This invention relates to improvements in and relating to ice pigging, and comprises a flowable slush of frozen particles for ice pigging a pipework, comprising, an aqueous liquid medium, a multiplicity of frozen particulates of said aqueous liquid medium, a freezing point depressant, selected from a hydroxide ion, said hydroxide ion present in the range of less than 10 wt %.

A clean-in-place system for piping systems uses a pig train having a dry ice and glycol section. The pig train is moved through the piping system as part of a cleaning sequence. The system and method of the disclosure provide an alternative, effective clean-in-place system that significantly reduces water, chemical and energy usage as well as significantly reducing the related environmental impact.