Methods of Tube Expansion in Tube to Tub

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 Tube expansion is the art of reducing tube wall by compressing the OD of the tube against a fix container.

To a!oid...

•   "ludge accumulation •  "econdary side I#$%"&& cre!ices •  &orrosion in tube sheet • Damage to the tube due to !ibration

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(y welding only

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(y expansion only

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(y welding and expansion

1. Parallel tube expansion

2. Flaring tube expansion

'. +echanical , $ mechanical tube expander consists of an odd number roller -usually * os./0 a taper mandrel to push the roller outward0 a cage to house the roller and a collar to set the location of the expansion. $ typical Expander is shown in fig.

). 1ydraulic,

This is differs from other 2nown anchoring methods in that the tube is ph simply by means of pressuri3ed liquid. The amount of pressuri3ed liquid introduced i proportion of elastic and plastic expansion occurring in the tube and tube sheet. In t two 4O5 rings at appropriate location is inserted into the tube sheet. 1ydraulic pressur two 4O5 rings causes the tube in that region to expand.

H&dro E(')n"ion

FEATURES

· Expands in one action tubes with a large wall thickness. · Expands tubes over a long length. · Eliminates the need for step tube expanding. · No work hardening of the tube as this is not a rolling type expansion. · Eliminates distortion of the tube sheet, as there is no extension of the tube during expansion. · Does not therefore stress welded tube ends. · Increased holding strength between tube and tube sheet. · Tighter tubes in ring grooved tube sheets. · mooth contour change between expanded and non expanded part of the tube. · Eliminates the need to clean down after expanding. · No rotary reaction of the tube to hold.

7 Reduced operator fatigue.

+, E('-o"i.! !(')n"ion 'roc!"" ◦

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The controlled detonation of specific and precisely positioned explosi!e charges generates high pressures in the   bores of the tubes resulting in the almost instantaneous expansion of the appropriate sections. The outside of   the expanded lengths of tube are 4coined5 or pressed into the tubesheet holes 8 resulting in a high integrity bond regardless of tubesheet hole o!ality or surface finish.

EXPLOSIVE WELDING

a. linked strand cortex b. kwik lok fastener c. polythene insert d. plastic insert e. tubesheet f. tube

EXPLOSIVE WELDING OPERATIONAL STEPS

AD/ANTAGES OF EXP*OSI/E ◦

 o practical limitations exist on the length of expansion that can be produced by one detonation 8 multiple % stepped roller expansion can often be a!oided with consequential0 much reduced 9oint production times and costs.

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 $ number of explosi!e expansion charges can be detonated in one 4shot5 8 significantly reducing 

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 production times % costs.

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 Restricted access is often much less of a limitation than with other mechanical tube % tubesheet fixing methods.  Tube wall thinning0 wor2 hardening and lengthening of the explosi!ely expanded sections of tubes are normally negligible.  "atisfactory 9oints can often be produced in tubesheet holes where o!ality and surface finish would preclude the use of alternati!e mechanical 9ointing systems.

Percentage thinning = (Do - Di) - (d - Di w) 2S Where, Di w = Average tube inside diameter after rolling Di = Average tube inside diameter before rolling Do = Average tube OD before rolling d = Average hole diameter S = Do - Di 2

Percentage thinning shall be in the range of  3-6%

: ;repare a procedure qualification bloc2 0 which has to simulate the 9ob condition. : &arry out the expansion as per procedures. : Ta2e adequate trial to get the parameter by which < thinning0 ;ull out test0 helium lea2 test%bubble test 0 !isual chec2 meet the required !alues. If the abo!e !alues are meeting the requirement the process is qualified to perform on 9ob. During production control is exercised in rolling quality control bloc2 -R&(s/

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The person who are engaged for qualifying machine is automatically qualified for performing on the 9ob.  =or other ◦

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 '> nos. tubes hole to be rolled and following is the test required on that. < thinning of that rolled tube within limit.

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 ;ull out test on all tube

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 Out of '> tubes ) tube ID to be sectioning for scratch free expansion.

 In case of R&( Tube s fails to meet the acceptance criteria two successi!e tubes shall be rolled and shall meet the acceptance criteria before proceeding on the  9ob

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 If roller brea2s during rolling all the pre!ious holes rolled using the abo!e tool shall be inspected for any damage.

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The holes0 where rolling is incomplete or interrupted due to power failure0 shall be identified and rolling shall be performed after all other holes rolling completed.

 On 9ob rolling shall be performed only after R&(5s satisfactory results on abo!e holes.

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 There are few mores other than this.

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=ollowing record to be 2ept for expansion of tubes ◦

 o. of tube rolled -with location R x &/ for each shift0 day0 operator0 equipment and settings.

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 &orrelation of R&(s with the tube locations0 equipment and operator.

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+elt and heat no. of tube and bloc2.

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Report of < thinning and surface inspection of '< tubes in the tube sheet.

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 ;ull out test and < thinning results of R&(s &ertificate of chec2ing of length of expansion and termination from secondary side .  on conformance list