In industrial production, the sealing performance of equipment is crucial, as it directly affects production efficiency, safety, and environmental protection. Graphite packing, as an efficient sealing material, is widely used in various equipment such as pumps and valves. However, the correct installation and maintenance of graphite packing are key to ensuring its sealing performance. This article will detail the installation steps, maintenance points, and related precautions of graphite packing to help you better understand and apply this important sealing technology.
Cutting graphite packing is the first step in the installation process and is also a crucial one. The correct cutting method can ensure that the packing fits tightly with the equipment after installation, thereby achieving a good sealing effect.
If conditions permit, it is best to use a specialized packing cutting machine to accurately cut the required length of packing rings. This machine can ensure the precision and quality of the cutting, avoiding sealing problems caused by improper cutting. If there is no packing cutting machine, the packing can also be manually cut according to the formula L = (shaft diameter d + packing width s). When cutting, attention should be paid to the cutting angle. For rotating shafts, a 90° straight cut is usually used; for valves, a 45° cutting angle is used.
When cutting packing, do not try to use the packing to encircle the stuffing box to determine the length. This practice may result in the packing being too long or too short, thereby affecting the sealing effect. The correct method is to encircle a tube with the same diameter as the valve stem with the packing, press it tightly, but do not stretch the packing. Then cut it into a sample ring and check whether it can correctly fill the space and ensure that there are no gaps at the joint. If the sample ring meets the requirements, it can be used as a standard to cut the other packing rings.
If the packing is soft or easily deformed, a small strip can be made according to the sample ring, and then the remaining packing rings can be made according to this strip. This can ensure that the size and shape of each packing ring meet the requirements.
The installation of graphite packing needs to be carried out strictly according to certain steps to ensure its sealing performance. The detailed steps for installing graphite packing are as follows:
Before installing graphite packing, adequate preparation work is necessary. First, familiarize yourself with the relevant equipment and tools, such as packing cutters, torque wrenches or wrenches, safety helmets, inside and outside calipers, lubricants for the fasteners, mirrors, packing extractors, packing grooving tools, vernier calipers, etc. These tools and equipment will help you complete the installation work more efficiently and safely.
Removing the old graphite packing is the first step in installing new packing. When removing the old packing, a specialized packing extractor should be used to avoid damaging the equipment. After removing the old packing, thoroughly clean the stuffing box of the shaft/rod to ensure that there are no residual old packing or other impurities.
Before installing new packing, the equipment needs to be carefully inspected. Check whether the shaft/rod has corrosion, dents, scratches, or excessive wear, and whether other parts have burrs, cracks, wear, etc. These defects may reduce the life of the sealing packing, so parts with significant defects should be replaced in a timely manner.
Measuring and recording the diameter of the shaft/rod, the stuffing box hole diameter, and depth is a very important step. If a water seal ring is used, the distance from the bottom to the top of the stuffing box also needs to be recorded. These data will help you select the appropriate graphite packing and calculate the required amount of packing.
When installing new packing, ensure that each packing ring is free of dust or other debris. If necessary, the packing ring should be lubricated with the same clean lubricating oil used on the valve stem. Install each packing ring alternately at 90°, and slowly pull the rings apart axially.
After the packing is installed, the gland nut needs to be tightened. When tightening the gland nut, it should be done slowly to avoid exerting excessive pressure on the packing. After starting the pump, adjust the gland nut, allowing slightly more leakage at this time. Then slowly tighten the gland nut to gradually reduce the leakage until it reaches an acceptable level. If the leakage suddenly stops, the gland nut should be loosened and readjusted to prevent the packing from overheating.
The maintenance and inspection of graphite packing are key to ensuring its long-term stable operation. Regular maintenance and inspection can promptly identify potential problems and take corresponding measures to resolve them.
During the operation of the equipment, the adjustment status of the gland needs to be regularly checked. If it is found that the gland can no longer be further adjusted, the flexible graphite packing must be replaced. In addition, the wear condition of the packing should be checked, and packing with severe wear should be replaced in a timely manner.
For flexible graphite packing used in valves, the gland nut should be tightened according to the specified torque by the manufacturer or technical department. The general steps are as follows: apply torque to the gland nut up to 30% of the full torque or the specified compression percentage; repeatedly open and close the valve several times, and apply the full torque when the valve is in the closed position; repeat the above steps 2 to 4 times.
It is recommended to install a water seal ring whenever possible and inject lubricating oil into the stuffing box through the water seal ring to lubricate the shaft and packing. The position of the water seal ring needs to be aligned with the injection hole. This can effectively reduce the wear of the packing and extend its service life.
The performance of graphite packing directly affects its sealing effect and service life. Therefore, when selecting graphite packing, it is necessary to choose the appropriate packing according to the specific application scenario and requirements.
The weaving density of graphite packing is a key factor affecting its performance. Generally speaking, the higher the weaving density, the better the sealing performance of the packing. Therefore, in most application scenarios, it is recommended to select packing that has been woven as tightly and orderly as possible.
There are mainly two types of graphite packing: graphite braided packing and graphite packing rings. The performance of the two is basically the same, but each has its advantages and disadvantages. Graphite braided packing has good lubricity and expansibility, but its disadvantage is that it is brittle and is usually installed in the middle part of the stuffing box. Graphite woven packing has good performance and is resistant to compression, and is generally installed in the upper/lower layers of the stuffing box. Its function is to fix the expanded graphite packing, protect its integrity, and prevent graphite powder from falling into the circuit.
When selecting graphite packing, the specific application scenario also needs to be considered. For example, in places with extremely high sealing requirements such as nuclear power stations, high-quality and high-performance graphite packing should be selected, and installation and maintenance should be carried out strictly in accordance with relevant standards and specifications.
The installation and use of graphite packing not only relate to the sealing performance of the equipment but also involve safety and environmental protection issues. Therefore, when installing and using graphite packing, it is necessary to strictly comply with relevant safety regulations and environmental protection requirements.
When installing and replacing graphite packing, standard safety equipment such as safety helmets and gloves should be used, and relevant safety operating procedures should be strictly followed. For example, when removing old packing, the fixing nut of the stuffing box should be loosened slowly to release all residual pressure in the flexible graphite packing assembly to avoid accidents.
In industrial production, the sealing performance of equipment directly affects environmental protection. If the equipment is not well sealed, it may lead to the leakage of harmful substances and cause environmental pollution. Therefore, selecting high-quality graphite packing and correctly installing and maintaining it are important measures to ensure the sealing performance of the equipment and protect the environment.
As an efficient sealing material, graphite packing has a wide range of applications in industrial production. Correct installation and maintenance of graphite packing are key to ensuring the sealing performance of equipment. Through the introduction of this article, you should have a deeper understanding of the cutting, installation, maintenance, and performance selection of graphite packing. In practical applications, strictly following the relevant steps and requirements can effectively improve the sealing performance of equipment, extend the service life of equipment, and also help ensure production safety and environmental protection.
In summary, the installation and maintenance of graphite packing is a meticulous and important task. Only through scientific methods and a rigorous attitude can we ensure that graphite packing plays its due role in industrial equipment and provides strong support for the stable operation of industrial production.