ONE‐FOR‐ONE CONDENSER RETUBING

Kevin Squires, Sr. Project Coordinator – Day & Zimmermann (Condenser Services)

October 11, 2017 • Diplomat Resort and Spa • Hollywood, Florida, USA

ONE‐FOR‐ONE CONDENSER RETUBING

With Titanium Alloy Tubing



Presentation Outline

• Considerations for Retubing• Why Retube with Titanium?• Titanium Tubing Requirements• Project Planning / Planning for “Murphy”• Vibration and Uplift Analyses

• Vibration Resolution• Uplift Consideration

• Pullout Testing• Serrations• Cathodic Protection Considerations• Steps for a Retubing

Successfully performing a condenser retubing with new titanium tubes requires advanced planning, extensive expertise in condenser design and operation, and superb project execution.



Considerations for Retubing Your Condenser

10% or more of the total amount of tubes are either plugged and/or have failed

Severe wall loss

Existing tube material leaches out onto components (turbine, feedwater heaters, etc.) or deposits unacceptable chemicals into cooling water source, harmful to ecosystem



Why Retube with Titanium?

Immune to:• Contaminants from cooling water

• Chloride attack• Under deposit pitting



Why Retube with Titanium?

Improved Tooling & Field Processes Ensure:• Successful expansion of thin‐walled material• Enhanced tube‐to‐tubesheet joint strength• Vibration Resolution



Project Planning

Considerations – when retubing with Titanium, include the following:

Pullout Test Tubesheet Serrations

Vibration & Uplift

Analyses

Tubesheet Replacement

Cathodic Protection Analysis

Coating Tubesheets & Waterboxes



Project Planning

Project Duration – on average, most condenser retubingsrequire approximately 4 to 6 weeks to complete; however, the duration of the project depends upon many factors:

Number and length of tubes

Analyses to be performed

Presence of plugs, inserts, stakes, and/or

coating on tubesheets/waterboxes

Complexity / amount of interferences requiring

removalAccess to work area Anticipated major

repairs needed



Project PlanningPreparation of Work Scope / RFQ:

Determine the scope of work and schedule/time available to perform retubing

Outline who will be responsible for providing what services, materials, tooling and equipment, etc., which should include (as a minimum):

Replacement tubes (lead times can be extensive)

Training / Backgrounds / Drug Testing

Interference Removal / Reinstallation

Scaffolding (provide, erect/adjust/dismantle)

Replacement nuts, bolts, gaskets, Circ water expansion joints

Lifting beam / off-loading /staging new tubes

On-site Utilities (electric, air,water)

On-site Facilities / LaydownAreas

Confined space program Overhead crane (if applicable) Lifting beam Scrap tube containers/disposal



Project Planning

Preparation of Work Scope / RFQ:

Conduct pre-bid meeting and site walk down with all bidders present

Review bids, check references, and select contractor

Issue specification to qualified contractors at least 6-12 months before work is to be performed



Project Planning

• Distortion• Misalignment• Damage• Corrosion• Erosion• Dezincification• Warpage

Tubesheetand/or Support Plate:

Anticipating Issues (Known Unknowns & Unknown Unknowns) – There are a number of common issues which can arise during a retubing that may or may not be known during the planning stages:



Project Planning

• Connections• Baffles• Perforated Pipes• Impingement Plates / Tubing

Internal Damage:

Anticipating Issues (Known Unknowns & Unknown Unknowns) – Continued:



Project Planning

•Ammonia Attack•Excessive Cutouts

Other Conditions:

Anticipating Issues (Known Unknowns & Unknown Unknowns) – Continued:



Vibration and Uplift Analysis

When changing existing tube material to titanium, which is a lighter weight and generally a thinner wall thickness, the following analyses are recommended.

Uplift analysis is performed to determine if modifications are required in the anchoring areas

Vibration analysis is performed to determine whether or not the existing support plate spacing (taking into consideration the new condenser tube material) exceeds the maximum allowable spacing in accordance with HEI standards.



Tube Vibration Resolution

Modern methods of tube vibration resolution:

• In 1978, HEI releases new edition of standards significantly expanding on the design and manufacture of steam surface condensers

• Included limitations on the allowable distance between support plates

• Specified a calculation model for predicting vibration which became the industry accepted standard for vibration calculation

• Conner’s Equation is another widely accepted model

Specific condenser configurations require stakes of different designs



Tube Vibration ResolutionCradle‐Lock® Anti‐Vibration Tubes Stakes: If vibration or the potential for vibration is an issue, Cradle‐Lock® stakes are the industry’s standard for vibration resolution.

Patented design cradles tubes midway between support plates, locking the tubes into a vibration-free unit

Cradle-Lock® eliminates the need to rebundle when that is deemed the solution to vibration problems



Tube Vibration Resolution

Sample Staking Plan (Modern Approach/Complex)

Detailed plan needs to be prepared showing the location of stakes

Each stake should be identified by size, style, or other parameter

Potential interferences should be considered for stake locations

Identify any areas that must be staked before tube installation can proceed



Uplift AnalysisConsiderations

• Condensers experience an upward force due to the vacuum created in the condenser.

• It is possible that too much weight has been removed and additional restraints need to be added to ensure the condenser will not move relative to the many attachments found on most condensers.

• If on springs, adjustments are generally needed

• If on feet, additional anchors may needed

With installation of thinner and lighter tubes, analysis is required to potential effects with vacuum uplift of the condenser.



