Need a photograph and description of cold rolling (sometimes called
cold expansion or hard rolling) of tubes into tubesheets in a boiler
or heat exchanger. Simple terminology preferred, for non-technical
audience.
Hello chris2003-ga,
Information about creating Tube-to-Tubesheet Joints can be found at
the website of HydroPro, Inc.
http://www.hpro.com/reference/ref_hp105061798.html
“The theoretical model that one tries to achieve is to put the
material of the tube past its yield point and into the plastic range
while at the same time keeping the material of the tubesheet below its
yield point and in its elastic range. In this manner, when the system
that is applying the forces to create the joint are removed, the
tendency will be for the tubesheet to contract back to its original
dimensions. The tubes themselves, having been permanently deformed,
resist this movement, thus creating the necessary force for a proper
joint.”
------
“Past Methods of Creating Tube-to-Tubesheet Joints
The most common method of tube-to-tubesheet joints is mechanical
rolling (ref hp102061798). A set of hardened rolls in a cage rotates
around a tapered mandrel. As the rolls travel up the mandrel, they
cause an increasing radial force exerted at the contact point between
the rolls and the tube. This increasing force moves the tube material
outwards until it contacts the ID of the tubesheet hole and continues
until supposedly the tubesheet material is just below its yield
point.”
A description and pictures of tube to tubesheet fabrication can be
found at the website of the Copper Development Association
http://www.cda.org.uk/megab2/corr_rs/pub139/page6.htm
“In heat exchangers and condensers, tubes are joined to tubesheets to
prevent leakage between the tube side and shell side. Often the
easiest and least expensive method is to expand the tube mechanically
into the drilled hole in the tubesheet, usually by roller expansion.
Ideally, the tubesheet should be harder and less galvanically noble
than the tubes.”
Other references:
Titanium Metals Corporation
Titanium Design and Fabrication Handbook for Industrial Applications
ROLLER EXPANSION
http://www.timet.com/fab-p25.htm
“The most commonly use method of making tube/tube sheet joints is
roller expansion.
Roller expansion procedures for titanium tubes into tube sheets are
similar to those used for other materials. For best results, the tube
sheet holes should be within the limits specified by TEMA (Tubular
Exchanger Manufacturers Association) for shell and tube heat
exchangers (Table 21) or within the limits specified by HEI (Heat
Exchange Institute) Standards for steam surface condensers.”
Enerquip, Incorporated
http://www.enerquip.com/pharm.html
“The tube expansion process overexpands the tube inside the tubesheet,
ensuring that the space between the two components is always forced
closed.”
Schlechtriem, “Expansion limit for expansion of tubes”
http://www.schlechtriem.de/einwalze.htm
Heat Exchangers Online, Shell & Tube Heat Exchangers
http://www.heatexchangersonline.com/shellandtube.htm
metal-mart.com
http://www.metal-mart.com/Dictionary/dictletc.htm#I35
“COLD ROLLING
Rolling metal at a temperature below the softening point of the metal
to create strain hardening (work-hardening). Same as cold reduction,
except that the working method is limited to rolling. Cold rolling
changes the mechanical properties of strip and produces certain useful
combinations of hardness, strength, stiffness, ductility and other
characteristics known as tempers.”
I hope you have found this information helpful. If you have any
questions, please request clarification prior to rating the answer.
Googlenut
Google Search Terms:
"cold rolling" OR "hard rolling" OR "cold expansion" tube tubesheet OR
sheet
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rolling OR expansion tubesheets
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tubesheet rolling
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tubesheet rolling process boiler OR exchanger
://www.google.com/search?q=tubesheet+rolling+process+boiler+OR+exchanger&btnG=Google+Search&hl=en&lr=&ie=ISO-8859-1&safe=off
tube tubesheet process OR description
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&safe=off&q=tube+tubesheet+process+OR+description&btnG=Google+Search Outokumpu - Steel Properties: Available Surface Finishes - Cold Rolled::
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Cold Rolling