5.4 Bending moment of the shank 5.4.1 General The following load actions shall be taken into consideration, when determining the total bending moment of the hook shank: a horizontal fo
Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 12100:2010 and ISO 4306-1:2007 and the following apply
3.1.1 hook shank upper part of the hook, from which the hook is suspended to the hoist media of the crane
3.1.2 hook body lower, curved part of the hook below the shank
3.1.3 hook seat bottom part of the hook body, where the load lifting attachment is resting
3.1.4 hook articulation feature of the hook suspension, allowing the hook to tilt along the inclined load line
3.1.5 stand alone hook hook which is designed, manufactured and released to the market as a component or as part of a hook block, without connection to a specific crane or application
3.1.6 total deformation ratio ratio of the area of the cast cross section to the forged cross section
NOTE The following terms might also be used in technical literature for the same: reduction rate, reduction ratio, forging reduction.
Symbols and abbreviations
A d1 Cross section area of the forged, shank
A d4 Cross section area of the critical section of hook shank
A v Minimum impact toughness of material a Acceleration a 1 Seat circle diameter a 2 Throat opening a 3 Height of the hook point b max Maximum width in the critical hook body section b ref Reference width
C Total number of working cycles during the design life of crane
C t Relative tilting resistance of the hook suspension c e Coefficient for load eccentricity
The Palmgren-Miner hypothesis addresses cumulative damage in fatigue, highlighting the importance of various diameters in the design of forged shanks Key dimensions include the diameter of the forged shank (d1), the principal diameter of the thread (d3), the diameter of the undercut section of the shank (d4), and the thread core diameter (d5) Additionally, the distance of the vertical load line from the center line of the shank (eR) plays a crucial role in understanding the structural integrity under load.
F H Vertical force on hook due to occasional or exceptional loads
F Rd,s , F Rd,f Limit design forces, static/fatigue
F Sd,s Vertical design force for the proof of static strength
F Sd,f Vertical design force for the proof of fatigue strength f 1 , f 2 , f 3 Factors of further influences f Rd Limit design stress f y Yield stress f u Ultimate strength g Acceleration due to gravity, g = 9,81 m/s 2
H Sd,s Horizontal design force of hook
The horizontal design force, denoted as H Sd,f, is essential for verifying the fatigue strength of the hook The section heights of the hook body are represented by h1 and h2, while h indicates the vertical distance from the seat bottom of the hook body to the center of articulation.
Symbols, abbreviations Description h s Vertical distance from the seat bottom of the hook body to critical section of hook shank i Index for a lifting cycle or a stress cycle
I Reference moment of inertia for curved beam
I d1 Moment of inertia of the forged shank
The moment of inertia for the critical section of the hook shank is denoted as \( I_d \) The conversion factor for the stress spectrum and classified duty is represented by \( k_C \) Stress spectrum factors are indicated by \( k_h \) and \( k_s \) The load spectrum factor, in accordance with EN 13001–1, is referred to as \( k_Q \) Additionally, the specific spectrum ratio factor is defined with \( m = 5 \) as \( k_5 \) Finally, logarithmic calculations are based on the base 10, represented as \( \lg \).
M 1 , M 2 , M 3 , M 4 Bending moments of hook shank
M 1,f,i , M 2,f,i , M 3,f,i Bending moments of hook shank for the proof of fatigue strength, lifting cycle i
M Sd,s Static design bending moment m Slope parameter of the characteristic fatigue design curve m RC Mass of rated hoist load m i Mass of the hook load in a lifting cycle i
N Total number of stress cycles/lifting cycles
N D Reference number of stress cycles, N D = 2 × 10 6 p Pitch of thread p a Average number of accelerations related to one lifting cycle
R Radius of hook body curvature
R a Average depth of surface profile in accordance with EN ISO 4287:1998
The R z value represents the maximum depth of the surface profile as defined by EN ISO 4287:1998 The relief radius of the undercut is denoted as r 9, while r th indicates the thread bottom radius The length of the undercut is represented by s, and the stress history parameters are indicated by s h and s s Additionally, the load history parameter is referred to as s Q, and the depth of the thread is represented by t.
T Operation temperature u S , u T Depths of notches α Angle α S , α T Stress concentration factors β Angle or direction of hook inclination β n , β nS , β nT Notch effect factors
The article outlines various symbols and abbreviations related to load dynamics and fatigue strength in engineering Key terms include \$\phi_2\$, the dynamic factor for hoisting unrestrained grounded loads, and \$\phi_5\$, which addresses acceleration changes Risk coefficients are denoted by \$\gamma_n\$, while partial safety and general resistance factors are represented by \$\gamma_p\$ and \$\gamma_m\$, respectively Specific resistance is indicated by \$\gamma_{sm}\$, and fatigue strength factors are denoted as \$\gamma_{Hf}\$ and \$\gamma_{Sf}\$ The edge distance of a hook body section is represented by \$\eta_1\$, and load components are factored by \$\nu\$ Stress cycles are quantified with \$\nu_h\$ and \$\nu_s\$, while mean stress influence is captured by \$\mu\$ Shank stresses due to axial force and bending moment are represented by \$\sigma_a\$ and \$\sigma_b\$, respectively Mean stress in a cycle is denoted by \$\sigma_m\$, with stress amplitude represented by \$\sigma_A\$ Design stress is indicated by \$\sigma_Sd\$, and basic fatigue strength amplitude for un-notched pieces is \$\sigma_M\$ The total stress range in a pulsating cycle is \$\sigma_p\$, while \$\sigma_W\$ refers to fatigue strength amplitude for notched pieces Transformed stress amplitudes are represented by \$\sigma_{Tmax}\$, \$\sigma_{T1}\$, and \$\sigma_{T2}\$ Characteristic fatigue strength is denoted by \$\Delta\sigma_c\$, with limit fatigue design stress as \$\Delta\sigma_{Rd}\$ Stress ranges in lifting cycles are indicated by \$\Delta\sigma_{Sd,i}\$, and the maximum stress range is represented by \$\Delta\sigma_{Sd,max}\$.
Materials
The hook material must meet the requirements of this clause regardless of the material standard used or whether material classification is applied In the finished product, the hook material should possess adequate ductility to permanently deform before it can no longer support the load at the specified temperatures for its use Specifically, the hook material must satisfy certain conditions to ensure its performance.
— the ratio of ultimate strength (f u) to yield stress (f y) f u/f y ≥ 1,2;
— the percentage elongation at fracture A ≥ 10 % on a gauge length L 0 =5,65× S 0 (where S 0 is the original cross-sectional area)
The hook material, after forging and heat treatment, shall have minimum Charpy-V impact toughness in accordance with Table 2
Table 2 — Impact test requirement for hook material
Operation temperature Impact test temperature Minimum impact toughness A v
To meet the operating temperature requirements, the manufacturer must choose a steel that, after appropriate heat treatment, aligns with the desired mechanical property grade for the specific hook design, considering its unique ruling thickness.
The steel must be fully killed and stabilized to prevent strain age embrittlement, requiring a minimum aluminum content of 0.025% Additionally, it should possess an austenitic grain size of 8 or finer, in compliance with EN ISO 643 standards.
The steel shall contain no more sulphur and phosphorus than the limits given in Table 3
Table 3 — Sulphur and phosphorus content
Element Maximum mass content as determined by
Quenched and tempered steel must meet the hardenability requirements specified by the Jominy-ratio, as outlined in Table 4 This ratio, J30/J1.5, compares the hardness at depths of 30 mm and 1.5 mm, respectively, as determined by the Jominy face-quenching test according to EN ISO 642 Testing is required for each melt, and the results should be included in the technical documentation, as referenced in Annex J For additional details on hardening properties and hardness profiles, refer to EN 10083-3.
