A gas scrubber cone condition monitoring system has a sealed gas scrubber cone (9) moveably mounted in a gas pipe (1), a collar (5) fixedly mounted radially outward of the cone in the gas pipe and a pressure tap (12) into the sealed cone. The pressure tap is coupled to a condition monitor (17,18) via an input line (16). An output line (14) from the condition monitor is coupled to a gas pipe (15), downstream of the sealed cone. The condition monitor includes at least one of a pressure gauge and a gas flow meter.

A pressure relief valve system has a fluid outlet (1) from a pressure vessel; a flexible expansion piece (4) at an end of the fluid outlet remote from the pressure vessel; a primary pressure relief valve has a valve seat and a valve lid (7). The valve seat has a flange (5) mounted on the expansion piece and the valve lid forms a valve seal with the flange. A fluid off-take (13) is connected to the fluid outlet (1) and a secondary pressure relief valve (11) receives fluid from the fluid off-take. The secondary pressure relief valve has an outlet (12) coupled to a valve opening actuator (15), whereby passage of fluid through the secondary pressure relief valve (11) causes the opening actuator to operate to open the valve lid (7).

A gas scrubber cone condition monitoring system has a sealed gas scrubber cone (9) moveably mounted in a gas pipe (1), a collar (5) fixedly mounted radially outward of the cone in the gas pipe and a pressure tap (12) into the sealed cone. The pressure tap is coupled to a condition monitor (17, 18) via an input line (16). An output line (14) from the condition monitor is coupled to a gas pipe (15), downstream of the sealed cone. The condition monitor includes at least one of a pressure gauge and a gas flow meter.