a refrigeration and defrost system utilizing various valves for opening a defrost line to hot gas and regulating the pressure in refrigerant lines . a slug surge suppressor is provided at several points in the defrost and refrigerant lines to alleviate hydraulic shock damage caused by liquid / gas &# 34 ; slugs &# 34 ; passing rapidly through the lines . the slugs are commonly formed by the required rapid opening of the various valve of the system . capillary passages in the suppressor resist liquid flow while allowing gas to flow freely .