Document No：KE-4032-02 Page：15/19
Ensure to provide a fuse or a short circuit breaker on the control panel to
prepare for accidental short circuits.
Protective measures for extraordinary pressure rises
When a floating-ball type ball valve is used for highly volatile liquid service,
rise of line temperature or ambient temperature may often cause an
extraordinary rise of the pressure of the fluid left within a body cavity and
result in seat damage or valve malfunction. This problem may be solved by
the following preventive measures:
For fully closed valves: Optional provision of a pressure equalization hole
through the upstream side of the ball, or a pressure equalization groove on the
upstream ball seat is recommended (Fig.18). This provision will make the fluid
flow uni-directional, so that care must be taken to decide mounting direction of
the valve on piping.
For fully open valves： Standard provision of a pressure equalization hole on the
top of the ball where it contacts with the valve stem is provided (Fig.19). Valve
mounting orientation remains bi-directional.
Countermeasures in piping loop
Extraordinary pressure rises also could be a problem for a valve mounted at the
end of the piping loop for liquid service. No effective solution could be
recommended for such a valve itself. The entire piping system needs an
appropriate design reconsideration in advance so that a pressure relief valve
may be installed or the piping loop may not be ended with a valve.
Fig. 18
Fig. 19
Pressure
equalization groove
Pressure
equalization hole
Pressure
equalization hole
Fully closed Fully open
Fluid flow direction
Body
cavity
