Tapping into a hydraulic system to sample fluid creates the potential to contaminate not only the fluid in the hydraulic system, but the fluid sample as well. To help prevent either from occurring, test ports designed for fluid sampling should be mounted permanently to the equipment and have protective caps to keep dirt away from the sampling port.
Offered by many different manufacturers, these test ports generally have a cap that is removed only when taking a fluid sample and replaced immediately afterward. One such product that minimizes the potential for contamination when sampling fluid from a hydraulic system is the Wear Chek oil sampling valve, from Fluid Line Products, Willoughby, Ohio. The Wear Chek lets a user draw fluid from a hydraulic system’s return line at pressures to 600 psi.
This low-pressure test fitting comes in a variety of port sizes and thread configurations to sample fluid from hydraulic return lines without having to shut down equipment. Pressing on its pushbutton opens a check valve that routes fluid from the hydraulic system out through a sampling port. Similar test ports for taking samples from high-pressure lines use a threaded connection instead of a pushbutton to open the check valve.
The test port avoids introducing external contaminants into the fluid extracted from the hydraulic system. However, to ensure accurate samples, tubing leading to the sampling vessel and the sampling vessel itself must be absolutely clean. The tube should be discarded after a sample is drawn and replaced with a new one before each subsequent sampling.