REG NASA-LLIS-0231-1993 Lessons Learned - Cooling Towers.pdf

1、Lessons Learned Entry: 0231Lesson Info:a71 Lesson Number: 0231a71 Lesson Date: 1993-06-22a71 Submitting Organization: LERCa71 Submitted by: S. PapellSubject: Cooling Towers Description of Driving Event: During winter operation of a cooling tower that was operating in a standby mode, a large section

2、of the tower collapsed due to an unusual accretion of ice in the central portion of the tower. The dead load of the ice overloaded the structural members and caused the collapse. When the mishap occurred the tower was not running within its design parameters. Valves controlling the minimum water flo

3、w to prevent freezing and to inhibit corrosion in the heat exchangers were opened wider than usual to reduce noise because of workmen in the area. An additional pump was also turned on to maintain the required flow.The combination of the increased water flow rate and restricted flow through the pipe

4、s returning water to the tower basin created a back pressure sufficient to permit water to flow up the riser pipe and into the tower distribution system. Because the tower was in standby, with no heat load, the water and air temperatures were both low enough to cause the water to freeze. The resulti

5、ng accumulation of ice created the load that led to the structural failure.Lesson(s) Learned: Off-design operation of cooling towers during winter months can cause severe damage to the wooden structure.Recommendation(s): Develop written standards and operating procedures which include permitted devi

6、ations from normal operating conditions depending on seasonal changes.Evidence of Recurrence Control Effectiveness: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s)

7、: a71 Environmenta71 Facilitiesa71 Ground Operationsa71 HardwareAdditional Info: Approval Info: a71 Approval Date: 1994-04-19a71 Approval Name: Maria Havenhilla71 Approval Organization: LERC/EBASa71 Approval Phone Number: 216-977-1483Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-