How to deal with internal leakage in a high-pressure globe valve? What are the emergency remedies?

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How to deal with internal leakage in a high-pressure globe valve? What are the emergency solutions? Our plant uses Kitz check valves with a diameter of DN150 and a pressure rating of PN100, which are used for the bypass of the MDEA liquid-phase control valve in the absorption tower. Ideally, this bypass should remain closed at all times; however, over time internal leakage began to occur, causing the opening degree of the control valve to gradually decrease. The leakage rate is approximately 38 m3/h. It is initially suspected that contamination might be the cause. Several attempts at cleaning did not yield good results – in fact, they were ineffective. The valve body itself is made of carbon steel; it’s just not clear what material the valve stem is made of. I wonder if corrosion could be the issue Our factory uses the decarburization solvent NCMA produced by Sinopec. We are not sure what requirements this solvent places on the materials used in pipeline equipment, or whether it causes corrosion. Production at the factory is still ongoing, and the equipment has not been taken apart for inspection. We have tried to shut it off using an F wrench several times, but with little success; in fact, it became impossible to shut it off. Do you have any information regarding Kitz’s globe valves? Is the material of their internal valve cores resistant to this decarburization solvent? Are there any other ways to relieve internal leakage without stopping the machine?