A vessel system comprises an outer shell of carbon fibers held in a binder, a coolant circulation mechanism and control mechanism and an inner shell comprised of a refractory material and is of light weight and capable of withstanding the extreme temperature and pressure environment of, for example, a coal gasification process. The control mechanism can be computer controlled and can be used to monitor and modulate the coolant which is provided through the circulation mechanism for cooling and protecting the carbon fiber and outer shell. The control mechanism is also used to locate any isolated hot spots which may occur through the local disintegration of the inner refractory shell.

A continuous chain bit for hard rock drilling is disclosed which is capable of downhole cycling. A drill head assembly moves axially relative to a support body while the chain on the head assembly is held in position so that the bodily movement of the chain cycles the chain to present new composite links for drilling. A pair of spring fingers on opposite sides of the chain hold the chain against movement. The chain is held in tension by a spring-biased tensioning bar. A head at the working end of the chain supports the working links. The chain is centered by a reversing pawl and piston actuated by the pressure of the drilling mud. Detent pins lock the head assembly with respect to the support body and are also operated by the drilling mud pressure. A restricted nozzle with a divergent outlet sprays drilling mud into the cavity to remove debris. Indication of the centered position of the chain is provided by noting a low pressure reading indicating proper alignment of drilling mud slots on the links with the corresponding feed branches.