SPOOL PIECE WITH
CORNER RELIEF EXPANSION JOINTS
FOR HIGH TEMPERATURES (+800°C)

For a hot gas pipeline at a performance centre for turbochargers for large engines in Germany, Belman designed and manufactured a special double-walled spool piece with Corner Relief Expansion Joints. To ease transportation and handling, it was delivered in two sections for on-site assembly.

 

CLIENT ISSUE
The client required a complex spool piece with Corner Relief Expansion Joints to accommodate the axial and lateral movements generated during operation. Because the installation point is a high temperature hot gas pipeline (+800°C), the client needed the complete spool piece insulated with Superwool to limit the outer wall temperature to +250°C. This demanding scope called for a highly experienced Expansion Joint manufacturer with proven capability within both large dimensions, complex designs and high-level engineering, testing and craftmanship, which is why the client selected Belman.

 

BELMAN SOLUTION

Spool piece with Corner Relief Expansion Joints delivered in two sections

As per the client drawings and request, the spool piece exceeded 8 metres x 6 metres, making transportation and handling impractical. Therefore, it was split into two sections and assembled on-site using two flanged connections.

Belman designed and manufactured the double-spool piece with Elbow Expansion Joints. The dimensions of the two Elbow Expansion Joints were:

• 3.77 metre-long, DN 1000 Elbow Expansion Joint weighing in at 2.7 tonnes
• 4.45 metre-long DN 1000 Elbow Expansion Joint weighing in at 3.55 tonnes

The complete spool pieces with Expansion Joints were divided into the following two transportable sections, with the dimensions:

• Section 1: spool piece with the 3.7-metre-long Elbow Expansion Joint, the tee section and the blind flange measuring 5.5 x 2 metres
• Section 2: spool piece with the 4.45-metre-long Elbow Expansion Joint and two reducers measuring 4 x 4.5 metres

The application required a double-walled design for all components and Expansion Joints in the spool piece. The inner wall was made from 1.4876H (for +800°C hot-gas exposure) and acted as an inner sleeve, while the outer wall was made from 16Mo3. Superwool insulation was placed between the walls. Only one reducer was not insulated, as this was designed to act as a transition piece between the piping section and the connecting pipe of the piping system. For structural integrity, the Elbow Expansion Joints’ end plates were reinforced to withstand loads and tie rods strategically placed to control and limit movement absorption.

After each section was assembled, blind flanges were mounted on the spool piece ends and the sections were pressure-tested at 12.26 barg. Following the pressure test, the water was fully drained. Once the spool pieces were dry, Superwool insulation was blown into the cavity between the two walls. In addition to the pressure test, a visual test and tightness test were carried out. The spool pieces are CE-marked, have partial traceability and come with a Manufacturing Data Book (MDB).

 

Why use 16Mo3 and 1.4876H material?

Because the media temperature in the pipeline reaches +800°C, the spool piece with Corner Relief Expansion Joints was made from material 1.4876H (inner parts) and 16Mo3 (outer part). Both steels are heat-resistant, but they were selected for different roles. 1.4876H (Alloy 800H) was used for the parts in direct contact with the hot gas media. It offers excellent resistance to high-temperature corrosion, oxidation and nitridation and maintains high creep strength at elevated temperatures. Its high nickel content makes it especially suitable for aggressive hot-gas environments. 16Mo3, meanwhile, was applied to the external parts where the temperature and corrosion exposure would be lower. It provides adequate heat resistance for this part (typically up to around +500°C to +530°C) while being significantly more cost-efficient and easier to source, weld and fabricate. By combining these two materials, the design achieved maximum durability and performance where the thermal load is highest while keeping the overall solution cost-effective.

 

Why were venting holes added to the spool piece with Elbow Expansion Joints?

Due to the high media temperature of +800°C, the double-walled spool pieces with Corner Relief Expansion Joints had to be manufactured from heat-resistant materials. To optimise the design both technically and financially, the inner wall was made thinner to reduce the use of costly high-temperature material. However, the optimised inner wall was not strong enough to withstand the high operating pressure on its own. Therefore, venting holes were incorporated to transmit the internal pressure to the outer wall. The venting holes were carefully sized so they were large enough to ensure smooth flow and pressure equalization while also preventing insulation from passing through the holes and entering the pipeline. The venting holes were strategically positioned and numbered in a defined pattern to secure efficient and uniform pressure transfer from the inner wall to the outer shell. The outside wall (shell) was produced from a thicker, more economical material, as full heat resistance was not required on this layer. Its greater thickness enables it to withstand the high-pressure load and thereby relieve the thinner inner wall.

A comprehensive ANSYS analysis and supporting calculations confirmed that Ø20 mm venting holes, arranged as 64 x Ø20 mm per mb, provided the optimum solution.

 

Special transport due to oversized dimensions

Due to the oversized dimensions, the spool pieces with Elbow Expansion Joints were shipped by special road transport on a lowboy trailer. The truck was accompanied along the entire route by an escort vehicle. To protect the spool pieces with Expansion Joints during transport, each section was packed in specially built ISPM 15 wooden boxes. Because of the heavy weight of the spool pieces, the bottoms of the wooden boxes were reinforced to allow safe lifting and handling. The ISPM 15 wooden boxes also allowed the client to store the spool pieces safely in the same packaging until installation. To prevent water ingress and protect the spool pieces, the inside of each box was lined with plastic. In addition, the boxes were covered with tarpaulin on top to safeguard the spool pieces against moisture and water during transport on the open trailer.

 

Belman – proven experience in large-dimension Expansion Joints

With over 30 years of experience in designing and manufacturing Expansion Joints, Belman has expertly designed, manufactured and supplied many large-dimension constructions and Expansion Joints. Having the facilities, capabilities, know-how and craftmanship, our experienced staff has ensured clients’ successful deliveries of large-dimension constructions for various industries and applications. Some standout examples are a 10-metre-long, DN 2800 Expansion Joint for a steel plant weighing 40 tonnes, as well as a 4-metre-long DN 2500 Finger Type Pressure Balanced Expansion Joint with a balancing Bellow of DN 3800.