ANAD Powertrain VS works wide variety of engines
October 13, 2011
ANNISTON ARMY DEPOT, Ala. -- With production lines that can be reconfigured quickly and a computer system programmed to assist mechanics working on a variety of engine types, Anniston Army Depot's Powertrain Value Stream is capable of handling a wide variety of ground combat vehicle engines.
"I would venture to say that, in the U.S. Army, there isn't any ground vehicle engine we don't have the capability to overhaul in this facility," said Warren Turner, process optimization manager for the value stream.
The depot currently repairs or overhauls six different types of engines, including the AGT 1500, which powers the M1 Abrams tank and is the only turbine engine currently in the depot's workload.
The Turbine Drive Train Division is currently configured for the AGT 1500 due to the workload devoted to that engine. Conversely, the Reciprocating Drive Train Division, housed in the depot's Powertrain Flexible Maintenance Facility, is arranged to perform work on any engine in the depot's workload.
Currently, the five reciprocating engines repaired by the depot are the AVDS-1790 series engine, which can be found in the M88, AVLB and other heavy tracked vehicles; the 6V and 8V Detroit diesel engines, which power light tracked vehicles; the 903 Cummins engine, which can be found in the M9ACE; and the 3126 Caterpillar engine for the Stryker.
No matter the engine, both shops follow the same basic procedures beginning with induction, where the engine's serial number is recorded and the engine is prepared for disassembly.
For all engines, preparations include the draining of fluids, if needed, and, for the AGT 1500, involves removal of the wiring harness. Reciprocating engines are pre-cleaned during the induction process in one of two large washers.
Disassembly of the AGT 1500 begins with dividing it into four modules. Each module is sent to its respective disassembly line where the internal components are removed until all that remains is a metal engine husk.
Reciprocating engines enter a disassembly bay where mechanics remove the internal components of the engine utilizing Material Maintenance Information System Technology, a computer system that instructs mechanics how the engine should be disassembled then tracks the engine and its components through the reclamation and reassembly processes.
"We can pull a mechanic out of another building and the MMIST will tell him or her, step by step, what to do," said James McKinney, chief of the Reciprocating Drive Train Division.
The turbine engine shop also utilizes a computer system, one that ensures each engine is disassembled and assembled in exactly the same way.
"The electronic instructions have standardized the way we do things," said Chris Williams, chief of the turbine drive train division. "The work is done the same way every time, which is important when you are assembling engines with a very close tolerance."
Component testing and reclamation
Throughout the disassembly process, mechanics scrap any engine parts that cannot be reclaimed. The rest are cleaned and stripped in preparation for the reclamation process.
Each part is tested along the way -- for cracks, proper thickness and weight. If the parts meet the appropriate specifications, they are placed in stock and sent to the assembly lines. For parts not meeting specifications that can be reclaimed, welding, machining and metalizing ensure the parts meet tolerances.
Checking for defects means a visit to non-destructive testing. At NDT, chemicals are sprayed on each part, highlighting defects.
"If there is a crack in a part, it will show up under the black light," said Jesse Smith, a mechanic who operates the NDT station. "If an internal part is cracked, it can't be repaired, so we discharge it and order a new part."
Smith says the NDT process is vital to the quality of each engine produced since it ensures no defective parts are used in the engines.
Even new parts go through testing before they are assembled on the engine. In another part of the reciprocating division, Jonathon Vaughn uses a computer-controlled air check measuring system, ensuring all pistons set for assembly in reciprocating engines meet specifications. The computer takes seven measurements simultaneously and even new parts are checked for tolerance.
"Sometimes a new part will be bad," he said. "So we check everything."
The rotors that go into the AGT 1500 are also carefully checked -- each must be balanced to an extremely tight specification before assembly in the engine.
Each rotor blade is weighed and the weight is dispersed evenly along the shaft. Then, the rotors are tested by a computer. If the assemblies are out of balance, the rotor is reworked by mechanics until it is right.
"Spinning at the extreme revolutions per minute these parts spin at -- 30,000 to 40,000 RPMs -- they have to be balanced just right or the engines bearings and seals will wear out," said Williams.
Multiple Lean events have been held throughout the value stream, streamlining the processes so that each work station has exactly what is needed to do the job at hand.
"When we Leaned the assembly process, and set up the assembly-line style work flow we have now, we turned in thousands of dollars worth of tools that were no longer needed," said Williams.
Testing and verification of parts continues through the assembly process as the engines are rebuilt from the inside out.
The AGT 1500's component kits are put together by Honeywell from reclaimed and new parts. In the reciprocating division, the reclaimed parts rarely leave the Powertrain Flexible Maintenance Facility.
"The only things that leave this building are parts being zinc or chrome plated," said McKinney. "Everything else is reclaimed right here."
Once each engine is fully assembled, it goes to a dynamometer test cell where it is checked for leaks, horsepower, torque, vibration and numerous other details.
"There are 160 different parameters we test," said David Estes of the Turbine Drive Train Division.
The dynamometer simulates realistic conditions for each engine, putting the same load the engine would experience in an actual combat vehicle and requiring it to pull the same weight.
Once testing is complete, the engine is final dressed. It is then ready to be installed in a vehicle or placed into storage.
When running at full capacity, the Turbine Drive Train Division can complete 1,680 engines per year and the Powertrain Flexible Maintenance Facility is capable of completing 1,875 engines per year.