Main Reasons for Failures of Pressure Vessels
The failure rates of equipment are related to various factors, not only the engineering level of the whole industries, but also the social culture and the population quality.
Under the same circumstances, pressure vessels
get higher failure rates than other equipment. Most pressure vessels
generally withstand loads which are static and relatively steady.
Thus, pressure vessels
will not break down like rotating machinery due to the overuse, and not be out of operation like high-speed engines owing to the fatigue.
According to the research and practice, the reasons for pressure vessels' high failure rates are listed below.
- Pressure vessels have strict working conditions.
Not only various loads of pressure (pulsatile pressure generally) do pressure vessels withstand, but also pressure vessels withstand some other loads. Moreover, pressure vessels, sometimes, need to be operated in cryogenic conditions or tough working environments with high temperatures or corrosive working media.
- Pressure vessels are overloaded easily.
The pressure inside the pressure vessels usually rises due to the misoperation and the abnormal reaction. Besides, pressure vessels are always broken before the abnormal conditions are noticed.
Pressure vessels have complex local stress. For example, the opening and the other discontinuous constructions of pressure vessels are always fractured by fatigue because of not only excessively high local stress but also continual loading and unloading.
- There are some hidden problems of pressure vessels.
Welded or forged containers can easily get serious defects such as fine cracks in manufacture. These defects might become more serious in operation and make pressure vessels broken in certain conditions.
- Inadequate management of pressure vessels increases the risk of failures.
Pressure vessels are used illegally sometimes.
In order to escape from supervision and management, some factories buy equipment produced by unauthorized and uncertified manufacturers and the equipment is used as pressure vessels, which can cause serious failures.
Legal pressure vessels are operated without normative management.
Enterprises have supervisory engineering staff without knowing professional knowledge and regulations of pressure vessels. Failures occur easily when pressure vessel operators neither have qualifications nor experience of professional training.
There are no safety regulations for operations, technical documents of equipment, periodic inspections for equipment and qualified employees or management personnel.
As a result, pressure vessels and their safety accessories, with abnormal use and disordered management, are not in safety management. Without authorization, pressure vessels are not only used in wrong conditions, but also even refitted.
Managers of factories neglect the safety operation of pressure vessels and the pressure vessels are used in unsuitable working environments for adapting to certain processing technologies. Moreover, even some broken pressure vessels are also put into use. Thus, the wrong operation and the overuse of pressure vessels can result in serious problems.
The local supervision department in charge of safety production, relevant administrative departments and relevant law enforcement authorities do not work effectively and have not yet adapted to the progress of the socialist market economy. The rapidly increased quantity of small widespread private enterprises causes wrong operation, illegal equipment control and loose supervision of relevant departments.