Armstrong & Sons - Resources

Resources for Professionals

Instructional Guides for the Tube Removal Specialist

Resources for Professionals

Thank you for your interest in Armstrong & Sons. With over 80 years of experience in the heat exchanger, chiller and steam condenser tube replacement industry we have a lot to offer in the way of guidance and advice.

On this page you will find information on how to cut stainless steel boiler tubes, retubing a boiler and rolling the boiler tubes to complete the installation. We plan to add more articles soon so please check this page frequently for more information.

Armstong & Sons ~ “Tools you can count on. Experience you can trust.”

Retubing 101

Tube Rolling 101

How to cut Stainless Steel Tubes

Armstrong PN-AA4 internal tube cutter

This guide is designed to give you some basic pointers when cutting stainless steel tubes.Cutting stainless is a very time consuming tedious process when compared to cutting softer tubes like Copper or Brass.

Production times vary greatly in comparison, in some cases anywhere from 2-8 tubes a minute can be expected.Using a low speed (160 RPM) cutter is critical when cutting harder exotic materials.

 Items you will need:

  • Internal Tube Cutter – we recommend our AA4 Armstrong Cutter (160 RPM)
  • AnchorLube cutting fluid
  • Steel brush or compressed air
  • Plenty of cutting bits
  • A few spare Spindles
  • PPE – especially work gloves

Step 1:  Setting up

As with any project, setup is key to a successful venture. Having the proper tools and knowledge base is very important. 

Preparation would include:

  • Setting up your Internal Tube Cutter to the specifications of the tubes .
  • Set how deep of a cut you want, ideally you want to cut the tube close to the sheet
  • Adjust how far the blade is extending
  • Ensure your drive is running at correct speed.

We recommend setting the depth of the cut just inside the tube sheet, making sure to be past the sheet is imperative.  We suggest this since cutting this harder material creates excessive heat and having the sheet close to the cut will help absorb that heat and prolong the life of each cutting bit.

Step 2: Prepping the tubes

In order to use an internal tube cutter you must be sure to remove all obstacles from the tube, this would include any plugs, built up scale or anything that would inhibit your from inserting the tube cutter.

Step 3:  Cutting

Before cutting, confirm what pattern is right for your project, we recommend beginning your cuts in the bottom rows of the sheet and work your way up, unless your job has other needs.  When it comes to cutting Stainless Steel it is imperative that plenty of AnchorLube Cutting Fluid is used.  A great deal of heat will be generated and this will help prolong the life of your cutting bits.  It is key not to force the cutting bit into the tube with any harsh movement, doing so may break the bit before you can even start cutting.  Cutting in small steady strokes is important to ensure you get the most life from each cutting blade.  Also pulling the cutter out of the tube to remove any cut fragments and reapply cutting lubricant is important and will help improve your productivity.  Depending on the tube gauge and size, you will feel the tube break free and in most cases can hear the RPMs on the cutter increase when there is no further resistance.  Until you get comfortable with the process it is always a good idea to give a visual check to make sure the tube has been cut completely.  In most cases the cut tube will drop slightly so you can easily see it. 

What to expect:

  • There are a few things to expect when cutting hard material tubes, first being the amount of heat generated. Be careful not to touch the cutting bit or Adapter until it has cooled down. 
  • Cutting bits will break, be sure that you have plenty before you begin the process.
  • Spindles will wear down, having spare spindles is always a good idea as they can easily be gouged by a stainless steel tube.
  • Prepare your workforce for what can be a long tedious process.

Retubing 101

This article is written to outline our tube pulling process, it is our hope that it will help you get an idea of how to budget your time during your next retube project.As a rule of thumb we tell our customers to expect at least 250 tubes a day, that is driven by several factors, such as labor force, tube material, unit, etc.

Though that is considered a general estimate, we have routinely experienced instances where we can pulled between 50-100 tubes an hour under normal circumstances.Considering that the tools for the job is exhaustive list it is important to note that Armstrong and Sons will work closely with you to be sure to ascertain the specific items needed for each situation.