Uplift AnalysisTypical Considerations (Sample) – In this instance, the springs will need to be decompressed by an amount equal to the difference in condenser weight.

Uplift Analysis Spring Adjustments

Aluminum Brass –17BWG

90‐10 Copper Nickel ‐20BWG

Titanium Grade 2 –22BWG

Original Compressed Spring Length

“A” Supports ‐‐‐ 18.609″“B” Supports ‐‐‐ 18.016″

Reduced Operating Weight Base 118,102 lbs 263,460 lbs

Overall Spring Rate 294,400 lbs per inch

Spring Adjustment 0 +0.401″ +0.896″

Adjusted Compressed Spring Length – “A” 18.609″ 19.01″ 19.505″

Adjusted Compressed Spring Length – “B” 18.016″ 18.417″ 18.912″



Pullout Test

Critical to ensure optimum tube-to-tubesheet joint strength is obtained during tube expansion

Testing designed specifically for each application in order to mimic field conditions.

Customer participation is encouraged.



Pullout Test

Test results provide valuable data such as:

How serrations affect tube pull out strength

Which torque value will provide optimal tube‐to‐tubesheet seal during tube expansion

Average wall reduction

Tube pull out strength under a range of loads



Pullout TestPullout Test Data – Original v. Retubed Condenser – Allowable Loads

Original Condenser Retubed Condenser

Tubing

Original Basis with 90/10 CuNi Tubes,

Lmax

Tubing

Test Loads with Gr. 2 Titanium Tubes

Allowable Design Load, Lmax, lbs.

Ratio of Test Loads to

Original Basis

Ratio of Retubed Allowable Loads to Original Allowable Loads

19 BWG, 90/10 Cu/Ni

Inlet924 lbs.

22 BWG, Ti, Inlet

3036 lbs. 1263 lbs. 3.3 1.4

20 BWG, Ti, Inlet

3120 lbs. 1298 lbs. 3.0 1.6

19 BWG, 90/10 Cu/Ni

Outlet

1102 lbs.22 BWG, Ti,

Outlet2935 lbs. 1221 lbs. 2.7 1.1

20 BWG, Ti,Outlet

3032 lbs. 1261 lbs. 2.4 1.1



Pullout Test

Summary of Recommendations – Sample

Summary of Recommendations – Main Bundle and Peripheral Tubes

Location and Gauge

Rolling Torque, in‐lbs.

Expected AWR AWR Limits Joint Strength, lbs.

22 BWG Inlets 72 23.3 % 19.3 – 27.3 % 3036

20 BWG Inlets 72 23.5 % 19.5 – 27.5 % 3120

22 BWG Outlets 75 21.4 % 17.4 – 25.4 % 2935

20 BWG Outlets 75 19.2 % 15.2 – 23.2 % 3032



Serrating

Through the expansion process, the tube material is forced into each serration, providing additional barriers against tube‐to‐tubesheet leakage & superior pullout strength.

Installed in plain holesCan be positioned over OEM‐installed single or

double grooves



SerratingSerrations are

created by using special cutting bits

Bits include a flat section between the 4th & 5th tooth

to ensure accuracy when measuring

benchmark holes.



Serrating

Serrated Hole

Tube after being pushed out



Considerations for Cathodic Protection

Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. There are two common methods used today to prevent corrosion:

Galvanic System ‐ this takes the form of galvanic anodes, which are more active than the steel structure. This practice is also referred to as a sacrificial system, since the galvanic anodes—typically zinc or aluminum—sacrifice themselves to protect the structural steel from corrosion.

Impressed Current System (ICCP) - Due to the high currents involved in many seawater systems, an impressed‐current system may be used. This consists of anodes connected to a DC power source, often a transformer‐rectifier connected to AC power.



Coating of Tubesheets and WaterboxesThe standard method of coating is to apply a thick film of epoxy coating (approximately 250 mils). Reasons to consider tubesheetcoatings may include:

Coating the waterboxes may also be done to eliminate and prevent future damage as well as for restoration purposes

Dissimilar metal combinations

Used in combination or lieu of traditional cathodic protection (sacrificial anodes)

Restore lost material due to severe damage



Steps for Condenser Retubing

Typical Major Retubing Activities:Remove interferences

Remove waterboxes or waterbox covers (usually one end only)

Cut tubes on opposite end from “long” pulling

Remove tubes using specialty equipment; tubes are flattened and chopped into 4" to 6" piecesClean support plates and tubesheets as well as condenser internals

Serrate tubesheets (if required)



Steps for Condenser Retubing

Typical Major Retubing Activities (Cont):

Install tubes

Stake tubes (if required)

Expand tubes

Trim, flare and/or lip tubes (as required)

Steam side hydrostatic test

Coat tubesheets and/or waterboxes (if required)

Circulating system hydrostatic test



Waterbox Removal



Tubesheet Array/Design



Tube Removal



Tube Chopper



Tubesheet Replacement / QA Marking



Staging New Tube Boxes



Preparation for New Tube Installation



New Tube Installation



Tube Expansion



Installation of Anti‐Vibration Tube Stakes



Conclusion

With proper planning in advance of the project, the selection of a qualified retubing contractor, and performing the required/recommended analyses and testing, your retubing project can be completed with minimal setbacks, on time in accordance with the project schedule, and maintain budgeting forecasts.



Questions?

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ONE‐FOR‐ONE CONDENSER RETUBING