Welker Constant Pressure Floating Piston Sample Cylinders collect and maintain gas or liquid samples at full pipeline conditions – regardless of pressure and temperature – and provide collection, storage and transport of liquid or gas samples at pipeline conditions. These cylinders provide superior vortex mixing action in a compact, manageable, easy to use package. D.O.T. approved models are available for working pressures up to 3600 psi. DNV and Transport Canada approved models are available in several sizes with working pressure up to 1800 psi.