Armstrong Boiler Tube Hydraulic Puller

Step 1:  Information gathering

This step is often overlooked, but it’s very important.  Gathering as much information as possible about the unit that is being retubed is critical in the planning of your project.  Also keep in mind any required testing and/or classes potential vendors need to attend prior to gaining access to the job sites.  The following are some of the key elements needed to gather prior to the project start:

  • Tube size and gauge
  • Tube material
  • Tube Length
  • Tube Sheet material and thickness
  • Are there serrations in the tube sheet
  • Type of Unit (Chiller, steam condenser, heat exchanger etc)
  • Site power options (air and electric)

Step 2: Identify what tooling you will need

In this step it is helpful to shop around for what tools you will need, in some instances tubes can be removed manually (as much as we hate to admit it). Though this method is very labor intensive and not recommended as it carries a high potential to damage the tube sheet if done carelessly.  With 80 years of experience Armstrong and Sons will put you on the right path towards making the best decisions for your project.

Step 3:  Prepping the unit/site

Here is where the unit is officially taken offline, drained and heads (if applicable) on both ends are removed. 

  • Erecting scaffolding where needed
  • Confirming the site has the proper electrical/compressor needs
  • Lining up any vendors for equipment or delivery

Step 4:  Begin work

  1. A) The first step in removing thin or leaking tubes from a vessel is to cut the tube at one end of the unit.  This is the opposite end of the unit from where there is enough room to remove the intact tube.  Armstrong and Sons offers a variety of pneumatic tube cutting machines, each designed to meet your specific needs (tube material, size, etc.).  Cutting adapters are available to be customized to meet the specific size of the tube being removed.   Production speed depends on a few key factors, such as tube material, gauge and operator; but you can expect to cut up to 10-20 tubes per minute under normal circumstances.  With regard to what type of pattern to cut , we recommend cutting from the bottom of the shell and work your way up.  If the tubes are finned it is we highly recommended to cut every other row to help avoid “fin lock” (when two tubes become locked into place).  This issue tends to be something that everyone wants to avoid because it may require a window to be cut into the shell.  This creates unnecessary delays and added expense.
  2. B) The second step is to pull the now cut tubes free of the roll.  This is done on the opposite end from where the tubes were cut. The Armstrong HDP Tube Puller will pull the tube free of the roll and extract the tube from the sheet by approximately 3 1/2″ by grabbing the ID of the free tube.  Placement of the tube puller is important and should be flush with the tube sheet and away from the adjacent tube so as not to compromise or crush the adjacent tube.  This is easily done but requires the operator’s attention to avoid unnecessary setbacks.  The operator can then grab the tube and either manually remove the tube or use our Armstrong Tube Stripper for fast and easy removal.  Pulling pattern is dependent on the spacing between tubes, it is recommended to pull every other tube in a row allowing the operator to easily grab the exposed tube with the Armstrong Tube Stripper. 
  3. C) The third step is the complete removal of the tube from the unit.  This is accomplished by using our Pneumatic Armstrong Tube Stripper, this tool will grab hold of the OD of the tube and continuously, and with little effort, remove the tube from the shell.  The worn tube is then handled by a third man and walked to the Tube Chopper for scrapping.  It is noteworthy to know that this tool has a pulling capacity that is intentionally limited to 5k lbs.  Our research has demonstrated that higher forces can increase the risk of damage to the units internal supports. 
  4. D) The final step in the tube removal is the disposal of the scrap tubes.  After the entire tube is removed from the unit, Armstrong’s high speed, self feeding rotary Chopper will efficiently complete the job.  This tool automatically flattens and chops cuts the tube into manageable 4″ pieces expelling them downward into a containment vessel, either a 55 gallon drum, large bin or onto a conveyor.  The advantage for of using this tool is it will save you both time and money as typical scrap yards will pay higher value for partially processed scrap, not to mention it eliminates the cumbersome need of transporting full length tubes. 

Step 5:  Cleaning and prepping the tube and support sheet holes

It is very important to clean each hole to ensure a solid seal is made during the last step of the retube.  If the sheets have a serration (groove in each hole) then its critical to clean the ring out, typically it can be done using a small pick.  We also recommend using a slightly oversized steel brush to remove any additional foreign material (dust, rust etc.)

