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Feedwater Systems Reliability Users Group (Jan 2014)

San Antonio, TX

Stuffing Box Design & Configurations

Presenter:

Art Washburn, P.E.

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What is going on at this House?

No Driveway, No Sidewalk…

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City of Raleigh Public Utilities Water Booster StationPumps 45 Million Gallons per Day

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Virginia Beach Pump Station (Lake House)

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Pump Station (Greek Architecture)

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Office Building?...

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Electrical Sub-Station

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DISCUSSION POINTS• Two Rules to Get You Home and Plant Priorities

• Case 1: API Plan 11 – Packing Injection Flush… Exhibits Excessive Leakage During Operation and Standby (Horizontal Multi-Stage Pump in Auxiliary Service Water Service)

• Case 2: API Plan 13 – Reverse Flush System… Exhibits No Reverse Flush (Static System), Excessive Packing Leakage, Excessive Packing Sleeve Wear and Severe Stuffing Box Bearing Damage (Vertical Pump in Screen Wash Service)

• Case 3: API Plan 13 – Reverse Flush System… Exhibits Excessive Packing Leakage (Vertical Pump in Condensate Service)

• Case 4: API Plan 13 – Reverse Flush System with Bypass Port (Water Service and Hydrocarbon Service)

• Source References

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Two Rules:

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Two Rules:

Rule #1 – Make Conservative Decisions

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Two Rules:

Rule #1 – Make Conservative Decisions

Rule #2 – Maintain Design Control

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Two Rules:

Rule #1 – Make Conservative Decisions

Rule #2 – Maintain Design Control

Plant Priorities:

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Two Rules:

Rule #1 – Make Conservative Decisions

Rule #2 – Maintain Design Control

Plant Priorities:

1. Nuclear Safety

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Two Rules:

Rule #1 – Make Conservative Decisions

Rule #2 – Maintain Design Control

Plant Priorities:

1. Nuclear Safety

2. Legal Requirements

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Two Rules:

Rule #1 – Make Conservative Decisions

Rule #2 – Maintain Design Control

Plant Priorities:

1. Nuclear Safety

2. Legal Requirements

3. Efficiency

Case 1: API Plan 11 – Packing Injection Flush (Original)

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Conditions:

Excessive Packing Leakage

- In Service

- In Standby

Case 1: Horizontal Multi-Stage Pump SectionalAux Service Water Pump

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Stg 1, 260 psi

Psuction, 30 psi

Case 1: In-Board Bearing Housing Assembly

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Conditions:

Packing Leakage Sprays Directly on Bearing Housing

Water Intrusion in Bearing Housing Displaces Approx. 50% of Oil

Case 1: Stuffing Box Configuration (Original)

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Conditions:

Lantern Ring Mis-Aligned

Inner Packing Rings - What Can You Do For Me Today?

Case 1: API Plan 11 – Injection Flush System (Original)

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Stg 1 – 260 psi

Psuction, 30 psi

Pstuff box, 260 psi

Pstuff box, 260 psi

Measured Stuffing Box Pressure

Case 1: Stuffing Box Configuration (Updated)

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Case 1: API Plan 11 – Injection Flush System

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Stg 1 – 260 psi

Psuction, 30 psi

Pstuff box, 35 psi

Pstuff box, 35 psi

Case 1: Stuffing Box Configuration (Updated)

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Case 1: Stuffing Box Configuration (Updated)

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Results:

1.Packing Sleeve Diameter, 4.000 Inches

2.Required Flush for Packing or Mechanical Seal in Water Service and Fluid Temperature Less Than 150oF (1 GPM per 1 Inch of Shaft Diameter): 5 GPM

3.Stuffing Box Pressure: Maintains Positive Pressure, Easier to Adjust Packing, Reduced Frequency of Packing Adjustments, Eliminate Risk of Packing Spray Impingement on Bearing Housing

Case 1: Stuffing Box Configuration (Updated)

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Analysis Process:

1.Simplify Equation of State to 2 Pressure Drop Devices or Less

2.Iterate Pressure Drop Determination for Both Devices to Share the Total Pressure Until a Mass Balance is Achieved (in GPM)

