If a
liquid fuel pump should fail ( either Roper or
IMO brands )
during turbine operation, it is important to thoroughly clean the system piping
that could become contaminated. Most fuel systems are equipped with both a
low-pressure (LP) and high-pressure (HP) filter. The LP filter is located
upstream of the fuel oil stop valve. The HP filter is located downstream of the
fuel pump and upstream of the flow divider.
Thus,
debris from the pump could contaminate the bypass loop. See Figure 1 below
First, the
failed pump is removed and inspected. Before it is replaced, the inlet and
discharge fuel piping also should be inspected. It is imperative that piping leading to and from the
bypass valve be clean of debris resulting in the pump failure. Please refer to
the photograph in Figure 2 below
he piping
“tee” in the pump discharge line shows how fuel can flow either
through the HP filter or up through the bypass valve toward
suction of the pump. The return line from the bypass valve is connected to
another piping “tee” as shown in Figure 1 above. The flow divider shown in
Figure 3 below is protected because it is downstream of the HP filter.
Debris
from a failed fuel pump (typically brass particles from the thrust bearing and
pieces of rubber seals) could clog the bypass valve throat. See Figure 4 below
for the return pipe loop. The foreign matter would collect in the throat
opening of the valve, choking off fuel flow.
This can
be a very serious problem during the restart of the gas turbine once the new
pump is installed.
Assume
that the pipes were NOT cleaned
after a pump failure. During start-up, the turbine may trip on over temperature, because the bypass valve (clogged) cannot
divert sufficient fuel back to the suction side of the pump. That is, after the
fuel stop valve trips, the flow divider may likely continue to turn, distributing
the excess fuel to the combustion. Fuel could continue to flow (evacuating the
fuel lines and HP filter) for as long as 15 seconds. This “over burn” could
cause serious damage to the hot gas path of the gas turbine.
Contact David Lucier or Charlie
Pond if you have had a fuel pump failure and
need technical assistance.
Also, Pond And Lucier, LLC has a
full-service hydraulics lab in its new facility in Amsterdam, NY.
Please
contact us there on Tel: 518-843-3634 for
details. Visit the reconditioning section
of this website for the pricing chart for fuel and hydraulic systems components
we service.