstage coolers on the spot, without changing the original equipment layout, the reasonable maximum radius of curvature of the elbow is calculated, see Table 4. Analyze and deal with the vibration fault of the pipeline system of the oxygen-separating compressor. It is proposed to increase the radius of curvature of the pipe elbow without changing the equipment layout. Vibration has obvious effects. This economical and convenient method is also applicable to the elimination of the vibration of some large centrifugal compressors and high-pressure pump pipes, and has certain practical value.
NINGBO BRIGHT MAX CO., LTD. , https://www.smartrider-horserugs.com