Table 4 — Hardenability of quenched and tempered materials, Jominy-ratio
Jominy-ratio J30/J1,5 Typical material qualities
European Standards outline the required materials and their characteristics Table 5 presents a selection of appropriate material grades and qualities for forged hooks For comprehensive details, refer to the relevant European Standard.
Table 5 — Suitable materials for forged hooks Material standard Selected qualities
25CrMo4+QT 34CrMo4+QT 36CrNiMo4+QT
Grades and qualities not listed in the aforementioned standards and Table 5 may be utilized, provided that the criteria outlined in section 4.1.1 are met, and that the mechanical properties and chemical composition are detailed in accordance with applicable European Standards.
Table 6 provides a classification of materials for forged hooks When the hook material is identified by class reference, the mechanical properties listed in Table 6 should be utilized as design values, with the hook manufacturer specifying these as minimum values.
Table 6 — Mechanical properties for classified materials
Classification of material is not mandatory Acceptable strength properties of hook material are not limited to those shown in Table 6.
Workmanship
The manufacturing process, factory tests and delivery conditions shall meet the requirements of
EN 10254 or EN 10250-1 as relevant
Each hook body must be hot-forged as a single piece, ensuring that the macroscopic flow lines align with the hook's body outline in regions experiencing the highest tensile stresses It is essential to remove any excess metal from the forging process cleanly, resulting in a surface that is free from sharp edges Additionally, the total deformation ratio must comply with the specifications outlined in Table 7.
Table 7 — Requirement for the deformation ratio
Shank diameter d 1 [mm] Minimum, total deformation ratio d 1 ≤ 50 mm 8 : 1
Profile cutting from a rolled plate is not permissible for forged hooks
Hook forging shall be inspected for surface defects using appropriate NDT-methods in conformance to
To meet the requirements of EN 10228-1 or EN 10228-2 for quality class 3, grinding may be employed to achieve the necessary surface quality It is essential that any grinding marks are oriented in the circumferential direction relative to the seat circle.
Hook forging shall be inspected for volumetric defects using appropriate NDT-methods in conformance to EN 10228-3 and requirements of quality class 3 of EN 10228-3 shall be met
After heat treatment, furnace scale shall be removed and the hook shall be free from harmful defects, including cracks
No welding shall be carried out at any stage of manufacture.
Manufacturing tolerances of forgings
In general all dimensions of forged hooks shall be within [0 ; +7 %] of the nominal dimension However, for the hooks listed in Annexes A and B tolerances given in Annex C may be applied
The centre line of the machined shank shall not deviate from the seat centre more than ± 0,02 a 1
The hook's shape must ensure that the centers of the material sections defined by its two flanks are positioned between two parallel planes, maintaining a spacing of 0.05 times the dimension \(d_1\).
Heat treatment
Heat treatment of forged hooks shall be done in accordance with the applicable European material standard listed in Table 5.
Cold forming by proof loading
As the last stage of the manufacturing process, a hook may be subjected to a “proof load test” and cold forming as a result See guidance in Annex K
The current version of this European Standard does not address the benefits gained from applying proof loading in relation to subsequent fatigue performance and the QA Management process.
NOTE 2 Cold forming by “proof load test” is outside of testing of hooks in accordance with 7.3.
Hook body geometry
Proportions of hook sections shall be such that stresses do not exceed stresses in the critical sections specified in 5.5.1
The hook's seat must be circular, with the center of curvature aligning with the centerline of the machined shank in a single hook For a ramshorn hook, the seat circle should be tangentially positioned.
A ramshorn hook shall be symmetrical in respect to the centre line of the shank
The diameter of the forged shank (d 1) shall be proportioned to circle diameter (a 1) as follows: d 1 ≥ 0,55 a 1
The bifurcation point between the inner edge and the seat circle (a 1) shall be from the horizontal in minimum as follows: for a single hook α ≥ 60°, for a ramshorn hook α ≥ 90°
The full throat opening (a 2), without consideration to a latch shall be proportioned to the seat circle diameter as follows: a 2 ≤ 0,85 a 1 The effective throat opening with a latch shall be in minimum a o ≥ 0,7 a1
The point height of a hook (a 3) shall be in minimum as follows: a 3 ≥ a 1
Annexes A and B present example sets of hook body dimensions, which fulfil the requirements of this clause.
Hook shank machining
Figure 2 — Machined dimensions of shank
The length of the threaded portion of the shank shall be not less than 0,8 d 3
The pitch of the thread (p) shall be proportioned to the principal diameter of the thread (d 3) as follows: 0,055 d 3 ≤ p ≤ 0,15 d 3
The depth of the thread (t) shall be proportioned to the pitch of the thread (p) as follows: 0,45 p ≤ t ≤ 0,61 p
The bottom radius of the thread profile (r th) shall be no less than 0,14 p A thread type, where the bottom radius is not specified, shall not be used
The shank must feature an undercut with a diameter of \(d_4\) below the last threads, with a length \(s\) that is at least \(2(d_3 - d_4)\) This undercut should extend deeper than the core diameter of the thread profile, ensuring that \(d_4\) is less than or equal to \(d_5 - 0.3 \, \text{mm}\) Additionally, the undercut must be machined using a form ground tool to achieve a surface finish of \(R_a \leq 6.3 \, \mu m\).
In the transition from the threaded section to the undercut area, a relief radius (r₉) must be established This radius should be at least 0.06 times the diameter of the undercut (d₄), ensuring that r₉ ≥ 0.06 d₄ Additionally, the relief transition does not have to conform to a complete circular quadrant shape.
The thinnest section of the machined shank (consequently d 4) shall fulfil the condition d 4 ≥ 0,65 d 1, where d 1 is the diameter of the forged part of the shank, see Figure 1
The whole machined section of the shank shall have a radius at each change in diameter The machined section shall not reach the curved part of the forged body
Screwed threads shall conform to the tolerance requirements of ISO 965-1 (coarse series) and be of medium fit class 6g
Annex F presents example sets of machined shank and thread dimensions, which fulfil the geometric requirements.
Nut
The mechanical properties of the nut material must meet or exceed those specified for the hook as per section 4.1 However, for standard metric nuts up to size M45 made from materials compliant with EN ISO 898-2, only the yield stress of the nut needs to align with the required yield stress of the hook material.
The height of the nut shall be such that the threaded length of the hook shank is fully engaged with the nut thread
To ensure the nut remains securely fastened to the shank and prevents unscrewing, it must be positively locked against rotation without obstructing the lower two-thirds of the nut/shank thread connection This locking mechanism should permit relative axial movement between the shank and the nut, accommodating any play in the threaded connection If a dowel or similar fixing method is used for locking, it is crucial that the load-bearing thread flanks of the nut and shank are in contact during the locking process to prevent load transmission through the locking media.
The nut's support allows the hook to rotate around the vertical axis, while the contact surface's height must be positioned within the lower half of the threaded connection.
Screwed threads of the nut must meet the tolerance standards outlined in ISO 965-1 (coarse series) and should be classified as medium fit class 6H Additionally, the bottom radius of the thread profile for the nut must be at least 0.07 times the pitch (p) of the thread It is important to avoid using thread types that do not specify a bottom radius.
NOTE Distribution of the load to larger part of the thread length can be achieved by the design of the nut.
Effect of hook suspension
For stand-alone hooks, it is essential that the hook suspension, potentially utilizing a hoist rope reeving system, permits free tilting of the hook in any direction along the load line If this articulation is not included, it must be specifically considered in the hook's design calculations Additionally, if altering the crane or hook block configuration can lead to a rigid hook suspension, this factor should also be incorporated into the design calculations.
