GRV Piping failure, Hypochlorite 2000ppm

Published on by in Maintenance

I experienced a GRV (200dia )pipe burst incident on the hypochlorite dosing line to the intake bay for seawater desalination ( hypochlorite 2000 ppm is produced in-house via our electrochlorination plant).

The failure has been attributed to a combination of  chemical degradation  and  calcareous scaling , both of which have severely compromised the integrity of the GRV (Glass Reinforced Vinyl Ester) piping system. (the system is operational for 2 decades)

I am currently conducting a root cause (RC) analysis.

Initial findings have identified the following primary failure mechanisms:

Secondary contributing factors include:

Internal calcareous scaling damaged the pipe’s vinyl ester coating, leaving the underlying fibers exposed and prone to cracking and subsequent pipe failure.

I am seeking effective strategies to improve the integrity of the hypochlorite piping system and mitigate chemical degradation, calcareous, and salt scaling issues. Also, any other economicle and best solutions.

QAK
(qusrooATgmail)


 

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3 Answers

  1. Answer from Open AI, CHatGPT 4.0: 

    Given the age of your GRV (Glass Reinforced Vinyl Ester) piping system (since 2004) and the harsh service conditions (2000 ppm hypochlorite, thermal stress, and scaling from seawater), the failure you're observing is consistent with long-term exposure to oxidative and scaling stress. Below are strategic recommendations divided into short-term mitigation , medium-term upgrades , and long-term redesign , each with a focus on economy and practicality.

    🔍 Root Cause Context Summary

    Your findings are technically sound:

    • Primary mechanisms : Oxidative degradation, resin breakdown, fiber exposure, and structural cracking.

    • Secondary contributors : Scaling (internal & external), flow abrasion, pipe supports, thermal aging.

    ✅ Short-Term Mitigation Strategies

    1. Scale Inhibitor Dosing

    • Use polyphosphates or organophosphonates (like HEDP or PBTC) upstream to reduce calcium and magnesium precipitation.

    • Apply antiscalants specifically rated for hypochlorite and electrochlorination brine circuits.

    2. Internal Pipe Cleaning & Flushing

    • Perform periodic pigging or high-pressure flushing using acid (citric or HCl at controlled concentrations) to remove scale layers without damaging pipe resin.

    • Avoid mechanical scraping — it worsens fiber exposure.

    3. Lower Hypochlorite Concentration at Point of Contact

    • Dilute hypochlorite closer to dosing point to reduce aggressive oxidative degradation in the upstream piping.

    • Implement injection quills or dilution rings at the discharge manifold.

    4. UV Shielding & Pipe Wraps

    • Apply external UV-protective coatings or wraps to exposed sections. UV exacerbates resin degradation over time.

    • Consider elastomeric external wraps that help resist environmental aging.

    🛠️ Medium-Term Upgrade Options

    5. Replace Aged Sections with Upgraded Materials

    • GRV is vulnerable to long-term hypochlorite exposure.

    • Consider replacements in critical zones using:

      • HDPE with UV-stabilized and chemically resistant grades

      • CPVC (Chlorinated Polyvinyl Chloride) — excellent hypochlorite resistance up to 90°C

      • PP-RCT (Polypropylene Random Copolymer) — resists chlorine better than GRV

      • Dual-laminate pipes — vinyl ester resin inner layer with thermoplastic liner (PVDF, ECTFE)

    6. Recoat Internals with Chlorine-Resistant Liners

    • Apply spray-on fluoropolymer linings or chlorinated rubber coatings inside the pipe where GRV degradation is superficial.

    • May extend life by 3–5 years before full replacement is needed.

    🧠 Long-Term Recommendations

    7. Switch to Full HDPE or Dual Laminate System

    • Modern desalination plants increasingly use HDPE piping for hypochlorite lines , with butt-fusion joints and no resin-fiber matrix to degrade.

    • Dual-laminate (thermoplastic + resin) systems also perform well over 20+ years in similar environments.

    8. Redesign Pipe Supports and Expansion Loops

    • Poor support accelerates stress cracking in GRV.

    • Add adequate support spacing (based on manufacturer specs) and expansion loops to accommodate thermal movement.

    9. Introduce Redundancy or Bypass Lines

    • In case of pipe failures, bypasses reduce downtime.

    • Install bypass loop with isolation valves for high-risk segments.

    ⚠️ Warning on Continuing with GRV

    Vinyl ester-based GRV, even when well-formulated, is not the best long-term choice for hypochlorite >1000 ppm over 20+ years. You're well beyond typical service life (10–15 years), and failure likelihood will continue rising exponentially.

    🔄 Maintenance & Monitoring

    • Implement thickness gauging and fiber exposure monitoring using ultrasound or portable scanners.

    • Log corrosion and abrasion rates quarterly.

    • Use condition-based maintenance instead of time-based only.

  3. I would recommend PVC-C or PVDF for2000 ppm Hypochlorite,  It's more resistent. Check it in corrosion lists. GF, AGRU or Simona ASAHI. May you have a second pipe and change weekly and flush the standby with water.

    1 Comment

    1. Thank you for your response. Could you please provide further insights on this matter?
      The plant has been operational since 2004, and replacing all the piping at once would significantly impact operations and is not in the best interest of business continuity.

      I am seeking additional insights or references regarding preventive maintenance strategies for GRV pipes and effective approaches for condition monitoring.