for pig launchers/receivers, long curvature fittings, and full
port valves. Install high point vents to remove trapped air.
Low point drains are not required on interterminal pipelines.
Surge Analysis. Conduct a complete surge analysis of
system operation using a computer simulation program for all
systems with quick closing valves and for aircraft hydrant and
direct fueling systems with more than two outlets. Give full
consideration to the causes and effects of hydraulic shock.
This is especially important in closed fueling systems such as
aircraft fueling systems where the receiving tanks or
dispensing equipment may be damaged by shock pressure. Reduce
the possibility of shock by limiting flow velocity and
avoiding the use of quick opening/closing valves except where
required for system operation such as hydrant pit valves.
Every reasonable effort must be made to control hydraulic
surge or shock within acceptable limits by the design of the
piping system rather than by the use of surge suppressors.
Surge suppressors are strictly a last resort solution and
require the approval of Service Headquarters prior to
designing into a system. For all aircraft direct
fueling/hydrant system designs, the loop backpressure control
valve is critical in preventing excessive hydraulic shock.
Use the following design criteria:
techniques to determine if surge suppression is required.
Conduct a run at steady state flow conditions to establish
system flow rates for the scenario being modeled. After that,
conduct a transient surge analysis imposing worst-case
operating conditions on the system. For hydrant systems
simulate this valve as an active modulating valve. If
acceptable peak pressures are exceeded, discuss the results
with the Service Headquarters fuels engineer to review
parameters used and consider alternatives. If this
consultation produces no workable solution, perform a second
surge analysis to model the use of surge suppressors in the
system. This analysis must indicate that damaging peak
pressures are not exceeded. Do not use manual surge
calculations, except as found under (c) below, because they do
not account for dampening effects of the system and yield
overly conservative results.