NOTE Usually the hook suspension consists of nut, cross head and bearing For the purpose of this standard, the rope reeving is taken as part of the suspension
General
The static strength proof for hooks must adhere to the guidelines set forth in EN 13001-1 and EN 13001-2, with the primary design limit for static strength being associated with the material's yielding.
The proof will be provided for the critical sections of the hook, considering the most unfavorable load effects from load combinations A, B, or C as per EN 13001-2 Relevant partial safety factors, γ p, will be applied, along with risk coefficients, γ n, when necessary for specific applications or as outlined in the applicable European crane type standard.
Vertical design load
The vertical design force for a hook F Sd,s when hoisting the rated hook load, shall be calculated as follows: γ γ
The maximum load considerations for hoisting unrestrained grounded loads are defined by the dynamic factors \$\phi_2\$ and \$\phi_5\$ as per EN 13001–2 Here, \$\phi_2\$ accounts for the dynamic effects of the load, while \$\phi_5\$ pertains to the dynamic factors resulting from hoist acceleration The vertical acceleration or deceleration is represented by \$a\$, and the mass of the rated hook load is denoted as \$m_{RC}\$ The acceleration due to gravity is \$g = 9.81 \, \text{m/s}^2\$ The partial safety factor, \$\gamma_p\$, varies based on load conditions: \$\gamma_p = 1.34\$ for regular loads (load combinations A), \$\gamma_p = 1.22\$ for occasional loads (load combinations B), and \$\gamma_p = 1.10\$ for exceptional loads (load combinations C) Additionally, \$\gamma_p = 1.0\$ applies to the exceptional load case of 5.4.5 (load combinations C), while \$\gamma_n\$ represents the risk coefficient.
Other load actions and combinations outlined in EN 13001-2 can generate vertical forces on the hook, necessitating a thorough analysis of these load actions The vertical design force in these scenarios is represented in a general format as follows: γ γ.
F H represents the vertical force on the hook resulting from loads other than the rated hoisting load, such as test loads or peak loads during overload conditions The partial safety factor, denoted as γ p, is defined in accordance with EN 13001–2, while γ n signifies the risk coefficient.
Horizontal design force
The primary horizontal forces affecting hook strength arise from the horizontal accelerations during crane operations Additional horizontal forces, such as those from wind or lateral pulls, should be considered if they are substantial It is important to assume that the horizontal force acts at the bottom of the hook seat.
The horizontal design force of hook H Sd,s due to horizontal accelerations shall be calculated as follows: γ γ × × × ×
The formula for the H C F h (3) incorporates several key variables: \( m_{RC} \) represents the mass of the rated hook load, while \( a \) denotes the acceleration or deceleration of horizontal motion The dynamic factor for loads due to horizontal acceleration is indicated by \( \phi_5 \), as specified in EN 13001–2 For hook suspensions that are not rigidly connected to the crane's moving part in the horizontal direction, \( \phi_5 \) should be set to 1 Additionally, \( \gamma_p \) is the partial safety factor referenced in Formula (1), and \( \gamma_n \) signifies the risk coefficient.
C t is the relative tilting resistance of the hook suspension in accordance with Annex H;
The vertical design force, denoted as \$F_{Sd,s}\$, is determined according to section 5.2, which pertains to the specified loading condition of \$H_{Sd,s}\$ Additionally, \$h\$ represents the vertical distance from the bottom of the hook body's seat to the center of articulation.
Bending moment of the shank
When calculating the total bending moment of the hook shank, it is essential to consider several load actions: a) horizontal forces (refer to section 5.4.2); b) the inclination of the hook suspension (see section 5.4.3); c) the eccentric action of vertical force at the hook seat (consult section 5.4.4); and d) for ramshorn hooks, the impact of half the rated load on a single prong (see section 5.4.5).
The bending moments caused through these load actions shall be addressed to the same load combinations, which the primary loads or operational conditions causing the bending belong to
5.4.2Bending moment due to horizontal force
This clause addresses the shank bending moment resulting from external horizontal forces The moment \( M_1 \) must be calculated at the critical hook shank section, as specified in section 5.6, based on the horizontal design force \( H_{Sd,s} \).
The horizontal design force, denoted as \$H_{Sd,s}\$, is defined in accordance with section 5.3, while \$h_s\$ represents the vertical distance from the bottom of the hook body seat to the upper end of the hook shank's thinnest section, as illustrated in Figure 1.
5.4.3Bending moment due to inclination of hook suspension
When designing hoist mechanisms, it is crucial to account for the bending moment at the shank caused by the inclination of the hook suspension under load This inclination may arise from various factors, including differences in hoist travel distances between separate hoist drives, tilting of a single rope reeving during operation, the tilting of a crane part to which the hook is attached, or two-blocking of a bottom block in the uppermost hoist position followed by tilting of the crane part.
Figure 3 — Tilting of a hook in case of different hoist travel distances
The vertical force, due to an inclination, generates a component that acts perpendicular to the hook shank's axis, which must be considered alongside horizontal forces The bending moment \( M_2 \) at the critical section of the hook shank is directly proportional to the vertical design force, represented as \( \beta \).
The vertical design force, denoted as F Sd,s, is determined according to section 5.2 and is influenced by the hook inclination angle, β This angle represents the maximum total inclination for each applicable load combination Additionally, h s refers to the vertical distance measured from the bottom of the hook body seat to the upper end of the hook shank's thinnest section.
In a rope balanced hook suspension system featuring multiple rope falls and a single running rope from the drum, the hoisting and lowering actions lead to a tilt in the hook suspension The angle of inclination can be determined using specific calculations.
The relative tilting resistance of the hook suspension is denoted as \$C_t\$ according to Annex H, while \$h\$ represents the vertical distance from the bottom of the hook body's seat to the center of the articulation.
Figure 4 — Tilting of a hook suspension in a single rope reeving system
The maximum inclination, the related vertical force and the consequent moment M 2 shall be calculated separately for all relevant loading conditions of the crane
5.4.4 Bending moment due to eccentricity of vertical force
A hoist load attachment may not always align centrally on the hook seat, leading to a deviation of the vertical load action line from the shank's center line This misalignment results in a bending moment, which can be calculated accordingly.
F Sd,s is the vertical design force in accordance with 5.2; a 1 is the seat circle diameter of the hook body; c e is a coefficient for the eccentricity; c e = 0,05
A smaller eccentricity may be used in the design calculations, if a positive, mechanical means is provided ensuring that the hoist load attachment settles closer to the hook seat centre
5.4.5 Exceptional case for ramshorn hooks
When considering the potential misuse of a ramshorn hook loaded on only one prong, it is essential to treat this as an exceptional load case In this scenario, it is assumed that half of the rated load is applied to one prong while the other prong remains unloaded This specific loading condition is incorporated into the calculations for load combination C, with a safety factor of γ p = 1, as outlined in section 5.2.
For a ramshorn hook subjected to one-sided loading, the bending moment \( M_4 \) resulting from the eccentric loading at the machined undercut section with a diameter \( d_4 \) must be calculated, particularly at the thinnest section of the hook shank as illustrated in Figure 1.
The vertical design force, denoted as \$F_{Sd,s}\$, is defined in accordance with section 5.2 The diameter of the forged shank is represented by \$d_1\$, while \$a_1\$ indicates the seat circle diameter of the hook The distance from the load action point at the hook seat to the center line of the shank is referred to as \$e_R\$ Additionally, \$h\$ is the vertical distance from the seat bottom of the hook body to the center of the articulation, and \$h_s\$ represents the vertical distance from the seat bottom of the hook body to the upper end of the hook undercut section, as illustrated in Figure 1.
