Railway Spike Pull-Out Test: Procedure and Acceptance
Railway spikes - dog spikes and screw spikes - are key components that keep rails firmly anchored to the sleepers. Their anchorage quality directly affects track stability and safety, so the pull-out (extraction) test is an indispensable verification step. The test measures the holding power of the spike in the sleeper (wood or concrete), not a bond with the rail itself.
1. Test Purpose
The main purpose of the pull-out test is to verify that the spike achieves the anchorage (holding) force required by the design and the applicable track standard. The measured pull-out resistance confirms that the fastening can withstand the vertical and lateral forces generated by train operation, ensuring railway safety. Results are used both for acceptance of newly installed spikes and for periodic inspection of in-service track.
2. Test Equipment
Pull-out (extraction) test machine - a calibrated hydraulic or mechanical rig with a reaction frame that grips the spike head and pulls vertically
Load cell or dynamometer with calibration traceable to a national standard.
- Displacement/force recorder (electronic data logger preferred)
- Measuring tools (calipers, dial indicators) for setup checks
- Safety equipment (barriers, protective wear) for operators
All equipment must be calibrated and verified before testing to ensure result accuracy.
3. Operation Steps
Select a representative spike sample; the sleeper (or spike-sleeper assembly) must match the production condition (same sleeper type, pre-drilling, and spike size).
Fix the test specimen in the rig so that the pull direction is vertical and aligned with the spike axis.
Set the loading parameters: a controlled pull rate (per the standard; a typical range is 5–10 mm/min for acceptance tests) and the maximum force limit.
Start the test and record force vs. displacement continuously.
Stop when the spike is withdrawn or the specified maximum load is reached; record the peak pull-out force and failure mode (spike withdrawal, thread stripping, sleeper splitting).
Compare the peak force against the acceptance criterion (e.g., minimum pull-out force per the track standard) and record the result.
4. Acceptance and In-Service Testing
For acceptance testing, the pull-out test is normally destructive (spike withdrawn to failure) on a defined sample size per lot. For in-service inspection, a non-destructive procedure is used: load the spike to a specified inspection load (below the design anchorage), hold for a set time, and confirm there is no excessive residual displacement. Acceptance values depend on the sleeper and spike type - for example, screw spikes in concrete sleepers typically require a minimum pull-out force in the range of 60 kN or higher per the relevant standard - and must be confirmed against the project specification.
5. Safety Precautions
Strictly follow safe operating procedures: keep personnel clear of the test rig during loading, use barriers, check the equipment regularly for wear or hydraulic leaks, and never exceed the machine's rated capacity. Calibrate the load cell annually and after any impact damage.
By following this procedure, the performance and quality of railway spikes can be effectively evaluated, providing a strong guarantee for the safety of railway transportation.
Get a Quote for Railway Spikes
The Railway Spike Pull-Out Test is used to verify the holding capacity and mechanical performance of rail spikes under specified test conditions. GNEE RAIL supplies railway spikes with material, dimensional, and mechanical requirements matched to the applicable rail fastening system and project specifications.
