NEWS | March 2, 2021

New Scanning and Inspection Method for Submarine, Ship Propulsion Shafts Saves Time and Money

By Todd A. Hurley, NSWC Carderock Division, Public Affairs

The Shaft Taper Analysis Verification Evaluation (STAVE) system is a digital scanning technology and inspection process, which was developed to replace the plug and ring gauge system submarines, nuclear aircraft carriers and other ship classes with fixed-pitch propulsion shaft taper refurbishment, aligning with NAVSEA’s strategic framework in transforming digital capability.

The project goal for STAVE was for it to be authorized on all submarine propulsion shaft repairs and refits, to reduce the shaft repair manpower requirements, as well as reducing the cost of shaft tooling and to increase consistency and quality of shaft tapers. This aligns directly with Naval Surface Warfare Center (NSWC), Carderock Division’s strategic plan under the platform integrity and performance pillar of sustainment-based technologies. STAVE is easy to implement and maintain and creates a digital record of the shaft during construction and repairs, all while eliminating contact percentage variability between machinists.

“Taper gauges are used to inspect shaft tapers when getting repaired,” said Anthony Brock, 3D Measurement Lead Engineer in Carderock’s Performance Evaluation Branch. “But they are expensive to build and maintain. A lot of rigging is required to lift the gauges, which are roughly 2,000 pounds. We came up with an idea to develop a solution to replace these gauges since they are heavy, cumbersome and involve massive logistic issues.”

The idea is saving the Navy money. A STAVE system unit can inspect all submarine classes and nuclear aircraft carriers at a shipyard; subsequently, the Navy's is no longer purchasing new gages for shaft refurbishment. The implementation of STAVE also will eliminate the costs for periodic refurbishment and logistics associated with shipping gauges between facilities.

The STAVE System also saves time. It does not require the removal of the tail stock for measurements on lathe, nor does it require rigger support to set up and use. This frees the riggers for other critical jobs and allows the shafting shop to perform inspections on any shaft, even on short notice.

This system, which has been in development at Carderock for nearly 13 years and is led by the Structures and Composites Division, has finally been put into the fleet. Brock presented the STAVE system at the virtual NAVSEA Industrial Innovation Partnership Day on Dec. 8.

This project originally started in 2008 as a cumbersome work practice (CWP) by former NSWC Carderock Division employee, Alan Cohn.

“At the time, I was tasked with investigating the use of a laser tracker as a means of performing shaft measurements without using gauges,” Cohn said. “After some early experimentation, it was determined that a laser tracker would not provide the necessary resolution or accuracy to capture the minute surface defects that would affect contact with the coupling sleeve. I continued to investigate other technologies including Photogrammetry and Structured Light. It was determined that structured light was the only technology capable of the resolution and accuracy needed for the contact mapping.”

Cohn has since retired from the Navy, but continues to support the project as an employee of Propulsor Technology Inc. (PTI). The current iteration of the project has been led by Brock since 2016, with Amy Moore and Lyshawn Dean (SEA04T), Quoc B. Nguyen and Dave Lytkowski (SEA05Z), Jose Bernardo (PTI) and Mike Agronin (Direct Dimensions Inc.) joining at various times over the years.

“We had a white-light scanner with a smaller field of view,” Bernardo said. “It was a good piece of equipment, but struggled to do anything aside from scanning a taper, and only had a 33 percent chance of success. We decided we wanted to design a better process, which is what we did with the digital scanner. It was a gigantic improvement and started solving a lot of our issues with better accuracy and more smoothness to data – it took the process from hours to about 12 minutes.”

Agronin’s employer, Direct Dimension’s Inc., was responsible for coming up with the hardware to measure large surface area with proper accuracy, while Bernardo’s employer designed the software to put the measurements together.

“The technology simply wasn’t there when we first started this process,” Brock said. “But, in the last six or so years, 3D scanners have gotten to a point where they are good enough to measure large areas with extreme accuracy.”

Since developing STAVE, Brock and his team have been in contact with the four major naval shipyards – Norfolk, Pearl Harbor, Puget Sound and Portsmouth – in order to get their system to the fleet. So far, they have been able to get STAVE delivered to Norfolk and Portsmouth, with the next step being to deliver it to Pearl Harbor and Puget Sound.

“We received tremendous support from all the shipyards,” Brock said. “One reason STAVE turned out so well is that the concept had so many false starts before this point. That really encouraged us to take a more customer-driven approach, which led to us visiting all of the shipyards more than once. We took our equipment to each of the shipyards to not only interact with them and show them how the system worked and how it was evolving, but also to show that we weren’t hiding anything – we wanted them to be there with us to contribute their concerns and ideas. If we didn’t go to the shipyards, we wouldn’t have noticed simple changes that could completely change the accuracy of the system.”

With the success of STAVE, Brock and his team have since discussed a Rudder Analysis Verification Evaluation (RAVE) tool concept.

RAVE will be a digital scanning technology and inspection process developed to replace the piece-by-piece blue-hit inspection for nuclear-powered aircraft carrier steering rudder stock tapers and submarine rudder stock and diving stock tapers.

The goal of RAVE is to have it authorized for use as an inspection tool on rudder repairs and refits; to reduce the rudder repair manpower requirements; and, to increase the consistency and quality of data for rudder tapers. The RAVE project is set to begin as soon as funding is available.