C t is the relative tilting resistance of the hook suspension, see Annex H
Formula (8) provides a conservative approach for calculating the moment at the machined section of the shank The calculation of stresses in the forged shank section of ramshorn hooks for this specific case is detailed in section 5.5.3 and is represented by Formula (12).
5.4.6Design bending moment of the shank
The design bending moment at the critical shank section, denoted as \( M_{Sd,s} \), must be calculated individually for each applicable load combination, in accordance with sections 5.4.2 to 5.4.4.
M 1 to M 3 are the bending moments in accordance with 5.4.2 to 5.4.4;
C t is the relative tilting resistance of the hook suspension, see Annex H;
F Sd,s is the vertical design force in accordance with 5.2
Additionally to the above, the design bending moment in accordance with the exceptional case of 5.4.5 shall be taken into account in a load combination C as follows:
M 4 is the bending moment in accordance with 5.4.5;
H Sd,s is the horizontal design force in accordance with 5.3, calculated with a half of the rated load.
Hook body, design stresses
The vertical design force \$F_{Sd,s}\$ is symmetrically divided into two components that act at the center of the seat circle, positioned on opposite sides of the vertical center line and at an angle \$\alpha\$ relative to the vertical, as illustrated in Figure 5.
As a minimum value of α, it shall be assumed that α = 45°
For ramshorn hooks, an equal load distribution is assumed between the two prongs in load combinations A and B
In the analysis of ramshorn hooks, it is assumed that in a unique loading scenario, half of the vertical force is applied to one prong while the other prong remains unloaded This specific loading case is incorporated into the calculations for load combination C.
The horizontal forces may be neglected in the hook body calculations
Figure 5 — Load actions on hook body and critical sections for calculation
Stresses in the designated sections of a hook body shall be analysed by any of the following:
— the theory of curved beam bending in accordance with Annex G;
Stresses in section B of a ramshorn hook may, however be analysed by the conventional beam bending theory
The following clauses are based upon the theory of curved beam bending
The design stresses σ Sd in sections A and B of single hooks and in the section A of ramshorn hooks shall be calculated as follows: σ η η × × ×
R a and ν = 1 for section B of single hooks; ν = 0,5 × tan α for section A of single and ramshorn hooks, α = 45°; where
R is the hook curvature radius determined by the centroid of the section;
F Sd,s is the vertical design force in accordance with 5.2;
The reference moment of inertia for a curved beam is denoted as \( I \) The diameter of the hook's seat circle is represented by \( a_1 \), while \( \eta_1 \) indicates the absolute value of the coordinate \( y \) at the inner edge of a specific section Additionally, \( \alpha \) refers to the angle of the load action lines relative to the vertical, as illustrated in Figure 5.
The quantities η 1 and I are specific to each section and will be determined according to Annex G For the exceptional case outlined in section 5.4.5, the design stress in the forged shank section B of the ramshorn hook is calculated using the formula: \$\sigma = + \times \times \times Sd,s Sd,s \times 1\$.
The vertical design force, denoted as \$F_{Sd,s}\$, is defined according to section 5.2 The variable \$h\$ represents the vertical distance from the bottom of the hook body seat to the center of articulation, while \$e\$ indicates the distance from the center of section B to the load's action line in one prong In cases where the hook suspension is completely rigid, set \$e\$ equal to \$e_R\$.
A d1 is the cross section area of the forged shank;
I d1 is the moment of inertia of the forged shank; d 1 is the diameter of the forged shank; a 1 is the seat circle diameter of the hook
The calculation of the dimension e in the Formula (12) is valid for hook seats of circular shape For other seat shapes the dimension e shall be calculated accordingly.
Hook shank, design stresses
The vertical design forces and bending moments must be considered in the proof calculations of a hook shank, as outlined in sections 5.2 and 5.4 The critical section of the shank is typically located just below the threaded area, specifically at the undercut part with a diameter of \(d_4\) The maximum design stress, denoted as \(\sigma_{Sd,s}\), is determined as a nominal stress without accounting for stress concentration factors, utilizing conventional beam bending theory, expressed by the formula: \(\sigma_{Sd,s} = Sd,s + Sd,s \times \frac{4}{d_4}\).
F Sd,s is the vertical design hook force;
M Sd,s is the design bending moment in the critical section, see 5.4.6;
A d4 is the cross section area of the critical section of the hook shank;
I d4 is the moment of inertia of the critical section of the hook shank.
Hook, proof of static strength
5.7.1 General for hook body and shank
To ensure safety and compliance, it must be demonstrated that the maximum design stress (\$σ_{Sd,s}\$) for both the hook body and shank does not exceed the limit design stress (\$f_{Rd}\$), as defined by the equation \$σ_{Sd,s} ≤ R_d = 1 × γ_m × y γ_{sm} f_f f\$ (14) Here, \$σ_{Sd,s}\$ is determined according to sections 5.5 and 5.6, while \$f_{Rd}\$ represents the limit design stress The yield stress of the material in the finished product is denoted as \$f_y\$, and \$f_1\$ is the influence factor for operational temperature The general resistance coefficient, \$γ_m = 1.1\$, follows EN 13001–2 standards, and the specific resistance coefficients for different sections are \$γ_{sm} = 0.75\$ for the hook body section B, \$γ_{sm} = 0.81\$ for section A, and \$γ_{sm} = 0.95\$ for the shank sections, as illustrated in Figure 5.
In the absence of other data, the factor f 1 taking into consideration the reduction of the yield stress in high temperatures may be calculated as follows:
T is the operation temperature in degrees Celsius (°C)
The dimensions of the ramshorn hooks outlined in Annex B are designed to ensure that section B of the hook body does not dominate the static strength of the body, eliminating the need for a specific proof as mentioned in section 5.4.5 for these hooks.
5.7.2The use of static limit design force for verification of the hook body
When the chosen hook body complies with Annexes A or B, the static strength proof can be based on the static limit design forces outlined in Annex D This proof must demonstrate that the hook body can withstand all relevant load actions and combinations specified in 5.2, ensuring its structural integrity under various loading conditions.
F Sd,s is the vertical design force in accordance with 5.2;
F Rd,s is the static limit design force in accordance with Annex D; f 1 is the influence factor for the operation temperature in accordance with Formula (15)
The static limit design force ensures the static strength verification for sections A and B of single hooks, as well as section A of ramshorn hooks, calculated according to the parameters outlined in section 5.5.3.
For a single hook the static limit design force is calculated separately for the two sections A and B and the smaller value of the two is used
Additionally, the proof of static strength for the shank shall be carried out in accordance with 5.7.1
General
The fatigue strength proof for hooks must adhere to the guidelines outlined in EN 13001-1 and EN 13001-2 It is essential that the hook's design life is at least equal to that of the corresponding crane or hoist The assessment should focus on the critical sections of the hook, considering the most unfavorable load effects from load combinations A as specified in EN 13001-2, incorporating the risk coefficient γ n where applicable, while maintaining all partial safety factors γ p at 1.
The proof of stress cycles for cranes or hoists is determined by the total working cycles throughout their design life, as outlined in EN 13001-1 Typically, each lifting cycle corresponds to one stress cycle for the hook body If a working cycle includes multiple lifting cycles, this must be considered in the stress cycle count Furthermore, for the hook shank, the number of positioning movements must also be included when calculating the bending stress cycles, in accordance with EN 13001-1.
