TABLE OF CONTENTS...2 APPENDIX A ANCHORHEADS...3 APPENDIX B WEDGE PROPERTIES...5 APPENDIX C

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1 Table of ontents TABLE OF CONTENTS...2 APPENDIX A ANCHORHEADS...3 APPENDIX B WEDGE PROPERTIES...5 APPENDIX C 18 MM DYFORM STRANDS...6 APPENDIX D OPERATION CYCLES STRANDJACK UNIT...7 D.1 JACK UP CYCLE (LIFTING THE LOAD)...7 D.2 JACK DOWN CYCLE (LOWERING THE LOAD)...10 APPENDIX E CALCULATIONS WEDGE MODEL...15 E.1 AREAS AND PROJECTED WEDGE AREAS A IN, A OUT, A INEFF EN A OUTEFF...16 E.2 HORIZONTAL WEDGE EQUILIBRIUM...17 E.3 VERTICAL WEDGE EQUILIBRIUM...18 E.4 WEDGE OPERATING RANGE...18 E.5 VERTICAL CABLE EQUILIBRIUM...19 APPENDIX F MALFUNCTION OF THE WEDGE...20 F.1 WEDGE OPERATION WITH : Μ KIN CONSTANT, INCREASING Μ KOUT...20 F.2 WEDGE OPERATION WITH : Μ KOUT CONSTANT, DECREASING Μ KIN...21 F.3 WEDGE OPERATION WITH: INCREASING Μ KOUT, DECREASING Μ KIN...21 APPENDIX G MICRO SLIP DURING JACK UP...23 Researh strand jak wedges Appendies By H.G.M.R. van Hoof 2

2 APPENDIX A Anhorheads An anhor head is drilled with a number of tapered holes suitable for aepting jak temporary wedges. An anhor head of the 830 SSL strand jak unit for example ontains 54 tapered holes (Figure 3). In Figure 1 a harateristi example of an anhor head is presented. The quantity of tapered holes of the anhor heads is saled to the required apaity. SECTION A-A The main speifiations of the anhor heads are presented in Table 1. Figure 1:Anhor head of 830 SSL strand jak unit Table 1: Speifiations Anhor heads. Soure: [ Mammoet] Anhor heads Speifiations SSL830 SSL550 SSL300 SSL100 Main dimensions(mm) : 520x x x x150 Weight (kg) : Material : 34CrNiMo6 34CrNiMo6 34CrNiMo6 34CrNiMo6 Wedges / holes (Qty) : Surfae treatment : Nitroarburizing(duth: teniferen) Nitroarburizing(duth: teniferen) Nitroarburizing(duth: teniferen) Nitroarburizing(duth: teniferen) Layer thikness surfae treatment (mm) : Solid lubriant : Molyote D321 R Molyote D321 R Molyote D321 R Molyote D321 R Optimal layer thikness lubriant (m) : Note that the surfae treatment of the anhor heads is nitro arburizing. Figure 2: 830 SSL anhor head with 54 wedges Figure 3: Tapered wedge seatings of an anhor head Researh strand jak wedges Appendies By H.G.M.R. van Hoof 3

3 In order to redue frition, the wedge seats of the anhor head are pre-treated with Molykote D321 R, a dry lubriant (see Figure 4). Figure 4: Molykote D321 R Pre-treated Anhor head Researh strand jak wedges Appendies By H.G.M.R. van Hoof 4

4 APPENDIX B WEDGE PROPERTIES The wedges used in the strand jak units ontain three wedge parts. The wedge is equipped with a frition or grip profile on the inside of eah part. The main dimensions of the wedge and wedge parts are presented in Figure 5 en Figure 6. DETAIL GRIP PROFILE WEDGE Figure 5: Assembled wedge and wedge part Figure 6:Detail grip profile The three wedge parts are assembled with an elasti rubber ring. This ring retains the three wedge segments/parts together during operation (Figure 7). Table 2: Speifiations TT 18/44 wedge (soures : Mammoet,KANIGEN ) Wedge Main speifiations TT 18/44 Wedge Figure 7: Assembled wedge with rubber ring Rubber ring Main dimensions(mm) : 25x 44x 18x80 Total weight (kg) : Material : DIN (SAE 8620) Wedge parts (Qty) : 3 Weight wedge part (kg) : Hardening (Carburizing) temperature ( C): Tempering temperature ( C): Hardness of substrate after tempering (indiation*) (HV): Surfae treatment : Eletroless Nikel plated (KANIGEN method) Proes temperature surfae treatment ( C) : Hardness of surfae layer (indiation*) (HV): Hardness substrate after surfae treatment (indiation*) (HV): Layer thikness surfae treatment (m) : Solid lubriant : Molyote D321 R Optimal layer thikness lubriant (m) : 5-20 Total ost (euro): 20 Manufaturer : TT Fijnmehania * Values for referene only, exat values have to be determined by material tests For main speifiations of the urrently used TT 18/44 wedge is referred to Table 2(In Table 2 several speifiations are noted with indiation, these values need to be reviewed by hardness tests). In order to redue frition, the wedges are pre-treated before operation with Molykote D321 R, a dry lubriant. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 5

5 APPENDIX C 18 mm DYFORM strands The strand bundle ontains several Dyform strands with a maximum operation apaity of 167 kn/strand (speified by Mammoet). The quantity of strands depends on the used unit type.the Dyform strand ontains 7 twisted, high apaity, steel wires with a flattened side (see Figure 8). They are speially developed for heavy lifting and its length an be up to 1500 meters to meet the job requirements. DYFORM STRAND P P Cross setion P-P Flattened side(6x) Wire (7x) Figure 8: Dyform strand The main speifiations of the Dyform strand are presented in Table 3. Table 3: Main speifiations Dyform strand. Soure :[ Bridon wire Ltd ] Strand Main speifiations BS5896 (DYFORM) Nominal values Toleranes Nominal diameter (mm) : Mass (kg/m) : % -2% Tensile strength (Rm) (N/mm 2 ) 1700 Surfae hardness of wires (HV) Steel area (mm 2 ) 223 Breag load (Fm) (kn) % proof load (Fp 0.1) (kn) 323 Load at 1% elongation (Ft 1.0) (kn) 334 Wires (Qty) 7 Manufaturer : Carrington Wire Ltd / Bridon Wire Ltd Researh strand jak wedges Appendies By H.G.M.R. van Hoof 6

