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Tank Talk ®Page 2

President’s Corner by Steven P. Roetter, P.E., President, Tank Industry Consultants

One of the biggestmistakes I see tank owners make is select-

ing a tank inspectionservice based on the way the inspectionis performed. For instance, it is not un-common for owners to solicit proposalsfor diving inspections on their tank. I ask owners, “Why do you want a diving in-spection?” The answer is usually, “Ican’t drain my tank.” Well, if the tank truly cannot be drained, an inspection is awaste of money because any deficienciescannot be fixed. I think what the ownersreally mean is, “The cost of product orloss of service pressures make it very

inconvenient for me to drain a tank forinspection.” While this is a valid re-sponse, it usually misses some importantanalysis.

Underwater inspections (either divingor remote operated vehicles) cannot be asthorough as drain-down inspections.Perspective is lost as the diver or vehicletravels around the tank and is able to see(or video) only a short distance. Addi-tionally, sediment stirred from the bot-tom or scraping the shell can signifi-cantly reduce visibility. I know you haveall seen crystal clear photos from under-water inspections; however, in reality,underwater photos are usually blurred bythe water and sediment in the tank.

So, what type of evaluation is best foryour specific circumstances? I recom-mend you retain the most qualified tank consultant who can assist your utility inALL phases of your tank ownership.Involve this specialist in the planning of both the evaluation of tanks and the pri-oritization of maintenance. As an owner,you are really buying information andrecommendations, not an inspection.The consultant should be able to discussthe pros and cons of different types of inspections under different conditions

and then assist you in getting the neces-sary information given the water systemsconstraints. For instance, the consultant

might suggest a drain-down inspection of an older deteriorated tank with a follow-up rafting inspection of the roof structurein order to get all the information neces-sary to plan for future maintenance. Theconsultant may also suggest that a divinginspection be performed on a differenttank because it is in better condition andyou only need to update its condition. Afirm that performs all types of inspec-tions will be more likely to give unbiasedadvice on inspection types than a firmthat only dives.

With this information, a good con-sultant will be able to assist you in priori-tizing maintenance based on availablefunding. This involves spending scarceresources where it will do the communitythe most good. You might elect to dosafety upgrades to multiple tanks in thefirst year, paint the outside of one tank and the inside of another tank in yeartwo, and paint two complete tanks inyear three. There is no rule that dictatesthat funds cannot be split among tanks.It is difficult for general consultants tohave the depth of experience or the per-spective to make these prioritization de-cisions, and a “tank inspector” doesn’thave the experience or the resources toexecute a project like this.

I heard a quote attributed to the leg-endary oil well firefighter Red Adair.During the first Gulf War when the costof his services was being debated, he wasreported to have said “If you think i t’sexpensive to hire an expert, try hiring anamateur.” How many of you rememberthe results? The fires were extinguishedin a fraction of the time that was thoughtnecessary and in the process saved mil-lions of barrels of oil and minimized theenvironmental disaster. Sometimes thecheapest ain’t the cheapest after all.

Emerging IssuesWatch for Chip Stein’s article,

A Specifier’s Perspective on Tank Paint-ing: A Review of Four Practical Issues

in the May edition of Journal of Protective Coatings and Linings.

Visit us on theWeb

TankIndustry.com

Choosing a TankEvaluation Firm

So...it’s been a while since you’ve had yourwater tank evaluated. Or maybe the coatingon the outside of the tank looks pretty bad

and you’d like to know if it needs to be re-painted. What should you look for whenselecting a firm to evaluate your tank?

AWWA M42— Steel Water-StorageTanks, the benchmark for water tank evalua-tions which has replaced D101, lists thefollowing qualifications for a tank mainte-nance engineer:• Knowledge• Effective communications skills• Climbing ability

If you compare TIC's qualifications to otherfirms you will find that we excel in each of

these areas. But in addition, there are somekey differences between our evaluations andthose provided by most firms.

• TIC's evaluation reports are easy toread and understand . The reports arein narrative format, not a fill-in-the-blank form. This allows a smooth tran-sition into the design phase withoutextensive, costly rework.

• TIC provides pertinent dimensions which allow structural calculations tobe performed (if necessary) and verifi-cation of compliance with safety, sani-

tary, and operational standards.• TIC has the coatings laboratory

tested for the three most regulatedcommon ingredients in coatings: lead,cadmium, and chromium.

• TIC provides repair and coating alter-natives specifically for the tank basedon coating condition, the environment,the existing tank condition, and futureand immediate system requirements.

• TIC includes color photos with cap-tions keyed to the appropriate observa-tions in the evaluation report for easeof reference.

• TIC provides economic factors withthe report. This allows for comparisonsof different recommended alternativesand assists in the budgeting process.

• A Registered Professional Engineeron our full-time staff will certify theevaluation report.

Contact us for more information on the tank evaluation services offered by Tank Indus-try Consultants.

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Tank Talk ® Page 3

The revision to AWWA D100 is complete andis expected to be approved by the AWWABoard at the Annual Conference in San Fran-cisco. This revision is quite extensive andaffects nearly every section of the Standard.The following summarizes the major changes.

Contractual Language EliminatedAt the direction of the Standards Council, allsections have been revised to eliminate con-tractual language such as “purchaser shall…”and “constructor shall…”

Restructuring the StandardsSeveral sections of the previous edition con-tained a mixture of requirements (i.e., mate-rial, design, welding, fabrication, erection, andinspection requirements). These requirements

have been segregated and moved to appropri-ate sections for ease of use. The previous edi-tion also contained many recommendationsthat were not considered minimum require-ments. These recommendations have beenmoved to a new Appendix A as commentary.

Title and Scope The title and scope of the standard has beenrevised to emphasize that the scope is newtanks constructed of welded carbon steel.

