Page 40 - Handbook of Materials Failure Analysis

3 Case Studies 33

records, apparent surface features, and laboratory testing results are required. In
addition, a careful review of each aspect of investigation procedure is important
because there might be legal claims involved. The conclusion could also impose seri-
ous concerns to designers, manufacturers, and operators. It is therefore a great
responsibility over the shoulders of failure analyst to comment on critical issues
and highlight major discrepancies in the product or device that caused failure.
The conclusion should be concise, elaborative, and effective stating the facts and
do not include misleading comments.

2.7 SUGGESTING REMEDIES
Once the conclusion is drawn on the basis of findings and laboratory test results, an
expert approach is required to suggest actions to be taken to prevent such failure.
It may describe the procedure to either decrease the frequency of failure or to prevent
it. The best engineering practice demands the detailed discussion on the all possibil-
ities which could arise in product designing, manufacturing, properties, perfor-
mance, and operating conditions. The preventive measures and standard
procedures should be simple, easy to adopt, economically and technically feasible.

3 CASE STUDIES

The two failure case studies have been presented here for guidance and as examples.
The first study describes the failure of spent caustic drainage line pipe which leaked
just after 8 months from installation. The failure was occurring frequently at the same
location even after replacement of the line pipe between continuous flow line (CFL)
and intermittent flow line (IFL) connected with the caustic storage tank. The second
case belongs to the failure of plate heat exchanger integrated with the power gener-
ation system of a textile mill. The frequent perforation and fouling of 316L stainless
steel plates at open-circuit cooling water-side of heat exchanger were hindering the
smooth operation of mill power unit. The brief history, description of investigation
procedure, causes, and remedial suggestions are provided in the following sections.

3.1 STUDY OF A SPENT CAUSTIC DRAINAGE LINE PIPE FAILURE
IN AN OIL REFINERY
Reprinted from Virk et al. [23]. Copyright 2010, with permission from Elsevier.

3.1.1 Background
This case study will describe the failure of a 4-in. line pipe connected with a spent
caustic storage tank in a crude oil refinery. About 40 m line leaked at many locations
due to pitting and this happened in just 8 months after its installation. The spent caus-
tic was designed to flow through this horizontal line by three inlets designated as 300,
400, and 500 as shown in Figure 2.3. The damaged line portion is highlighted in black