6 APPENDIX D Operation yles Strandjak unit In this appendix a review is presented on two main operation yles of the strand jak unit SSL to familiarize the reader with the general onepts of the Strand jak-unit SSL.: Jak up yle (lifting the load) Jak down yle (lowering the load) D.1 Jak up yle (lifting the load) In the next paragraph the Jak up yle of the hydrauli Strand jak units is desribed. This priniple onerns all types. START POSITION STEP 1 WEDGE UPPER ANCHOR HEAD RELEASE PIPE UPPER RELEASE CILINDER UPPER RELEASE PLATE WEDGE LOWER ANCHOR HEAD RELEASE PIPE LOWER RELEASE CILINDER LOWER RELEASE PLATE STROKE LOAD LOAD STROKE Figure 9: Start position and Step 1 of the Jak up yle The start position (see Figure 9): The 18 mm dyform ompat strands are installed through the unit and the load is onneted. Both upper and lower anhor heads are loked (red in Figure 9). Step 1 (see Figure 9):The piston of the jak extends and raises the upper anhor head inluding the loked strands and onneted load. During this movement the wedges in the lower anhor head are pulled up slightly by the movement of the strands; the lower anhor head is still losed. In ase of failure of the upper anhor head, the wedges in the lower anhor head seure the load. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 7

7 STEP 2 STEP 3 STROKE -15 mm LOAD LOAD Figure 10: Step 2 and Step 3 of the Jak up yle Step 2 (see Figure 10): In top position the load is transferred from the upper anhor head to the lower anhor head by slightly retrating the piston, approx. 15 mm. During this load transfer both anhor heads remain loked. Step 3 (see Figure 10): After the transfer, the upper anhor head is opened hydraulially. The upper release ylinder lifts the release plate with the release tubes and shifts the wedges/grips up and out of their seatings (Note the differene between left and right detail piture).the upper anhor head is now unloked (blue in Figure 10) allowing free passage of the strands. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 8

8 STEP 4 STEP 5 -STROKE LOAD LOAD Figure 11: Step 4 and Step 5 of the Jak up yle Step 4 (see Figure 11): With the upper anhor head unloked, the piston of the jak retrats and returns to the starting position. The strands slide through the wedges in the upper anhor head. Step 5 (see Figure 11): At the end of step 4, the upper anhor head is loked again by the upper release ylinder retrating the release plate and release tubes. The jak up yle of step 1 to 5 is repeated till the required jak up distane is aomplished. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 9

9 D.2 Jak down yle (lowering the load) In the next paragraph the Jak down yle of the hydrauli Strand jak units is desribed. This priniple onerns all types. START POSITION WEDGE UPPER ANCHOR HEAD RELEASE PIPE UPPER RELEASE CILINDER UPPER RELEASE PLATE STEP 1 WEDGE LOWER ANCHOR HEAD RELEASE PIPE LOWER RELEASE CILINDER LOWER RELEASE PLATE LOAD Figure 12: Start position and Step 1 of the Jak down yle The start position (see Figure 12): The 18 mm dyform ompat strands are installed through the unit and the load is onneted. Both upper and lower anhor heads are loked (red in Figure 12). Step 1 (see Figure 12): The upper anhor head is opened hydraulially. The upper release ylinder lifts the release plate with the release tubes and shifts the wedges/grips up and out of their seatings (Note the differene between detail piture of the upper anhor head in Start position and Step1). The upper anhor head is now unloked (blue in Figure 12) allowing free passage of the strands. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 10

10 STEP 2 STEP 3 LOAD LOAD Figure 13: Step 2 and Step 3 of the Jak down yle Step 2 (see Figure 13): With the upper anhor head unloked, the piston of the jak extends till approx. 15 mm before end of the outward stroke (ompare the position of the main hydrauli ylinder in step 1 and step 2). The strands slide through the wedges in the upper anhor head during the stroke. Step 3 (see Figure 13): In the position 15 mm before end of the outward stroke the upper anhor head is loked by the upper release ylinder retrating the release plate and release tubes (red in detail upper anhor head in see Figure 13 step 3). Researh strand jak wedges Appendies By H.G.M.R. van Hoof 11

11 STEP 4 STEP 5 LOAD LOAD Figure 14: Step 4 and Step 5 of the Jak down yle Step 4 (see Figure 14): The load is transferred from the lower anhor head to the upper anhor head by slightly extending the piston of the main ylinder further (approx. +15 mm) to the end of the stroke. During this load transfer both anhor heads remain loked (both red in Figure 14 step 4). During this movement the wedges in the lower anhor head are pulled up slightly by the movement of the strands; the lower anhor head is still losed. In ase of failure of the upper anhor head, the wedges in the lower anhor head seure the load. Step 5 (see Figure 14): After the transfer, the lower anhor head is opened hydraulially ( unloked ; blue in detail of lower anhor head step 5). The lower release ylinder lifts the release plate with the release tubes and shifts the wedges/grips up and out of their seatings (Note the differene between left and right detail piture step 4 and step 5).The lower anhor head is now unloked (blue in Figure 14) allowing free passage of the strands. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 12

12 STEP 6 Figure 15: Step 6 and Step 7 of the Jak down yle Step 6 (see Figure 15): The piston of the jak retrats and lowers the losed upper anhor head inluding the strands and load (movement is stroke) until approx. 15 mm before end of the inward stroke. The lower anhor head is still unloked (blue in Figure 15) during this movement and allows free passage of the strands. Step 7 (see Figure 15): In the position 15 mm before end of inward stroke, the lower anhor head is loked hydraulially by the lower release ylinder retrating the release plate and release tubes (red in detail lower anhor head in Figure 15 step 7). Researh strand jak wedges Appendies By H.G.M.R. van Hoof 13

