A 316L stainless steel stack with a platform tower for a refinery in Romania

The challenge

An engineering contractor needed a stack for an installation it was building at a refinery in Romania. The stack had to take the installation’s flue gas from a flanged duct at its base to a safe discharge height, and the operators needed safe access to the measurement level on the shell.

The contractor specified AISI 316L stainless steel for the shell, so the stack would not depend on a coating to resist the flue gas and the weather.

Our approach & engineering

Axces engineered the stack as a freestanding single-wall chimney: the 6 mm 316L shell, 36 inches in diameter, is both the gas path and the load-bearing structure, anchored to the concrete foundation. Our guide to choosing an industrial stack configuration explains when a self-supporting shell is the right choice.

Designed and CE-marked as a chimney

The stack is designed to EN 13084-7 and EN 1993-3-2 for mechanical resistance and stability, and carries the CE marking under EN 13084-7 for a design temperature of 150 °C. The welds are made to execution class EXC 3 of EN 1090-2, with quality level C to EN ISO 5817, and the main materials come with EN 10204 3.1 certificates. The lower part of the shell is insulated and clad on the outside.

A separate frame for the platform and ladder

The access platform and the cage ladder sit on their own hot-dip galvanised steel frame, which stands next to the stack on the same foundation. The frame has its own declaration of performance, so the stack and the access structure are each documented for what they are.

• Freestanding single-wall stack: no guy wires and no carrier steelwork
• 6 mm AISI 316L shell, 36 inches in diameter
• CE marking to EN 13084-7, design temperature 150 °C
• Flanged NB 800 inlet, a Ø620 mm manhole and earthing lugs
• Galvanised steel frame with an access platform and a cage ladder

Scope of supply

• 1 × freestanding single-wall stack, 36", 6 mm AISI 316L, insulated and clad over its lower part
• Flanged NB 800 inlet connection, Ø620 mm manhole and earthing lugs
• 1 × hot-dip galvanised steel frame with access platform and cage ladder
• Anchors, bolts, nuts and washers
• Declarations of performance for the stack and the steel frame
• Manufacturing data book with 3.1 material certificates, weld procedure and welder qualifications, visual and dimensional inspection reports

Results

The stack, the frame, the platform and the ladder were delivered to the refinery in May 2024. By November 2024 the stack stood on its foundation, connected to the installation’s ducting, with the platform tower beside it.

• One stainless steel stack in service at a refinery in Romania
• 316L shell with no coating to maintain
• CE-marked to EN 13084-7, welded to EXC 3
• Safe access to the measurement level from a separate galvanised frame

Related reading

• Freestanding, guyed, or self-supporting: choosing an industrial stack configuration: how site constraints, height and structural loads decide the stack type
• Industrial stack design loads: wind, seismic, and vortex shedding explained: the load cases that govern a stack’s design
• Steel structures and platforms for industrial plant: an EPC supplier guide: platforms, access and support steel around process equipment