3. Result: Highly Predictable System Behavior

Water Intrusion – Traditional Oil Deflector vs. INPRO Deflector

See EPRI NMAC Lube Notes, November 2004, Bearing Operation with an Oil-Water Mixture

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Case 2: API Plan 13 – Reverse Flush System (Original)

Conditions: Screen Wash Pump

Pdischarge, 85 PSI

Lantern Ring, Grease Filled

Packing exposed to pump discharge pressure

Bearing, High Pressure Breakdown Device(Static, melts)

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Case 2: API Plan 13 – Reverse Flush System (Original)

Conditions:

ExcessivePacking Wear

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Case 2: API Plan 13 – Reverse Flush System (Updated)

Conditions:

Screen Wash Pump

Pdischarge, 85 PSI

Replaced Bottom Packing with Spacer (Controlled Clearance)

Lantern Ring, Leak Off Thru Tubing (Orifice) to Sump

Bearing dP, 82 PSITubing dP, 3 PSIPacking, 3 PSI

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Case 2: API Plan 13 – Reverse Flush System (Updated)

Analysis Seeks Mass Balance Thru the Bushing and Orifice:

Bushing:

Orifice:

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Case 3: API Plan 13 – Reverse Flush System (Original)

Conditions:

Condensate Pump

Excessive Packing Leakage

Pdischarge, 515 PSI

Pabove bushing, 170 PSI

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Case 3: API Plan 13 – Reverse Flush System (Original)Conditions:

Condensate Pump

Bottom Lantern Ring Significantly Blocking Plan 13 Return to Suction

Lantern Ring Annulus Area too Small – Region Under Packing Does Not Depressurize

Packing Sleeve Wear Excessive

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Case 3: API Plan 13 – Reverse Flush System (Updated)

Conditions: Condensate Pump

Bottom Lantern Ring Resized to Assure Plan 13 Return is Not Blocked

Lantern Ring Annulus Area Increased to Allow Depressurizing Region 360 Degrees Around Shaft

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Case 3: API Plan 13 – Reverse Flush System (Updated)

Conditions:

Condensate Pump

Interstage Pressure Acting on Packing Rings is Low, Gland Water Injection Maintains Positive Pressure on Packing to Prevent Air In-Leakage

Packing Leak-Off Easily Controlled and Sleeve Wear Low

Condensate Pump

Interstage Pressure Acting on Packing Rings is Low, Gland Water Injection Maintains Positive Pressure on Packing to Prevent Air In-Leakage

Packing Leak-Off Easily Controlled and Sleeve Wear Low

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Case 4: API Plan 13 – Reverse Flush System with Bypass Port(s)

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Case 4: API Plan 13 – Reverse Flush System with Bypass Port(s)

Conditions:

Bypass Port(s) may Not be Required for Water Service

Bypass Port(s) are Required for Hydrocarbon Service (Low Specific Gravity Product)

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Case 4: API Plan 13 – Reverse Flush System with Bypass Port(s)

Conditions:

Bypass Port(s) may Not be Required for Water Service

Bypass Port(s) are Required for Hydrocarbon Service (Low Specific Gravity Product)

SOURCE REFERENCES:• Centrifugal Pumps: Design & Application, Lobanoff and Ross

(practical application)• Centrifugal and Axial Flow Pumps, Stepanoff (theory)• Centrifugal Pumps, Gülich

• Vertical Turbine, Mixed Flow & Propeller Pumps, Dicmus• Centrifugal Pump Handbook, Sulzer• Pump Handbook, Karassik• Centrifugal Pump Clinic, Karassik• Centrifugal Pumps Selection & Operation, Karassik• Centrifugal Pumps, Karassik• In-Tandem 3.0 for Windows, EG&G Sealol (John Crane)• ABZ Inc, Design Flow Solutions Software

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WHO IS THIS SYSTEM ENGINEER?

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TAYLOR SMITH – Comanche Peak

THE (HAPPY) END

QUESTIONS ?

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