Heat Exchanger Daily Inspection and Maintenance

 
Heat exchangers play a crucial role in industrial processes, with their performance directly affecting the overall efficiency and stability of the system. Routine inspections are essential not only for ensuring the proper operation of heat exchangers but also for identifying and addressing potential issues in a timely manner, thereby preventing equipment failures and production interruptions. The following guide provides a detailed overview of common inspection items and maintenance measures for heat exchangers.

Temperature Monitoring

 
Temperature is a core indicator for assessing the operating condition of heat exchangers. By measuring the inlet and outlet temperatures of fluids, the effectiveness of heat exchange can be evaluated. These temperature data help in analyzing fluid flow and heat transfer efficiency.

1. Temperature Variation Analysis

 
Regularly measure the inlet and outlet temperatures of the heat exchanger and record the data to create temperature variation charts. This helps in analyzing heat transfer efficiency. Although heat transfer coefficients change minimally over short periods, a sustained decrease may indicate reduced heat transfer efficiency. In such cases, consider cleaning the tube bundle to improve the heat transfer coefficient.

2. Temperature Fluctuation Control

 
It is crucial to prevent abrupt temperature changes. Sudden temperature variations can cause uneven expansion and contraction of internal components, leading to thermal stress. Long-term thermal stress may result in the separation of tube bundles from tube sheets, localized deformation, or cracking, and can accelerate corrosion and thermal fatigue cracking.

3. Cooling Medium Management

 
When using water as a cooling medium, ensure the outlet temperature is controlled below 38°C. Temperatures above this can accelerate microbial growth and decomposition of corrosion products, leading to tube corrosion and increased scaling. Ideally, the maximum outlet temperature should not exceed 45°C.

Pressure Monitoring

 
Monitoring pressure variations helps in identifying issues such as scaling, clogging, or leakage within the heat exchanger.

1. Pressure Differential Measurement

 
Regularly measure the pressure and pressure differential of the fluids to detect any scaling or blockage inside the heat exchanger. A rapid increase in the pressure of the low-pressure fluid due to leakage from the high-pressure fluid can lead to overpressure, causing various adverse effects. Therefore, pay particular attention to sudden pressure changes in high-pressure heat exchangers and check for other system issues such as valve damage or mechanical failures.

2. Leakage Awareness

 
Leakage of high-pressure fluids into low-pressure areas can cause a sudden rise in low-pressure fluid pressure and lead to overpressure. Thus, it is essential to monitor high-pressure heat exchangers carefully to prevent leakage issues.

External Leakage Detection

 
External leakage is usually easier to detect during routine maintenance, especially for gases with low toxicity.

1. Gas Leakage Detection

 
Use soapy water or foam agents to detect minor gas leaks of low-toxicity media. Test strips can also be used to identify color changes indicating leakage. Peeling of coating on the shell surface can also predict leakage, which is suitable for low-pressure heat exchangers.

2. High Toxicity Media Handling

 
For medium to high toxicity media, apply coatings sensitive to the specific toxic media at potential leakage points such as flanges and connections. A change in the coating color indicates leakage, allowing for rapid identification and action.

3. Air Sampling Analysis

 
Regularly sample and analyze the air around the connections of the shell to accurately determine leakage and its volume. This method is not only accurate and reliable but also convenient, suitable for both internal and external leaks, and enables automatic analysis, recording, and alarming.

Internal Leakage Detection

 
Internal leaks are typically harder to detect directly but can be identified through the following methods.

1. Medium Abnormalities Detection

 
Observe anomalies in the medium's temperature, pressure, flow rate, and any unusual noises or vibrations to identify internal leaks. For example, when high-pressure gas leaks into low-pressure liquid, the liquid pressure gauge will show increased and fluctuating pressure, and vigorous agitation of the liquid can cause pressure fluctuations. Use a listening device to detect abnormal noises within the shell.

2. Vibration Monitoring

 
If the leakage is significant, vibrations can be felt by touching the shell and liquid outlet pipes. For coolers, install sample tubes on the low-pressure medium pipes at the cooling water outlet to periodically sample and check for contamination by cooling media.

3. Gas Accumulation Alarm

 
If the cooling medium is gas, install a gas accumulation alarm on the upper part of the cooling water outlet pipe to detect leakage.

Vibration and Insulation Inspection

 
The vibration and insulation state of the heat exchanger directly affect its performance.

1. Vibration Control

 
High fluid flow rates can cause vibrations in the support structures. Improperly positioned supports or loose or broken bolts can exacerbate vibrations. Vibration deviations should be controlled to below 250μm; values exceeding this require timely inspection and correction.

2. Insulation Maintenance

 
Damage to insulation layers directly impacts the heat exchanger's heat transfer efficiency. Additionally, damaged insulation can lead to external water accumulation, causing localized corrosion. Repair any insulation damage immediately and take measures to prevent moisture from entering the insulation layer.
 
Routine inspection and maintenance of heat exchangers are fundamental to ensuring their efficient operation. By regularly monitoring temperature, pressure, leakage, and the condition of vibrations and insulation, potential issues can be effectively prevented and resolved, maintaining equipment stability and system efficiency. Regular inspections and timely maintenance not only extend equipment life but also enhance the overall system efficiency.