BASIC DESIGN OF WATER WALLS USED IN WATER TUBE BOILER

USE -

Water walls are used in water tube boilers to contain the heat of the furnace and reduce the amount of refractory material required. They also contribute to the evaporation rate by receiving radiant heat; indeed, in radiant heat boilers the water walls provide the bulk of steam generation.

TYPE  

1. PARTIALLY STUDDED

The partially studded water wall has a relatively wide pitch and so does not unduly weaken the tube plates or headers, but to seal the gaps between the tubes a refractory material must be used, this being keyed in place by steel studs resistance-welded to the water wall tubes.

2. TANGENTIAL 

In the case of the tangential type water wall a much smaller pitch is used, the off-set tube ends allowing the use of staggered holes to prevent undue weakening of tube plates and headers. However, some radiant heat can still penetrate the wall and a layer of suitable refactory material must be placed behind the water to protect the boiler casing.

3. DIAPHRAGM

Diaphragm type water walls are constructed by welding longitudinal fins between adjacent plain tubes, as in the membrane wall, or alternatively welding finned tubes together along the line of contact, as in the monowall. In both cases similar gastight panels are formed which can be used to surround the furnace, the welded fins being omitted in way of any required gas passages. As no radiant heat can penetrate these walls, no refractory material need be fitted behind them and a single boiler casing can be used.