Key points for preventing freezing and condensation in chemical plants (II: Inspection)

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This post was last edited by Zhizhi Ming on 2025-1-3 at 18:27. The inspection for anti-freezing and anti-condensation measures is an extremely important part of such efforts; conducting regular inspections allows for the timely detection and resolution of any issues that arise during this process, thereby preventing further complications related to freezing. The anti-freezing and anti-condensation inspection primarily aims to assess the effectiveness of these measures, identify any gaps, and further improve them. 01 Inspection of steam tracing pipelines: 1. Regularly check the drainage function of the traps; address any abnormal drainage issues promptly. 2. In cases where it is not possible to directly check the hydrophobicity (for example, when the water is directed to a hydrophobic recovery station), a temperature gun or the hand can be used to touch the body of the hydrophobic valve (an inspection hole must be left available when insulation is in place). As a general guideline, a temperature of 30°C or higher, or a feeling of heat, indicates normal operation; however, the sensation of heat does not necessarily confirm that the hydrophobic function is working properly, especially in situations where the water is sent to a hydrophobic recovery station, as heat conduction from nearby normal drainage pipes can lead to misleading results. 02 Hot water tracing inspection: 1. Check the water flow by using a flow indicator, or use a temperature gun to verify that the temperature of the electric tracing tape is normal. 2. When the heat-traced hot water pipelines are collected together, experience should also be used to avoid interference from the heat conduction of the regular hot water pipelines, which could affect inspection and judgment. 03 Electric heat tracing inspection: 1. For electric heat tracing systems with temperature indicators, it is necessary to regularly check the temperature readings; in addition, a thermometer or the hand should be used to touch the designated inspection points on the heat tracing cable, in order to prevent inaccurate temperature readings and ensure that the temperature of the heat tracing cable remains within the normal range. Electric heat tracing systems without temperature indicators still require temperature monitoring. 04 Inspection of enclosed workshops and valve chambers
1. Enclosed workshops should be equipped with thermometers. It is necessary to regularly check the sealing of doors and windows as well as the heating temperature, and adjust the amount of heat supplied indoors according to the indoor temperature. 2. Check the insulation and sealing condition of the valve chamber, and monitor its internal temperature if necessary. 05 Inspection of drainage pipelines: 1. Regularly check whether there is any material flowing out or freezing and blockage at the low points of the drainage equipment and pipelines; alternatively, use a wrench to tap on the pipelines to assess the situation. If freezing and blockage is detected, identify the source of the material promptly and take appropriate action. 06 Inspection of the anti-freezing circulation line: 1. Regularly inspect the anti-freezing circulation components of the equipment and pipelines; if there are flow indicators or sight glasses, check whether their readings are normal. 2. In the absence of a flow indicator or sight glass, a temperature gun or by touching the device itself or the relevant anti-freezing wiring can be used to determine the temperature; when it is difficult to make such a judgment based on temperature, a listening rod can also be used to assess the flow of material within the device or pipelines. For materials that use a small amount of discharge and circulation for anti-freezing purposes, regularly check whether the discharge volume and circulation volume are normal. 07 Inspection of Instrument Heating 1. Regularly check the sealing condition of the instrument heating box as well as the temperature inside it; meanwhile, depending on the heating method, inspect the instrument heating in accordance with the aforementioned procedures. 2. A comparison can be made using on-site and remote sensors, and the normal readings of these sensors can be used to determine whether the sensor is frozen or blocked. 08 Inspection of Moving Equipment 1. Spare moving equipment should be rotated regularly to detect in advance any signs of freezing or blockage. 2. For equipment that cannot be cranked (such as canned motor pumps), in addition to conducting anti-freeze circulation checks, a trial start should be performed prior to actual startup. Measure the temperature of parts prone to freezing (such as the rear housing of the canned motor pump); only proceed with the startup if the temperature readings are normal. 09 Pipeline drain inspection: 1. For the drain valves at the ends of gas (steam) pipelines, the drain valves at the lowest points of U-shaped bends, and the valves at the hose stations, ensure they are kept at an appropriate opening degree or conduct regular drainage checks to prevent material from accumulating in those low points and causing the pipelines to freeze up. 2. Regularly check the outlets of the drainage facilities to ensure that water is not flowing out or that there is no freezing blockage at the low-point drainage valves. If any problems are detected, clear them promptly and verify that the valves at the source are properly closed. 10 Inspection of instrument air 1. For instrument air, regular inspections should be carried out to drain water from the ends of the main pipelines and at their lowest points. 2. During the period of producing specialized anti-freezing and anti-condensation products, it is necessary to record and monitor the dew point temperature of the instrument air on a daily basis; this temperature should not exceed -18°C, in order to prevent water accumulation inside the instruments, which could lead to malfunctioning of those instruments. 11 Venting inspections: 1. Regularly inspect the system’s venting and breathing exhaust ports, such as the storage tank’s breather valves and flame arresters, emergency venting pressure relief ports, air compressor vent ports, and boiler safety valve vent ports, to ensure that these vents remain unobstructed. 2. Regularly check the protective nets and filters at the inlet of outdoor fans, as well as those at the inlets of the cooling fans of motors and other equipment, to ensure that there is no freezing and blockage. Blockages are likely to occur if steam is released in the vicinity of such equipment or during snowy weather. 12 Key Points to Pay Attention To: 1. Regularly check whether the liquid in the outdoor water seal groove or liquid seal tank has frozen and caused blockages; address any abnormalities promptly to ensure its proper functioning. 2. In the event of a significant drop in temperature or at night, inspections should be intensified. The amount of heat supplied, as well as the heating capacity of the factory buildings and the volume of fluid used in anti-freezing systems, should be adjusted according to the temperature conditions. Regular inspections are necessary to prevent blockages due to freezing.