Two pilots report about the crew oxygen system on their B737-700 aircraft that would not give a prop...

Narrative:

I flew a B737-700 aircraft. The following day; this aircraft would not give a proper test of the oxygen system. It was reported by a contract mechanic that the valve on the oxygen bottle was not open. The bottle had last been replaced three days earlier. We did not notice any abnormal oxygen pressure readings during the preflight checks on the five legs that we flew the aircraft that day. I have preflighted an aircraft [before] with a 'closed' oxygen valve. The pressure will read zero during the test and remain there. The facts of this event suggest to me that the valve on the oxygen bottle may have been only partially opened after installation. The inspecting mechanic would have known this only if he attempted to close the valve as his first course of action during troubleshooting. [Recommend that] after installation of a new oxygen bottle; verification of normal pressure on the flight deck pressure gauge should be accomplished. The gauge will read zero until the bottle is opened. This may be [the] maintenance procedure currently. There is no procedure which; from the flight deck; which would necessarily reveal a partially opened oxygen valve.

Original NASA ASRS Text

Title: Two pilots report about the Crew Oxygen System on their B737-700 aircraft that would not give a proper test after they had flown the aircraft for five legs. Contract Maintenance had reported the oxygen bottle valve handle was not open.

Narrative: I flew a B737-700 aircraft. The following day; this aircraft would not give a proper test of the Oxygen System. It was reported by a Contract Mechanic that the valve on the oxygen bottle was not open. The bottle had last been replaced three days earlier. We did not notice any abnormal oxygen pressure readings during the preflight checks on the five legs that we flew the aircraft that day. I have preflighted an aircraft [before] with a 'Closed' oxygen valve. The pressure will read zero during the test and remain there. The facts of this event suggest to me that the valve on the oxygen bottle may have been only partially opened after installation. The inspecting Mechanic would have known this only if he attempted to close the valve as his first course of action during troubleshooting. [Recommend that] after installation of a new oxygen bottle; verification of normal pressure on the flight deck pressure gauge should be accomplished. The gauge will read zero until the bottle is opened. This may be [the] maintenance procedure currently. There is no procedure which; from the flight deck; which would necessarily reveal a partially opened oxygen valve.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1074583
Time
Date	201303
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Oxygen System/Crew
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 159 Flight Crew Type 10000
Person 2
Function	First Officer
Experience	Flight Crew Last 90 Days 183
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

Two pilots report about the crew oxygen system on their B737-700 aircraft that would not give a proper test after they had flown the aircraft for five legs. Contract maintenance had reported the oxygen bottle valve handle was not open.