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{{#Wiki_filter:Water Hammer at San Onofre 1 Section 7.3 What is Water Hammer?A pressure transient which creates fluid shock waves in piping systems due to changesinfluidvelocityorpressure 2 changes in fluid velocity or pressure.
{{#Wiki_filter:Water Hammer at San Onofre Section 7.3 1
Learning Objective 1Describe three types of water hammer and their causes.
3 Learning Objective 2 Describe corrective actions that were taken to prevent previoussteamgenerator 4 previous steam generator water hammer problems.
Learning Objective 3Describe the damage caused by the water hammer event atSanOnofreNuclear 5 at San Onofre Nuclear Generating Station Unit 1 (SONGS-1).
Learning Objective 4Describe how multiple check valve failures contributed to theinitiationofthewater 6 the initiation of the water hammer at SONGS-1.
Learning Objective 5Discuss how check valve testing required by the American Society of Mechanical EngineersBoilerandPressure 7 Engineers Boiler and Pressure Vessel code could haveprevented the SONGS-1 water


hammer incident.
What is Water Hammer?
Types of Water Hammer(Section 7.3.2)*Classical water hammer*Condensation induced water hammer 8 hammer*Steam Generator water hammer Classical Water Hammer Boom!9Generally a shock wave created by a moving fluid column suddenly stopping. Usually accompanied by
A pressure transient which creates fluid shock waves in piping systems due to changes in fluid velocity or pressure.
pressure 2


noise.
Learning Objective 1 Describe three types of water hammer and their causes.
Classical Water Hammer -Common Causes Boom!10Failure to properly fill and vent system before establishing flow.Sudden valve closure.
3
Condensation-induced Water HammerBegins w/ a long horizontal steam filled pipe being filled by relatively cool water (AFW).
11As the cool water begins to fill the pipe, the steam is condensed and waves are


formed.
Learning Objective 2 Describe corrective actions that were taken to prevent previous steam generator water hammer problems.
Condensation-induced Water HammerAs the water level & waves increase, a volume of steam can be trapped, where it will condense rapidly.
4
12 The collapsing steam pockets


create localized low pressure
Learning Objective 3 Describe the damage caused by the water hammer event at San Onofre Nuclear Generating Station Unit 1 (SONGS-1).
5


areas.Slugs of water accelerate towards the low pressure areas.
Learning Objective 4 Describe how multiple check valve failures contributed to the initiation of the water hammer at SONGS-1.
Condensation-induced Water Hammer Boom!13 The collapsing steam pockets create localized low pressure
6


areas.Slugs of water accelerate towards the low pressure areas.
Learning Objective 5 Discuss how check valve testing required by the American Society of Mechanical Engineers Boiler and Pressure Vessel code could have prevented the SONGS-1 water hammer incident.
S/G Water Hammer is condensation-induced water hammer in a feedwater line.Causes are generally the same.14Damage is generally in S/G feedring and its supports, the FW nozzle, and FW piping
7


snubbers & supports.
Types of Water Hammer (Section 7.3.2)
3 Modifications to prevent water hammer. (Section 7.3.1) 15 1) Installing J-tubes to prevent draining feedring.
* Classical water hammer
3 Modifications to prevent water hammer. (continued)
* Condensation induced water hammer
: 2) Shorten Horizontal runs of FW piping adjacent to S/Gs.
* Steam Generator water hammer 8
163) Limit AFW flow to avoid rapid refill of horizontal runs of FW piping.
 
SGsSONGS -1 Water Hammer (Sections 7.3.3 & 7.3.4)East MFP 17 AFWWest MFP SGsEast MFPE-MFP lost due to Aux Transformer problem.
Classical Water Hammer Boom!
18 AFWWest MFPMFP Check ValveMFP Check Valve As Found SGsEast MFP Check valve downstream of FRV was leaking too.
Generally a shock wave created by a moving fluid column suddenly stopping. Usually accompanied by noise.
19 AFWWest MFPFRV Check Valve As Found SGs Boom!East MFP Operators closed FWIS valves.
9
20 AFWWest MFP Consequence / Damage (Section 7.3.5)*Cracked feedwater pipe.*Several damaged pipe supports 21 supports.*Several damaged valves.
 
CAUSESFailure of 5 safety related check valves.Inadequatecheck 22 Inadequate check valve testing.
Classical Water Hammer -
Questions 23 24 Fig. 7.3-13 MFP Discharge Check Valve Fully Assembled 25 Fig. 7.3-13 MFP Discharge Check Valve As Found Fig. 7.3-12 Check Valve Downstream of FRV As 26 Found}}
Common Causes Boom!
Failure to properly fill and vent system before establishing flow.
Sudden valve closure.
10
 
Condensation-induced Water Hammer Begins w/ a long horizontal steam filled pipe being filled by relatively cool water (AFW).
As the cool water begins to fill the pipe, the steam is condensed and waves are formed.
11
 
Condensation-induced Water Hammer As the water level & waves increase, a volume of steam can be trapped, where it will condense rapidly.
The collapsing steam pockets create localized low pressure areas.
Slugs of water accelerate towards the low pressure areas.
12
 
Condensation-induced Water Hammer Boom!
The collapsing steam pockets create localized low pressure areas.
Slugs of water accelerate towards the low pressure areas.
13
 
