Diaphragm valve and method for exchanging valve seat thereof

1. A diaphragm valve comprising:

a body having a flow inlet and a flow outlet;

a valve seat provided in the body;

a diaphragm that is opened and closed by contacting and separating from the valve seat provided in the body;

a primary-side opening section provided in the body so as to be in communication with the flow inlet;

an outer wall section for valve seat mounting provided in the primary-side opening section;

a stepped section provided in an inner periphery of the outer wall section;

a seat ring press-fitted into and fixed to the stepped section;

a flange section provided in the seat ring; and

a press-fitting groove for valve seat mounting configured to define a space between the seat ring and the outer wall section and having the flange section as a bottom portion of the press-fitting groove,

wherein the valve seat press-fitted into and fixed to the press-fitting groove has its upper portion slightly protruding from the press-fitting groove so as to form a first extension section and a second extension section, wherein an outer periphery of the first extension section is increased in the upper portion of the valve seat and covers a position in a vicinity of a top portion of the outer wall section, and an inner periphery of the second extension section is decreased in the upper portion of the valve seat and covers a position in a vicinity of a top portion of the seat ring, and

wherein the top portion of the seat ring has a height which is smaller than a height of the outer wall section, and an inner diameter of the seat ring is larger than an inner diameter of the primary-side opening section.

2. The diaphragm valve according to claim 1 , wherein an inner peripheral surface of the seat ring is provided with a female screw section.

3. The diaphragm valve according to claim 1 , wherein the stepped section is further provided with a press-fitting stepped section, and the seat ring is press-fitted into the press-fitting stepped section to press-fit and fix the seat ring into and to the body.

4. The diaphragm valve according to claim 1 , wherein an engagement section is provided in the outer wall section, and an outer periphery of a bottom portion of the valve seat has a large diameter section having an increased outer diameter such that, upon the valve seat being press-fitted into and fixed to the press-fitting groove, the large diameter section engages with the engagement section so that the valve seat that has been press-fitted and fixed does not come out of the press-fitting groove.

5. A method for replacing a valve seat in the diaphragm valve according to claim 1 , the method comprising:

removing the valve seat by screwing a jig provided with a male screw section into a female screw section provided on an inner peripheral surface of the seat ring to pull up the jig so as to extract the valve seat while locking a bottom portion of the valve seat by the flange section in the seat ring; and

mounting a replacement valve seat by press-fitting a bottom portion of the replacement valve seat into the press-fitting groove with the bottom portion contacting an upper surface of the flange section so as to fix the bottom portion of the replacement valve seat to the press-fitting groove.