Anchorage DetailsAnchorage detail requirements have beenadded for anchor bolts and anchor straps. Aminimum width requirement has been addedfor butt-welded annulus plates.

Wind LoadsWind load requirements are based on ASCE 7-02. The wind stiffening requirements forshells have been revised to allow the use of theas-ordered shell thickness less the specifiedcorrosion allowance. A one-third increase inthe foundation allowable bearing stress forwind loads when specified in the geotechnicalreport is now permitted.

Allowable Local Buckling CompressionTwo new methods for determining the allow-able local buckling compressive stress for wa-

ter-filled shells have been added. These meth-ods permit an increase in the allowable stressdue to pressure stabilization. Measurement anddocumentation is required for shells usingthese methods.

Roof Rafters Roof rafters designed using a roof live load of 50 lb/ft 2 or less must be designed using allow-able stresses for A36 material, regardless of the material used. Roof rafters designed usinga roof live load greater than 50 lb/ft 2 may util-ize higher allowable stresses when using

material with minimum specified yieldstrength greater than A36 material.

Corrosion AllowanceThe thickness to which corrosion allowance isadded has been changed to the thickness deter-mined by design for elements other than bot-tom plates of flat-bottom ground tanks.

Splices in Tension-BracingThe requirement that welded splices in ten-sion-bracing for multicolumn tanks must bedesigned for 100% joint efficiency has beenclarified.

Flush-Type CleanoutsThe 1/16 in. (1.59 mm) additional shell thick-ness requirement for flush-type cleanouts hasbeen eliminated to match the current require-ments of API 650.

Communications EquipmentRecommendations for antennas and relatedcommunications equipment have been addedto Appendix A as commentary.

Section 6 Eliminated Section 6 (AWWA D100-96), entitled “Sizingof Ground-Supported Standpipes and Reser-voirs” has been deleted.

Dissimilar MetalsElectrical isolation requirements for dissimilarmetals inside the tank below the TCL havenow been included.

Welding Procedures & TestingFull-size proof test requirements for the quali-fication of welding procedure specificationsfor tension bracing splice welds to 4/3 timesthe published minimum yield strength of thebracing member have been revised.

Minimum fillet weld size requirements rela-tive to roof opening have been clarified. Amaximum roof opening requirement (3/16 in.[4.76 mm]) has been added. Seal weldingrequirements for corrosion protection are alsoclarified as are preheat requirements.

Inspection based on sectional segments

has been eliminated. Visual inspection of allwelds and new acceptance criteria are added.

Qualification of welder and productiontesting requirements have been added for ten-sion-bracing splice welds. The proof test fortension-bracing splice welds has been in-creased to 4/3 times the published minimumyield strength of the bracing material.

Seismic Design

The seismic design requirements have beenchanged extensively to align with the seismicload requirements of FEMA 450 and ASCE 7-

05 which are based on a maximum consideredearthquake ground motion for an event with a2% probability of exceedance within a 50-year

period (recurrence interval of approximately2,500 years). General and site-specific proce-dures for determining design response spectraare included. Alternate procedures for ele-vated tanks have been added and allow the useof soil-structure and fluid-structure interaction.Soil structure interaction procedures are addedfor ground storage tanks.

Vertical design acceleration requirementsare now mandatory for all tanks. The require-ment that P-delta effects be considered hasbeen added for all elevated tank styles. Acritical buckling check for pedestal type ele-vated tanks has been added to guard againstpremature buckling failure. Equations havebeen added to calculate the overturning mo-ment for mat or pile cap foundations support-ing flat-bottom tanks. Minimum freeboardrequirements similar to those of ASCE 7-05have been added for all tanks. Piping flexibil-ity requirements similar to those of ASCE 7-05 have been added for all tanks.

AppendicesA new Appendix A, “Commentary for WeldedCarbon Steel Tanks for Water Storage,” hasbeen added to provide background informationfor many of the requirements contained in thestandard.

Appendix B, “Default Checklist,” hasbeen added to highlight a few key issues thatusers of the standard may wish to evaluate todetermine if the default requirement in thestandard meets their needs.

Major Revisions to AWWA D100-05 – Welded Carbon Steel Tanks for Water StorageStephen W. Meier, P.E., S.E.

Vice President, Engineering and Technology—Chair, AWWA Steel Tank Committee

Steve Meier, TIC Vice President of Engineer-ing and Technology, chairs the AWWA SteelTank Committee which oversees the activitiesof the standards committees and revision task

forces. Steve is noted as one of the foremost structural engineering experts for the design,construction and rehabilitation of concreteand steel structures for storage systems, with

specialized expertise in seismic design.

For a schedule of tank-related committeemeetings at AWWA ACE ‘05, contact Tank Industry Consultants or log on to the AWWAwebsite at www.awwa.org and follow thelinks to ACE ‘05.

Watch for information on TIC’s up-coming seminars and presentations onthe changes in D100-05.

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Tank Talk ®Page 4

Tank Talk® is published as an informational resource for thestorage tank industry. For past issues of Tank Talk, or to learn

more about the services offered by TIC, please contact:

T ank Industry Consultants7740 West New York Street, Indianapolis, Indiana 46214

317 / 271-3100 (phone) — 317 / 271-3300 (fax)

Articles from previous issues of Tank Talk can be found on ourweb site

www.TankIndustry.com

Email: snodgrass@TankIndustry.com

Offices Nationwide

Copyright© 2005Tank Industry Consultants, Inc.

All Rights Reserved

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AWWA ACE 2005 Special Edition

See you in San Francisco

Stop by Booth # 913at the

AWWA Annual Conference and Exposition in San Franciscoand we’ll

Talk about Tanks!