60 Panels Boiler Membrane Wall With Submerged Arc Welding

60 Panels Boiler Membrane Wall with Submerged Arc Welding for Maintenance of Power Plant Boiler
 

Introduction

Membrane water wall is an air-tight structure consisting of pipes and fins.The advantages are less air leakage in furnace; can use pipe-laying wall, less load on steel structure and lower cost of boiler; easy to use suspension structure and improve thermal expansion system, suitable for large-scale mechanized production, high assembly rate, low heat storage capacity and shorten star-up and shutdown time. The disadvantage is that the manufacturing process is complex. Membrane water wall is often used in large capacity, high temperature and high pressure boilers.

Strong points of membrane water wall

(1) Ensure the sealing of furnace wall and reduce air leakage in combustion chamber.

(2)The realization of full water cooling in combustion chamber is beneficial to prevent coking under the condition of intensified combustion.

(3)The cooling time of start-up and shutdown of boilers can be shortened because of its small heat storage capacity, fast temperature rise and fast cooling in combustion chamber.

(4)Pipe-laying furnace wall is suitable, which greatly reduces the load of boiler frame and it is convenient for suspension and lifting.

(5)Compared with the bare tube type, the heat absorption capacity of the tube is improved.

(6)It improves the per-assembly degree of boiler components, facilitates and reduces the installation workload.

According to the different manufacturing process, the membrane water wall can be divided into three types(see Fig. 1):1.rolled fin tubes are welded in rows, with less welding workload, but the fin tubes are expensive. 2.bare tube and fin(flat steel) are welded in rows, which has low material cost and can easily meet the requirements of various pitches, but flat steel requires high precision and finishing equipment.3.Bare tube fusion welding,the fins between tubes are formed by filling the welding wire, mostly used for the small pitch between the tubes. The pitch between tubes of membrane water wall is related to factors such as boiler pressure and furnace heat load, usually s/d is 1.2-1.5.

Specification

The main function of water wall panels in boiler is to absorb the heat generated by high temperature flame or flue and to generate steam or hot water in tubes, hence to reduce the temperature in the chamber .

• Membrane boiler water wall panel: spot welds many rolled finned tubes into a sealed combined heating surface, which improves the airtightness of the furnace and reduces air leakage.
• Studded water wall tubing: welds pins of 20 to 25 mm in length and 6 to 12 mm in diameter on the water wall tube, and then applies a chrome ore refractory plastic to reduce the water wall panel’s heat absorption, and increase the temperature in the combustion zone. It is appropriate for situations where it is difficult to set fire to the fuel, as well as specific slag tapping furnaces.
• Plain tube boiler water wall panel: composed of a whole row of seamless steel pipes, the simplest structure.
• Wall-attached boiler water wall tubing: embedded in the inner wall of the furnace wall, single-sided heat absorption.
• Double-sided heated water wall panel: installed in the middle of the large boiler furnace, which is divided into two parts that are independent of each other, and both sides are heated.