Floating Roof Stability

1
Floating Roof Stability
This presentation is provided to clarify the
issues surrounding the current budget proposal to
fund the SC-AST project Seismic Sloshing Waves.
Really the project is to do the technical work
needed to understand the behavior of floating
roofs under any load conditions including
sloshing waves. Many floating roofs exist which
do not meet the broad API 650 strength
requirements outlined in API 650 Appendices C and
H. However, the industry takes the vendor
communities word for it that they have provided
sufficient strengh to meet the standards. Many
examples and case histories show that this is not
the case. By performing this work not only with
the basic requirements provide the industry with
a tool to easily assess the strength of floating
roofs to perform as intended but the work will
provide the basis for designs needed in regions
and areas subject to seismic activity. Also
attached is the original API proposal that was
submitted to the CRE during the last meeting
cycle.
2
Pre-Read Background

• These slides will not be covered on the call but
  are provided for background in order to get all
  on the same page prior to the call

3
Is Your Facility Vulnerable
This map shows the basic regions where this work
will have the highest impact
4
Floating Roof Critical to Tank Safety

• Vaporization stopped
• Caps fire risk to rim fires (minor events)
• Reduces fire protection needs (foam, etc) to rim
  area (not tank area)
• Prevents escalation to fully involved tank and
  terminal fires
• Single most important fire and safety defense of
  all tank components

5
Floating Roof Vulnerabilities

• Floating roofs are vulnerable to
• Sinking
• Rain (In Houston, Storm Allison caused over 100
  floating roofs to sink)
• Gas (as from producing or pipeline operations)
• Corrosion
• API 650 has performance based rules which have
  proven to be inadequate

6
Why Is API 650 Inadequate

• Rules require 2 flooded compartments plus
  centerdeck and,
• 10 inches of rain in 24 hours
• Performance based rules are fine
• But nobody knows how to design to the rules
• Result is the industry depends on vendors for
  this
• There have been many suits resulting from sunk
  floating roofs
• Industry needs to have simple rules, tables and
  formulas that ensure roof is strong enough for
  this
• This information needs to be in the hands of
  industry, not just for vendors to use

7
Seismic Background

• Seismic technology changed so codes changed
• API 650 Appendix E revised accordingly
• But job is only half complete
• Seismic Committee intended to address
• Tank shell and bottom first (appendix E does
  this)
• Then Floating roof stability (this is current
  proposal)

8
Seismic Failure Modes

• Bottom separates from shell
• Shell elephant foot
• Tearing piping
• Floating roof collapse
• First 3 covered by new Appendix E (completed)
• Floating roof (yet to complete)

9
What we observed in the last major refinery
earthquake tank sloshing waves
Seismic waves cause floating roof to lose bouyancy
Seismic waves cause failure deck and floating
roof sinking
This results in full surface fire and tank
burndown
10
Ismet Turkey
11
Ismit, Turkey 1998
12
CRE Presentation

• This is where we will start on the conf call

13
Is Sloshing Wave Floating Roof Risk Real?

• Hokaido
• 4 fully involved tank fires
• 2 fully involved due to floating roof collapse
  from SWs
• 50
• Ismet Turkey
• 23 major tank fires
• 17 due to SWs
• gt50
• Anchorage
• Commingled data but many floating roofs collapsed
• API AST Leadership Committee thinks seismic work
  not complete
• API AST Leadership Committee also thinks that
  seismic sloshing is important and should be
  completed

14
Compare this project to other funded work

• Seismic has 2 major incidents (ismet and hokaido)
• Emergency venting (comparable funding)
• No incidents since about 1990
• Tank Settlement
• No incidents resulting in fires or serious
  incidents
• Support The above 2 projects not requested by
  outside institutions or companies
• Seismic Requests by Alyeska as well as PAJ with
  50 funding guarantee

15
Current CRE Plan for AST funding

• 30K for Jacking Tanks in 2006
• AST would rather spend this on seismic (25)
  because
• Jacking not ready yet (results of settlement
  still in committee for another year)
• Jacking is low impact compared to seismic
• Jacking is much lest risk than seismic

16
Business Case

• At least 25 floating roofs per year sinking in US
  alone
• About ½ are due to corrosion other half water or
  gas
• Of the half, about 1/3 are due to inadequate
  design
• This is about 4 per year sinking due to
  inadequate structural stability
• These would not sink or are preventable if the
  API Companies had simple means to evaluate
  floating roof stability
• Proposed work will result in this deliverable

17
Business Case Continued

• The lowerbound estimate for the Ismet and Hokaido
  Incidents are 100MM
• At least ½ of the floating roofs causing fires
  would not have occurred
• Cost savings from these standards would be
  roughly 30MM
• It is unknown how many fatalities occurred in
  Ismet, but some costs can be attributed to this
• By comparison, this work is at least as important
  than any other project funded in the last 5 years
  by SCAST when compared on a line basis

18
Funding Requirements

• 50 M for 2006 and 2007 (100M for 2 year
  project)
• PAJ agreed to 50 sharing of costs
• API funding is 25 for 2006 and 2007
• For 2006
• AST has 30M budgeted for tank jacking
• Cancel or defer this work and fund 2006 SSW with
  this
• Will submit budget item for 2007 to cover balance
  of work for 25M

19
Final Statement of Benefit To Cost

• Benefits
• Project has high value seismically vulnerable
  areas
• Chevron and Alyeska support this activity
• Work will result in not only adequate floating
  roofs for seismic areas
• Will result in general understanding of floating
  roofs for other load conditions (gas, rainwater,
  etc)
• Project is leveraged
• Costs
• None in 2006 (deferral of tank jacking)
• 25M in 2007