Belman has supplied 41 sets of Refractory Lined Universal Expansion Joints to a Polish power plant.

The company has installed them on the plant’s pulverised fuel ducts situated on the boilers and due to the supercritical coal dust media, the expansion joints were refractory-lined.

Critical design parameters

This power plant was equipped with supercritical once-through pulverized fuel boiler for bituminous coal and an extraction-condensing turbo set in a closed cooling water system with a wet cooling tower.

The media in the fuel ducts is a mixture of air with pulverized coal dust, this lead to the requirement for the special insulation of the expansion joints. Coal dust is extremely abrasive and can backfill in the bellows of the expansion joints. For that reason, the expansion joints were designed with DENSIT® to prevent the erosion of the inner lining.

Ceramic wool was additionally installed around the bellow. Additional insulation using special braided hose was also added to provide further protection against the aggressive medium.

Articulated expansion joints

The expansion joints are articulated with a section of flanged pipe between the two angular expansion joints. As the two angular expansion joints are articulated they can work in the same way as a universal expansion joint by absorbing movements simultaneously in several planes.

This solution was selected as the boilers tended towards movement in all three planes. Additionally, all the expansion joints were designed in accordance with their position in the system to increase the working efficiency and lengthen life cycles.

Special primer and coating required

As per the customer’s specifications, the expansion joints were coated with a primer which is a two-ingredient ethyl-zinc-silicate grey paint and further coated with a grey single ingredient matrix paint. This special paint provides improved protection against corrosion to the expansion joints. This type of ethyl-zinc-silicate primer can provide protection for many years.

Experienced in Refractory Lined Expansion Joints

Belman is highly experienced in the design and supply of customized refractory lined expansion joints for both boilers, FCC and other critical applications in various types of plants.

Design parameters

The refractory-lined expansion joints have the following design parameters:

Dimension: DN 600 • Length: 3460 mm • Medium: Air mixture of coal dust • Design temperature: 140°C • Design pressure: 0,05 barG • AX: +/-80 mm • LA: +/-596,6 mm • Bellows: 1.4541 • Welding ends: 1.0345 • Flanges: 1.0425 • Middle pipe: 1.0345