Superbolt_sole_source_Main__Stub_Shaft_Studs_2018-signed.pdf

July 6, 2018

MEMORANDUM FOR FILE

SUBJECT: Use of Superbolt Nuts for the Turbines at Truman Power Plant

1. The U. S. Army Corps of Engineers, Truman Power Plant, 29564 Powerhouse Road, Warsaw, MO 65355, has a requirement for torque nuts (“Supernuts”) and associated hardware for the turbine main shaft and stub shaft studs. The fasteners are manufactured by Superbolt, Inc. These fasteners are very complex in nature and are patented. These fasteners allow for tightening the studs in pure tension, which will result in better fatigue resistance.

2. The stub shaft studs are 4 ½” diameter, and the main shaft studs are 5 ½” in diameter.

Proper tightening of fasteners this large is critical to the long-term reliability of the turbines.

During turbine repair in the 1990’s, these fasteners were of the conventional hex-head nut type. During that time, the fastening was accomplished by inserting heaters into a hole in the stud, thereby stretching the stud due to thermal expansion. After the studs were stretched, the hex-nuts were tightened by turning the nut to a specific angle. This process takes a very long time. When the power plant attempted to try this method in the 2012/2013 time frame, multiple heaters failed, and the attempts were unsuccessful.

3. The Supernuts are not like a typical hex headed nut. They consist of a hardened washer, a round nut body, and several jack bolts around the perimeter of the nut body. The jack bolts are tightened using ordinary hand tools. This process results in the fastener being in pure tension, which greatly increases the fatigue resistance of the fasteners. The process also saves time when compared to the bolt-heating method.

4. The Supernuts are currently being installed in Unit 6 main and stub shaft studs. They have been used on some of the thrust bearing housings at Truman. They are also in use in the runner hub at Stockton Power Plant in the Kansas City District and many other Corps of Engineers power plants.

5. Referring to FAR 6.302-1,(a)(2)(ii), “Supplies may be deemed to be available only from the original source in the case of a follow-on contract for the continued development or production of a major system or highly specialized equipment, including major components thereof, when it is likely that award to any other source would result in (A) substantial duplication of cost to the Government that is not expected to be recovered through competition, or (B) unacceptable delays in fulfilling the agency’s requirements.”

6. DETERMINATION. Based on the above findings, it is hereby determined the “Supernuts” from Superbolt, Inc. is fair and reasonable and is in the best interest of the government.

Colleen Roberts, P.E.

Project Manager, PMC-J 816-389-3017