Flexible hoses (flexhoses) are used for many applications onboard Navy ships, piping various fluids including freshwater, seawater and lubrication oil throughout the ship.
U.S. Navy ships use flexhoses in both gravity-fed, seawater flush systems to collect, hold, and transfer (CHT) sewage while at sea, and newer ships use a vacuum collection, holding, and transfer system (VCHT).
VCHT has the same basic design as the CHT system, except waste collection is assisted by vacuum and special “low flow” sanitary fixtures in heads. VCHT has been used on commercial aircraft and cruise ships for years because it requires less weight and space, provides more design flexibility, and reduces sewage disposal costs.
There are limitations to synthetic rubber flexhoses: Both in storage and in use, hoses deteriorate until they eventually become unserviceable. Little, if any, indication shows on the outside of hoses that failures are occurring inside.
USS McFaul (DDG 74) had a failure to one of the two forward VCHT ejector pump hoses recently, and the other pump hose was beginning to crack. Both required replacement, so McFaul transited to Southeast Regional Maintenance Center (SERMC) in Mayport, Fla. to troubleshoot the cause of the discharge pump failure.
“Vacuum leaks and clogging are common problems on VCHT systems, and can be difficult to troubleshoot. Both can cause pumps to run for extended periods, which leads to heat buildup and increased wear and tear,” said GSM1 Drew Kleinknecht of SERMC’s Flex Hose Shop.
SERMC’s Flex Hose Shop got the call late on a Thursday afternoon regarding McFaul, and immediately commenced manufacturing new hoses, sometime after 2:00 a.m. Friday morning. The old ejector hoses were removed from McFaul and SERMC craftsmen measured and cut new sections of hose. After cutting, the hose assemblies were attached; the units were cleaned, inspected and tested before installation.
“The hoses we fabricated are exact duplications of the original in length, outside diameter, material, contour, and markings,” said MM2 Jason Plum of the Flex Hose Shop.
Frank Watson, of SERMC’s Engineering Department performed troubleshooting and provided expertise. “While I was onboard, Damage Controlman Chief Donnell Chapman, McFaul’s Repair Division Leading Chief, asked if I would inspect the aft VCHT system as well. I found restriction problems in the aft vacuum piping where even small objects/debris would cause it to clog. It just happened to begin clogging when we entered the space, so it made it very easy to explain what was happening to both systems,” Watson said.
While onboard, Watson also conducted training with the crew on chemically cleaning the VCHT system in accordance with applicable guidance, and troubleshooting the vacuum system to identify the difference between restrictions and vacuum leaks.
“We discussed how vacuum leaks and restrictions are detrimental to the VCHT system, and how to correct both. The discussions with the crew were enlightening. VCHT systems aren’t a new technology but they are installed on newer ships. Regular training helps ensure the crew is comfortable with the technology and can maintain it to its full potential,” Watson added.
McFaul’s commanding officer, Cmdr. Janet Days commended SERMC in an email to the commanding officer, Capt. Dave Gombas.
“On behalf of the entire crew of USS McFaul, I want to offer my personal heart-felt BRAVO ZULU for your tenacious support over the last five days. From distance support to greeting us on the pier and the multiple face-to-face updates each day, your commitment to McFaul’s mission and the health and comfort of our crew was impeccable.
“Your around the clock support, can-do attitude and commitment to ships were of the highest levels I have seen in my 19-years of commissioned service. You have a friend in USS McFaul, thank you again.”
“SERMC’s greatest asset is its people and their enthusiasm to meet any challenge. Our combatant commanders rely on SERMC to provide the assets they need when they are needed, so our ability to deliver ships on-time and of the highest quality is critical to the Fleet,” said Gombas.