On the down-comer from the cyclone on a fluidized bed boiler, there is an expansion joint to take the axial expansion of the duct.

The normal design is a standard fabric expansion joint, with upstands of the refractory lined duct. This system operates well for a short period of time, but due to high ash content in the duct, a seizing up of the joint cavity soon takes place. This blocking of the joint imposes large forces into the ducting causing cracking.

DEKOMTE have worked on an engineering solution which surpasses the lone function of the fabric component, and considers how to develop an envelope of space allowing movement of the duct.

The introduction of sealing air as part of the internal refractory and flow plate design, ensures space for the axial compression of the joint.

DEKOMTE have in service many joints which are functioning for over 10 years with no maintenance.

: Original Expansion joint in Ville Berrenrath, installed by OEM

Installation location of expansion joint

Mlada Boleslav

Ville Berrenrath

: Position of expansion joint installation element in Mlada Boleslav / Sko Energo

: Position of expansion joint installation element in Ville Berrenrath

Design solution: expansion joint with aerodynamic ash barrier

Operating conditions:

Pipe temperature	900°C
Movement	axial: 120mm (expansion) lateral: ± 20mm

Operating Conditions:

Pipe temperature	870°C
Movement	axial: 190mm (expansion) lateral: ±10mm

DEKOMTE solution with single-level aerodynamic sealing:

permanent air sealing,
in operation since beginning of 2002.

DEKOMTE solution with double-level additional aerodynamic sealing:

minimised amount of permanent sealing air,

temporary sealing air,
in operation since beginning of June 2006.

	Permanent sealing air (75 mbar, 0,59m³/s)
	Temporary extraction (0,59m³/s)
	Flue gas / Ash down pipe

	Permanent sealing air (40 mbar, 0,1m³/s)
	Temporary sealing air (75 mbar, 0,59m³/s)
	Temporary extraction (0,59m³/s)
	Flue gas / Ash down pipe
	Manometer connections