A gas processing system includes a vessel defining a cavity for processing a gas. The vessel includes a process gas inlet for accepting process gas at an input pressure, and a process gas outlet for discharging process gas at an output pressure. The gas processing system further includes a shaft coupled to the vessel and a multistage sealing system comprising multiple seals spaced along the shaft. The shaft is configured to transfer mechanical energy to or from gas in the vessel. Each adjacent pair of seals defines a corresponding pressure space therebetween. One of the pressure spaces is an equalizing pressure space in hydraulic communication with the process gas inlet via a flow line, such that in operation, pressure in the equalizing pressure space is maintained at an equalized pressure with respect to a pressure in the process gas inlet.