13 Figure 16: Step 8 of the Jak down yle Step 8 (see Figure 16): After log the lower anhor head, the load is transferred from the upper anhor head to the lower anhor head by slightly retrating the piston of the main ylinder further to the end of the inward stroke, approx. -15 mm. During this load transfer both anhor heads remain loked. The jak down yle of step 1 to 8 is repeated until the required jak down distane is aomplished. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 14

14 APPENDIX E Calulations wedge model In this appendix a mathematial model of the strand log system is presented. In the following onsiderations a single wedge part is examined and the spring fore of the prestress spring is negleted. STRAND WEDGE PART ANCHORHEAD Dstrand 2 x Ri Nout CW CW S < L L out out w w F = L A able F L Figure 17 : Shemati presentation of mathematial wedge model = Kineti oeffiient of frition between outer wedge surfae and anhor head surfae = Kineti oeffiient of frition on inner wedge surfae and able surfae N out = Normal fore on outer wedge surfae N in = Normal fore on inner wedge surfae σ w = Compressive stress between wedge and able σ Nout = Compressive stress perpendiular wedge surfae and anhor head σ = Tensile stress in able as result of F L F L = Load fore α = Wedge angle τ out = Frition shear stress between outer wedge surfae and anhor head τ w = Frition shear stress between wedge and able S = Position of slip front (for detailed information is referred to Appendix G2.2) R i = Inner radius of wedge and therefore outer radius of strand/able A able = Cross setion area of able From Figure 17, the following equations an be obtained: Researh strand jak wedges Appendies By H.G.M.R. van Hoof 15

15 τ out = σnout (a) and w = σw τ (b) E.1 Areas and projeted wedge areas A in, A out, A ineff en A outeff The estimation of the theoretial outer and inner surfae of a single wedge part (assuming ylindrial), A in and A out, is formulated as : A in 2 = π R i S () and 3 A 2 = π R 3 S os ( α) out out (d) This aording to Figure 18. TOP VIEW WEDGE PART SIDE VIEW WEDGE PART Ri Rout S COS ( ) S Figure 18: Top view and side view wedge part in relation to A in and A out The estimated projeted effetive outer and inner surfae of a single wedge part, A ineff and A outeff, an formulated as: S Aineff = Ri S 3 (e) and Aouteff = R out 3 (f) os( α) These equations an be derived from Figure 19. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 16

16 TOP VIEW WEDGE PART Ri x 3 Rout Ri Rout x 3 Rout Ri Figure 19: Top view and side view wedge part in relation to A ineff and A outeff The total normal fore N out ating perpendiular on the effetive surfae of the wedge part beomes (see also Figure 17) : N out S = σnout Aouteff = σnout R out 3 (g) os( α) The total normal fore N in ating perpendiular on the inner surfae of the wedge part beomes (see also Figure 17) : N in = σ A = σ R S 3 (h) w ineff w i E.2 Horizontal wedge equilibrium The total equilibrium of the horizontal fores on the wedgepart results in the following equation (aording to Figure 17): N out os( α) = N τ sin( α) A (i) in out outeff After substitution of equations a, g, h and f in i S σnout R out 3 os( α) = σw R os( α) After solving and rearranging, we get σ R (1 tan( α)) = σ R or Nout out w i i S 3 σ R σ Nout sin( α) R out out Nout (1 tan( α)) Ri S os( α) (j) = σ w 3 Researh strand jak wedges Appendies By H.G.M.R. van Hoof 17

17 E.3 Vertial wedge equilibrium The total equilibrium of the vertial fores on the wedgepart results in the following equation (aording to Figure 17): A τ τ os( α) A σ sin( α) A 0 + (k) in w out out Nout out = After substitution of equations b,, a, d in k, we get 2 π Ri S 3 σ Nout σ w 2 sin( α) π R 3 out σ S os Nout ( α) 2 os( α) π R 3 = 0 After solving and rearranging, this results in out S os ( α) R σ = σ R ( + tan( α)) or i w Nout out Rout σw = σnout ( + tan( α)) (l) R i E.4 Wedge operating range Substituting equation j in l results in σ Nout R R out After rearranging i (1 tan( α)) = σ Nout R R out i ( + tan( α)) tan( α) = and so 1+ tan( α) + tan( α) = (m) 1 tan( α) These two equations represent the borderline of the wedge operating range. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 18

18 E.5 Vertial able equilibrium When the equilibrium of the vertial fores on the able/strand in Figure 17 is onsidered, the following equation an be aquired: F L = 2 π R τ S (n) i w With F L able 2 i = σ A = σ π R (o) and w = σw τ (b) After substitution of o and b in equation n, the result is: 2 i σ π R = 2 π R σ S (p) After rearranging : i w S σ = 2 σw (q) R i Researh strand jak wedges Appendies By H.G.M.R. van Hoof 19

19 APPENDIX F Malfuntion of the wedge For the benefit of the analysis, three possible ases are desribed to larify the malfuntion of the wedge, aording to the mehanial wedge model: 1. Wedge operation with : Constant, inreasing 2. Wedge operation with : Constant, dereasing 3. Wedge operation with : Inreasing, dereasing In the following paragraphs these load ases are desribed in detail. F.1 Wedge operation with : Constant, inreasing When the wedge operation is started, a proper and normal operation of the wedge is assumed.this implies that the frition onditions are below the good/bad borderline in Figure 20. For example, fitive estimated start values of and in operation are 0,2 and 0,5 (see start operation point A in Figure 20). 0.6 Frition oeffiients 0.4 Malfuntion of wedge (slipping of strand, situation 2) B ` 0.2 A Wedge operating properly (situation 1) α =8.19 Figure 20:Wedge operation with inreasing With inreased, the operation point B is positioned in the red Malfuntion Area.The frition fore between wedge outer surfae and tapered hole surfae is too high and onsequently gripping ation is less; the strand slips through the wedge. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 20

