When a barrier fluid is added to a standard CURC™ gland some fluid will escape to atmosphere (past the restriction bush).
The CRCO™ option substitutes the carbon restriction bushing with an oil seal and is capable of sealing secondary fluids, at barrier pressures up to 10 psig (2/3 of a barg). Thin oil is an ideal barrier fluid, with a Water/Soluble oil mixture an acceptable alternative