CRH Hammering

8/10/2019 CRH Hammering

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1 X 500 MW, SGTPS, BIRSINGHPUR

REPORT

ON

CRH LINE HAMMERING

Planned Shutdown of unit was taken on 19/09/2008 at 23:31 hours to attend the problem ofNMEJ.

After attending the problem of NMEJ boiler was lighted up on 21/09/2008 at 17:53 hours.

On 21/09/2008 at 21:39 hours Drum Press=40ksc, MS Temp=287.7 Deg.C, HPBP warm upvalves were opened.

On 21/09/2008 at 21:44 hours HPBP valves (BP-1 & BP-2) were opened (first 5% then

10%, and then 15%). LPBP was in Auto and Auto Controller Interface was ON.

On analysis it was found that HPBP temperature set point was 0.0 Deg.C and HPBP pressureset point 48.2 KSC.

At 21:44 hrs both Spray valves (BPE-1 & BPE-2) went to Auto (since BP-1 & BP-2 wereopened by operator) and opened 100%. These valves remained at 100% for about 25 minuteswith BP-1 & BP-2 opened 5%-10%.

This has happened because temperature set point was 0.0 Deg.C. However this

remained unnoticed and there was heavy water ingress into CRH line.

At 22:09 hrs hammering sound heard from CRH line for about 10 minutes.

Boiler was hand tripped at 22:36 hrs

On inspection of CRH line, it was found that line had moved down by about 100mm.

Various supports on CRH line were twisted and broken or disturbed from their positions.

From Trend summary following data were noted down.

Date Time HPBP spray Tempset point

Remarks

20/09/2008 12:10 hrs 280 Deg.C

20/09/2008 12:12 hrs 0.0 Deg.C

21/09/2008 21:43 hrs 0.0 Deg.C

21/09/2008 21:44 hrs 0.0 Deg.C HPBP(BP-1& BP-2)

opened

21/09/2008 21:46 hrs HPBP (BPE-1 &

BPE-2) 98% Open

21/09/2008 22:09 hrs HPBP (BPE-1 &BPE-2) 98% Open

21/09/2008 22:09 hrs CRH line

hammering


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Special Notes:-

BHEL personnel had analyzed the trend data on 21/09/2008 at 22:30 hours

and taken printouts of trends at the time of hammering.However, on 22/09/2008 at 09:30 hours it was surprisingly found that all

trend data for the period 20/09/2008 (23:40 hrs) to 22/09/2008 (01:40 hrs)

was deleted. Therefore, above referred trends, which had been fortunately

saved earlier by BHEL personnel are now not available in system. This

indicates the intention (of customer) to hide essential data and impede

later analysis.

List of Damaged supports (first observation)

1.

CRH NRV line support at 0 M 02 nos hangers/ supports damaged.

2. CRH to HPH# 6A supports broken

3. CRH to HPH # 6A line found bent.4.

CRH to D/A pegging steam line hangers and supports broken

5.

CRH Line inlet to Reheater at 51 M line support twisted

6. CRH line drain pot drain line to Steam drain flash tank support broken7.

Cantilever beam (from Column No. 59) for HRH line support is sheared from

Column.

8. HPBP to CRH line support trunion broken.

9. MS to HPBP support channel bent. (C-D bay)

10.

At 8.5 M vertical line hanger support beam bent (CRH line).11.At 27 M Main Steam line trunion support beam bent (CD bay).

12.At 25 M, CRH line horizontal trunion after Y-piece, support column bent andtwisted

13.

CRH line (left) before Y-piece displaced forward at 35.0 M CD bay.

14.CRH vertical trunion below MS line (right side) at 70 M, support beam bent.


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Picture 1: Hammering sound heard from CRH at this moment


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Picture 2: Bypass spray valve were in full opened, unnoticed for

about 25 minutes


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Picture 3: HPBP temp set point was 0.0 Deg.C


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Picture 4: All trend data were surprisingly found deleted later.


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Photographs of some damaged supports

Photo 1: CRH TO D/A pegging steam line moved downward


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Photo 2: CRH TO D/A pegging steam line spring support broken and

fell down


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Photo 3: CRH to HPH 6A and 6B line support broken and line is bent


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Photo 4: CRH to reheater inlet line support at 51 M twisted

Documents

CRH Hammering