Requirements of API 6D and API 608 Concerning Ball Valves (Part Three)

Requirements of API 6D and API 608 Concerning Ball Valves (Part Three)


2.4 Requirements for installation and maintenance
API 608 ball valves belong to process pipeline ball valves. Generally, they can be installed in the factory. If the construction site is flat, the storage and transportation are convenient. Generally, there is a supporting structure for the installation of general pipelines and accessories. The stress conditions of valves are better.
 
API 6D ball valves are installed on long-distance pipelines, most of which are in the open air in the field, and some of them are in the valve room. Long-distance pipeline projects range from tens of kilometers to thousands of kilometers. The pipeline is long and the construction site is widely distributed. The pipeline is buried in the ground, over mountains and ridges, and crosses the river. The construction environment is particularly harsh, and there are residual sand, gravel and mud in the pipeline. The period from the pipeline's construction to going into operation is long. Additional stresses, external loads and other influencing factors of pipelines cannot be ignored. In addition to the different professionalism of construction personnel, these effects on the valve's performance are difficult to be avoided, and the final quality is not well controlled.
 
During the installation of API 6D pipeline ball valves, sometimes there are situations where the construction personnel are not very responsible, the construction site protection is not in place, and the installation and adjustment are not carried out in accordance with the procedures. Sand,  stones and soil in the pipeline which are not removed enter the valve cavity, and welding spatters adhere to the spherical surface or the valve seat, causing damage to the sealing pair, corrosion of the inner cavity surface of the valve body and valve seat, soil scaling, and jamming of valves, and directly affecting the sealing performance of the valve. Therefore, the on-site installation of the valve must be carried out in strict accordance with the construction process.
 
After the pipeline ball valve is put into operation, it is in the open state for a long time. It must have good reliability. Therefore, it is necessary to strengthen the routine maintenance of the pipeline ball valve. For the maintenance of the ball valve seat, it is necessary to properly inject the lubricating oil. The amount of injection should be based on the use condition and frequency of the ball valve. This can not only ensure its sealing performance, but also prevent the entry of impurities. Meanwhile, the bonding of the ball and seat can be avoided, and friction can be prevented when the ball is in motion, protecting the valve seat and ball, and having a significant effect on the normal operation of the pipeline ball valve.
 
2.5 Measures to dealing with the accident
The impact caused by the failure of the API 608 ball valve is usually limited to the factory and its surroundings. The general accident can be handled, and the social impact is controllable. However, once the API 6D long-distance pipeline ball valve fails, it will have a great impact on the operation of the entire long-distance pipeline and is difficult to be handled. It will cause a large amount of energy loss, a conflagration as well as delay the smooth implementation of some important projects, which will cause immeasurable losses to the country and enterprises, and have a greater social impact. When handling the accident, the public security department, fire department, safety supervision department, transportation department, medical department, environmental protection department, pipeline repair department, and search and rescue support department need to be present in time and cooperate with each other.
 
3. Conclusion
According to the requirements of API 608 and API 6D specifications on ball valves, analyze the situation in combination with actual engineering. Long-distance pipeline engineering has special characteristics such as great length, large diameters, harsh construction environment, etc. API 6D standard clearly shows the difference between API 6D ball valves and API 608 ball valves in terms of functions and structure.
 
The construction and use time of long-distance pipeline projects in China is not long, and the development of pipeline valves started relatively late. Some manufacturers who produce API 608 ball valves do not have a thorough understanding of the relevant specifications and requirements of pipeline ball valves when they manufacture pipeline valves. They have insufficient knowledge of the particularity of long-distance pipeline engineering, and fail to fully understand the technical requirements put forward by the owners for pipeline ball valves. The requirements which are put forward for functions such as the sealing structure, sewage, venting and grease injection are especially not carried out. The pipeline valve is still designed and manufactured according to the design concept for the technical requirements of general industrial users, resulting in many quality problems that are difficult to be solved in the operation. In the end, the valve had to be replaced, causing a great loss.
 
Only by carefully studying the relevant requirements of the API 6D standard, paying full attention to the particularity of the long-distance pipeline engineering, and getting rid of the constraints of the API 608 specifications, can the designer of the pipeline ball valve design a pipeline ball valve that meets the requirements of the long-distance pipeline project.