REG NASA-LLIS-0935-2000 Lessons Learned High Velocity OxyFuel (HVOF) Thermal Spray System Incident.pdf

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1、Lessons Learned Entry: 0935Lesson Info:a71 Lesson Number: 0935a71 Lesson Date: 2000-02-22a71 Submitting Organization: MSFCa71 Submitted by: Frank ZimmermanSubject: High Velocity OxyFuel (HVOF) Thermal Spray System Incident Description of Driving Event: During routine starting of the HVOF thermal spr

2、ay gun, an incident occurred that resulted in the unintended mixing and ignition of liquid fuel (kerosene) and oxygen in the HVOF system. By some mechanism, the kerosene fuel was allowed to mix with gaseous oxygen upstream of the oxygen check valve in the combustion chamber of the gun. Upon starting

3、 the HVOF spray gun, this fuel ignited outside of the combustion chamber, in which it normally mixes and is burned. The flame front traveled up stream in the oxygen supply line and into the controller console, burning or melting several plastic tubes and lines in the cabinet, and contaminating the o

4、xygen-regulating portion of the system. No personnel were injured and the equipment sustained approximately $7,800 worth of damage.As the manufacturer (TAFA) repaired the equipment, they offered the most likely cause of the mishap and suggested some corrective actions. If the HVOF gun is not mounted

5、 in! a slightly (at least 5 degrees) downhill orientation (barrel is lower than the rear of the gun), it is possible for a small amount of residual fuel to seep into the oxygen supply line. This can lead to “hard“ starts or, as in this extreme case, damage the equipment. It is suspected that the HVO

6、F gun was mounted level (parallel to the floor), or even slightly uphill, though not enough to be perceived by the operator. While the equipment manufacturer recommends this practice, it was not described or included in the documentation that originally came with the HVOF system. Consequently, the o

7、perator had no idea of the potential consequences related to gun orientation. This equipment had been in operation for over 6 years witout incident before this mishap.Lesson(s) Learned: 1. The potential exists for kerosene and oxygen to mix outside the combustion chamber of a TAFA model JP5000 HVOF

8、gun.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2. If a mixture of kerosene and oxygen is ignited outside the combustion chamber of the HVOF gun, it will damage the oxygen-regulating circuit of the controller.3. TAFA, the manufacturer of the JP50

9、00 HVOF system does not notify customers of updated in safe operating procedures.Recommendation(s): 1. Mount the HVOF gun at a 5-degree downward orientation. Periodically verify down hill orientation. do not operate by hand.2. Purge the HVOF gun for at least 20 seconds before ignition to ensure no r

10、esidual kerosene is present.3. Request updates and bulletins from the HVOF system manufacturer. Periodically check with manufacturer that all documentation on hand is current. Update procedures as the manufacturer revises them.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Les

11、son: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Ground Equipmenta71 Test Facilitya71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2001-04-30a71 Approval Name: Eric Raynora71 Approval Organization: QSa71 Approval Phone Number: 202-358-4738Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-