Do You Really Know How To Tighten Bolts and Nuts?
The core specification for the installation of flange bolts and nuts is contained in this article.
In flange connection systems, bolts and nuts may seem inconspicuous, but they are the key to ensuring tight flange sealing and stable pipeline operation. Many industrial practitioners have the misconception that "tightening is enough" during installation. Incorrect installation methods can lead to uneven stress on plastic flanges, seal failure, and ultimately cause medium leakage and pipeline damage. Plastic flanges are made of special materials with much lower toughness and rigidity than metal flanges, and the standardization of bolt installation is of utmost importance.
Preparation before installation: Control details and avoid hidden dangers from the source.
The core of the installation of flange bolts and nuts is to do a good job of "adaptation" and "cleanliness", and to make solid preparations in advance, which can greatly reduce the risk of leakage in the later stage. This is also the construction habit that our team has always adhered to.
The bolts and nuts used must match the specifications of the flange. PPH/FRPP/PVDF flanges are mostly used for conveying corrosive media. We usually provide stainless steel materials such as 304 and 316 to prevent chemical corrosion from damaging the interface. The bolt specifications should accurately correspond to the flange bolt holes, and the diameter and length should meet the design requirements. It is strictly prohibited to use bolts and nuts that do not meet the specifications - excessive thickness will crack the bolt holes, and excessive specification will not achieve the tightening effect. After tightening, the exposed length of the bolt should be controlled within 1/2 of the screw diameter, not less than the thickness of the nut, to ensure connection strength and avoid collision between the bolt and other components during pipeline vibration.
Before installation, it is necessary to thoroughly clean the bolt, nut, and flange bolt holes, wipe off surface oil stains, rust, and dust, and clean the debris inside the bolt holes to avoid impurities affecting the fastening effect and causing later loosening. If the bolt thread is damaged or has burrs, it should be replaced immediately. Unqualified bolts and nuts are strictly prohibited from use, otherwise it will affect the thread engagement and reduce the connection strength. In addition, it is necessary to check the flange sealing surface to ensure that it is flat, smooth, without burrs or radial grooves, laying a foundation for subsequent bolt tightening.
Flange sealing relies on gaskets. Before installation, it is necessary to confirm that the gasket material matches the conveying medium and flange material, and that the gasket size is consistent with the flange sealing surface, without any damage, deformation, aging, or other issues. It should be noted that it is strictly prohibited to use two or more gaskets on one sealing surface, otherwise it will cause uneven stress on the flange and lead to leakage. The flange gaskets we provide are precisely matched and can be made of rubber or fluorine rubber, which can be directly adapted to the corresponding specification flange without additional selection.
Installation process specification: precise operation to avoid flange damage
When installing flange bolts, avoid excessive force or improper operation, otherwise it may cause flange cracking and pipeline leakage.
1. Flange alignment: Ensure that the two flanges are coaxial and the sealing surfaces are parallel. Adjust the flange position during installation to ensure precise alignment of bolt holes and consistent flange axis, ensuring that bolts and nuts can easily penetrate. At the same time, ensure that the sealing surface is parallel, without tilting or misalignment. If the flange end face is not perpendicular to the pipeline axis, it should be adjusted in a timely manner, otherwise it will cause uneven stress on the bolts and nuts and excessive local pressure to crack the flange.
2. Bolts installation: Unified direction and smooth penetration. Insert the bolt smoothly into the flange bolt hole, keeping the bolt installation direction consistent. During the insertion process, avoid hitting forcefully to prevent damage to the edge of the plastic flange bolt hole, which may cause the flange to crack. If it is difficult to insert the bolt, do not force it forcefully. Check the flange alignment and adjust it before installation to avoid damage caused by friction between the bolt and the bolt hole.
3. Gasket installation: Place in the center and fit tightly. Place the gasket steadily between the two flange sealing surfaces, ensuring that the gasket is aligned in the center, without any offset or wrinkles, and fits tightly to avoid uneven stress on the sealing surface caused by gasket offset and potential leakage hazards. After installing the gasket, gently press it to ensure that it is initially in contact with the sealing surface, preparing for subsequent tightening.
4. Bolt tightening: diagonally distributed, with even force. Follow the principle of "starting with the middle, then moving to the sides, and taking diagonal steps". The purpose of doing this is to ensure uniform force distribution on the flange surface, smooth compression of the gasket, and avoid deformation of the flange and loose fitting of the gasket caused by one-sided force. The number of bolts and nuts varies, and the order also needs to be adjusted. For example, four bolts and nuts directly tightened diagonally, and eight bolts and nuts are installed in order to ensure that each bolt is subjected to consistent force.
Professional companies provide full protection throughout the entire process, making pipeline operation safer.
Every detail of the installation of flange bolts and nuts is related to the safety and stability of the pipeline system, and standardized operation cannot be separated from professional guidance and high-quality supporting products. We can not only provide PP/FRPP/PVDF full material and full specification flanges, but also provide matching bolts and nuts and special gaskets. All products adopt new national standards and high-quality new raw materials.
The installation of flange bolts, as long as it follows the standard operation, combined with our company's high-quality products and professional guidance, can completely avoid the risk of leakage, safeguard the safety of pipeline systems, and make industrial production more worry free and reassuring.
