TIL 1213 R1

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BACKGROUND DISCUSSIONSpiral wound gaskets are used in many gas turbinepiping systems on raised-face and flat-faced flanges.Proper flange bolt tightening is required for uniformcompression and proper gasket function. However, insome cases achieving consistent gasket compressionhas proven difficult in practice during installation andmaintenance.Recently several field incidents have identified issues atflanged joints using spiral wound Style CG gaskets (seefigure 1). These issues may have been caused by any ofthe following:

• Incorrect installation and tightening procedures forflange bolts.

• Lack of pressure / leak testing of entire pipingsystems after periodic maintenance on any area ofthe specific system.

• Use of spiral wound gaskets not manufactured bythe Flexitallic* Group, Inc.

• Piping distortion caused by welding of the piping,mis-handling of the skid, or shipping conditions.

• Distortion of the skid from improper setting on thefoundation.

• Improper flange loading due to spring hanger mis-adjustment.

• Mis-handling of the gasket prior to installing.

Figure 1: Flexitallic* CG gasket Illustration

Incorrect installation and tightening procedures will beevident by:

• Flange leaks.

• The inner diameter of unevenly compressedgaskets "peaking" at the spiral resulting in thewinding protruding into the flow path.

• Distortion of the backing ring with accompanyingdistress to the spiral.

• Liberation of spiral windings.

If the Style CG gasket is non-uniformly loaded, or notcentered in the piping bore the spiral windings maybecome damaged, unravel and liberate.

By using Style CGI gaskets (see Figure 2), the chance ofthe gasket unraveling is greatly reduced.

Style CGIFigure 2: Flexitallic* CGI gasket Illustration

Engineering has reviewed sealing techniques and a riskanalysis has revealed Style CG gasket failures canresult in operational problems, delays and unnecessarycost.

In an effort to improve equipment reliability andminimize the consequences of improper gasketinstallation, GE has decided to implement the use ofStyle CGI gaskets in place of the Style CG. The risk ofnot upgrading increases the chances of gasket windingand filler material entering the combustion system andother components if the gaskets are not installedproperly.Style CG

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RECOMMENDATIONSTo reduce the potential for problems with flangedconnections using spiral wound gaskets, the followingrecommendations should be incorporated into normalperiodic maintenance and installation routines.

1. Installation and tightening procedure for spiralwound metal gaskets:

• If a hammer, crowbar, or any type of pincherbar is required to remove or install the bolts,with the flanges against the gasket, theflanges are out of alignment tolerance. Checkangularity of flange faces. Total gapmeasurement is not to vary more than 1/8-inch. Flange faces should not spring openmore than 1/4-inch.

• Clean flange surfaces and upgrade to a newFlexitallic* brand Style CGI gasket. Ensure thegasket is properly centered within the flange.

• Install bolts with anti-seize compound (GE part287A1397) on threads and seating surfacesand run up all bolts until seating surfaces arein light contact (snug tight).

• Tighten bolts to less than 30% of the finaltorque value utilizing proper tighteningsequence. Refer to the torque value table inthe Inspection and Maintenance Manualprovided with your gas turbine. If more than30% of the final torque value is initially applied,the spiral may experience serious damage thatcannot be offset by subsequent tightening.

• Complete the torquing sequence in two moresteps using a pattern of alternating oppositebolts. Finally, make a final tightening in aclockwise direction at the final torque again.

• Mark flanges to show the tightening procedurehas been accomplished.

2. Pressure / leak testing of system piping (ReferenceMLI 0204):

• Flanged connections can loosen as a functionof time, temperature and vibration. Users areencouraged to pressure / leak test the entireon-base piping system after installation ormaintenance on any area of the specificsystem. Leak tests could include use air ornitrogen (or other inert gas).

• Leak checks, especially on fuel gas flanges,should include taping around the flanges withmasking tape. A small hole can be poked inthe tape at a convenient location for leaktesting. Using a soap bubble solution or othermethod, check for leaks.

• Another indication of leaking flanges is thefailure of the system to hold pressure duringthe test.

• When replacing gaskets either afterdisassembly of any piping system, or afterperforming a system leak check, ensure thatonly Flexitallic* spiral wound Style CGI or ZG

gaskets (see Figure 3) are used asreplacements.