20 F.2 Wedge operation with : Constant, dereasing When the wedge operation is started, a proper and normal operation of the wedge is assumed. For example, fitive estimated start values of and in operation are 0,2 and 0,5 (see start operation point A in Figure 21). 0.6 Frition oeffiients 0.4 Malfuntion of wedge (slipping of strand, situation 2) 0.2 C A Wedge operating properly (situation 1) α =8.19 Figure 21: Wedge operation with dereasing When dereases during operation below the value 0,35 and the value is onstant, the operation point of the wedge is moved from A to point C (see Figure 21 ). Operation point C is positioned in the red Malfuntion Area.The frition fore between wedge inner surfae and able surfae is too low, onsequently the gripping ation is less; the strand slips through the wedge. F.3 Wedge operation with: Inreasing, dereasing In most pratial ases the values of the frition oeffiients will hange simultaneously, influened by environmental irumstanes (temperature, relative humidity et.). Researh strand jak wedges Appendies By H.G.M.R. van Hoof 21

21 A ombination of inreasing and dereasing will lead to mal-funtion of the wedge onform Figure 22, the operation point of the wedge is moved from A to point D. Malfuntion of the wedge appears. 0.6 Frition oeffiients 0.4 Malfuntion of wedge (slipping of strand, situation 2) D 0.2 A Wedge operating properly (situation 1) α =8.19 Figure 22: Wedge operation with dereasing and inreasing Researh strand jak wedges Appendies By H.G.M.R. van Hoof 22

22 APPENDIX G Miro slip during jak up In every load yle (jak up and jak down) miro slip will our in the wedges of the upper and lower anhor head. This is a result of the differene in axial strain (as a result of the load fore F L ) between the able and wedge in onsequene of the differene in stiffness. The axial strain in the able is larger than in the wedge. Hene the strain in the loaded able an not be followed by the wedge what results in a relative displaement between the able outer surfae and wedge inner surfae. Miro slip in ombination with a load fore results in wear of the inner frition surfae of the wedge and eventually in a redution of the inner frition oeffiient. Finally this will ause malfuntion of the wedge. When the piston of the jak extends, the losed upper anhor head is raised inluding the strands. The load fore F L and related strain in the strand inrease during this movement until the anhor head bears the total present load fore F L. The situation of the full loaded wedge in the anhor head is desribed shemati in Figure 23. F L = Load fore V = Spring fore (pre-stress) Figure 23: Loaded wedge during raising of upper anhor head Researh strand jak wedges Appendies By H.G.M.R. van Hoof 23

23 N in = Normal fore on inner wedge surfae = Kineti oeffiient of frition on inner wedge surfae Q = Length ar of wedge part α = Wedge angle σ w = Compressive stress between wedge and able σ = Tensile stress in able as result of F L ε = Strain in able S = Position of slip front L = Length of frition profile A able = Cross setion area of able E = Modulus elastiity of able τ w = Frition shear stress At the end of the trajetory of the inreasing load fore F L (the upper anhor head bears the total load fore F L ), the slip front has propelled to distane S. In the ross setion of the able on position S, the tensile stress σ = 0. Along the inner frition surfae of the wedge part, width Q and length L, exists a ompressive stress σ w between wedge and able as a result of the normal fore N in. The (pre-stress) spring fore V is negleted and the stiffness of the wedge is onsidered infinite in the following onsiderations. This ompressive stress σ w present on the 3 wedge parts is formulated as: σ w = N in 3 Q L The ompressive stress σ w is able to transmit an average frition shear stress τ f on the ontat area: τ = σ w w The load fore F L is ompensated by three inner frition surfaes, with an area of Q s and thus is derived for F L : F L = 3 Q s τ w = 3 Q s σ w 3 Q s N = 3 Q L in = s N L in A inreasing fore F L results in a inreasing value of s, as soon as s > L total slip and F L = F max = ours. N in If s > L : maroslip ours, the strand slips through the wedge If 0<F L <F max : miroslip ats along length s. For the tensile stress σ and strain ε in the able we an write σ = F A L able ε σ = E = E FL A able The length s an be alulated from the relation s = FL N in L (Eq. G.1) Researh strand jak wedges Appendies By H.G.M.R. van Hoof 24

24 The tensile stress aording to σ diminishes linear with values on positions x = 0 to x = s (see Figure 23 ) σ = 0 and (x 0) = σ (x = s) And analogially with the equations for the tensile stress σ 0 ε (x= 0) = = = 0 and E E A able ε (x= s) F = A L able A graph of the x- position against strain ε is provided in Figure 24. σ, equations for strain ε are σ FL = = E E A able Figure 24 Graph of position x, strain and tensile stress in able wedge With usage of Figure 24 the total able elongation dl in the wedge is derived. The elongation dl of the able in the wedge orresponds with area P 1 dl = P = ε (x= s) s 2 With σ L ε (x= s) = = and E E Aable F FL L s = N in After substitution, dl beomes Researh strand jak wedges Appendies By H.G.M.R. van Hoof 25

25 dl 1 2 = ε(x= s) s = 2 E F A 2 L able L N in Funtion ε (x ) an be desribed as (see Figure 24 ) F x L ε (x) = for 0 x s E Aable du ε dx du FL x = dx E A With the definition = (x) follows able To obtain the loal relative displaement funtion u(x) du FL x u(x) = [ ] dx = [ ] dx dx for 0 x s E A able This leads to the relative displaement funtion u(x) 2 FL x u(x) = + C for 0 x s 2 E A able With u (0) = 0 onsequently C = 0, relative displaement funtion u(x) beomes F u(x) = 2 E L x A 2 able for 0 x s (Eq. G.2) Researh strand jak wedges Appendies By H.G.M.R. van Hoof 26

26 Equation G-2 is presented graphially in Figure 25. Figure 25: Graph of relative displaement u(x) of the outer able surfae against inner frition profile The magnitude of relative displaement u(x) (and thus wear) of the outer able surfae against the frition profile depends mainly on the loation of the slip front S, assuming F L, A able, E onstant. Maximum slip is loated at the loaded outlet of the able at position S. Researh strand jak wedges Appendies By H.G.M.R. van Hoof 27

