Gas Turbine Engines Are Improving Reliability By Switching to a Unique Industrial Clutch Design on TDI TurboStart Air Starters

DAYTON, OH--June 11, 2013: Field-users of Gas Turbine Engines from companies like GE, Rolls Royce, Pratt & Whitney, and Detroit Diesel are achieving improved starting reliability by replacing original equipment starters with an industrial turbine air starter featuring a unique, more reliable clutch design.  TDI TurboStart's sprag clutch handles the higher torque capacity compared to traditional clutches offered on most other air starters. "Instead of just one point of contact, or three points of contact common to other clutch designs, we have 22 contact points which evenly disperse the torque through the entire start cycle," states Dave Rawlins, Senior Product Manager of Tech Development. "Because there are more load carrying members, and greater contact area, TurboStarts handle torque loads which often cause other clutches to fail."

Clutch failure on the air starter is one of the most significant reasons for gas turbine engines not being on line or available during critical operation cycles.  In volatile environments it is not uncommon for contaminants to enter a roller clutch.  When this happens the clutch can actually be damaged to the extent of lock up and prevent the engine from starting.  Fast ramp-ups can cause pawl and ratchet clutches to shear off teeth and fail to crank.  "These kind of problems shouldn't be surprising given many of the air starters and clutch mechanics were originally designed for aircraft -- not industrial applications," continued TDI's Rawlins.  "TDI has the only air starter and clutch system specifically designed to withstand harsh industrial environments."

This URL (Sprag Clutch ) shows the 22 points of contact on the TDI sprag clutch as well as an image of the other two prevalent clutch designs.  Mechanically, you'll notice the sprag clutch has an inner and outer cylindrical race, which is connected through a series of cams, or what TDI call sprags.  As the inner race rotates in one direction, torque is transmitted through the clutch to the outer race and output shaft. Once the engine has started, the outer race becomes driven and the sprags shift in the opposite direction, which deflect against an energizing spring and permits the outer race to rotate -- without driving the inner race.  At a pre-determined speeds the sprags will lift off completely so there is virtually no contact between the inner and outer race during normal running operation.

"There's been a frustration among gas turbine engine users who are tired of broken clutches because of rigorous wear conditions," continued Rawlins.  "The mechanics appreciate the durability of the sprag clutch, but the engineers really love the simple and reliable mechanical design."

Unlike the more expensive turbine air starters, which are aeroderivatives, TDI TurboStart Air Starters were specifically designed for rugged industrial applications.  The standard 56 Series Turbine Air Starters deliver 155 hp on just 50 psig (3.3 BAR).  Reliability is further enhanced by the simplicity of the TurboStart's single planetary gear design, which reduces moving parts, maintenance, and ultimately downtime.

TDI engineers estimate that by spreading the clutch contact across 22 points, it reduces wear by over 400% vs. common clutch design.  In addition, TurboStart often times costs 3-4 times less than aeroderivative-style air starters and eliminates the need for temperamental ramping controls.

TurboStarts fit all gas turbine engines including: GE, Allison, Detroit Diesel, Dresser-Rand, Pratt & Whitney, Rolls Royce, Solar, and Volvo.

Tech Development is the world's number one manufacturer of turbine air starters with a reputation for high performance in the world's most challenging environments.