Vertical fatigue design force
The vertical design force F Sd,f,i for a lifting cycle i shall be calculated as follows: γ
The formula \$F = \Phi m g\$ (18) represents the force exerted when hoisting an unrestrained grounded load, where \$\Phi\$ is the dynamic factor and \$\gamma_n\$ is the risk coefficient, as defined in EN 13001–2 In this equation, \$m_i\$ denotes the mass of the hook load during lifting cycle \$i\$, and \$g\$ is the acceleration due to gravity, approximately \$9.81 \, \text{m/s}^2\$.
Horizontal fatigue design force
The horizontal design force H Sd,f,i for a lifting cycle i due to horizontal accelerations shall be calculated as follows: γ × ×ϕ
In a lifting cycle, the hook load mass is represented by \( m_i \), while \( a \) denotes the acceleration or deceleration of horizontal motion The dynamic factor for loads resulting from horizontal acceleration is indicated by \( \phi_5 \), as specified in EN 13001–2 For hook suspensions that are not rigidly connected to the crane's moving part in the horizontal direction, \( \phi_5 \) should be set to 1 Additionally, the risk coefficient is represented by \( \gamma_n \), according to EN 13001–2.
The relative tilting resistance of the hook suspension is denoted as \( C_t \) (refer to Annex H) The acceleration due to gravity is \( g = 9.81 \, \text{m/s}^2 \) Additionally, \( h \) represents the vertical distance from the bottom of the hook body seat to the center of the articulation.
Fatigue design bending moment of shank
6.4.1 Bending moment due to horizontal force
The moment M 1,f,i shall be calculated at the critical hook shank section, due to the horizontal design force H Sd,f,i in accordance with 6.3:
The horizontal design force during lifting cycle \(i\) is denoted as \(H_{Sd,f,i}\) as per section 6.3 Additionally, \(h_s\) represents the vertical distance from the bottom of the hook body seat to the upper end of the hook shank's thinnest section, as illustrated in Figure 1.
6.4.2Bending moment due to inclination of hook suspension
The calculation of inclination and its underlying basis should align with section 5.4.3 To assess fatigue strength, it is essential to evaluate which loading events in load combination A are considered regular loadings, taking into account the specific crane configuration and its application.
In each lifting cycle, it is essential to recognize that a rope balanced hook suspension with multiple falls and a single running rope from the drum will experience tilting during the hoisting and lowering movements This tilting leads to a bending moment, denoted as \( M_{2,f,i} \), at the critical hook shank section, which can be calculated accordingly.
The vertical design force during lifting cycle \(i\) is denoted as \(F_{Sd,f,i}\) as per section 6.2 The variable \(h_s\) represents the vertical distance from the bottom of the hook body seat to the upper end of the hook shank's thinnest section Additionally, \(\beta\) indicates the inclination of the hook suspension, following Formula (6).
6.4.3 Bending moment due to eccentricity of vertical force
A hoist load attachment may not always align centrally on the hook seat, leading to a deviation of the vertical load action line from the shank's center line This misalignment results in a bending moment, which can be calculated accordingly.
F Sd,f,i is the vertical design force in a lifting cycle i, in accordance with 6.2; a 1 is the seat circle diameter of the hook body; c e is a coefficient for the eccentricity, c e = 0,05
A smaller eccentricity may be used in the design calculations, if a positive, mechanical means is provided ensuring the hoist load attachment settles closer to the hook seat centre.
Proof of fatigue strength, hook body
The proof of fatigue strength shall be based on cumulative effect of stress ranges in the critical sections
Each lifting cycle is based on the assumption that the load is grounded, meaning the hook load varies from zero to the full load while accounting for dynamic factors.
Calculation of the stress ranges is comparable to that of the static design stress in 5.5.3, when applying the vertical fatigue design load from 6.2: σ σ
∆ Sd,i = Sd, s in accordance with Formula (11) in 5.5.3, when setting F Sd,s = F Sd,f,i where i is the index of a lifting cycle; Δσ Sd,i is the stress range in a cycle i;
F Sd,f,i is the vertical fatigue design force in accordance with 6.2
The cumulative fatigue effect of the stress history from all of the stress cycles is condensed to a single stress history parameter s h This is calculated as follows: ν
N (25) where k h is the stress spectrum factor; ν h is the relative number of stress cycles; i is the index of a lifting cycle;
N is the total number of lifting cycles;
The reference number of cycles is set at \$N_D = 2 \times 10^6\$ The stress range for cycle \$i\$ is denoted as \$\Delta\sigma_{Sd,i}\$, while the maximum stress range is represented by \$\Delta\sigma_{Sd,max}\$ Additionally, the slope parameter of the characteristic fatigue design curve is defined as \$m = 5\$.
The total number of lifting cycles (N) shall conform to the total number of working cycles (C) during the design life of the crane as specified in EN 13001-1
6.5.3Stress history based upon classified duty
The hook body is a unique scenario where stress variations are solely influenced by hoist load variations Consequently, the stress history parameter can be directly obtained from the Q and U classes of EN 13001-1, eliminating the need for case-specific stress history calculations as outlined in section 6.5.2 When the intended duty is defined exclusively through the Q and U classes, the calculation of the stress history parameter should be performed as described in this article.
A load history parameter s Q is defined by the formula:
Q / D s kQ N N (26) where kQ is the load spectrum factor in accordance with Table 8, see also EN 13001–1;
The total number of lifting cycles, denoted as N, is typically determined by the number of work cycles (C) specified for the crane according to class U of EN 13001–1 Additionally, each time the load is grounded during a work cycle, it must be counted as an extra lifting cycle and included in the total value of N.
N D = 2 × 10 6 is the reference number of cycles
The load spectrum factor (kQ) is determined using an exponent of 3, while the fatigue of the hook body is assessed through a fatigue curve with a slope of m = 5 To link the load spectrum of EN 13001-1 with the stress history parameter of the hook body (s h), a conversion factor (k 5*) for a specific load distribution shape must be calculated For classified duties, the continuous load distributions outlined in EN 13001-1, Annex B should be utilized.
The stress history parameter s h for a hook body shall be calculated as follows:
* 5 5 h k kQ k (28) where k 5* is the specific spectrum ratio factor Standardized values, calculated in accordance with the formulae given in EN 13001-1, Annex B are listed in Table 8 and shall be used
Table 8 — Fatigue design parameters for classified duty
The fundamental premise is that fatigue strength curves plotted on a log(σ)/log(N) scale appear as straight lines, sharing a consistent slope (m) across all material grades This approximation holds true particularly in the high cycle fatigue region, where fatigue becomes the primary design consideration.
The limit fatigue design stress at the reference point N D is calculated as follows: σ σ
The limit fatigue design stress, represented as \$\Delta \sigma_{Rd}\$, is calculated using the formula \$\Delta \sigma_{Rd} = f_1 \times f_2 \times \Delta \sigma_c\$, where \$\Delta \sigma_c\$ denotes the characteristic fatigue strength at \$N_D = 2 \times 10^6\$ cycles, which varies based on the material The factors \$f_1\$ and \$f_2\$ account for the influence of operational temperature and material thickness, respectively, as defined in Formulas (31) and (32).
The characteristic fatigue strength, denoted as Δσ c, is influenced by the material's ultimate strength For the material grades listed in Table 6, the corresponding fatigue strength values can be found in Table 9.
