Español
Pусский
In the petrochemical industry, various companies adopt welded metal bellow mechanical seals for high-temperature heavy oil pumps. This article discusses some problems and solutions in practical applications.
In view of phenomena of carbon deposition，solid particles existence and coking on inner side of metal bellows , the various solutions previously proposed (such as steam purging, hard vs hard friction pair materials, external flushing, etc.) are not ideal in practical applications, it is recommended that the following measures should be adopted in combination:
a）Metal bellows is designed into a rotating structure, which can reduce deposition on the outer periphery and coking on the inner side of the bellows.
b) For friction pair materials, it is recommended to use‘hard vs hard’structure, generally tungsten carbide vs tungsten carbide (YG6-YG6 is selected) and tungsten carbide vs silicon carbide.
When choosing a ‘hard vs hard’structure, you must pay attention to the following points:
1) Cooling system must be ensured——cooling water is prohibited from being interrupted to prevent the end surface from heating up, and to prevent flashing of the lubricating film which will reduce lubrication of the sealing end face and will aggravate wear;
2) During installation process of the mechanical seal, some lubricating oil should be applied to the end faces of the seal to prevent dry friction when the pump is started;
3) Use of clean external flushing is one of the more effective methods to solve problem of accumulation of solvent particles, but due to various reasons, many enterprises, especially some small and medium-sized ones, do not have oil sealing systems or have abandoned them. In view of this, it is recommended to use a multi-seal structure equipped with isolation medium.
In view of phenomena of carbon deposition，solid particles existence and coking on inner side of metal bellows , the various solutions previously proposed (such as steam purging, hard vs hard friction pair materials, external flushing, etc.) are not ideal in practical applications, it is recommended that the following measures should be adopted in combination:
a）Metal bellows is designed into a rotating structure, which can reduce deposition on the outer periphery and coking on the inner side of the bellows.
b) For friction pair materials, it is recommended to use‘hard vs hard’structure, generally tungsten carbide vs tungsten carbide (YG6-YG6 is selected) and tungsten carbide vs silicon carbide.
When choosing a ‘hard vs hard’structure, you must pay attention to the following points:
1) Cooling system must be ensured——cooling water is prohibited from being interrupted to prevent the end surface from heating up, and to prevent flashing of the lubricating film which will reduce lubrication of the sealing end face and will aggravate wear;
2) During installation process of the mechanical seal, some lubricating oil should be applied to the end faces of the seal to prevent dry friction when the pump is started;
3) Use of clean external flushing is one of the more effective methods to solve problem of accumulation of solvent particles, but due to various reasons, many enterprises, especially some small and medium-sized ones, do not have oil sealing systems or have abandoned them. In view of this, it is recommended to use a multi-seal structure equipped with isolation medium.
