A “Toolbox” for Forensic Engineers

Fluid Transport 181
all was done apart from topping up the brake fluid, with the leak again going
unnoticed.
The widow’s claim that the brakes had been maliciously tampered with
was clearly without foundation, but the dealer and the garage who issued the
MoT certificate were prosecuted and fined heavily.
6.3.3 Stainless Steel Pipe Clamp Corrosion
Instructions were to ascertain the cause of failure of a pipe clamp that split
open after a period of service on a pipe carrying pressurized hot water at
98°C, allowing an escape of water that led to extensive flooding damage. A
large claim had been lodged against the firm who had installed the clamp
and the firm, in turn, alleged that the failure had nothing to do with its
fitting, but was the fault of the clamp manufacturers.
Figure 6.6 is a general view of the clamp, which is essentially a sleeve of
thin (0.7 mm) type 316 stainless steel with a “T” junction, fitted to the pipe
like a saddle, tightened by bolts passing through end pieces. It is lined with
a soft gasket to make a water-tight seal. The T branch projecting from the
side is not an off-take but rather it allows monitoring devices to be inserted
without interfering with the flow of water. The clamp bolts were still tight
at their original positions.
In what direction would the greatest tensile stress be acting when the
clamp was attached to a pipe? It is the hoop stress, normal to the axis of the
pipe.
The stainless steel had split from top to bottom, releasing the clamping
force and allowing the water to force its way under the gasket and escape to
outside. The bottom end of the split is shown in Figure 6.7A and at the top
Figure 6.6 General view of the pipe clamp as received.