Table 9 — Characteristic fatigue strength of forged hook materials
For other materials and in cases where the classification of material is not applied, the characteristic fatigue strength Δσ c shall be calculated as follows: σ
13001 0,282 f lg f (30) where f u is the ultimate strength of the material in Newton per square millimetre (N/mm 2 )
The influence factor f 1 for the operation temperature is calculated as follows:
T is the operation temperature in degrees Celsius (°C)
The influence factor f 2 for the material thickness is calculated as follows:
2 ref max f b b for 25 mm ≤ b max ≤ 150 mm (32)
2=0,74 f for b max > 150 mm where b ref is the reference width, b ref = 25 mm; b max is the maximum width in the critical hook body section, see Figure 5 in 5.5.1
The proof shall be carried out separately for all relevant sections of the hook body
For the proof of fatigue strength, it shall be proven that σ σ σ γ γ
The maximum stress range within the total stress history is represented by \$\Delta\sigma_{Sd,max}\$, while the limit fatigue design stress is defined by Formula (29) as \$\Delta\sigma_{Rd}\$ The fatigue strength specific resistance factor, denoted as \$\gamma_{Hf}\$, is outlined in Table 10 The slope parameter of the characteristic fatigue design curve is set at \$m = 5\$ Additionally, \$s_h\$ represents the stress history parameter, and \$k_5\$ is the specific spectrum ratio factor for \$m = 5\$ Lastly, \$s_Q\$ indicates the load history parameter.
Table 10 — Fatigue strength specific resistance factor
Section A of single and ramshorn hooks 1,35
For the calculation utilizing the classification in accordance with EN 13001-1, the values for the conversion factor k C are given in Table 8
6.5.6 The use of fatigue limit design force for verification of the hook body
When the chosen hook body aligns with Annexes A or B, the fatigue strength proof can rely on the fatigue limit design force outlined in Annex E This proof must be validated for all applicable load actions and combinations detailed in section 6.2.
F Sd,f is the maximum vertical fatigue design load in accordance with 6.2;
F Rd,f is the fatigue limit design force in accordance with Annex E; f 1 is the influence factor for the operation temperature in accordance with Formula (31)
The fatigue limit design force is calculated with parameters as defined in 5.5.3, as follows:
For a single hook, the fatigue limit design force is calculated separately for the two sections A and B and the smaller value of the two is used.
Proof of fatigue strength, hook shank
The total number of stress cycles is calculated based on the overall lifting cycles (N), which must align with the total working cycles (C) defined for the crane's design life, as outlined in EN 13001-1.
The following symbols are used throughout 6.6:
The total number of lifting cycles for the crane is denoted as \( N \), while \( p_a \) represents the average number of accelerations associated with each lifting cycle, as outlined in EN 13001–1 Additionally, \( i \) indicates the index of a stress or lifting cycle.
N D = 2 × 10 6 is the reference number of cycles; m is the slope parameter of a characteristic fatigue design curve; f u is the ultimate strength of the material; f y is the yield stress of the material
The design stresses must be determined in the undercut section of the shank, just below the threads with a diameter of \(d_4\) (refer to Figure 1) Basic stress calculations are performed without considering stress concentration factors, utilizing conventional beam bending theory The provided formulas are general and applicable for any vertical design force and design bending moment as outlined in section 6.6.
M I (37) where σ a is the shank stress (axial) due to vertical design force; σ b is the shank stress (bending) due to design bending moment;
F is the vertical design force in a fatigue load cycle;
M is the design bending moment in a fatigue load cycle;
A d4 is the cross section area of the critical section of the hook shank;
I d4 is the moment of inertia of the critical section of the hook shank
Within each lifting cycle, the following two types of stress cycles shall be considered, as relevant:
Cycle Type 1 involves a stress cycle resulting from lifting and lowering a load, taking into account bending stress from hook suspension inclination and vertical load eccentricity The axial stress is defined as \$\sigma_{a1} = \sigma_{a}(F_{Sd,f,i})\$ (Formula (36)), with \$F_{Sd,f,i}\$ specified in section 6.2 Bending stress is given by \$\sigma_{b1} = \sigma_{b}(M)\$ (Formula (37)), where \$M = \max[M_{2,f,i}, M_{3,f,i}]\$ according to sections 6.4.2 and 6.4.3 The pulsating stress cycle ranges from 0 to \$\sigma_{a1} + \sigma_{b1}\$, with a mean stress of \$\sigma_{m1,i} = \frac{\sigma_{a1} + \sigma_{b1}}{2}\$ and a stress amplitude of \$\sigma_{A1,i} = \sigma_{m1,i}\$ The total number of stress cycles is represented as \$N_{1} = N\$.
Cycle Type 2 involves a stress cycle caused by horizontal acceleration and load sway, which includes considerations for axial stress similar to Cycle Type 1 Bending stress is defined by the equation \$\sigma_{b2,i} = \sigma_{b}(M_{1,f,i})\$ (refer to Formula (37)), where \$M_{1,f,i}\$ is determined according to section 6.4.1 Each stress cycle has a mean stress of \$\sigma_{m2,i} = \sigma_{a1,i}\$ and a stress amplitude of \$\sigma_{A2,i} = \sigma_{b2,i}\$ The total number of stress cycles is calculated as \$N_{2} = p N_{a} \times\$.
Within each lifting cycle, the hook load specific for that cycle shall be used
NOTE The axial stresses within the Cycle Type 2 may be calculated without the effect of the factor ϕ 2 in 6.2 The parameter p a shall be selected in accordance with Table 11
Table 11 — Average number of horizontal accelerations p a
1 Process applications, where horizontal load movements are regularly a part of each work cycle 8
2 Special applications, where horizontal movements are operated at all times under control of a signaller, with low speeds and short distances 2
3 A special load sway control is used in the drive system of the horizontal movement 2
4 All other applications and stand alone hooks, where the application is not known 4
6.6.4 Basic fatigue strength of material
The basic alternating fatigue strength of a material, under zero mean stress (\$σ_m = 0\$) and a reference number of stress cycles (\$N_D = 2,000,000\$), is determined using the ultimate strength of the material This relationship is expressed by the formula: \$σ = M \cdot 0.45 \times f_u\$.
6.6.5Stress concentration effects from geometry
This article discusses the stress concentration factor α and the notch effect factor β n, which are calculated separately for the shoulder and thread bottom using the formulas provided in Table 12 The maximum value of the two β n factors will be utilized to verify the fatigue strength of the shank.
NOTE The thread is assumed to be of a single lead type
Table 12 — Parameters for calculation of stress concentration factors
Geometric stress concentration factor α S (Formula (39)) α T (Formula (40))
Notch effect factor β n β nS =α S n β nT =α T n α = +
The geometric symbols presented in Table 12 and in Formulas (39) and (40) align with those illustrated in Figure 2 Additionally, the yield stress \( f_y \) used in the formula for \( n \) should be expressed in Newtons per square millimetre (N/mm²).
6.6.6 Fatigue strength of notched shank
The analysis focuses on the more critical shank section, where the basic material fatigue strength is adjusted to align with the nominal stresses present in the shank.
The basic fatigue strength of the material is represented by \$\sigma_M\$, while \$\beta_n\$ is determined by the maximum values of \$\beta_{nS}\$ and \$\beta_{nT}\$ Additionally, \$f_1\$ serves as the influence factor for the operating temperature, as defined by Formula (31), and \$f_3\$ represents the influence factor for surface roughness.
R a is the surface finish grade in micrometres (àm) within the limits 0,4 àm ≤ R a ≤ 6,3 àm; f u is the ultimate strength of the material in Newton per square millimetre (N/mm 2 ), f u ≥ 300 N/mm 2
The material strength reduction factor associated with an increase in diameter is not considered in this document Instead, the design calculations utilize the actual material properties corresponding to the true diameter.
The σ W values are relevant for pure alternating stress with zero mean stress, particularly for components like the hook shank, where increased mean stress reduces fatigue strength This relationship is depicted in the principal Smith Diagram (Figure 6), which shows that a) the fatigue strength σ W is constant at a mean stress σ m = 0; b) the upper limit line is defined by a mean stress influence factor; and c) stress amplitudes corresponding to a specific mean stress must fall between the diagram's lower and upper limits.
