🧿1. Treatment Methods for Leaking DN500 Stainless Steel Purified Water Pipe Elbows

The treatment process should adhere to the principles of safety, compliance, and efficiency, especially ensuring that the repair process does not affect the water quality of the entire purified water system.

Step 1: Emergency Response and Assessment

1. Safety First: Immediately set up warning signs to prevent slips. If the leak is near electrical equipment, take protective measures or disconnect the power supply.

2. Assess the Leakage Extent: Determine whether it is dripping, spraying, or seeping. Collect the water in a clean container to prevent it from spreading to critical areas.

3. Report and Isolate: Immediately notify the equipment department and quality management team. Quickly identify and close the inlet and outlet valves of the relevant pipe section, and drain and depressurize the system if necessary. A "Maintenance in Progress, Do Not Operate" lockout sign must be displayed.

Step 2: Cause Analysis (Critical Step)

Before repairs begin, a preliminary assessment of the leak's cause is essential. This will determine the subsequent repair plan and preventive measures.

Weld cracking: The most common cause may be due to poor welding quality, unrelieved pipe stress, water hammer, or vibration fatigue.
Pitting corrosion perforation: Commonly found in the heat-affected zone of the weld or where the passive layer has been damaged, caused by contaminants such as Cl- ions.
Mechanical damage: Accidental bumps during installation or maintenance.
Material or manufacturing defects: Sand holes or cracks in the elbow itself.

Step 3: Repair Plan Selection and Implementation

For large-diameter pipes such as DN500 (500mm diameter), there are two main repair options:

Option A: Use a stainless steel emergency repair joint

This is the fastest and most common method. See Section 3 for advantages.

1. Preparation: Ensure the pipeline is depressurized and drained. Thoroughly clean the area around the leak with a sterile clean cloth (such as lint-free tissue) and purified water or water for injection (if the system allows) to remove dirt and impurities.

2. Selecting a Repair Fitting: Choose a DN500 food-grade/sanitary stainless steel repair fitting with a sealing ring made of FDA-compliant materials such as EPDM or silicone.
3. Installation:
Snap the two halves of the repair fitting together at the leak site, ensuring the sealing ring is aligned with the leak.
Tighten the bolts evenly and symmetrically until the leak stops. Avoid overtightening individual bolts, as this may deform the repair fitting or cause uneven sealing.

Option B: Welding Repair (Permanent Solution, but with High Requirements)

Suitable for workshops with available facilities, but strict control is required.

1. System Treatment: The entire subsystem or related piping must be completely evacuated and purged with high-purity nitrogen to ensure that the piping is free of water and flammable or explosive gases. This is an absolute prerequisite for safe welding.
2. Welding Preparation: Performed by a certified welder using an automatic orbital welder. Grind and clean the area around the leak to remove oxide layers and contaminants.

3. Welding Operation: Perform GTAW welding (GTAW) to ensure adequate argon shielding (back protection) on the inner wall to prevent oxidation within the weld, which can lead to future corrosion and microbial growth.
4. Post-weld Treatment: After welding, an endoscope inspection must be performed to ensure the inner surface of the weld is smooth and flat, free of pits. Acid pickling and passivation should then be performed again to restore corrosion resistance.

🧿II. Maintenance Considerations for Purified Water Stainless Steel Pipes

1. GMP Compliance is Paramount:

Change Control: Any permanent repair (especially welding) must be subject to a change control procedure.

Deviation Handling: A leak incident itself is a deviation and must be documented, investigated, and approved according to the deviation handling process.

Complete Records: The entire repair process (time, personnel, methods, materials, parameters, etc.) must be recorded in detail and included in the equipment documentation.
2. Microbiological and Contamination Control:

Environmental Requirements: Repair operations should be performed in the cleanest possible environment to prevent the entry of external contaminants into the system. Material Compatibility: All repair materials that come into contact with purified water (such as seals in the repair section) must be biocompatible, non-detachable, non-dissolving, and able to withstand the high temperatures of Sanitary-in-Place (SIP).
Avoiding Dead Spots: Welded repairs must ensure smooth internal surfaces, free of cracks, incomplete welds, and other defects that can serve as breeding grounds for microbial growth. Repair sections themselves can introduce minor dead spots, which must be noted in the records.
3. System Restoration and Verification:
Flushing and Disinfection: After repairs are completed, the repaired section and affected areas must be thoroughly flushed and then pasteurized or sterilized with pure steam.
Confirmation of Compliance: After disinfection, the water quality at the outlet must be tested (especially for microbiological indicators). Only after passing the test can the system be put into full production use.
4. Root Cause Analysis and Prevention:
Repairs are not just about plugging leaks; they also involve analyzing the root cause of the leak (such as vibration, stress, or water quality issues) and implementing preventive measures to prevent recurrence.

🧿 III. Advantages of Using a Repair Joint

For large-diameter pipes (DN500), the advantages of a repair joint are particularly pronounced:

1. Fast and efficient, minimizing downtime:
From preparation to installation, the repair can typically be completed in tens of minutes to an hour, eliminating the lengthy draining, purging, welding, and passivation processes typically associated with welding. This is crucial for ensuring production continuity.

2. Safe and easy to operate, requiring no hot work:
This eliminates the high risk of welding on pipes that may contain flammable or explosive gases. It also eliminates the need for specialized welders and complex welding equipment.

3. Temporary leak closure under pressure or in wet conditions:
A high-quality repair joint can stop minor leaks under pressure, buying valuable time for planned system downtime and drainage.

4. Minimal system disruption:
No large volumes of purified water need to be discharged, nor does it require a thorough blowdown of the system, saving resources and time.

5. Cost-effective:
The cost of the repair joint itself is significantly lower than the labor, equipment, time, and verification required to organize a compliant welding repair.

Disadvantages and Limitations:

Perceived as a "Best" Measure: In a strict GMP audit, a patch joint may be questioned as a best measure. A documented evaluation and plan are required to demonstrate its suitability as a permanent solution or when to transition to a permanent weld repair.
Introduction of Minor Dead Spots: Compared to the smooth interior of a butt weld, a patch joint introduces a minor dead spot, which requires evaluation during cleaning validation.
Long-Term Reliability: Under long-term exposure to water hammer or vibration, its sealing performance may be weaker than that of a weld.

The housing is typically made of metals such as ductile iron and carbon steel, which are corrosion-resistant and high-strength. It can last the same life as the original pipe, eliminating the need for frequent repairs. Baoshuo brand carbon steel half joints are available in a variety of rubber materials, including NBR, EPDM, FKM, and silicone rubber. The half joint body is available in Q235 carbon steel and 304 and 316L stainless steel.

The following are Baoshuo brand oil-resistant pipe repair clamps, high-temperature-resistant pipe repair clamps, acid- and alkali-resistant pipe repair clamps, stainless steel pipe repair clamps, high-pressure-resistant pipe repair clamps, and large-diameter pipe repair clamps.

Summary and Recommendations

Emergency/Short-Term Solution: High-quality stainless steel patch joints are preferred. They quickly and safely restore system operation, minimizing production disruptions. Long-term/Permanent Solution: During the next scheduled outage window, a compliant weld repair should be arranged and verified through change control to completely eliminate the leak and any dead spots introduced by the repair.

Regardless of the solution, thorough documentation, cleaning and disinfection, and post-repair water quality verification are essential.