It is described in detail in the link attached.
When the Space Shuttle is on the ground, de-ionized water is circulated throughout the vectoring system for the solid rocket boosters. Various flow rates are required at different times as a pressure regulator tries to maintain 20 PSI on the system. A thousand feet away from the regulator and booster rockets, a 5 HP pump with a pressure switch and pressure tank cycled on and off as needed. The booster rocket is equipped with rupture disc at 21.5 PSI. The pump cycling on and off was causing a transient pressure wave that the 20 PSI regulator could not contain. This caused the rupture disc to rupture on a regular basis. Adding a CSV1Z Cycle Stop Valve between the pump and tank keeps the pump running steady, eliminating the cycling. The CSV solved the problem as the rupture disc no longer ruptures.
The pump was operating on a 30/50 pressure switch with a pressure reducing valve on the discharge set for 20 PSI. This is exactly like the system described earlier in this thread that was using a 70/90 pressure switch setting with a discharge pressure reducer set at 65 PSI. Even with a pressure regulator on the discharge of the tank/switch trying to hold a steady 20 or 65 PSI, every time the pump cycles on, the transient pressure wave flies right through the pressure regulator, and in the case of NASA was blowing a 21.5 PSI rupture disc. The CSV is working with the same pressure tank, pump, and 30/50 pressure switch. However the CSV is maintaining a constant 40 PSI to the pressure regulator instead of on/off at 30/50 over and over. When it was given a constant 40 PSI from the CSV to work with, the pressure regulator was able to maintain 20 PSI so consistently, that is never blew a 21.5 PSI rupture disc again.
