Hard Chrome Plating in Feedwater Pumps Presented By

Hard Chrome Plating in Feedwater Pumps Presented By: Kurt J. Weis Rotating Equipment Repair, Inc. 2015 FSRUG

The Hard Chrome Plating Process • Prep Machining (typically 0. 004”-0. 005” per side) • Surface cleaning/polishing • “Stop-off” of surfaces that are not to be plated. • Lacquers, foils, tapes & waxes 2015 FSRUG

Chrome Plating Process Continued… • Immersion into chrome plating tank • Chromic Acid • Insoluble lead alloy anode • Part acts as the cathode • Plating rate of 0. 001” per hour 2015 FSRUG

Chrome Plating Process Continued… • Finish Grinding • Excellent dimensional control • Tolerances as tight as +/- 0. 0005” are achievable 2015 FSRUG

Hard Chrome Properties • Ultra Hard (65 -70 HRC) • High galling resistance • Excellent adhesion (>10, 000 PSI) • Adheres to a wide range of materials • Steel, Stainless Steel, Aluminum, Copper, Bronze etc. • High abrasion resistance • Corrosion resistant 2015 FSRUG

Applications in Feedwater Pumps • Dimensional restoration • Bearing journals, shaft fits, impeller bores, etc. Bearing journal damage on a high speed feedpump shaft 2015 FSRUG Damage was repaired via hard chrome plating and grinding

Proximity Probes • How do proximity probes work? 2015 FSRUG

Proximity Probes Continued… • Eddy Current Transducer • Modulations in DC voltage directly proportional to air gap distance between probe tip and shaft surface • Modulations in AC voltage directly proportional to vibration 2015 FSRUG

Material Effects on Proximity Probes • Slope of linear relationship between air gap and DC voltage is strongly material dependent • This relationship can be dramatically changed with the addition of a chromium layer 2015 FSRUG

Bently Nevada 3300 XL 8 mm proximitor 4140 vs 4140 w/ 20 mil chrome layer 30 25 20 Voltage (-V) 4140 20 mils chrome on 4140 Linear(4140) 15 Linear(20 mils chrome on 4140) 10 5 0 0 10 2015 FSRUG 20 30 40 50 Gap Distance (mils) 60 70 80 90

Case Study • In April 2011, a newly rebuilt Flowserve CHTA BFP trips upon initial startup due to high vibration readings 2015 FSRUG

Case Study Continued. . • Pump ran for approximately 4 -8 seconds before IB proximity probe registered vibrations of 4. 69 mils resulting in a trip 2015 FSRUG

Case Study Continued. . • After discussions between RER and plant engineering, proximity probe logic adjusted to subtract 2 mils to allow further readings to be taken • Hand held vibration equipment 2015 FSRUG

Case Study Continued. . • Actual vibration registered by handheld: 0. 07 -0. 08 in/s 2015 FSRUG

Case Study Continued. . • Plant records were consulted, chrome repair during previous repair was discovered • GE-Bently Nevada (vibration probe manufacturer) contacted • Custom logic provided for 410 SS w/ 0. 020” chrome layer 2015 FSRUG

How do we deal with this? • Know the exact axial location of each proximity probe • Combat this phenomenon by allowing for a relief in the shaft where chrome is not applied 2015 FSRUG

Delaval Tilt Pad Journal Bearings • Bearing design/vibration probe location makes a relief from chrome impractical 2015 FSRUG

Custom Logic • If incorporation of a shaft relief is not possible, contact your proximity probe supplier, as custom logic programing is available that will account for the chrome layer 2015 FSRUG

Questions? 2015 FSRUG