Environmental Engineering Reference
In-Depth Information
Figure 4.18
Design and arrangement of channels and angles to avoid water accumula-
tion.
4.
Provide for easy drainage . This applies particularly to tanks. Any accumu-
lation of corrosive liquid due to improper drainage is harmful. Steel tank
storing concentrated sulfuric acid is an example. The residual acid absorbs
moisture, gets diluted, and aggravates corrosion of steel. Even the residual
moisture will create differential aeration conditions for corrosion to take
place. Improper and proper drainage provisions are exemplified in Fig. 4.17.
Channels should be provided with drain holes (Fig. 4.18a) and V angles
should be used inverted (Fig. 4.18b) to avoid accumulation of moisture.
Provision of ventilation holes in closed structures is a must to avoid accu-
mulation of residual moisture.
5.
Avoid sharp corners . Sharp corners should be replaced by rounded corners
as the applied paint coats tend to be thinner at the sharp corners. Paint
failures often start from such points.
6.
Avoid sharp bends and protrutions in piping systems . Sharp bends cause
impingement attack in high-velocity fluids (Fig. 4.19a), which can be
avoided by smooth rounding off (Fig. 4.19b). Protrutions and troughs cause
turbulence and result in erosion corrosion (Fig. 4.20). It is also proper to
avoid T joints where the flowing fluid directly impinges on the facing wall
(Fig. 4.21a). The design can be improved and baffle plates provided in vul-
nerable places (Fig. 4.21b).
7.
Avoid mechanical stresses . Excess mechanical stresses and stress concen-
tration should be avoided in the design of structures to minimize the occur-
rence of SCC.
8.
Avoid vapor pockets . Frequently, interfaces between air and liquids are the
Search WWH ::




Custom Search