Unseen Corrosion Creates Need

Corrosion Under Insulation (CUI), which occurs when moisture builds up on the external surface of insulated equipment, is one of the worst problems for refineries and process plants that typically operate at high temperatures.

One of the most common causes of CUI is when water seeps into, and is absorbed by, the thermal insulation jacketing. When this occurs, the equipment will either begin to corrode as it is exposed to water and oxygen, or in the case of stainless steels, stress corrosion cracking and pitting will occur.

Refineries build in the 1970s are faced with several safety and economical concerns as a result of CUI. Some of these concerns include sudden and hazardous leaks and plant shutdowns with high losses of production volumes. Leaks are of special concern because if they are not discovered in time, they have the potential to release toxic gas and explode.


Prior to installing the new surface cleaning and painting systems, the local EPA office was contacted to initiate the permit process. Among the design challenges for the new blast booth
ventilation system was the need for it to handle the large variety of pipe sizes the customer manages daily. It was imperative that the new system was able to account for the numerous pipe sizes, which range up to 16” (400mm) in diameter and from 10’ to 15’ (3m to 4.5m) in length, with 40’ (12m) lengths occasionally being utilized.


An AAF OptiFlo® cartridge collector was installed to draw the dust generated from the abrasive blasting process into the slotted hoods. Abrasive dust traveling through the ductwork enters the OptiFlo® through the abrasion resistant inlets, allowing the heavier dust to drop out before it comes in contact with the filters. The remaining light dust is filtered by AAF’s REDClean® media to achieve MERV15 (F9) filter efficiency. Eighty percent of the exhaust air is returned into the blast booth along with twenty percent fresh air from outside, saving both heating and cooling costs.


The completed system has resulted in an effective low energy solution that improves air quality, visibility and a safer working environment for the employees. Less filter change-outs means longer filter life and minimal landfill waste, thus minimizing the environmental impact.