A320neo – HPV failed in CLOSE position
Reference: 36.11.00.115
A320FAM neo – HPV failed in CLOSE position leading to HP VALVE FAULT or BLEED ABNORMAL PR
Engineering Support
Applicability:
A320FAM neo
References:
TFU 36.11.00106A320FAM neo HPV failed open leading to AIR ENG BLEED FAULT
Description:
Several E/W”AIR ENG x HP VALVE FAULT“associated to “HP BLEED-V (4000HAx)” have been reported on A320FAM neo aircraft
which lead toHPV PN 70645A020001 removalto solve the issue.
On some cases analyzed, the bleed system experienced alow pressure scenarioat top of descent during cruise phase and theHPV failed in closed position identified byE/W”AIR ENG x BLEED ABNORMAL PR“associated to “HP BLEED-V (4000HAx)”.
Root cause analysis:
Root cause analysis investigation has been completedin April 2019 and two major contributors of HPV failure have been identified:
HPV internal pollution:HPVinternal contaminationdue to the use of JP1932 graphite material on both actuator seals and the pressure reducer clapper guide. Such material has been identified torelease aluminium phosphatewhich acts as a strong adhesiveon both piston seal ring and the regulation clapper. Release of aluminium phosphate has been confirmed to occur when JP1932 is subjected tohigh humidityandtemperatureenvironments.
This finding is the main contributor to the issue(65% of the HPVs sent to LTS between 2018 and 2020 have this contributor).
HPV solenoid failed:HPV solenoid failures in open circuit have been confirmed in shop on some removed valves.
This contributor concerns few HPV removals(12% of the HPVs sent to LTS between 2018 and 2020 have this contributor).
Solution:
1. For graphite parts exudation, a modifiedHPV PN 70645A020001 AMDT A(from SN 70645-04740) isavailableand delivered to FAL from Summer 2021.This will prevent the HPV internal pollution by replacing JP1932 material by purified graphite andcover the majority of the failure.
For in-service AC, this modification is documented through a recommendedVSB 70645-36-01 dispatched on 22 July 2021.
Ensure to put the reason for removal with PFR copy when HPV are sent to Liebherr.
2. For solenoid failure, corrections will be introduced innext standard HPV PN 70645A030001(ref. TFU 36.11.00106 for follow up of PN 70645A030001 introduction) and consists inmaterial changeand addition of aprotective sleevein the weakest area.
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