Step 6 Installing the new tube

This step is rather self explanatory, in this phase you will be inserting the new tube into the vessel.  This process can take 2-3 members of the team to complete efficiently.  One man positioned on one end of the unit who is responsible for making sure the tube follows the correct line and doesn’t jump into another hole.  The next man is on the tube entry side of the vessel at the face of the sheet inserting the new tube while the last man is simply supplying the next tube and helping keep the tube level.  It’s easy common for a tube to be inserted on an angle and therefore making it easy to jump tube holes, so keeping it level will help avoid this. 

Passing the new tube through each baffle/support sheet can prove to be tricky, slightly spinning the tube will allow the tube to help efficiently find the hole. The man on the opposite side of the unit will becomes key in guiding it’s path through each hole.  Tube guilds/pilots are often used in this process to help eliminate any frustration and ultimately speed up the process.  They are inserted into the tube ID and removed once the tube is in place. 

Step 7 Final installation and rolling

The last step in the tube installation process is known as Tube Rolling, this is where the tube is expanded to create a bond between the new tube and the tube sheet.  Prior to rolling, it is important to notate the inlet and return sides on the unit, it is often suggested to have the tubes protrude from the sheet at around 1/8″ or flush against the sheet. The reasoning is to allow better flow for the unit once it is back online.  This can be accomplished by precise placement of the tube prior to rolling or once the tube is rolled to use a Trim Stop attachment on our AA series Internal Cutter to trim the excess tube. 

Rolling the tube can begin once the tubes are in place and ready as outlined. Please see our Guide for Tube Rolling to help better understand this critical process.

Step 8 Pressure testing

This is the final step in the retube process.  The goal here is to ensure that a proper bond now exists between the tube and the sheet.  The two most common tests are a Hydro and a Gas test.  During this phase the unit is filled with a predetermined amount of pressure and then each end of the unit is closely examined for leaks.   If leaks are found, simply make a very slight adjustment to our your Rolling Motor and reroll the leaky tube, being very careful not to overdo it as over rolling tubes can create significant issues with the unit.

Once the team is confident that no leaks are present it is time to complete any remaining tasks outside of the retube and put the unit back into service.

Tube Rolling 101

Boiler Tube Rolling 101

The purpose of tube expanding is to compress the OD (outer dimension) of the tube against a fixed surface (i.e. tube sheet) to create a secure joint or seal.

The wall of the tube must be reduced by a certain percentage based on a few factors, most importantly is the tube material, the basic rule of thumb is that the harder the material the less of a crush is required.

The following are tools/items you will need for this project:

  • Expander (pre-ordered to specific size)
  • Rolling Motor (speed based on material type)
  • Hole Gauges (two sizes, one for the tube sheet hole and one for the tube)
  • Calipers
  • Loctite
  • Small hammer

The process can be very cumbersome and to some, very intimidating, since if a tube is over rolled it runs the risk of failing sooner then later.  Carefully following these steps will ensure a successful project outcome:

Step 1:  Most critical – Get your measurements from 5 random locations (helps create a better random number) 

  • Using a 3 point hole gauge measure the ID (inner dimension) of the tube sheet hole.
  • Second measure the ID of the tube
  • Lastly measure the OD (outer dimension) of the tube

Step 2:  Calculate your measurements to find your target crush number (in thousandths)

  • Visit this calculator to easily find your final number or use this calculation to gain the final figures

STEP

TUBE #

Example

1

2

3

4

5

A

Tube Sheet Hole

.760”

 

 

 

 

 

B

-Tube O.D.

.750″

 

 

 

 

 

C

=Clearance

.010″

 

 

 

 

 

D

+ Tube 1. D.

.620″

 

 

 

 

 

E

+ 5% Reduction

.006″

 

 

 

 

 

F

Finished 1. D.