The gasket changing should take place during aplanned outage and should not affect outage duration.Customers have the option of upgrading to Style CGI gaskets immediately or just replace unit spares withStyle CGI gaskets when Style CG gaskets are depleted.It is recommended that Style CGI gaskets be used onpiping joints 2 inches and greater in diameter. For pipeflanges smaller than this, ZG serrated gaskets arerecommended due to Style CGI inner gasket diameterbeing smaller than the bore of the pipe.

The recommended steps are:

• Identify gaskets that need ordering

• Order the replacement Style CGI gaskets

• Communicate proper gasket installationprocedures to the installation/maintenancelabor

Figure 3: ZG Serrated gaskets

ZG Serrated gasket

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By implementing this gasket upgrade, there will be areduced chance of incorrect flange tightening causinggasket failure. This should result in fewer opportunitiesof internal piping contamination. These defects cancause serious operational problems, such as exhaustspreads. The upgraded gaskets are also less likely tobe damaged by handling prior to installation.

PLANNING INFORMATION

Compliance• Compliance Category: M • Timing Code:7

Manpower SkillsNo special manpower skills are needed. Gasketinstallers should be fully educated on proper handlingand torquing methods.

PartsCGI gaskets: N5606ZG Serrated Gaskets 372A1159Flexitallic* is the only authorized supplier for spiralwound gaskets.

Special ToolingNone

Reference DocumentsMLI 0204Applied Piping Practice 351A3700 (Please consult withyour local GE I&FS Service Manager or ContractPerformance Manager if you need a copy of this

document)

Previous ModificationsNone

Scope of WorkThere no additional man-hours needed.

Contact your local GE I&FS Service Manager orContract Performance Manager for assistance or foradditional information.

NOTE: If you would like to receive future TILs by email,

contact your local GE I&FS Service Manager or ContractPerformance Manager for assistance.

* Flexitallic is a registered trademark of The Flexitallic Group, Inc.,which is not affiliated with the General Electric Company.

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TIL COMPLIANCE RECORDCompliance with this TIL must be entered in local records. GE requests that the customer notify GE upon compliance ofthis TIL.

Complete the following TIL Compliance Record and FAX it to:

TIL ComplianceFAX: (678) 844-3451Toll free FAX: 1-888-896-TILS (1-888-896-8457)

TIL COMPLIANCE RECORD For Internal Records Only #

Site Name: Customer Name:Customer Contact Information GE Contact InformationContact Name: Contact Name:Address: Address:

Email: Email:Phone: Phone:FAX: FAX:Turbine Serial Number(s):

INSTALLED EQUIPMENT TIL Completed Date:

100% TIL Completed:Description:

Unit Numbers: Part Description: Part Number MLI Number

Comments:

NOTE: If there are any redlined drawings that pertain to this TIL implementation, please FAX the drawings along withthis TIL Compliance Record.

FAX this form to: TIL ComplianceFAX: (678) 844-3451Toll free FAX: 1-888-896-TILS (1-888-896-8457)

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USER SATISFACTION SURVEYGE values your opinions and comments.

GE requests that you complete the User Satisfaction Survey below to help us better serve you with accurate and timelyinformation on your equipment.

Complete the following TIL Compliance Record and FAX it to:

TIL SurveyGE Product ServiceFAX: (678) 844-6737Toll free FAX: 1-866-604-2668

USER SATISFACTION SURVEY

Serial Number: Date:

1. How many days after TIL issue date did you receive this TIL?

1 - 5 days 6 - 10 days + 10 daysNOTE: If you would like to receive future TILs by email, contact your local GE Energy Services representative for assistance.

Rate the following based on a scale of 1 to 5, where 1 is Excellent and 5 is Poor.

2. Please rate how well this document informed you of the technical issue.

1 2 3 4 5

3. Please rate the overall effectiveness of this TIL.

1 2 3 4 5

Comments / Suggestions:

FAX this form to: TIL SurveyGE Product ServiceFAX: (678) 844-6737Toll free FAX: 1-866-604-2668

TIL 1213 R1

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