GRE (Glass Reinforced Epoxy/Plastic) Pipe plays a critical and increasingly popular role in marine Exhaust Gas Cleaning Systems (Scrubbers). Its excellent corrosion resistance, light weight, design flexibility, and long service life make it ideally suited for the harsh chemical environment of scrubber systems.

1.  Core Application Areas: Handling Corrosive Media

Scrubber operations generate highly corrosive fluids. GRE piping is extensively used to transport these media due to its inherent corrosion resistance.

• Scrubber Liquor Recirculation Piping (The Core Application):

• Function: Connects the scrubber sump, recirculation pumps, and seawater coolers to form a closed loop for continuous exhaust gas spraying.

• Media Characteristics: Low temperature (typically <70°C), highly acidic (pH 2-4), slurry containing high concentrations of sulfuric acid, sulfurous acid, chlorides, and solid particulates (soot, sulfate crystals). This is the most corrosive medium in the entire system.

• Why GRE is Preferred: Compared to expensive high-grade stainless steel (e.g., 254 SMO) and rubber-lined carbon steel pipes (which face aging and repair issues), GRE piping provides a near-perfect corrosion-resistant solution with a lower total life-cycle cost.

Effluent Discharge Piping:

• Function: Pumps treated and compliant washwater overboard.

• Media Characteristics: Although treated, it remains slightly acidic with residual contaminants.

• Why GRE is Used: Ensures corrosion resistance along the entire path from the treatment unit to the hull valve, including sections prone to seawater backflow.

Alkali Dosing Piping (For Closed-Loop/Hybrid Systems):

• Function: Transports sodium hydroxide (NaOH) solution to neutralize acidity in the circulating water.

• Media Characteristics: Concentrated alkaline solution.

• Crucial Consideration: Must use GRE with a specific alkali-resistant epoxy resin formulation (e.g., bisphenol-A or vinyl ester based). This is a key material selection point.

Drain Piping for Exhaust Gas Condensate:

• Function: Drains concentrated acidic condensate formed from cleaned exhaust gas in the funnel.

• Media Characteristics: Low flow, but highly acidic condensate.

2. Core Advantages Over Traditional Metallic Piping

Superior Corrosion Resistance: Eliminates fundamental issues like pitting, crevice corrosion, and galvanic corrosion faced by metallic pipes. No cathodic protection is needed, with a typical design life exceeding 20 years.

Low Maintenance Cost: 

Virtually no inspection, repair, or replacement due to corrosion is required throughout its service life, significantly reducing operational costs and off-hire time.

Excellent Hydraulic Properties:

Very smooth inner bore (Hazen-Williams C-factor as high as 150-155) reduces fluid friction, which can lower the pump head requirement and operational energy consumption.

The smooth surface minimizes scaling and sludge adhesion, reducing clogging risk and maintenance frequency.

Light Weight: 

Density is about 1/4 that of steel, substantially reducing system weight, benefiting ship stability and deadweight capacity.

Ease of Installation:

Allows for adhesive socket joints or flanged connections. Socket joints offer high strength and excellent sealing, eliminating welding, thereby reducing onboard hot work risks and costs.

Pipes are easy to cut and adjust on-site, improving installation efficiency.

Good Insulating Properties: 

Non-conductive, eliminating galvanic corrosion risk; low thermal conductivity helps maintain fluid temperature and reduces heat loss.

In marine scrubber systems, GRE piping has become the "gold standard" for transporting corrosive scrubber liquor and effluent. It provides shipowners with a safe, reliable, and cost-effective solution due to its unparalleled corrosion resistance, long life, and low maintenance.

With the widespread adoption of scrubbers and evolving technology, the application standards for GRE piping are now well-established and continuously supported by all major Classification Societies' rules. It is an indispensable component of modern marine environmental protection systems.