S/G Water Hammer is condensation-induced water hammer in a feedwater line.
Causes are generally the same.
Damage is generally in S/G feedring and its supports, the FW nozzle, and FW piping snubbers & supports.
14
 
3 Modifications to prevent water hammer.
(Section 7.3.1)
: 1) Installing J-tubes to prevent draining feedring.
15
 
3 Modifications to prevent water hammer.
(continued)
: 2) Shorten Horizontal runs of FW piping adjacent to S/Gs.
: 3) Limit AFW flow to avoid rapid refill of horizontal runs of FW piping.
16
 
SONGS -1 Water Hammer (Sections 7.3.3 & 7.3.4)
East MFP SGs West MFP AFW 17
 
E-MFP lost due to Aux Transformer problem.
East MFP SGs West MFP AFW MFP Check Valve        MFP Check Valve As Found 18
 
Check valve downstream of FRV was leaking too.
East MFP SGs West MFP AFW FRV Check Valve As Found 19
 
Operators closed FWIS valves.
Boom!
East MFP SGs West MFP AFW 20
 
Consequence / Damage (Section 7.3.5)
* Cracked feedwater pipe.
* Several damaged pipe supports supports.
* Several damaged valves.
21
 
CAUSES Failure of 5 safety related check valves.
Inadequate check valve testing.
22
 
Questions 23
 
Fig. 7.3-13 MFP Discharge Check Valve Fully Assembled 24
 
Fig. 7.3-13 MFP Discharge Check Valve As Found 25
 
Fig. 7.3-12 Check Valve Downstream of FRV As Found 26}}

Latest revision as of 17:36, 12 November 2019

0523 - R504P - Westinghouse Advanced Technology - 07.3 - Water Hammer at San Onofre
ML11216A244
Person / Time
Site: San Onofre  Southern California Edison icon.png
Issue date: 12/12/2008
From:
NRC/HR/ADHRTD/RTTB-PWR
To:
References
Download: ML11216A244 (26)
v • d • e


Text

Water Hammer at San Onofre Section 7.3 1

What is Water Hammer?

A pressure transient which creates fluid shock waves in piping systems due to changes in fluid velocity or pressure.

pressure 2

Learning Objective 1 Describe three types of water hammer and their causes.

3

Learning Objective 2 Describe corrective actions that were taken to prevent previous steam generator water hammer problems.

4

Learning Objective 3 Describe the damage caused by the water hammer event at San Onofre Nuclear Generating Station Unit 1 (SONGS-1).

5

Learning Objective 4 Describe how multiple check valve failures contributed to the initiation of the water hammer at SONGS-1.

6

Learning Objective 5 Discuss how check valve testing required by the American Society of Mechanical Engineers Boiler and Pressure Vessel code could have prevented the SONGS-1 water hammer incident.

7

Types of Water Hammer (Section 7.3.2)

Classical Water Hammer Boom!

Generally a shock wave created by a moving fluid column suddenly stopping. Usually accompanied by noise.

9

Classical Water Hammer -

Common Causes Boom!

Failure to properly fill and vent system before establishing flow.

Sudden valve closure.

10

Condensation-induced Water Hammer Begins w/ a long horizontal steam filled pipe being filled by relatively cool water (AFW).

As the cool water begins to fill the pipe, the steam is condensed and waves are formed.

11

Condensation-induced Water Hammer As the water level & waves increase, a volume of steam can be trapped, where it will condense rapidly.

The collapsing steam pockets create localized low pressure areas.

Slugs of water accelerate towards the low pressure areas.

12

Condensation-induced Water Hammer Boom!

The collapsing steam pockets create localized low pressure areas.

Slugs of water accelerate towards the low pressure areas.

13

S/G Water Hammer is condensation-induced water hammer in a feedwater line.

Causes are generally the same.

Damage is generally in S/G feedring and its supports, the FW nozzle, and FW piping snubbers & supports.

14

3 Modifications to prevent water hammer.

(Section 7.3.1)

1) Installing J-tubes to prevent draining feedring.

15

3 Modifications to prevent water hammer.

(continued)

2) Shorten Horizontal runs of FW piping adjacent to S/Gs.
3) Limit AFW flow to avoid rapid refill of horizontal runs of FW piping.

16

SONGS -1 Water Hammer (Sections 7.3.3 & 7.3.4)

East MFP SGs West MFP AFW 17

E-MFP lost due to Aux Transformer problem.

East MFP SGs West MFP AFW MFP Check Valve MFP Check Valve As Found 18

Check valve downstream of FRV was leaking too.

East MFP SGs West MFP AFW FRV Check Valve As Found 19

Operators closed FWIS valves.

Boom!

East MFP SGs West MFP AFW 20

Consequence / Damage (Section 7.3.5)

  • Several damaged pipe supports supports.
  • Several damaged valves.

21

CAUSES Failure of 5 safety related check valves.

Inadequate check valve testing.

22

Questions 23

Fig. 7.3-13 MFP Discharge Check Valve Fully Assembled 24

Fig. 7.3-13 MFP Discharge Check Valve As Found 25

Fig. 7.3-12 Check Valve Downstream of FRV As Found 26

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