Defense Media Network

BUSINESS SPOTLIGHT: SSS Clutch Company, Inc. (Sponsored)

The U.S. Navy just commissioned the 7th vessel to bear the name of the First State. The USS Delaware, designated SSN 791, is a Virginia-class, nuclear-powered fast attack submarine and it is the first to bear the name of “Delaware” in more than 100 years. What makes this story that much more special is that Delawareans played a role in the building of this vessel.

SSS Clutch Company, Inc., located in New Castle, Delaware, provided the company’s namesake, the SSS Clutch, for the USS Delaware. SSS Clutch Company, Inc. is the North and South American affiliate Company of SSS Gears Limited, Sunbury-on-Thames, London, England, a Company that has been designing and manufacturing SSS Overrunning Clutches for nearly seventy years.

Seldom do all our employees get a chance to see the final installation of our product and to meet those who will utilize and operate our SSS Clutches. That is why the Commissioning of the USS Delaware in the Port of Wilmington in Delaware was to be such a special event; it is unfortunate the U. S. Navy League sponsored celebration had to be cancelled because of COVID-19 pandemic and the ship had to be “administratively” commissioned by the U.S. Navy.

At this point, you may be asking yourself, “What is an SSS Clutch?”

An SSS (Synchronous-Self-Shifting) Clutch is analogous to a bicycle freewheel. The clutch engages automatically whenever the driving side accelerates to the speed of the driven side and disengages automatically whenever the driving side slows down relative to the driven. Like a bicycle, when you peddle uphill, the freewheel in your bicycle transmits power to the back wheel through the chain and sprocket. SSS Clutches, however, transmit power or torque through concentric teeth and can be made to transmit up to 500,000 horsepower or operate in excess of 17,000 rpm in lower powers and physically can be anywhere from about three inches in diameter to five feet in diameter depending on the power (torque) they need to transmit.


SSS Clutch Operating Principle (SSS Clutch image)

SSS Clutch Operating Principle (SSS Clutch image)


Worldwide applications include SSS Clutches for naval marine propulsion of multi-engine ships operated by 50 navies worldwide, exhaust turbine driven generators in most of the world’s largest diesel engine driven container ships, SSS Clutches for gas fired combined cycle power stations, SSS Clutches for combined heat & power plants, and for peak load gas fired power plants in 55 countries. SSS Clutches are also supplied for mid & down-stream oil & gas applications such as dual driven natural gas pipelines, dual driven pumps, compressors, gas recirculation fans and generators in refineries, process plants, petrochemical plants, etc. It is a niche industry, but critical to the efficiency and durability of propulsion- and power-based technologies.

For instance, SSS Clutches are the key mechanism in large gas and steam turbine drives of combined cycle and peak load power stations as well as associated auxiliary drives such as gas and steam turbine slow speed turning gears, gas turbine starter drives and accelerator drives to run electrical generators for speed synchronization.



More than 400 SSS Clutches with power ratings up to 400 MW are installed in single shaft combined cycle generation plants to automatically connect and disconnect a steam turbine to a gas turbine generator at start up and shut down, and more than 600 are installed in peak load gas turbine generating plant to disconnect the gas turbine when power generation is not required and to allow the generator to stay connected to the grid like a motor to provide reactive power and rotating inertia for grid stability. This is all the more important as increasing numbers of renewable energy plants are commissioned, and these plants, which are replacing conventional gas and steam turbine generating plants cannot provide the reactive power and rotating inertia an electrical grid needs for stability.

An increasing number of SSS Clutches are installed in large and small combined heat and power plants; enabling a condensing steam turbine to be disconnected and steam used for district heating hot water piping in hospitals and university campuses, etc.

More than 25,000 SSS Clutches have been supplied for gas turbine starting disconnects and to disconnect an automatic turning gear used to slowly rotate the turbomachinery for cooldown after operation.

Since 1950, nearly 40,000 SSS Clutches have been supplied worldwide. About one quarter of these SSS Clutches are in service in North & South America, most of which were sold and are serviced by SSS Clutch Company, Inc.

SSS Clutches were first used by the U.S. Navy in the 1960s and many classes of ships, now retired, were retrofitted with SSS Clutches to improve service reliability as well as to reduce life cycle maintenance and associated costs. The first U.S. Navy ships to use SSS Clutches were the Asheville Class Patrol Gunboats in the 1950s, PG-84 Class and PG-92 Class, and this was followed by the supply of SSS Clutches for new ships such as the U.S. Navy Admiral Perry Class Frigates, U.S. Navy Spruance Class Destroyers, and US Coast Guard Hamilton Class High Endurance Cutters.

Today more than 1,400 SSS Clutches are currently in operation in twelve classes of U.S. Navy, U.S. Military Sealift Command, U.S. Coast Guard ships and three classes of US Navy submarines including the U.S. Navy Virginia Class, the latest of which is the USS Delaware, SSN791.


SSS Clutch is located in New Castle, Delaware. (SSS Clutch image)

SSS Clutch is located in New Castle, Delaware. (SSS Clutch image)


For ongoing new construction U.S. Navy ship programs, SSS Clutches are currently being supplied for every new DDG-51 Arleigh Burke Destroyer as well as for the Ship to Shore Connector hovercraft, LCAC-100, and the USS America Class amphibious assault ships. Every DDG-51 Destroyer has ten SSS Clutches; four in the main propulsion to automatically connect and disconnect the main gas turbine engines when needed, and six for normal and redundant starters for the three on board gas turbine generator sets. An eleventh SSS Clutch is being considered for use with an electric motor on board DDG-51 ships to give increased operating range and fuel efficiency when operating at lower speeds. This hybrid propulsion scheme is being adopted by many navies as well.

In the rotating equipment industry, one of the measures of reliability of rotating equipment is “mean time between failures” (MTBF). SSS Clutches have demonstrated a MTBF in excess of 275,000 hours, in three classes of U.S. Navy ships, each operating for over thirty years. This is a remarkable achievement for equipment operating in arduous naval marine applications.

In addition to the naval marine propulsion work, SSS Clutch Company continues to supply SSS Clutches for power generation and oil & gas applications, which represent nearly seventy-five percent of all new orders.

SSS Clutch Company continues to expand the type and number of applications for its product. With the periodic addition of new employees, the Company continues to grow and position itself for the future. Our employees consist of mechanical and electrical engineers, technicians, contract administrators and assistants, plus we periodically employ consultants with specific industry expertise. SSS Clutch Company also occasionally hires engineering students as interns from universities and technical schools in our region.


Morgan L. Hendry,