Abstract: A metal seal can be crushed evenly without forming wrinkles and scratches due to sliding against first and second flat surfaces. The seal comprises a first/second end surface arranged to face the first/second flat surface, respectively. The first end surface comprises a first convex part having a curved or flat surface that contacts the first flat surface, and a first projection that is formed shifted in a radial direction from the first convex part and has a ridge line that contacts the first flat surface. Prior to deformation, when the second end surface contacts the second flat surface and the first flat surface is separated from the first end surface, a point where a vertical distance between the first convex part and the second flat surface is the greatest and the ridge line are located on the same surface that is parallel to the first flat surface.

Abstract: A metal seal is annular, provided sandwiched between first and second flat surfaces. The seal includes a first/second end surface opposite to the first/second flat surface, respectively. The first end surface includes paired first protrusions formed displaced in a radial direction of the metal seal and have dihedral angles contacting the first flat surface, and the second end surface includes a second protrusion formed inward of one first protrusion and outward of the other first protrusion in the radial direction, and has a dihedral angle contacting the second flat surface, and paired third protrusions that are respectively formed inward and outward of the second protrusion and whose highest points to which perpendicular distances from a reference plane including the dihedral angles of the paired first protrusions are shorter than a perpendicular distance from the reference plane to the dihedral angle of the second protrusion.

Abstract: The present invention provides a filtered water monitoring device used for detecting damages in a filtration medium installed inside a membrane filtration water clarification device, thereby monitoring degradation of a performance thereof, in order to secure safety of filtered water flowing out from the membrane filtration water clarification device, comprising a branch filtered water pipeline system which is branched from a filtered water pipeline system connected to an outlet of the membrane filtration water clarification device, a filtered water observation plate which is installed in a certain position of the branch filtered water pipeline system, imaging means which takes an image of the filtered water in an observation tank of the filtered water observation plate and outputs image information thereon, and image analyzing means which receives the image information output from the imaging means, and compares the image information with a stored image pattern to identify impurities contained in the filtered