Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question dated 2020-09-28

1. The operating temperature and pressure must be within the specified ranges for double flanges. 2. The length of the capillary tube should be 2 meters more than the required length for the given range; too long a length will cause delays in measurement, while too short a length makes installation difficult. 3. For substances that tend to crystallize or solidify chemically, an isolation device is necessary; for special media, an insert-type design should be used. 4. The capillary tube needs to be fixed, and the amount of migration must be calculated. I spent a lot of time on this but realized I hadn’t understood the question properly – what exactly does “the flange” refer to?

”Does ‘flange’ mean an operating flange?

After tightening the bolt, turn it half a turn more

“\"Fastening the flange\" means securing the flange with bolts.

1. After the flange is installed, ensure that all bolts and nuts are tightened evenly. 2. For tightening bolts and nuts, washers should be used to prevent loosening due to vibrations. To prevent sticking between the threads at high temperatures, an anti-adhesive should be applied to the threaded areas during installation. 3. Used for high-temperature valves operating at temperatures above 300°C; after the temperature rises, it is necessary to retighten the flange connection bolts, the valve cover fastening bolts, the pressure seals, and the packing gland bolts. 4. When valves for low-temperature applications are installed at atmospheric temperature, a temperature difference arises, causing the flanges, gaskets, bolts, and nuts to contract. Moreover, since the materials of these components differ from one another, their linear expansion coefficients also vary, creating conditions that make leakage very likely. Based on this objective reality, when tightening bolts at atmospheric temperature, a torque that takes into account the shrinkage of various components at low temperatures must be used.

The flange surfaces of valves and piping should be free from damage, scratches, etc., and kept clean. Especially when metal washers (with oval or octagonal cross-sections) are used, the grooves on the flange must match those of the washer; red lead should be applied for lapping to ensure a good sealing condition. 2. The perpendicularity of the flange surface on the pipe to the pipe’s centerline, as well as the tolerances of the flange bolt holes, must be within the allowable ranges. The valve and piping centerlines must be aligned before installation. 3. When connecting two flanges, it is first necessary to ensure that the sealing surfaces of the flanges are pressed evenly against the gasket, thereby guaranteeing that the flanges are connected under equal bolt stress. 4. When tightening bolts, use a wrench that matches the nut. When using hydraulic or pneumatic tools for tightening, make sure not to exceed the specified torque. 5. When tightening the flanges, avoid uneven force; tighten them in a symmetrical, alternating sequence. 6. After installing the flange, ensure that all bolts and nuts are tight and even. 7. The material of bolts and nuts must meet the specified requirements. After tightening, the bolt head should protrude from the nut by about two pitches. 8. For tightening bolts and screws, washers should be used to prevent loosening due to vibration. To prevent sticking between the threads at high temperatures, an anti-adhesive (molybdenum disulfide) should be applied to the threaded areas during installation. 9. For high-temperature valves used at temperatures above 300 degrees Celsius, it is necessary to retighten the flange connection bolts, the valve cover fastening bolts, the pressure seal bolts, and the gasket compression bolt once the temperature rises. 10. Valves for low-temperature use are installed at atmospheric temperature. In practical applications, when the medium passes through, a low-temperature state is created. Due to the temperature difference, components such as flanges, gaskets, bolts, and nuts contract. Moreover, since the materials of these components vary, their respective linear expansion coefficients also differ, creating conditions that make leakage very likely. Based on this objective reality, when tightening bolts at atmospheric temperature, a torque that takes into account the shrinkage of various components at low temperatures must be used.

1. After the flange is installed, ensure that all bolts and nuts are tightened evenly. 2. For tightening bolts and nuts, washers should be used to prevent loosening due to vibrations. To prevent sticking between the threads at high temperatures, an anti-adhesive should be applied to the threaded areas during installation. 3. Used for high-temperature valves operating at temperatures above 300°C; after the temperature rises, it is necessary to retighten the flange connection bolts, the valve cover fastening bolts, the pressure seals, and the packing gland bolts. 4. When valves for low-temperature applications are installed at atmospheric temperature, a temperature difference arises, causing the flanges, gaskets, bolts, and nuts to contract. Moreover, since the materials of these components differ from one another, their linear expansion coefficients also vary, creating conditions that make leakage very likely. Based on this objective reality, when tightening bolts at atmospheric temperature, a torque that takes into account the shrinkage of various components at low temperatures must be used.

1. After the flange is installed, ensure that all bolts and nuts are tightened evenly. 2. For tightening bolts and nuts, washers should be used to prevent loosening due to vibrations. To prevent sticking between the threads at high temperatures, an anti-adhesive should be applied to the threaded areas during installation. 3. Used for high-temperature valves operating at temperatures above 300°C; after the temperature rises, it is necessary to retighten the flange connection bolts, the valve cover fastening bolts, the pressure seals, and the packing gland bolts. 4. When valves for low-temperature applications are installed at atmospheric temperature, a temperature difference arises, causing the flanges, gaskets, bolts, and nuts to contract. Moreover, since the materials of these components differ from one another, their linear expansion coefficients also vary, creating conditions that make leakage very likely. Based on this objective reality, when tightening bolts at atmospheric temperature, a torque that takes into account the shrinkage of various components at low temperatures must be used.

1. The operating temperature and pressure must be within the specified ranges for double flanges. 2. The length of the capillary tube should be 2 meters more than the required length for the given range; too long a length will cause delays in measurement, while too short a length makes installation difficult. 3. For substances that tend to crystallize or solidify chemically, an isolation device is necessary; for special media, an insert-type design should be used. 4. The capillary tube needs to be fixed, and the amount of migration must be calculated. I spent a lot of time on this but realized I hadn’t understood the question properly – what exactly does “the flange” refer to?

After tightening the bolt, turn it half a turn more