Access fittings located on bottom-of-the-line or near bottom-of-the-line positions may be packed with accumulated debris that can obstruct line pressure from passing into the retriever, thereby preventing pressure equalization.
To ensure safe working practices, a Back Pressure Pump must be used with all Cosasco Retrievers when pressure equalization is not achieved by normal operating procedures. Pressure equalization is crucial to prevent uncontrolled stroking, and to ensure safe removal of the plug assembly from the access fitting.
"Back Pressuring" pressurizes the retriever to a pressure slightly higher than the line pressure, thereby preventing a surge of pressure when the plug assembly is removed. Back pressuring also helps to loosen and push back any debris that may have accumulated in the access fitting.