27 STRANDJACK WEDGES Frition oeffiients, miro slip and handling Report nr. DCT By: H.G.M.R. van Hoof Idnr : November, 2005 Abstrat The ompany Mammoet BV meets diffiulties with able wedges/lamps of their strand jak units. Slipping of strand through the wedges and high maintenane osts of the strand jak units hene, are the main aspets. In this report general operation fundamentals of the urrent strand jak unit are explained and detailed information of essential omponents is provided. It also provides a straightforward theoretial/mathematial approah on the probable auses of malfuntion and unreliability of the strand jak wedge. To improve the servie life, reliability and handling properties of the wedge and strand, an alternative wedge design is presented. Researh strand jak wedges Report By H.G.M.R. van Hoof 1

28 Summary Mammoet is a leading ompany speialized in solving extreme heavy lifting and transport hallenges. With offies in 30 ountries and over more than 1500 employees around the world Mammoet provides its ustomers with knowledge, skills and equipment at onshore or offshore loation. The solutions that Mammoet provide are used in eonomi setors like the Petro Chemial industry, Civil works, Power plants and Offshore. The best projet example of the latter is of ourse the salvation of the Russian nulear submarine the Kursk. In various projets Mammoet applies a ompat Strand jak unit plaed on a gantry or mast for preise lifting, lowering or pulling of heavy loads. This unit is, due to its ompat design, very suitable in areas where onventional equipment as ranes annot be plaed. This Strand jak unit is generally based on a hydrauli ylinder with a wedge priniple to lok the strands in eah stroke. Two wedges, situated in the lower and upper anhor head in the ylinder, lok eah strand in the unit when the load is lifted or lowered. Mammoet meets diffiulties espeially with these wedge lamps of the strand jak units. Slipping of strand through the wedges and high maintenane osts of the strand jak units hene, are the main aspets. In the speialized and prestigious market of heavy lifting and transport safety and operating reliability are important topis, deisive in maintaining a good reputation. It s obvious that researh on the used wedge beame more than desirable. Aording to the alulations performed in Appendix E the proper operation area of the wedge an be haraterized as: tan( α) < and so: 1+ tan( α) > 1 + tan( α) tan( α) With: = Kineti oeffiient of frition between outer wedge surfae and anhor head surfae = Kineti oeffiient of frition on inner wedge surfae and able surfae α = Wedge angle F L = Load fore The wedge gripping quality depends on inner-and outer frition oeffiients in, out and the wedge angle α. The harateristi graph of Figure 13 provides the proper operation area and malfuntion area of the wedge, as a funtion of in, out (with α=8.19 ). Several environmental irumstanes and priniples an have an influene on the value of : For : o o o o Adhesion: between wedge outer surfae and tapered hole surfae Plowing /third body effets: between wedge outer surfae and tapered hole surfae Aumulation of dirt : between strand outer surfae and inner surfae of the wedge Wear on inner frition profile of wedge during load yles Researh strand jak wedges Report By H.G.M.R. van Hoof 2

29 During operation relative displaement ours between the inner frition profile and strand outer surfae. The relative displaement u(x) an be haraterized as : F u(x) = 2 E L x A 2 able F L = Load fore A able = Cross setion area of able E = E-modulus of able material This relative displaement whih initiates wear is alled miro slip The miro slip reduing design, presented in this report, an inrease servie life of the wedge. Applying 190 high apaity solid strands with diameter of 9 mm an realize the following objetives: o o No internal relative displaements between wires during operation: less elasti power is lost by frition/wear. Therefore no internal wear is initiated. In general a strand with a diameter of > 9 mm ontains multiple wires, and the internal wear and elasti energy loss will inrease drastially by an inreasing number of strand wires. The 9 mm strand also improves handling due to a weight redution of 1.25 kg/m ompared to the original 18 mm strand. In a proper 900-ton onfiguration of the strand jak unit SSL, 190 wires of 9 mm are used. In this 9 mm onfiguration, 380 small 9 mm low ost wedges are used. Researh strand jak wedges Report By H.G.M.R. van Hoof 3

30 Table of ontents SUMMARY...2 TABLE OF CONTENTS INTRODUCTION MAMMOET MERGER CLIENTS AND SCOPE OF WORK THE MAMMOET STRAND JACK SYSTEM HYDRAULIC STRAND JACK-UNIT SSL COMPONENTS HYDRAULIC STRAND JACK-UNIT SSL STRAND LOCKING PRINCIPLE Loked priniple Unloked priniple THEORETICAL PROBLEM ANALYSIS WEAR BY MICRO SLIP MICRO SLIP / WEAR REDUCING DESIGN WEAR REDUCTION ON THE BASE OF VERTICAL CABLE EQUILIBRIUM MM WEDGE / ANCHOR HEAD CONFIGURATION GENERAL CONCLUSION FUTURE PERSPECTIVES/ RECOMMENDATIONS...23 REFERENCES...24 Researh strand jak wedges Report By H.G.M.R. van Hoof 4

31 1 Introdution Mammoet is a leading ompany speialized in solving extreme heavy lifting and transport hallenges. With offies in 30 ountries and over more than 1500 employees around the world Mammoet provides its ustomers with knowledge, skills and equipment at onshore or offshore loation. The solutions that Mammoet provide are used in eonomi setors like the Petro Chemial industry, Civil works, Power plants and Offshore. The best projet example of the latter is of ourse the salvation of the Russian nulear submarine the Kursk. In various projets Mammoet applies a ompat Strand jak unit (see Figure 1and Figure 2) plaed on a gantry or mast for preise lifting, lowering or pulling of heavy loads. This unit is, due to its ompat design, very suitable in areas where onventional equipment as ranes annot be plaed. Figure 1: Lifting mtonnes dek with 12 strand jak units Figure 2: Two strand jak units on top of a mast This Strand jak unit is generally based on a hydrauli ylinder with a wedge priniple to lok the strands in eah stroke. Two wedges, situated in the lower and upper anhor head in the ylinder, lok eah strand in the unit when the load is lifted or lowered. Mammoet meets diffiulties espeially with these wedge lamps of the strand jak units. Slipping of strand through the wedges and high maintenane osts of the strand jak units hene, are the main aspets. In the speialized and prestigious market of heavy lifting and transport safety and operating reliability are important topis, deisive in maintaining a good reputation. It s obvious that researh on the used wedge beame more than desirable. In this researh report hapter two provides an overall view on Mammoet, its lients, mission statement and sope of work. In hapter three a profound and extensive examination is performed on the existing strand jak system and its omponents. General operation fundamentals of the urrent strand jak unit are explained and detailed information of essential omponents is provided. Chapter four provides a theoretial approah on the probable auses of mal-funtion and unreliability of the strand jak wedge. Mathematial equations, whih Researh strand jak wedges Report By H.G.M.R. van Hoof 5

