ROTATIONAL CAPACITY TEST – LONG BOLT PROCEDURE

For bolts long enough to fit in a tension measuring device

(Adapted from ASTM F3125-23, Appendix 2)

SCOPE

This IM provides the test procedure for determining the Rotational Capacity of bolt assemblies long enough to test using a bolt tension measuring device. The Rotational Capacity (RC) Test for all high strength fasteners shall be performed in the shop and in the field as required by Standard Specification 2408.03, S.

EQUIPMENT REQUIRED

· Calibrated bolt tension measuring device (Skidmore-Wilhelm or equivalent) of size appropriate for bolts to be tested. Calibration of the tension measuring device shall be verified by an approved testing agency at intervals not exceeding 12 months. Furnish the current calibration certificate with the tension measuring device.

· Calibrated manual torque wrench. When tested torque values from Step 5 are expected to exceed 600 ft.-lbs., a torque multiplier may be used in conjunction with the calibrated torque wrench, subject to the approval of the District Materials Engineer. Calibration of the torque wrench shall be verified by an approved testing agency at intervals not exceeding 12 months. Furnish the current calibration certificate with the torque wrench.

· Assortment of bolt spacers, to be placed within the grip of the fastener as necessary to position the nut at the proper location for testing. The bolt spacers must be of appropriate material type (steel or equivalent), thickness, hole diameter and cross-sectional area to permit full tightening of the bolt in accordance with the test procedure, without bending or damaging the test washer, bolt spacers or tension measuring device. Unless otherwise approved by the District Materials Engineer, the hole diameter of the bolt spacers shall not exceed the hole diameter of the test washer, and the cross-sectional area of the bolt spacers shall not be less than the cross- sectional area of the test washer.

· Rigid and accessible mounting location for the tension measuring device. The mounting location shall be adequately stable to prevent displacement of the tension measuring device during testing.

PROCEDURE

A minimum of two representative fastener assemblies, from each rotational capacity test lot, shall be tested for rotational capacity in accordance with Standard Specification 2408.03, S, 4, a. The following procedure shall be applied to each individual fastener tested for rotational capacity.

1. Obtain one representative fastener assembly, consisting of a bolt, nut, and washer, from the rotational capacity lot. Report the production lot numbers each for the bolt, nut, and washer components, as furnished by the manufacturer of the individual components. Report the rotational capacity lot number associated with the combined fastener assembly, as furnished by the supplier, in accordance with IM 453.06B. Report the date of testing, and assign a unique test number for each rotational capacity test (example: Lot##Test##).

2. Install the fastener assembly in the tension measuring device. When installed properly to finger-tight condition, bolt stick-out shall be at least flush with the nut, but not greater than 3 complete threads of stick-out past of the nut. This will typically provide 3 to 5 complete threads within the grip of the fastener. The washer from the rotational capacity lot (test washer) must be in direct contact with the nut. Up to 4 additional washers and/or approved bolt spacers may be used between the test washer and the faceplate of the tension measuring device, to establish proper positioning of the nut.

3. Using a manual wrench, tighten the nut to the target Snug Tension indicated in Table 391-A. Acceptable tolerance is -0 kips / +2 kips. Report actual snug tension achieved. When reporting actual snug tension, apply the appropriate correction factor to the gauge reading, as identified on the tension measuring device calibration report.

Table 391-A: Snug Tension

Bolt Diameter (in.)

¹/₂

⁵/₈

³/₄

⁷/₈

1 ¹/₈

1 ¹/₄

1 ³/₈

1 ¹/₂

Snug Tension

(kips)

4. Match mark the bolt tip, nut, and the faceplate of the tension measuring device in a straight line.

5. Using the calibrated manual torque wrench, tighten the nut as close as possible to, but not less than, the Minimum Service Tension indicated in Table 391-B. Read the torque and tension values simultaneously, with the nut in motion, when the actual service tension is attained. Report actual service tension achieved and the corresponding torque reading at actual service tension. When reporting actual service tension, apply the appropriate correction factor to the gauge reading, as identified on the tension measuring device calibration report.

Best Practice for Dial-Type Torque Wrenches - Read and record the torque when the Minimum Service Tension is achieved.

Best Practice for Click-Type Torque Wrenches - Set the torque wrench to click at a torque value that slightly exceeds the expected torque needed to tighten the assembly to the Minimum Service Tension. If the torque wrench clicks before the Minimum Service Tension is achieved, reset the torque wrench to a higher torque setting and resume tightening until at least the Minimum Service Tension is achieved. The new torque setting must be high enough to put the nut in motion prior to clicking. Read and record the actual tension which causes the torque wrench to click (nut in motion), and the torque setting of the wrench.

Table 391-B: Minimum Service Tension
Bolt Diam. (in.)	¹/₂	⁵/₈	³/₄	⁷/₈	1	1 ¹/₈	1 ¹/₄	1 ³/₈	1 ¹/₂
Min. Service Tension (kips)	12	19	28	39	51	64	81	97	118

6. Compare the torque recorded in Step 5 with the Maximum Service Torque, calculated using the following formula. Assemblies fail the test if the recorded torque from Step 5 exceeds the calculated Maximum Service Torque.

Maximum Service Torque (ft.-lbs.) = C x T x D

C = Constant = 0.25 x 1000 (lb./kip) / 12 (in./ft.) = 20.83 (ft.-lbs./in.-kips)

T = Actual Service Tension from Step 5 (kips)

D = Bolt Diameter (in.)

7. Further tighten the nut to achieve a total rotation as close as possible to, but not less than, the Full Test Rotation indicated in Table 391-C. The total rotation is measured from the initial match marking from Step 4. Assemblies that strip or fracture prior to this rotation fail the test.

Table 391-C: Full Test Rotation

Bolt Length

4x bolt diameter

or less

More than 4x, but no more than 8x bolt diameter

More than
8x bolt diameter

Full Test Rotation (turns)

²/₃

1 ¹/₃

8. Record the actual tension at the completion of the Full Test Rotation from Step 7. Compare the actual recorded tension to the Minimum Tension at Full Test Rotation indicated in Table 391-D. When reporting actual tension at full test rotation, apply the appropriate correction factor to the gauge reading, as identified on the tension measuring device calibration report. Assembles with actual tension values that do not meet the Minimum Tension at Full Test Rotation from Table 391-D fail the test.

Table 391-D: Minimum Tension at Full Test Rotation
Bolt Diam (in.)	¹/₂	⁵/₈	³/₄	⁷/₈	1	1 ¹/₈	1 ¹/₄	1 ³/₈	1 ¹/₂
Min. Tension at Full Test Rotation (kips)	14	22	32	45	59	74	94	112	136

9. Loosen and remove the fastener assembly from the tension measuring device. Inspect the nut and bolt for signs of visible damage. Rethread the nut on the bolt. Assemblies which do not accommodate turning of the nut by hand, from the tip of the bolt to the position the nut was in during the test, fail the test (nut does not need to thread past the position it was in during the test). Assemblies which show signs of thread failure, stripping, or torsional failure fail the test. Fractured or broken bolts fail the test.