plastocor / durocor - Cooling Water Cycle Corrosion and Erosion Protection Systems

Since 1963, durocor® / plastocor® systems have repaired and prophylactically protected thousands of heat exchangers and condensers, thus preventing their owners from spending huge sums on their replacement. plastocor-international SA specializes in protective coatings for complete cooling water cycles, especially tubes and tube sheets in heat exchangers and turbine condensers, including tube linings and tube inlet coatings.

TUBE SHEET CLADDING 2000

When tubes are rolled into a tube sheet of dissimilar metal, a galvanic element is formed resulting in severe pit corrosion around the tubes. This leads to weakened tube sheet joints with the risk of leakage and costly shutdown times.

The Epoxy Cladding System 2000 for tube sheets provides long-term protection for new and already-corroded tube sheets against galvanic corrosion and erosion. It has a proven track record of continued service in thousands of old and new installations.

Thin film tube sheet coatings (less than 1mm) are subject to mechanical and substrate deterioration because of long-term permeation. The Epoxy Cladding System 2000 was developed to completely cover the tube sheet and encapsulate the tube ends into an epoxy layer of 3mm to 5mm thickness. In severe cases, it can be applied at a thickness of 10mm or more.

CONDENSER AND HEAT EXCHANGER TUBE-END INLET COATING

Tube inlet erosion shortens the lifetime of condenser tubes, often leading to the necessity of retubing, involving high costs and long shutdowns.

The time and cost involved in tube-end inlet coating is a fraction of that of new tubes. For example, lining the 45,600 tube inlets of the NWK-Nuclear Power Plant Unterweser, Germany, using the plastocor® inlet system required only 20 workdays. This was in the 1970s. Since then more than two million tube inlet and outlet ends have been coated.

EDF recently reported in the internal weekly magazine of CNPE Cruas that within one year of operating with the plastocor inlet system in one unit at least 39 shutdowns were avoided, thus creating an additional €1.18 million in operational profit for an expenditure of only €120,000.

The tube-end inlet coating creates a feathered termination, eliminating the chance of step-erosion, a common problem with the use of plastic or metal inserts. This method can actually bridge small perforations of the tube wall, thereby repairing the tube and returning it to service. The need to retube is therefore postponed or eliminated. The joining of the tube sheet cladding with the inlet coating creates a uniform and smooth transition from waterbox to tube interior. This reduces fouling and turbulence, which raises flow efficiencies. The tube ID is not significantly reduced which permits the unrestricted use of eddy current testing and most tube cleaning methods. The tube-end inlet coating system can indefinitely protect condenser tubes against inlet and outlet end erosion.

CONDENSER AND HEAT EXCHANGER EPOXY TUBE LINING SYSTEM

The heat transfer rate as well as the integrity of condenser and heat exchanger tubes will deteriorate with time because of fouling, corrosion and/or erosion.

When tube damage considerably reduces the efficiency of the condenser or unit, retubing is necessary. Retubing is highly time consuming and costly.

The internal coating of tubes is an attractive alternative to prolong the life of condensers and heat exchangers. It can also offer more efficiency of condensers and coolers by reducing fouling.

Epoxy tube lining systems allow a layer of protective coating to be applied down the entire length of the inner tube surfaces on site within a short period of time. Tubes with a total length of up to 50ft (16m) and an inside diameter starting from 5/8in (16mm) can be coated on site.

Main advantage of internal tube lining:

• Fast completion time compared to retubing
• Shorter planning and lead time
• Ideal for life extension for a limited time span
• Prevents the discharge of copper and zinc ions into the cooling water and reduces other environmental problems, such as excessive chemical water treatment

All materials used in plastocor-international's application systems are 100% solids non-VOC materials.