32 haraterize the operation of the wedge, are derived and a graphial presentation of the wedge malfuntion area is presented. In hapter five wear by miro slip is disussed and a miro slip/wear reduing wedge design is presented in hapter six. The general onlusion and future perspetives/reommendations are arried out in hapter seven. Researh strand jak wedges Report By H.G.M.R. van Hoof 6

33 2 Mammoet Mammoet is a speialist in heavy lifting and transport; it has subsidiaries and agenies throughout the world. Besides ontrating on a turnkey basis, Mammoet offers rane rental and related servies. 2.1 Merger The new heavy lift ombination was formed on 12 July 2000, when the shares of Mammoet Transport BV were taken over by Van Seumeren Holland BV from Royal Ned Lloyd. Van Seumeren Group has aquired Mammoet s entire business, inluding its ativities in the United States, Asia, the Middle East and Europe. The merger of the two ompanies provided the possibility to offer a total pakage at the top of the market by saling up to ustomers. Synergy results in: Mobilisation/demobilisation savings Capaity utilisation of equipment International ommerial effetiveness A more effiient organisation Purhasing power Both Duth, heavy lifting and speial transportation ompanies Mammoet and Van Seumeren Holland BV were nearly equally sized when they joined fores. Mammoet was slightly stronger in horizontal transportation. Van Seumeren was slightly stronger in vertial transportation. The ombined expertise, the experiene and efforts of the 1500 employees of Mammoet Holding BV form a ruial fator for the suess and further growth opportunities of the ompany in the international projet market. The new ompany is positioned worldwide under the name and logo Mammoet, with the mention Van Seumeren Group. 2.2 Clients and sope of work Mammoet provides lients with tailor-made solutions and servies in all sopes of work for engineered heavy lifting and multimodal transport worldwide. In Table 1 Mammoet s lients and sope of work are indiated. Table 1:Mammoet s lients Mammoet s lients: Power generating industry Forwarders Constrution ompanies Chemial industry EPC ontrators Crane ompanies Petrohemial Industry Ship yards Engineering ompanies Offshore industry Vessel Fabriators Mahine buildings ompanies Steel onstrution ompanies Table 2: Mammoet s sope of work Mammoet s sope of work: Lifting Site moves Jag Rigging Transporting Shutdowns Skidding Barging Load outs Plaing Ballasting From fatory to foundation Load ins Shifting Weighing Researh strand jak wedges Report By H.G.M.R. van Hoof 7

34 Figure 3 shows a gantry-lifting system, lifting an offshore module. Figure 4 is an example of a projet in the hemial industry. Figure 3: Lifting a offshore module 600 mtonnes with 4 strand jak units on a gantry Figure 4: Lifting a 830 mtonnes vessel in the power hemial industry Researh strand jak wedges Report By H.G.M.R. van Hoof 8

35 3 The Mammoet strand jak system This hapter gives a broad view on of the Mammoet strand jak system with the Strand Jak Units SSL and desription of the worg mehanism with ourring defets in the strand-log priniple. Also a detailed desription of the used wedges is given. Mammoet has designed the Mammoet strand jak system to be used for installation of heavy equipment, suh as offshore-strutures, equipment for petrohemial and nulear power plants and bridges. The system has a modular set-up, designed for safe a preise lifting, lowering or pulling of heavy loads. 3.1 Hydrauli Strand jak-unit SSL The (multi) Strand Jak Unit SSL is designed for usage in the MSG (Mammoet Sliding Gantry) and in the transport of heavy loads, horizontally or vertially. Mammoet has several Strand jak units available with different apaities and dimensions. The apaity is (of ourse) oupled with the quantity of strands and the diameter of the main ylinder. The main dimensions and tehnial data of the available Mammoet equipment are presented in Figure 5. HEIGHT STROKE WIDTH LENGTH Strand jak units SSL830 Speifiations SSL830 SSL550 SSL300 (Double Anhored) SSL100 Capaity (kn): Strands (Qty): Strand diameter (mm) : Stroke (mm): Weight (kg) Length (mm): Width (mm): Height (mm): Type of able : Dyform Strand Dyform Strand Dyform Strand Dyform Strand Dyform Strand Worg oil pressure (bar) Wedges (Qty) : Test apaity (kn) : Figure 5: Tehnial data and main dimensions of the strand jak equipment Researh strand jak wedges Report By H.G.M.R. van Hoof 9

36 3.2 Components Hydrauli strand jak-unit SSL In Figure 6 shows a general ross-setion of a strand jak unit. The strand jak unit onsists of the following main omponents: Base plate: this plate is fixed on the foundation Lower anhor head (see Appendix A) Wedges (see Appendix B) Lower wedge-release-ylinder: with the lower wedge-release-ylinder the lower anhor head opens and loses. Hydrauli ylinder: the hydrauli ylinder extends and retrats the piston. This way the strand an be moved over a stroke of 400 or 480 mm. Upper wedge-release-ylinder: with the upper wedge-release-ylinder the upper anhor head opens and loses. Upper anhor head (see Appendix A) Strand guide tube (or pipe): the guide tubes to ensure that strands passing not deflet and apply side loadings onto the top anhor assembly. 18 mm ompat strands (DYFORM) (see Appendix C) Load fore Figure 6: Cross-setion Strand jak unit Researh strand jak wedges Report By H.G.M.R. van Hoof 10

