Seal leaks prematurely at High Pressure but holds at Low pressure

[fathimi]

Hi,

I would like to ask for some opinions. I had a double-seal that was leaked at high pressure, however, it holds (didn't leaks) at low pressure. The seal runs with plan 53B (barrier system), and the inboard seal-face materials are SiC-SiC:

1. When i perform hydrotest, whereas the seal barrier area was pressurized at 30barg, whereas the product side is 0 barg , it didn't show any leakages.
2. However, when i do dynamic test, i pressurize the seal at 18 barg (product side), and pressurize the barrier area at 20 barg (which make the differential pressure of 2 barg), the seal leaks at the inboard.
3. Then i lower down the product pressure to 5 barg, and then reduce the pressure at barrier area to 7barg, then the seal didn't show any leakages at the inboard.

Anyone has any idea on why this situations occured? Does the concave/convex seal faces has anything to do with this?

Thank you for your time

 

[1gibson]

It should have an air test from the vendor, and it should be used during performance testing of the pump. It is not typical to hydrotest mechanical seals.

What is a "dynamic test", is the seal rotating?

 

[Dougt115]

Need more data about the seals. Your statement about the high pressure leaking and low pressure not leaking is confusing at first. I read this as the high pressure has a low pressure difference between the two sides and the low pressure has a high pressure between the two sides. If this is the case then one reason is that the pressure difference is deforming the seals and resulting in a better seal. This is not unusual.

 

[u0406346]

What is the seal face config? concave or convex or dead flat?

 

[flexibox]

check flatness of seals.