Modification of plan 53 C to plan 52

[CaracasEC]

Dear All,
We are currently having a problem on the said seal flush plan. Currently the installed plan for the 4 pumps is plan 53 C. However, our licensure learned that applying plan 53 C once the seal wear will contaminate the process fluid (ethylene). The recommended solution now is change the plan from 53 C (barrier fluid) to 52 (buffer fluid). Operating temp is -36.3 deg C. Do you have any experience for this low temp application? thanks in advance. We are in construction process and next year will be the commissioning of these pumps.

 

[flexibox]

If my memory serves me right ethylene has a high vapor pressure. If you go with plan 52 you may experience issues with the primary seal. This is probably why you have dual pressurized seals. I would change from 53C to 53B which is a far superior system than 53C. Only issue is cost.

 

[CaracasEC]

Hi flexibox, the 4 pumps is already on site with plan 53C. The reason for changing is that our technology licensure found out that having the propyl alcohol as barrier seal of plan 53C will give problem on the process at higher seal leakage because the ppm value will contaminate the process. With this problem, they recommend to 52. We believe that the changing the seal plan type is the best solution to this issue considering the long term performance of the pumps and product guarantees. Please find attached seal plan drawing of one of the pump "Ethylene Fractionator Reflux Pump" thanks...

 

[bk19702]

Have you considered how to lubricate the primary seal when changing to plan 52? You'll need to take this into consideration assuming you plan on using the process fluid as the primary seal lubricant. As Flexibox mentioned, the advantage of the pressurized seal is that both the priamry and secondary seals see the barrier fluid as the face lubricant. If you don't address reliable lubrication of the primary seal, then switching to the Plan 52 arrangment is going to give you a new set of problems.

 

[CaracasEC]

Hi bk19702, due to the high vapor pressure of the process fluid (ethylene) we are considering the lubrication of the primary seal either plan 11 or 13 to satisfy API 682 requirements that "For arrangement 1 and 2, seal chamber pressure and support system for contacting wet seals shall be designed for a margin of not less than 30% between seal chamber pressure and maximum fluid pressure, or a 20 deg celcius product temperature margin based on the maximum fluid temperature. Another option is to have a plan 13 or 14 + 76 but a combination of wet seal as the primary and non contacting (dry gas) as the outboard seal. What is your opinion? thanks

 

[CaracasEC]

Do you have any idea of barrier fluid for ethylene service that will fit the process?One of our option also is to look for possible barrier fluid that will fit the process and plan 53 will not be changed only the barrier fluid which will have no cost impact?