37 3.3 Strand log priniple The Hydrauli strand jak unit SSL ontains a harateristi strand (or able) log priniple. This log-priniple is a deisive fator in the quality of performane of the strand jak unit SSL. In this paragraph a detailed desription is provided. The log priniple omprises two main positions; loked and unloked (examine Figure 7). For a detailed desription of the operation yles (jak-up and jak down) of the Hydrauli Strand jak-unit SSL is referred to Appendix D. "LOCKED" "UNLOCKED" Figure 7: Log priniple in loked and unloked position Loked priniple In the loked position, the release plate (or kik out plate) as well as the onneted release tubes are fully retrated; allowing the wedges in their tapered seatings, held down by the prestress springs (see Figure 7). A speial washer of either spigot or soket type is used between the spring and the wedge, to ensure that the spring pressure is applied equally to all three parts of the wedge (Figure 8). The initial spring fore (of magnitude ±400 N /spring) provokes an essential pre-bite of the wedge on the strand (Figure 8). The bite depth b of the pre-bite is negligible, however not to be overlooked for a proper operation of the gripping ation of the wedge. When the load fore on the strand (and thus on the wedge) inreases, the wedge drops over a distane D downward in the tapered seating and the bite depth b (or distane inwards) enlarges pro rata of the load fore (examine Figure 9). The strand is now loked by the bite of the grip profile of the wedge. Researh strand jak wedges Report By H.G.M.R. van Hoof 11

38 The bite depth b and distane D have values of roughly mm and mm respetively (depending on irumstanes in operation and differenes in hardness of grip profile and strand surfae). These values relate to the maximum Mammoet operation load of 167 kn /strand. SPRING SPIGOT OR SOCKET TYPE WASHER STRAND WEDGE D STRAND b WEDGE Figure 8: Pre-bite of wedge in strand Figure 9: Inrease of load fore results in bite depth b and distane downward D The radial movement (distane inward b) of the three wedge parts during an inrease of the load fore (onform Figure 8 and Figure 9) is presented shematially in Figure 10. TOPVIEW WEDGE (DISTANCE INWARD b) b Inreasing loadfore Figure 10: Radial movement of the wedge parts (segments) with inreasing load fore Researh strand jak wedges Report By H.G.M.R. van Hoof 12

39 3.3.2 Unloked priniple Before the Unlog proedure is atuated, the load fore on the wedges is redued to zero (to exlude any damage on release plate and tubes). Subsequently, by means of the additional hydrauli release ylinders (Figure 7) the release plate (or kik out plate with the onneted release tubes) is lifted into the anhor head and shifts the wedges out of their tapered seatings (Figure 7 and Figure 11). The strand is now Unloked ; note the differene between Figure 9 and Figure 11. WEDGE STRAND WEDGE RELEASE TUBE (shifted upwards) Figure 11: "Unloked position; the wedge shifted upwards By unlog, free passage of the strands through the wedges is allowed; a negligible fore is applied on the frition profile and no bite is generated (see detail Figure 11). Researh strand jak wedges Report By H.G.M.R. van Hoof 13

40 4 Theoretial problem analysis In this hapter a mehanial wedge model is presented. With this model the theoretial situations of mal-funtion of the wedge strand log system are explained. In Figure 12 the mehanial wedge model is presented with relevant parameters. F L Figure 12: Mehanial wedge model = Kineti oeffiient of frition between outer wedge surfae and anhor head surfae = Kineti oeffiient of frition on inner wedge surfae and able surfae α = Wedge angle F L = Load fore Aording to the alulations performed in Appendix E the borderline of operation of the wedge an be haraterized as: tan( α) = 1+ tan( α) and so = 1 + tan( α) (4a) tan( α) In the different load ases of the wedge, the following two situations an our : Situation 1 The strand jak wedge operates properly. And thus tan( α) < 1+ tan( α) and so: > 1 + tan( α) (4b) tan( α) Situation 2 The strand jak wedge doesn t operate properly. And thus Researh strand jak wedges Report By H.G.M.R. van Hoof 14

41 tan( α) > 1+ tan( α) and < 1 + tan( α) tan( α) (4) The equations 4a, 4b and 4 ombined in graph below for the wedge angle α = Frition oeffiients Borderline 0.4 Malfuntion of wedge (slipping of strand, situation 2) 0.2 Wedge operating properly (situation 1) α =8.19 Figure Figure 13: areas of proper resp. wrong operation of the wedge in a oeffiients of frition diagram The ombinations of frition oeffiients and, positioned in red area of Figure 13, will ause malfuntion of the strand log ation of the wedge (values of in Figure 13 below zero are of no pratial use). Note : With a wedge angle of 8.19, the inner frition oeffiient has to be > 0.14 for a proper wedge operation! For the interested reader, Appendix F larifies several ases of wedge malfuntion. Several environmental irumstanes and priniples an have an influene on the value of : Adhesion: between wedge outer surfae and tapered hole surfae Plowing /third body effets: between wedge outer surfae and tapered hole surfae For : Aumulation of dirt : between strand outer surfae and inner surfae of the wedge Wear on inner frition profile of wedge during load yles This last wear priniple is onsidered in detail in the following hapter. Researh strand jak wedges Report By H.G.M.R. van Hoof 15

42 5 Wear by miro slip In every load yle (jak up and jak down) miro slip will our between the wedges of the upper and lower anhor head and the strands. This is a result of the differene in axial strain (as a result of the load fore F L ) between the able and wedge in onsequene of the differene in stiffness. The axial strain in the able is larger than in the wedge. Hene the strain in the loaded able an not be followed by the wedge what results in a relative displaement between the able outer surfae and wedge inner surfae. Miro slip in ombination with a load fore results in wear of the inner frition surfae of the wedge and eventually in a redution of the inner frition oeffiient. Finally this will ause malfuntion of the wedge (aording to paragraph 4 and Appendix F). The load fore F L and related strain in the strand inrease during this movement until the anhor head bears the total present load fore F L. At the end of the trajetory of the inreasing load fore F L (the upper anhor head bears the total load fore F L ), the slip front has propelled to distane S. In the ross setion of the able on position S, the tensile stress σ = 0 Aording to the alulations performed in Appendix G the position of slipfront S an be haraterized as: s = FL N in L (5a) N in = Normal fore on inner wedge surfae = Kineti oeffiient of frition on inner wedge surfae F L = Load fore S = Position of slip front L = Total length of frition profile =0 N in =FL/Aable Figure 14: Wedge with relevant parameters onerning miroslip F L An inreasing fore F L results in a inreasing value of s, as soon as s > L total slip and F L = F max = ours. N in If s > L : maroslip ours, the strand slips through the wedge If 0<F L <F max : miroslip ats along length s. Aording to Appendix G the relative displaement u(x) between strand and wedge beomes: F u(x) = 2 E L x A 2 able (5b) Researh strand jak wedges Report By H.G.M.R. van Hoof 16

