The next LER had only one set pressure lift inaccuracy. These guys in the past had the majority of SRV setpoint failures every testing cycle. This is a huge win!!!
I am surprised I missed this one considering my interest in SRVs. The brand new excuse here industry wide is they machine the disc and set. They reassemble the value not allowing the corrosion to build up on them both. It seems they are thinking if they let the oxide layer to age and build up before assembly, they would have no more problems.
Corrosion bonding occurs when the protective oxide layers of the seat and disc break down and allow a crevice corrosion process to develop between the seat and disc. The seat is machined and then lapped with the disc to create a tight fit with one another. During the material removal process (machining) on both the seat and disc, the protective oxide layer that provides corrosion protection is removed. Because the SRV pilot valves are then assembled, the oxide layer is not given sufficient time to reestablish itself naturally, and no external process, such as pickling, is done to ensure that the oxide layer is reestablished to its full extent without any breaks or discontinuities. When the SRV pilot valves are assembled, the seat and disc are jammed together and air cannot reach the surfaces, therefore the full benefits of the oxide layer of the anti-corrosion material is diminished.
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