System for monitoring the mechanical parameters of a pressure vessel

A system for monitoring the structural integrity of a pressure vessel, comprising, in combination:

• a generally cylindrical pressure vessel assembled from a plurality of cast elements and formed with angularly spaced axially extending passages;
• an array of angularly spaced axially extending axial-stressing cables passing through said passages and axially stressed against said vessel, said axial-stressing cables including a number of normal-operation axial stressing cables adapted to take up these axial stresses of said vessel during normal operation and safety axial-stressing cables provided in addition to the normal-operating axial-stressing cables;
• an array of peripheral stressing cables bearing upon the periphery of said vessel and spaced therealong, said peripheral-stressing cables extending circumferentially about said vessel and including normal-operating peripheral-stressing cables adapted to take up all of the radial forces developed by said vessel during normal operation thereof, and safety peripheralstressing cables provided in addition to said normal-operating peripheral-stressing cables;
• at least one measuring device associated with one of said normal-operating cables for producing a signal representing the change in length of said one of said cables and the force applied thereby to said vessel;
• circuit means connected to said device and adapted to store a threshold value representing a fraction of the measurement produced by said device at the maximum safe operating pressure of said vessel;
• and
• means connected to said circuit means for signaling an alarm upon the actual measured value of the signal produced by said device reaching said threshold value, said threshold value being substantially 90% of the value which would be measured by said device at the maximum safe operating pressure of said vessel, said circuit means also being provided with a further stored threshold value of at least 10% below a normal operating pressure of said vessel, said means for signaling said alarm responding to a fall in the actual value of the measurement by said device below the further threshold value.