In petrochemical plants, the proportion of Sullair coolers is twice that of towers and troughs, and the reason for the shutdown of the plant is that the Sullair cooler damages about half of the oil leakage. The failure rate is three times that of towers and pipelines, so it is important to report the failure analysis of the Sullair Cooler.
First, vibration analysis
The main cause of damage to the Sullair cooler is vibration. The vibration damage of the Sullair cooler includes the wear between the tube and the baffle tube hole, the fatigue damage of the tube subjected to vibration and shear collision at the baffle, the collision between the tubes and the tube at the tube plate. Fatigue damage, etc.
1. Analysis of the cause of tube vibration:
There are many sources that cause the vibration of the Sullair Cooler, and one or several of them may be the source of the vibration that provokes harmful. The pulsation brought about by the reciprocating machinery (detailed description of the chemical vibrating screen) is a source of excitation; and some vibrations transmitted through the supporting members or connecting pipes are another source of excitation. Due to these types of excitation source frequencies It is relatively predictable for the system to decide. The mechanism of fluid mechanics excitation is more difficult to predict.
Fluid flow excitation can be divided into two major types: those excited by the flow parallel to the axis of the pipe (called longitudinal flow) and those excited by the flow perpendicular to the axis of the pipe (called lateral flow I). Lateral flow under normal conditions It can cause a large amplitude and is very harmful to the tube of the Sullair cooler.
2. The criterion for vibration
(1) For liquids, when the eddy current divergence frequency is greater than 1/3 of the natural frequency and the parallel fluid eddy current produces a dimensionless amplitude Y of the 16-8 vibration motor, >O. 0075 vibration may occur.
(2) For gas or swallow gas, in addition to the above criteria, there are audio and turbulence disturbance frequencies. When the turbulent disturbance frequency or the eddy current divergence frequency is greater than 1/3, the natural frequency or vibration may occur at 0.8-1.2 audio.
3. Method of eliminating vibration
There are usually several ways to eliminate vibration:
1) Reduce the shell line speed. When the flow boy cannot be changed, increase the tube center distance or increase the shell diameter.
2) To improve the natural frequency of the Sullair cooler tube, an effective method is to shorten the unsupported maximum span length of the tube or change the pipe material and increase the wall thickness, but the effect is not as remarkable as the method 1).
3) Change the baffle form or use the baffle bar to change the arrangement of the tubes under the premise of meeting the heat transfer and pressure drop.
4) Increase the diameter of the take-up when the take-up occurs.