Figure 6 — Smith diagram and transformation of stress amplitude
The upper limit line in the diagram is determined by the assumption that the total stress variation under pulsating stress is constrained to \$\sigma_p = 1.7 \sigma_W\$ Consequently, the mean stress influence factor is calculated in accordance with EN 13001-1 as \$\alpha_\sigma\$.
NOTE The mean stress influence parameters μ and α correspond to the parameters μ 1 and α 1 of EN 13001–1 so, that in this document α is counted always positive
6.6.8Transformation to stresses at zero mean stress
The stress amplitudes and their corresponding mean stresses, as outlined in section 6.6.3, are converted to a stress amplitude that reflects an equivalent fatigue impact, following the methodology detailed in EN 13001-1 This transformation is achieved by adjusting the stress cycle to a mean stress of zero.
Cycle Type 2: σ T2,i =σ A2,i + ìà σ m2,i (45) where σ T1,i, σ T2,i are the transformed stress amplitudes at zero mean stress, μ is the mean stress influence factor
The transformation of σ A,i to σ T,i is illustrated in Figure 6
6.6.9 Stress history parameter in general
The cumulative fatigue effect of the stress history from all of the stress cycles is condensed into a single stress history parameter s s This is calculated as follows: ν
In the context of stress analysis, the maximum transformed stress amplitudes, denoted as \$\sigma_{T1,i}\$ and \$\sigma_{T2,i}\$, are represented by \$\sigma_{Tmax}\$ The stress spectrum factor for the hook shank is indicated by \$k_s\$, while \$\nu_s\$ refers to the relative number of stress cycles The variable \$i\$ represents the index of a lifting cycle.
N is the total number of lifting cycles; m = 5 is the slope parameter of the characteristic fatigue design curve
6.6.10 Stress history parameter based upon classified duty
Fatigue design of hook shanks for stand alone hooks
For the design of standalone hook shanks with a finished shank, the following minimum assumptions must be considered: the fatigue limit design force of the hook body will serve as the fatigue design force for the shank; the number of shank bending cycles resulting from horizontal load sway is set at \( p_a = 4 \); the horizontal fatigue design force calculation assumes a horizontal acceleration of \( a = 0.2 \, \text{m/s}^2 \) and \( \phi_5 = 1 \); and the hook suspension's tilting resistance is based on a horizontal force at the hook seat equal to 2% of the vertical force.
7 Verification of the safety requirements and/or protective measures
General
Fulfilment of the requirements given in Clauses 5 and 6 shall be verified by design calculations
The design assumptions, including the intended duty and hook capacity, must align with the relevant design parameters of the associated crane or hoist, and this alignment should be confirmed through an engineering assessment.
All verifications outlined in Clause 7 must be documented within the technical file, ensuring compliance with Annex J Additionally, the tests conducted should adhere to the "type 3.1" requirements of EN 10204.
Scope of testing and sampling
Material tests, volumetric non-destructive testing (NDT) inspections, and test loading must be performed on each individual hook or based on the production batch principle Additionally, surface NDT inspections are required for every hook.
In batch testing, the maximum batch size consists of hooks made from the same raw material cast or billet, sharing the same total deformation ratio and undergoing identical heat treatment Furthermore, for test loading, the batch size is restricted to hooks with the same machining design of the finished shank.
Testing of mechanical properties
Tensile and impact testing samples should be taken longitudinally from the upper part of the hook shank, ideally at a distance of 1/3 radius from the surface If the shank is too small, testing can be performed on material from the same melt, ensuring it has the same total deformation ratio and has undergone the same heat treatment as the hook The tensile test must follow the guidelines of EN ISO 6892-1, while the impact test should adhere to EN ISO 148-1 standards.
Test loading
In addition to the requirements outlined in sections 7.1 and 7.2, the static strength and overall integrity of a hook must be evaluated through a load test This test can be conducted on the hook as an individual component or in conjunction with the load testing of the associated crane or hoist.
In component testing, the test load must match the static limit design force of the hook, with the suspension setup reflecting the intended configuration in the associated crane or hook block The application of the test load should create a resultant load effect on the hook as illustrated in Figure 7 This can be accomplished by either suspending a test load on the hook as shown in item a) of Figure 7, using item b) with an angle of α = 90°, or by applying a test force on the hook through two separate tests as depicted in item c) of Figure 7.
When conducting tests alongside the crane, it is essential to use the same dynamic and static test loads The sling arrangement on the hook must adhere to either option a) or b) from Figure 7, with an angle of α = 90°, or follow the specific sling arrangement relevant to the crane's application In the case of a ramshorn hook, the test load or force should be evenly distributed between the two prongs.
Load tests of a hook as a component may be replaced by cold forming by proof loading in accordance with 4.5 and Annex K
Figure 7 — Application of a test load or test forces on hook
A hook must endure the test load without significant permanent deflection, with the throat-opening dimension measured before and after testing at designated points (1) as shown in Figure 8 The allowable permanent set should not exceed 0.25% Additionally, the hook requires surface inspection according to the method outlined in section 4.2.
Maintenance and inspection
The hook shall be handled as an issue of its own in the maintenance and inspection manuals of the related crane
The maintenance manual must include essential guidelines for the upkeep of key components, specifically the thrust bearing located beneath the nut, the crosshead hinge, and welding procedures It is crucial to note that repair welding is strictly prohibited on the forged parts of both the hook and the nut.
The inspection instruction must include the following key items: the frequency of inspection and rejection criteria for permanent deformation (gap opening) of the hook body, wear of the hook body, and a thorough examination for surface defects, cracks, and corrosion, which requires disassembling the hook suspension to inspect the shank Additionally, it should address the safety locking of the nut and the presence of a safety latch, if applicable.
Permanent deformation (gap opening) of the hook body, measured from the dimensions y, y 1 and y 2 in Figure 8, shall be limited to 10 % of the initial value
The wear depth of the hook body at the bottom of the seat must not exceed 5% of the nominal height of the body section, as indicated by dimension h2 in Figure 1 Additionally, the worn areas should transition smoothly to adjacent regions and be devoid of any sharp marks, edges, or surface defects.
Marking
The hook body must feature a permanent marking, as illustrated in item 2 of Figure 8, which includes the following specifications: a defined identification for the size and shape of the hook, such as a hook number per Annex A or B; a material designation referencing the material class in Table 6 or another documented designation; the reference standard or specification number; the manufacturer's identification along with a traceability code, like a batch or serial number; and, if applicable, the proof loading marking as detailed in section 4.5.
EXAMPLE A hook fulfilling the requirements of this European Standard, size and shape being in accordance with number 12 of A.1 and being made from material P should have a marking:
The hook body itself shall have no marking indicating either the load or the duty classification
For small hook sizes, the limited space may necessitate a reduced marking, often consisting of just an identification code that ensures unique traceability to the hook's data in a separate document In the case of tailored, non-standard hooks, the marking should include the manufacturer's identification along with an identification code, also providing unique traceability to the hook data documented separately.
The hook must feature permanent center punch markings, as shown in item 1 of Figure 8 Relevant dimensions, y or y1 and y2, should be documented in the hook's records Whenever feasible, the y-dimensions may also be inscribed directly on the hook.
The fixed hoist media, which supports the suspended hook, will be designated as a component of the crane It will display the rated load mass and the corresponding duty classification, in accordance with the applicable crane type standard.