.636″

 

 

 

 

 

  • STEP A ‑ Measure tubesheet hole STEP B ‑ Measure tube 0. D.
  • STEP C ‑ Subtract “B” from “A”
  • STEP D ‑ Measure tube D.
  • STEP E ‑ Subtract tube D. from tube O.D. Multiply by 5% or 10%
  • STEP F ‑ Add “‘C”, “D” and “E” for finished rolled I.D.

Step 3:  Positioning the tubes

Not a critical step but common practice is to place your tube on the inlet side of the unit with 1/8’’ protruding from the sheet.  Uniform placement of tubes will have an impact on flow.  If the tubes are longer and projecting farther then desired we provide tube trimming accessories with our line of internal tube cutters.   

Step 5: Setup your expander

Be careful not to roll inside the sheet, doing so will weaken the wall of the tube and drastically reduce the life of the tube.  Recommended depth is to roll the tube within 75% of the sheet.

Step 6: Setting up your Rolling Motor 

To set your rolling motors torque setting begin with the lowest setting to ease yourself into the process, take note that when rolling harder material such as stainless steel and titanium that the process should be done quickly because these materials have a greater tendency to work harden; therefore minimal or no rerolling should be attempted. The Airtoole 720 rolling motor allows for an easy adjustment and then locked into place once the designed torque is reached. 

After each pass, measure the ID of the now rolled tube to see how close you are to your premeasured target.  Once the target ID is reached, lock in your RM torque setting and begin rolling the row of tubes.

Note: When inserting the expander into the tube you must make sure not to push the tube into the sheet. It is easy to tap a tube into the sheet and then begin rolling without knowing that the position of the tube has changed.

What happens if:  The tube is undersized and spins as you begin rolling it.  An easy way to overcome this problem is to lightly secure the other end of the tube with a pair of vise grips to keep it from spinning.

Step 7:  Leak testing

Once all the tubes of both the inlet and outlet have been successfully rolled it is now time to ensure that a proper joint has been accomplished.  Depending on the system and available options leak test can be done in various ways.  Hydro tests are very common but can lack the amount of pressure needed to make sure that no leaks are present. 

Pro tips:

Use of Loctite – Loctite provides an extra level of security in making sure your tubes are securely in place and free of any leaks.

Single pass vs. multi pass systems – depending on the system it is a good idea to note whether the system it is a single or multi pass system. This will come into play when setting the desired tube location (within 1/8” from the sheet on the inlet side.

Production – you can expect to roll 600-800 rolls a day depending on material and which roller you choose from. 

Tube material Guide:

Knowing how to determine wall reduction is important, however it is equally important to know the characterisitics of the popular tubing material.  You should know the proper wall reduction in which would apply to each material.  A rule of thumb is the harder the material the less wall reduction is required to obtain the proper joint.  The following  are recommendations for the amount of crush that should be applied to different material types. 

Copper and Cupro Nickel: 8-10%

Steel, Carbon Steet and Admiralty Brass – 7-8%

Stainless steel and titanium – 4-5%

Here are some often used terms:

Under rolling – when a tube is not rolled to your specifications, in most cases the tube will not create a bond that you are looking for.

Over Rolling – Is when a tube is expanded beyond your intended target ID.  Over rolling can do considerable damage to a vessel.  Over rolling will decrease the dimensions fo the ligament between tubes and weaken the bridge.  Once a ligament is weakened it will cause a reaction in all ligaments surrounding that weak ligament. If we descrease the strneth of the ligament the tube next to the tube being rolled will leak.

Over rolling will also cause distortion in the tube sheet, producing egg shaped holes.  Over rolling has been known to cause a tube sheet to bow or warp to the point where the standard length of the tube coul not be used in a vessel until the bowing or warpage is returned to normal. 

Improper preparation of tube sheet holes: Can cause tubes to leak, the tube sheet is gouged it is more difficult to expand a tube to fill these gouges or tears without over rolling.  The smoother the tube sheet hoel the easier the roll. 

CTI Industries uses Armstrong and Sons tube removal tools
Day & Zimmermann use Armstong tube extraction tools

Reach Out to Us

Contact Armstrong & Sons today to learn how we can help you complete your project more efficiently and cost effectively with our tools and consultants.

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