They are inserted in branches of the circuit where the free flow in one direction is allowed and the return flow in the opposite direction is not possible. The single-acting valves (in line) are of ball type with alignment guide made of composite high resistance material which allows a total passage and a great breaking strength and wear resistance. All this has been confirmed by numerous tests. The soft seal implemented through a special material sealing eliminates every leakage with the use of gas or liquid in general