Safe use
The user’s manual for the crane or standalone hook/hook block must address several critical safety issues: ensure the hook suspension articulation functions freely to allow proper alignment with the load during movement; provide clear instructions for lashing loads with a maximum angle of 90 degrees between slings; specify the shape requirements for load attachments to prevent damage to the hook seat; emphasize that the two prongs of a ramshorn hook must be loaded symmetrically and equally, prohibiting the loading of only one prong; allow safety latches to close freely after load attachment; and outline the temperature limits for the hook.
A series of single hooks of type RS/RSN, dimensions of forgings
Designations: RS without forged nose for latch
RSN with forged nose for latch
Figure A.1 — Symbols of dimensions for single hooks with concave flanks
Table A.1 — Dimensions of forgings for single hooks in millimetres (mm)
63 280 224 320 250 212 190 655 710 315 265 32 50 160 420 600 408 355 630 550 – 108 60 45 25 1120 NOTE Sizes 006 to 40 based upon DIN 15400 series of hooks Dimensions for guidance
Other values for the dimension L may be used.
A series of single hooks of type RF/RFN, dimensions of forgings
Designations: RS without forged nose for latch
RSN with forged nose for latch
Figure A.2 — Symbols of dimensions for single hooks with straight flanks
Table A.2 — Dimensions of forgings for single hooks in millimetres (mm)
400 710 560 755 630 530 475 1620 1830 800 630 80 125 405 1060 1480 1035 900 1600 1195 190 75 70 35 2950 NOTE Sizes 10 to 250 based upon DIN 15400 series of hooks Dimensions for guidance
Other values for the dimension L may be used.
A series of single hooks of type B, dimensions of forgings
Figure A.3 — Symbols of dimensions for single hooks
Table A.3 — Dimensions of forgings for single hooks in millimetres (mm)
Dimensions based upon BS 2903 series of hooks Dimensions for guidance NOTE 1 Second row gives a ratio of dimensions to a measure a 1
NOTE 2 Nose for attachment of latch is optional
NOTE 3 See F.4 for typical dimensions of machined shank
NOTE 4 Length of hook shank “L” to suit application.
A series of ramshorn hooks of type RS/RSN and RF/RFN, dimensions of forgings
Designations: RS/RSN concave flanks ( a ), without or with nose
RF/RFN straight flanks ( b ), without or with nose
Figure B.1 — Symbols of dimensions for ramshorn hooks
Table B.1 — Dimensions of forgings for ramshorn hooks in millimetres (mm)
400 560 450 730 475 475 2375 600 71 56 670 1045 300 85 60 40 10 2895 NOTE 1 Hook sizes 50–400 preferably with straight flanks
NOTE 2 Sizes 05 to 250 based upon DIN 15400 series of hooks
Other values for the dimension L may be used
Table C.1 — Single hooks, dimensional tolerances of forgings
Single hook Nos in Annex A
Permissible deviations of dimensions in [mm] a 1 a 2 a 3 b 1 b 2 d 1 h 1 h 2 e 3 f 1 f 2 f 3 g 1 L
Single hook Nos in Annex A
Types RS/RSN, RF/RFN and B
Symbols of dimensions refer to Figure A.1
Table C.2 — Ramshorn hooks, dimensional tolerances of forgings
Ramshorn hook Nos in Annex B
Permissible deviations of dimensions in [mm] a 1 a 2 a 3 b 1 d 1 f 1 f 2 h e f 3 g L
Ramshorn hook Nos in Annex B
Types RS/RSN and RF/RFN
Symbols of dimensions refer to Figure B.1
Static limit design forces of hook bodies
Static limit design forces of hook bodies for hooks of type RS and RF
Table D.1 — Static limit design forces F Rd,s in kilonewtons (kN)
Valid for temperature influence factor f 1 = 1 ( T ≤ 100 °C)
Single hooks, types RS and RF Ramshorn hooks, types RS and RF
Hook Classified materials Classified materials No
Static limit design forces of hook bodies for a series of hooks of type B, with
Table D.2 — Static limit design forces F Rd,s in kilonewtons (kN)
Valid for temperature influence factor f 1 = 1 ( T ≤ 100 °C)
Fatigue limit design forces of hook bodies
Fatigue limit design forces of hook bodies for hooks of type RS and RF
Table E.1 — Fatigue limit design forces F Rd,f in kilonewtons (kN)
Factors f 2 and γ Hf incorporated, temperature influence factor f 1 = 1 (T ≤ 100 °C)
Single hooks, types RS and RF Ramshorn hooks, types RS and RF
Hook Classified materials Classified materials No
Fatigue limit design forces of hook bodies for a series of hooks of type B, with
Table E.2 — Fatigue limit design forces F Rd,f in kilonewtons (kN) Factors f 2 and γ Hf incorporated, temperature influence factor f 1 = 1 ( T ≤ 100 °C)
Sets of hook shank and thread designs
A series of hook shank and thread designs, a knuckle thread
Figure F.1 — Symbols of dimensions for a hook shank and thread
Table F.1 — Dimensions of hook shank and thread in millimetres (mm)
The dimensions of the nut (D and D1) and the forged shank diameter (d1) are provided for reference only Machining of the shank and threading can be applied to any forged sizes and types that meet the criteria outlined in this European Standard.
A series of hook shank and thread designs, a metric thread
Figure F.2 — Symbols of dimensions for a hook shank and thread
Table F.2 — Dimensions of hook shank and thread in millimetres (mm)
A series of hook shank and thread designs, a modified metric thread
Figure F.3 — Symbols of dimensions for a hook shank and thread
Table F.3 — Dimensions of hook shank and thread in millimetres (mm)
The dimensions of the nut and the forged shank diameter (d₁) provided are for reference purposes only Machining and threading of the shank can be adapted for various forged sizes and types, in accordance with the specifications outlined in this European Standard.
Hook shank and thread designs for hooks of type B
Figure F.4 — Symbols of dimensions for a hook shank and thread
NOTE Width of undercut, s, is measured from the shoulder of the shank to the crest of the last full thread
Table F.4 — Dimensions of hook shank and thread in millimetres (mm)
B 63 120 M110 × 8 110 8 99,89 100,19 12 24 1,12 4,91 12 110 NOTE 1 For explanation of dimension e 1 , see A.3
NOTE 2 Width of undercut, s, is measured from the shoulder of the shank to the crest of the last full thread
Basic formulae for stresses
The calculated stresses represent the true primary tensile stresses in the cross section of a curved beam, based on the theory of elasticity and assuming no plastic behavior of the material The following formulas are presented in a general format applicable to the stress distribution in the cross section of the curved portion of the hook bowl body, as illustrated in Figure G.1 For a curved beam with a solid section, the reference moment of inertia is determined using the specified calculations.
In this context, \( y \) represents the radial distance from the centroid of the cross-section, with positive values indicating the distance between the centroid and the extrados, while negative values denote the distance between the intrados and the centroid Additionally, \( b \) refers to the width of the section at a specific location \( y \).
The radius of curvature, denoted as R, represents the curvature of the centroid axis of a curved beam at a specific cross section The variable η₁ indicates the absolute value of the coordinate y at the inner radius, while η₂ signifies the absolute value of the coordinate y at the outer radius.
Figure G.1 — Symbols for curved beam bending calculation
The maximum tensile stress in the cross section shown is at the intrados and is calculated as follows: σ η η
F is the force acting perpendicularly to the plane of the section and through the centre of the curvature;
R is the radius of curvature of centroid axis of the hook bowl at the cross section under consideration; η 1 is the absolute value of the coordinate y at the intrados;
I is the a reference moment of inertia of the section in accordance with Formula (G.1)
The formula (G.2) accounts for the combined effects of direct tension and bending moment, and it is applicable only when the bending force is applied through the center of the beam's curvature In this loading scenario, the neutral axis aligns with the centroid of the beam's cross-section.