Bladders or bust—Is there a better way? - Exploring the Heart of Logistics - fuel storage - Statistical Data Included

Air Force Journal of Logistics, Winter, 2001 by Merlinda B. Vergonio

If you ask fuels people about their deployment to Prince Sultan Air Base (PSAB), the first thing to come to mind will probably be fuel bladders. The 363 (d) Expeditionary Wing fuels flight manages more than 4.5 million gallons of jet fuel per month. On a daily basis, it issues, receives, and transports close to 200,000 gallons to support 12 different weapon systems and coalition aircraft To supplement this demand, the 363 (d) pioneered use of 210,000-gallon, fabric-coated tanks to store JP8 fuel. Before the these tanks were put into service at PSAB in 1998, 50,000-gallon bladders were the only size available. The larger bags increased the storage capacity and decreased the number of locations needed to place and maintain bladders. However, the bigger bags had bigger leaks.

These bigger bags with bigger leaks caused patch masters countless hours in repair time. After a leak was identified, all fuel had to be transferred from one bladder to another. Once the transfer was completed, the patching game began, which took several days. This process not only consumed man-hours but also caused a loss in storage capacity.

The manufacturer, Reliance Aeroproducts, was contacted concerning the quality and effectiveness of these larger bags. Reliance reengineered the bladders and delivered four to the 363 (d) in August 2001. These new fuel tanks were adjusted to include wider seams and thicker, heavier material on the outer fabric. The fuels flight eagerly went to work to install two of the improved bladders but were disappointed when seams ripped causing more leaks as the fuel was added. The fuels flight decided to prepatch the second pair of bladders where they thought there might be weak spots, thus reducing the time spent going through the patch mastering process. The results were not much better. Reliance again was asked to reevaluate the fuel bags. Reliance agreed not only to ship three upgraded bladders but also to come to PSAB and review installation and filling procedures.

To enhance the field evaluation process, Reliance selectively modified the three bladders and conducted additional tests in a desert environment. It pre-installed triple seam patches on one of the bladders and made bigger corners on another. The third bladder was left unchanged to serve as a control. These changes were made at the factory to determine what could be done to reduce repetitive maintenance and repairs in the field.

After arriving at PSAB in October 2001, the contractors assisted flight personnel in installing the three new bags. All bladders were inspected and minor preventive maintenance completed before adding fuel. The bag, modified with larger corners--bag MB4-01--still developed a minor seep. The seep was fixed with a clamp and an application of a liquefied rubber sealant called back brush. Bag MB4-08--customized with preinstalled triple seam patches--leaked after filling the bag with just 50,000 gallons of JP8 fuel.

Reliance representatives observed POL personnel's bladder-patching routine and offered their own mending techniques. Both teams were able to exchange valuable tips on site. Reliance took away ideas for improving its product; for example, it plans to send installation kits with new bladders. The kits will consist of new screws, seals, and grease to ensure proper fastening of the door fittings on the bladders. While installation kits are not part of the contract, Reliance must guarantee no seepage in these areas. Another suggested amendment includes pre-installation of patches at all triple seams to reinforce the joints and prevent possible seepage. Also, Reliance will make bigger corners similar to one of the test tanks installed during the visit. So far, the larger corners have proven to be more stable and are working well.

After watching the field installation process and talking with flight technicians, Reliance identified changes to reduce stress on the 210,000 bladders. It plans to move the fittings required for the bags so they all line up on one panel. Currently, the fittings are located according to the specifications outlined in MIL-T-53066B, which illustrates them staggered on different panels.

Furthermore, Reliance will change the way bladders are rolled during packing for future deliveries. According to the mil-spec, the bladders must be rolled at each end and meet in the middle. The bags will now be rolled from one end to the other, similar to a burrito, which will allow the bag to be unrolled more easily from one end of the berm. This will reduce dragging or constant repositioning of the bag. Currently, to achieve proper positioning, the bag has to be placed exactly in the middle of the berm, which is difficult with limited equipment.

Finally, Reliance will improve the 2-3-inch sling straps used to lift the bag out of its crate. In the future, Reliance will use a full-body sling to eliminate the stress and ensure even distribution of weight.

Another initiative resulting from the visit is the need to continue looking for better patching products. It will provide the fuels flight with PRC, better known as aircraft fuel cell adhesive, to use in repairing seeps. POL personnel will provide feedback to Reliance on the reliability of the product. Additionally, they will also conduct experiments with the use of a Kevlar ingredient on the inner tank to observe its effect on the seams. This test will take time and be accomplished at the manufacturer using a smaller tank. Testing is expected to take 6 months. If the Kevlar product is a success, then Reliance will attempt to transform it into a spray that can be used easily in the field.