Sealing renovation for Plan 52? What is the required temperature for the white oil? Where can I check it?

This post was last edited by svenzheng on 2016-8-17 07:40. The boiling point of white oil is between 163–223°C. When used as a cooling medium, it absorbs heat in the mechanical seal chamber, but releases heat in the heat exchange tank. Without the cooling effect of such a medium, the temperature of the white oil that is displaced remains high, and it cannot thus serve to cool and lubricate the mechanical seal. Are we not in a position to create a water seal tank on-site, nor to have 2 sealed water pumps? White oil is volatile. Prolonged operation under high-temperature cycles will lead to a reduction in performance; in my opinion, this is not beneficial for the mechanical seal.

1. White oil is a cooling medium; it’s not the case that no cooling is needed just because white oil can withstand a certain temperature – cooling serves to protect the seal. 2. The temperature of the liquefied gas is 35°C; how low can the cooling water be cooled? Plan 53B will allow white oil to enter the liquefied gas, which has a certain impact on the quality of the liquefied gas product. Currently, sealing manufacturers both domestically and internationally generally recommend the 11+52 or 11+72 scheme, including design institutes.

I happen to have a project on hand that uses some liquefied gas pumps, and it also involves issues related to the selection of mechanical seals; moreover, there is no circulating water system at the site. This is how we made the choice: when confirming the initial plan, there were three options available. 1. Shielded pump (leak-free, no sealing required) ； 2. A 11+52 system mineral oil seal is used; this system is suitable for liquefied gas pumps. When volatile leaks occur from the liquefied gas, it enters the liquid storage tank, and a flare line is installed at the top of the tank to allow for immediate flaring of any excess gas ； 3. The 11+76 system is used; dry gas sealing is particularly suitable for liquefied gas pumps. Its principle is the same as that of the 52 system, with leaks being directed into the liquid storage tank and then to the flare. After consulting with the workshop and taking into account the absence of nitrogen lines on site, we ultimately chose the 11+52 system, which requires a cooling water line connected to the liquid storage tank. During the process of lubricating, cooling, and sealing the secondary seal with white oil, the high-speed rotation of the seal generates heat, which raises the temperature of the white oil to 70–80°C. If this temperature is not cooled, it can affect the service life of the secondary seal. The sealing manufacturer also said that without cooling water, they cannot guarantee the service life of the seals, and the warranty period will be void. In practical applications, there are also cases where cooling water is not used, which indeed affects the service life of the seals. Therefore, we installed two dedicated circulating water lines to cool the white oil; if it is difficult to lay such water lines, you can also set up a small water tank nearby and use small pipeline pumps to connect it to the water lines in order to cool the storage tank.