HomeMy WebLinkAbout07.a. (Handout) Declare emergency re DAF tank malfunctionItem Ta
April 19, 2013
DAF Tank No. 1 Failure
Craig Mizutani, P.E.
Senior Engineer
May 2, 2013
Central Contra Costa Sanitary District
DAF Tank Failure
• Friday, April 19, during Graveyard Shift,
Operations notes that DAF drive unit turning but
the collector arms were not.
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1
DAF Tank Failure
DAF tank drained by 10:00 AM, found all 6
collector arms broken from
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DAF Tank Failure
• Significant damage to baffle and beach.
K,
DAF Tank Failure
• Operations immediately began feeding
polymer to WAS feed to remaining 2 DAF
Tanks.
• Vendor contacted at 6:30 PM to arrange
site inspection.
Marc
Inspection April 22, 2013
• Steve Olson of Case /Cotter Inc. -
Recommendations:
- Repair or replace 6 collector arms
- Repair beach
- Repair baffle
- Entire track likely to be corroded - replace
entire track
- Restore coating
- Corrosion noted on structural steel
- Check other tanks
D
3
Cause of Failure
• Track thinned due to
corrosion and wear
• Track failed (cracked)
and damaged roller
• Arm caught on baffle
and distorted baffle
• Remaining arms then
failed when rollers hit
distorted baffle section
9!. 41or
Recommended Repairs
• DAF Tank Repairs
- Repair damaged baffle section
- All new track
- Beach skirt repair
- New clutches (lower trip torque)
• Tests
- Test clutch and trip on DAF Tanks Nos. 2 and 3
- Torque test on DAF Tank No. I
REPAIRS
• District
- Cutout existing track
- Modify drive for new clutch
• Case /Cotter
- Supply new collector arms
- Onsite startup assistance
- Torque test
• D.W. Nicholson (TP Piping Renovations Project)
- Install new arms
- Welding of baffle, track, and other components
- Coating
D
SCHEDULE
• Cut existing track out - completed
• Repair baff le and install new track -
5/6/13
• Coating of repaired areas 5/10/13
• New arms arrive by 5/20/13
• Startup one week from arrival of arms,
5/27/13 or earlier
5
FUTURE WORK
• Coating of DAF Tank No. 1 structural steel
• Inspect DAF Tank Nos. 2 and 3
- Perform recommended repairs on DAF Tank
Nos. 2 and 3, i.e. track and coating
- Test drive torque cutout on DAF Tank Nos. 2
and 3
TA, MIN
EMERGENCY
• Can't process secondary sludge with only 1
DAF Tank
• Other tanks are of same age (26 years) and
will be inspected
• Polymer costs are $500 per day
• Risk violation if other DAF Tank fails
X.,
STAFF RECOMMENDATION
Declare an emergency and ratify the
General Manager's actions to direct
Case /Cotter Inc., D.W. Nicholson
Corporation, and District forces to perform
emergency repairs on damaged DAF Tank