I am familiar with RuhrPumpen as an alternate to Flowserve for coke cutting equipment for Delayed Cokers. If the problem you are having with the Flowserve equipment is high solids loading in the cutting water system, the RuhrPumpen system will have similar problems. There are some differences that would influence you to pick one vendor of the other; however, both need good quality water.
I think it is best to have the complete cutting system designed and constructed by a single company as all the parts, cutting tool, drill stem, hoist, crosshead, free fall arrester, decoking valve and the overall interlocks and position indication. That leaves you with Flowserve or RuhrPumpen.
BOC is a company that can provide a replacement decoking valve for either Flowserve or RuhrPumpen equipment. Their valve is hydraulically actuated and has been reliable. The design of the valve allows for all maintenance to be done without removing the valve from the field. The breakdown orifices for the bypass and pre-fill mode are easily accessible and replaceable.
DeltaValve made a cutting tool at one time. I do not have any information on it or its reliability. Again, I like to have a single vendor responsible for the performance of the overall system.