In May, before getting involved with the film, a broken valve caused a depth excursion.
On 22 June another incorrectly opened valve caused disruption in the ongoing test.
This valve, which has only one leaflet, can cause severe stenosis during infancy and may be fatal at an early age.
Partly closed valves (or the use of stopvalves) can also cause airlocks.
The triple valve also causes the brake cylinder to be exhausted to the atmosphere, releasing the brakes.
When the hygrostat calls for humidity, the valve is opened and causes a spray of water onto the biscuit.
In many cases, a bicuspid aortic valve will cause no problems.
The probe of the accident found that a valve with a rare left hand thread type caused confusion among the crew.
The blocked valve caused the pressure within the boiler to exceed its capacity, and it exploded.
The reversing valve, controlled by the thermostat, causes the change-over from heat to cool.