Crane Hook is considered a “Safety Related” component, having high-level tests and inspections before and during its life span.
We call “Testing” to quality controls performed when a hook is new (new production) and must be tested before making it operational. It is under hook manufacturer's responsibility to be performed by a qualified Quality Control team before selling for the first time. Those tests are performed once only, unless a substantial design modification is carried out from its initial version.
We call it “Inspection” when a hook is operational and following site safety protocols, it must be inspected periodically. It is under the crane owner's responsibility to be performed by a qualified maintenance team during its lifetime. Those inspections are performed once a year or following manufacturers' recommendations in the “Maintenance Guide” or following site “inspection protocols”.
In this post we are describing the Testing part to be performed to a “New Hook”, leaving the Inspection to a “Hook in Use” for a separate post. Follow us regularly to see the next post!
TESTS TO BE PERFORMED TO A NEW HOOK
EN13001-3.5 is followed to perform all necessary tests to ensure the new hook is complying with the required safety level. Other recognized rules can be followed for specific reasons: country standards, industry/site standards, or applicable crane classification.
There are 2 types of tests:
- Destructive tests: any test carried out on the material that does permanently change its physical, mechanical or dimensional properties. To perform, a sample is taken out for analysis as a “biopsy”
- Non-destructive tests: any test carried out on the material that does not permanently change its physical, mechanical or dimensional properties. To perform, the entire hook in its entirety-integrity is tested
DESTRUCTIVE TESTS
Also called “mechanical tests”, as material properties used to produce the hook are dissected.
Mandatory DT tests performed are:
1.1 TENSILE
A sample is subjected to a controlled tension until failure. Tensile Tests are carried out at Irizar Forge lab according to UNE-EN ISO 6892-1:2010 standard. The properties that are directly measured are:
- Tensile strength: the maximum stress that a material can withstand while being pulled before breaking. 0.2% is the stress applied (1% for stainless steel)
- Yield strength: the limit between the elastic and plastic behaviour in a material. Prior to the yield point, the material deforms only elastically ⟶ the material will return to the original shape when the stress is removed
- Elongation: how much has the sample deformed before breaking
- Necking: the ratio between the final area of the sample in the fracture zone and the initial area of the sample
1.2 IMPACT (Charpy)
The Charpy impact test is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. Charpy V-notch Tests are carried out at Irizar Forge according to UNE-EN ISO 148-1:2017 standard. The usual test temperature is between room temperature and -40 °C, but the test can be done at any temperature.
1.3 HARDNESS
With an indenter tool, a force is applied on the material surface during a specific time. Then, the diameter of the mark of the indenter in the material is measured to calculate the hardness. A hardness test is carried out at Irizar Forge after heat treatment according to ASTM E-10-07 or UNE_EN ISO 6506-1:2015 standards.
Other additional non-mandatory destructive tests can be carried out (upon request):
- Chemical Analysis: this test aims to check the real chemical composition of the piece. The test can be carried out according to different standards, e.g: ASTM E-415
- Grain size Analysis: determining the grain size and seeing if it is homogeneous can give information about the suitability of the applied thermomechanical treatments, as well as their mechanical properties. There are numerous standards under which the grain size can be determined, such as ASTM E-112 or UNE-EN ISO 643
- Fatigue Test: When cyclical loads are applied to a component, it can collapse, even if the applied load is lower than the material’s breaking load. fatigue tests help to determine the behaviour of the hook under conditions of cumulative cyclical loads. There are different standards for carrying out fatigue tests depending on the hook design parameters. A test bench is necessary to carry out this test
- Breaking Test: This test aims to know which is the load at which the hook collapses. A gradual tension is applied progressively that increases until the hook shows signs of collapse (cracks, plastic deformation or breaking). A test bench is necessary to carry out this test
NON DESTRUCTIVE TESTS
Internationally called NDT, where the integrity of the piece itself is tested.
Mandatory NDT tests performed are:
2.1 UT (Ultrasonic Test)
This inspection technique aims to detect the internal discontinuities inside the forging. This method is based on the phenomenon of the reflection of acoustic wave (echo) when discontinuities in the steel structure are found. The wave is reflected to its source (returned) if the discontinuity is in a normal position relative to the incident beam. The ultrasonic inspection is carried out at Irizar Forge according to EN-10228-3 or ASTM A388.
2.2 MPI (Magnetic Particle Inspection)
This inspection technique aims to detect discontinuities in the surface of the forging made by ferromagnetic steel grade. The forging surface is covered with magnetic metal powder (sprayed with spray or aqueous solution). This magnetic powder accumulates in the discontinuities when electromagnetic current is applied over the piece. Then, under ultraviolet light, the powder shines with a phosphor colour, making the discontinuity visible at a glance. The magnetic particle inspection is carried out at Irizar Forge according to EN-10228-1 or ASTM E709.
2.3 FAT (Functional Acceptance Test)
It consists of some testing operations which aim to ensure the correct functional operation of the different elements. Among the most common checks are the checking of the screws of hook thread with nut and the correct operation of the safety latches opening-closing.
2.4 PLT (Proof Load Test):
Mandatory in some countries (as the US, GB Common Wealth Countries…) and applications (Offshore, Subsea, Mooring, Nuclear…), this is the key test where a physical overload is applied to the real finished hook over its SWL (Safety Working Load) to ensure product safety factors (validation of design and geometry) and strength. This test is performed in a specific test bench previously calibrated, having all parameters such as load, time, and position during the test… under control. Proof Load Test is carried out at Irizar Forge premises having a variety of test benches available depending on the hook size and load. There are many different rules to perform the proof load test, and at Irizar Forge the most recognized and applicable worldwide rules are applied to perform with all necessary project and design criteria and specifications.
Mandatory DT & NDT test results are an integral part of EN10204-3.1 Certificate issued by the hook manufacturer, which can be validated by a recognized third party (LRS, BV, ABS, DNV) who has previously monitored key production processes and tests, having as result Certificate EN10204-3.2. For its relevance, PLT is certified separately to 3.1-3.2 showing the load graphic, loading time and progressive load.