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LoaDisc, Independent TestsBolt Load Accuracy TestTo test the bolt load accuracy and repeatability, 3 independent, electronically measured tests were performed by independent firms, including BASF AG, Lloyd’s Register, with calibrated HYTORC tools. An additional, independent LoaDisc test was performed by BASF AG, Germany, yet, with tapered Stretch Bolts. General testing condition for all three independent tests:HYTORC LoaDisc is installed underneath a standard hex nut. This allows a lateral-load free tightening of bolt connections without external support. Side loads do not occur during the bolt elongation. During the bolting operation, the thread segment of the LoaDisc is, first, fixed against the standard hex nut. From this point in, the bolt can no longer turn with the nut. Now, the force applied between the LoaDisc and the nut builds up until the thread segment shears at its intended break point and, then, the force is distributed to the entire bolt. The bolt is now further pretensioned up to the desired final load. Since the wrench reacts against the LoaDisc axially through the bolt, no transverse forces are introduced into the connection by the bolting operation. The geometry of the LoaDisc and the different frictional relations ensure that the LoaDisc does not turn on the contact surface. Therefore, backup wrenches and reaction arms are no longer needed. BASF AG Test & Result
The contact surface under the LoaDisc is only loaded by pressure. Loosening the connections required a maximum of only 1.6 times the tightening force. In standard hex connections this ratio can be up to three times. An additional test was performed by BASF AG, Germany, yet, with tapered stretch bolts. The test result showed a major bolt load accuracy improvement to + 4% due to the use of LoaDisc on high quality bolts. The same torque test on stretch bolts, yet without the HYTORC LoaDisc showed a bolt load variation of + 15%. The test results showed a major bolt load accuracy improvement to +/- 4% due to the use of LoaDisc on high quality bolts. The same torque test on Stretch Bolts, yet without the HYTORC LoaDisc showed a bolt load variation of +/- 15%.  Their Findings:Bolt Load Accuracy and Repeatability: Standard Industrial Bolts: +/- 10% Tapered Stretch Bolts: +/- 4% Heat Corrosion Test
The Result: Problem free disassembly without bolt thread damage. Explosion Test
The Result: The engaging threads showed no deformation. Bolt Relaxation TestA bolt relaxation test was performed on a calibrated load cell with a =/- ¼% gauge accuracy. The bolt was stretched to 100,000 lbs load by means of the HYTORC LoaDisc and left on the application for 3 days. A bolt load drop of merely 2% was registered. The test followed by hydraulic tensioners tests in Germany and the UK. One registered bolt relaxation of up to 63%, the other one did a bolt load fluctuation of =- 51%. The cause: Manual nut-turning. It is subject to incalculable variances: The human factor, the application, the field working conditions, the bolts and nuts used, their cleanliness, their tolerance, their perpendicularity and their friction.
The Result: the engaging threads showed no deformation. Lloyd's Register Test & Result
The test was performed by applying pump pressure of 4350 PSI to HYTORC Avanti-3 Tensioning machine to produce torque value of 1280 Ft. Lbs. to create bolt tension to achieve 60% yield of the B7 bolt. 1.1/2”-8UN B7 bolt used for the test was 14 inch long with 1.1/”-8UN LoaDisc underneath 2.3/8” AF 2H heavy hex nuts. Findings were 50% of LoaDisc displayed within +5% bolt load accuracy and the other 50% within +10% of accuracy. Lloyd’s Register Official Results PDF Load Accuracy & Result
The bolts tensioned with the LoaDisc showed that actual residual load variation of less than + 10% around the flange. This is within the official window of accuracy. Wheeler, the hydraulic tensioners, showed after repeated trials was merely 31% of bolts within 10% of the target load, 47% within 14% of the target load, and 22% of the bolts up to 51% from the target load on the same flange. Additionally, the LoaDisc tensioned all the bolts in less than half the time! Findings were 50% of LoaDisc displayed within + 5% bolt accuracy and the other 50% within + 10% of accuracy.  |
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The low scatter in the Pretensioning force values is due mainly to assembly conditions, which can be controlled and checked better than those of bolt connections with usual standard hex nuts. Since the surface quality of the LoaDisc is always the same, in all the tests the maximum scatter of load value was within the range of +/- 10% on standard industrial bolts.
A further test, performed by BASF, was a heat corrosion test. The assembly was exposed to 360’C for 3 months.
To assume the integrity of this new fastening system, BASF AG performed an Explosion Test, by pulling the 10.9 stud until stud failure.
Scope of inspection included 1) visual inspection including basic operation, 2) documentation review including material certificate and bolt load calculation procedure, 3) witness accuracy rest, 4) review accuracy test and 5) witness harness test.
The LoaDisc was subjected to head to head comparison tests with hydraulic tensioners to determine which would give the most consistent and repeatable load results from bolt to bolt. Both LoaDisc and manual nut seating hydraulic tensioners had 10% tool coverage