43 This equation is presented graphially in Figure 15. X Figure 15: Graph of relative displaement u(x) between the outer able surfae and inner frition profile of the wedge FL= Load fore Aable = Cross setion area of able E = E-modulus of able material The magnitude of relative displaement u(x) (and thus wear) of the outer able surfae against the frition profile depends on the loation. Maximum slip (relative displaement) is loated at the loaded outlet of the able at x = S (see Figure 15). Throughout the load yles, wear takes plae on the frition profile of the wedge due to the load fore and relative motion (miro slip). The frition profile is redued and flattened during operation (see Figure 16). Consequently the strand gripping ation of the wedge is less. Figure 16: Flattened frition profile of a wedge, mal-funtioning after 501 strokes at nominal load fore of 120 kn Researh strand jak wedges Report By H.G.M.R. van Hoof 17

44 6 Miro slip / wear reduing design As indiated in Appendix G and hapter 5 the relative displaement u(x) between wedge frition profile and able outer surfae is haraterized as (see Figure 17): F u(x) = 2 E L x A 2 able (6a) Figure 17: The paraboli haraterisation of the relative displaement u(x) between frition profile and able outer surfae. F L = Load fore A able = Cross setion area of able E = E-modulus of able material Aording to Ref [3], the design of a miro slip/hysteresis reduing grip onstrution of a plate is equipped with fingers whih an absorb the relative displaement u (x).the lengths of of the fingers are arranged a paraboli pattern (onform the equation of u(x)). The length F of eah finger an be designed proportional to the relative displaement u(x). The stiffness C of eah finger is proportional to finger length F 3 (see Figure 18). The miro slip (and relative displaement u(x)and thus frition) is redued by dimensioning the finger length loally in relation to u(x). Loally the stiffness of wedge is adapted; the wedge frition surfae an now follow the displaement (or strain) of the outer able surfae and redue the miro slip and thus wear of the grip profile. This results in the miro slip (and wear) reduing wedge designs of Figure 18. Figure 18: Miro slip and wear reduing wedge designs A and B Researh strand jak wedges Report By H.G.M.R. van Hoof 18

45 Figure 18a is theoretially the best alternative, the length of the fingers is onform the paraboli equation of u(x). Pratially the alternative B of Figure 18 an also redue the wear on the inner grip profile and is very straightforward to produe. The exat amount, dimensions and pattern of the fingers must be determined by pratial results. 6.1 Wear redution on the base of vertial able equilibrium From the vertial able equilibrium of Appendix E, equation 6.1a is obtained: σ = S 2 σ R i w (6.1a) With: = Kineti oeffiient of frition on inner wedge surfae and able surfae σ w = Compressive stress between wedge and able σ = Tensile stress in able S = Position of slip front (for detailed information is referred to Appendix G2.2) R i = Inner radius of wedge and therefore outer radius of strand/able The values of the parameters, σ w, σ of equation 6.1a an be onsidered as: : Constant, assuming a value between 0,05 and 1. σ w : Constant,being a maximum design or material stress value σ : Constant, being a maximum design or material stress value As a result of the assumptions of the above, the ratio S/R i of equation 6.1a must also have a onstant value. Nevertheless numerous ombinations of S and R i an satisfy this ondition. Ergo, if we design a wedge onfiguration with the assumed values of = 0.2, σ w =300 N/mm 2, σ = 745 N/mm 2 and α = 8.19, the ratio will be : S R i σ = = 6.2 (6.1b) 2 σ w and with equation 5a the ratio S/L beomes: S L = FL N in (6.1) and with N in (see Figure 14) being roughly : FL Nin = (6.1d) tan α Equation (6.1) beomes: Researh strand jak wedges Report By H.G.M.R. van Hoof 19

46 S L = tanα = 0.72 (6.1e) If we ombine equations 6.1b, 6.1, 6.1d and 6.1e, Table 3 an be omprised: Calulated properties of different strand/wedge ombinations Dimensions Strand Capaity of one strand Position slip front Lenght of frition profile Weight/m n strands needed for 900 ton Radius Ri (mm) Steel Area (mm²) Ratio S/Ri FL (kn) S (mm) L (mm) kg/m n 9** 223** ** ** * * Calulated with p*ri², ** Referene value of strand (Appendix C) Table 3: Calulated wedge/strand onfigurations When a strand with a diameter of 9 mm (R i =4.5) is hosen for example, a solid single high apaity wire an be used. This solid 9 mm wire has better wear/handling properties than the original 18 mm strand; No internal relative displaements between wires during operation: less elasti power is lost by frition/wear. Therefore no internal wear is initiated. In general a strand with a diameter of > 9 mm ontains multiple wires, and the internal wear and elasti energy loss will inrease drastially by an inreasing number of strand wires. (See Figure 19) The 9 mm strand also improves handling due to a redued weight (Table 3; a weight redution of 1.25 kg/m!). In a 900-ton onfiguration of the strand jak unit SSL, 190 wires of 9 mm are used. 1 WIRE 7 WIRES 31 WIRES During operation : * No internal relative displaement between wires * No internal wear between wires * No elasti power loss due to internal frition/wear During operation : * Internal relative displaement between wires * Internal wear between wires * Moderate elasti power loss due to internal frition/wear During operation : * Internal relative displaement between wires * Internal wear between wires * High elasti power loss due to internal frition/wear Figure 19: Examples of strands with 1 wire, 7 wires and 31 wires. Inreasing the number of wires will inrease the relative elasti power loss by frition/wear between the wires. Researh strand jak wedges Report By H.G.M.R. van Hoof 20