Rail Impact | Impatto ferroviario

MIL STD 810 G – Test Method 526 – Rail Impact

 

SCOPE

 

Purpose
The purpose of this test method is to replicate the railroad car impact conditions that occur during the life of transport of systems, subsystems and units, hereafter called materiel, and the tiedown arrangements during the specified logistic conditions.
NOTE: Although the number of railroad car impacts that occur throughout the life of the materiel may exceed the number applied in this Method, it is unlikely that the maximum impact at 12.9 km/h (8 mph) will occur more than once.
Application
The rail impact test is intended to test materiel that will be transported by rail; to determine the effect of railroad car impacts that may occur during rail shipment, to verify the structural integrity of the materiel, to evaluate the adequacy of the tiedown system and the tiedown procedures, and to assess transportability1 by the Military Surface Deployment and Distribution Command Transportation Engineering Agency (SDDCTEA). All items are to be tested at their maximum gross weight (fully loaded) rating unless otherwise specified in the transportability requirements for the materiel.
Limitations
This method is not intended for railcar crash conditions, or for separate testing of small, individually packaged pieces of materiel that would normally be shipped (and tested) when mounted on a pallet, or as part of larger materiel. For the latter, the referenced documents (paragraph 6.1) provide guidance on environments measured during rail impact that may be useful in specially tailored laboratory testing.

 

TEST PROCESS

 

Rail Impact Procedure
The method for accelerating the test car will vary depending on the test facility. Typically, the test car can be accelerated using a locomotive or an inclined track. Use the steps below that apply to your test facility.
  • Step 1a. (Locomotive). Brief the train crew on the procedure. Delegate one person to advise the appropriate member of the train crew when moves are to be made. Instruct all participants and observers to take precautions for their personal safety and observe safety practices of the carrier and/or company conducting the test. If desired, perform a test run without impacting the test item to establish accuracy of speed.
  • Step 1b. (Inclined track). A section of track can be calibrated using a test car and speed-measuring device. Release the test car from the designated starting point and allow it to roll freely down the inclined track. Drop markers at the locations where the test car reaches the desired speeds. Ensure no other cars are present on the test track during the calibration process. Repeat the process at least twice to ensure the accuracy of speed locations. Next, release the test car from the same starting point and make adjustments in markers if needed prior to impacting. Speeds still need to be measured during the actual test as described above in paragraph 4.4c.
  • Step 2a. (Locomotive). Pull the rail car carrying the test item a sufficient distance from the buffer cars. Next, push the test load car toward the buffer car(s) until the desired speed is obtained, and release it so it rolls freely into the buffer car(s) – having knuckles positioned for coupling.
  • Step 2b. (Inclined track). After determining speed locations, perform impacts by locating the buffer cars at the proper location for desired impact speed, and for releasing the test car from the designated starting point. This requires moving the buffer cars every time a different speed is required. In lieu of repositioning of the buffer cars at various positions on the track, release the test car from calibrated positions on the inclined track that correspond to the desired speeds
  • Step 3. Subject the test item to four impacts, the first three of which are in the same direction and at speeds of 6.4, 9.7, and 12.9 km/h (4, 6, and 8 mph) respectively, each speed with a tolerance of +0.8 km/h (+0.5 mph) for the 6.4 and 9.7 km/h impacts, and +0.8, -0.0 km/h (+0.5, -0.0 mph) for the 12.9 km/h impacts. Perform the fourth impact at 12.9 km/h (+0.8, -0.0 km/h) (8 mph (+0.5, -0.0 mph)) impacting the opposite end of the test car from the first three impacts. If it is not possible to turn the test car because of track layout, this may be accomplished by running the test item car to the opposite end of the buffer cars and impacting as above.
  • Step 4. If the lading or securement items loosen or fail during the test, photograph and document these items. If it appears necessary to adjust the lading or securement items to continue the test, correct the restraint and restart the test from the beginning and follow the guidance provided in paragraph 4.3.2.
  • Step 5. If the materiel can be shipped in two orientations (such as lengthwise and crosswise on the rail car), repeat the four impacts for each orientation or have two test items on the test railcar one mounted in each orientation.
  • Step 6. If operation of the test item is required, perform a post test operational check for comparison with pre-test data, and see paragraph 5 for analysis of results.
Additional Requirements
  • Step 1. Repeat any impacts that are below the required test speeds. If any readjustment of the lading or reconditioning of the bracing or items of securement is necessary, correct, photograph, and document the problem(s), correct the restraint, and restart the entire test beginning with the 6.4 km/h (4 mph) impact. Accept any impacts above the required test speed providing the test item satisfies the requirements of paragraph 5.
  • Step 2. If the tiedown chains or chock blocks become loose during the test, photograph and document the problem(s). The test director will notify SDDCTEA of the modifications required, and jointly decide if a retest is required.

 

NOTE: Tailoring is essential. Please, ask to your confidence laboratory for further details about tailoring of test methods.

 

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