Tooling up for Water Tube Boiler Re-Tubes
Are you in the process of planning your next boiler retube project? We've put together a list of 3 key things to consider when tooling up for your next boiler retube project.
NUMBER 1: Tube Removal
First, you'll want to consider carefully how you want to go about removing the existing tubes in the boiler. This will be the first step in the retube process for water tube boilers: tube removal. You'll need to identify any sections of water wall tubes being removed that have membrane in between them as these will require special tooling for removal of the membrane so that the new tubes can be welded into place. There are several ways in which you can remove the membrane in between the water wall tubes, some more time consuming and labor intensive than others.
Typically, we recommend renting the Esco Tool Panel Hog pneumatic track saw as a means of first cutting out the sections of water wall tubing from the boiler. The track saw can then be inverted to enable the saw to cut out the membrane in between the boiler tubes quickly and efficiently. This method saves time and labor hours as compared to traditional methods of membrane removal with a grinder.
The Esco Tool Panel Hog seen here first cutting out a section of water wall tubing and then being inverted to cut out membrane from between the tubes. Removing the membrane exposes the tubes so that the boilermaker can then utilize our Esco Millhog beveling tools to prep the tubes for welding.
In addition to the waterwall tubes, the tube stubs left behind at both the mud drum and the steam drum of the boiler will need to be removed. These can be tricky and downright tough to remove depending on the dimensions of the boiler. When it comes to tube removal at the mud drum or steam drum of the boiler there are several methods for doing this as well. Again, some methods are more time consuming and labor intensive than others and this is where the Esco Millhog line of tooling in conjunction with the Elliott Tool line can come in handy to decrease labor hours and help efficiency.
Every situation is different and needs to be evaluated before tool recommendations are made. However, we typically recommend (space permitting) that the boilermaker utilize the Esco Panel Hog in order to remove the tubes connecting the mud and steam drums. Once removed, this will leave behind tube stubs coming off of the mud and steam drums which will need to be removed. Tube stubs can be difficult to remove in a boiler because they are typically rolled into the drum or welded in or both.
Typically tubes in this application are flare rolled to increase the laminar flow of the feedwater (think of a funnel catching water and directing it into a space). The flared tubes cannot be pulled from the outside of the drum since the flared ends will catch onto the inside of the drum, so they must be pushed or knocked back into the drum until they come out. This is where the Elliott Tool "Jumbo Tube Buster" used with tube size specific knockout tool bits can save a tremendous amount of labor hours and effort over traditional methods of knocking the tube stubs out with a hammer.
For tube stubs that are seal or strength welded into the drums, you'll want to consider how you will remove the welds. We typically recommend renting an Esco Millhog beveling tool and utilizing our reverse bevel blades and flat blades to remove the seal welds so that the tube stubs can be removed, pictured below.
Pictured below is the Esco Tool Mini Millhog being used with reverse bevel blades for seal weld removal of tube stubs. More info on this tool can be found on Esco's website.
NUMBER 2: Weld Prep / Tube Beveling
The next step in the retube process for watertube boilers will be the weld preparation step. In this step we are going to look at the different ways in which we can weld prep the existing tube ends and drum holes to allow us to weld in the replacement boiler tubes.
Again here we will want to consider any tubes that have membrane in between them or any overlay weld on one side of the tubes. The Esco Tool Millhog brand of boiler tube bevelers has specialized tooling to account for both membrane and overlay removal in these scenarios. Building off of the membrane cutting we talked about with the Panel Hog on the initial tube removal, we recommend utilizing our membrane cutterhead with whichever size Millhog you are using to bevel the tubes. The membrane cutterhead and the Panel Hog saw can both be used alone for membrane removal, but for best results we recommend using both. This way the Panel Hog does the bulk of the membrane removal and the membrane cutterhead comes in for the final pass to clean up the outside of the tubes and leave a nice, machined bevel on the existing tubes. Here you can see a short video of our Ground Hog (0.5" ID - 2.25" OD tubes) performing a bevel while removing membrane from between the tubes.
Overlay welding can be removed in almost the same manner by simply switching the internal clam ribs of the tool to use our offset clamp ribs. The offset ribs will essentially cock the tool to cause it to favor one side which will in turn enable the tool to remove more material on the side of the water wall which has the overlay weld on it. this will leave behind a nice, clean, beveled tube for welding in new boiler tubes. This process can also be seen in the above video as we were removing both membrane and overlay with the same tool.
Esco tool has a wide range of boiler tube beveling tools which they have manufactured, sold and rented for over 60 years in the USA; building their legendary Millhog brand name. It is a family-owned business that demonstrates its steadfast values to its customers by providing quality tools with expert support. It has been our experience at GSI that Esco stands behind their products and provides us with the support we need to help our customers be successful on critical projects 24/7.
NUMBER 3: Tube Installation
Now that we have removed the tubes, tube subs and tube sections that need to be replaced and we have weld-prepped (or beveled) the tubes and drum holes where we need to install our new boiler tubes, it is time to install the new tubes.
Tube installation in a water tube boiler takes two forms: tube rolling into the drums and or welding new tubes in. Often times we see customers welding the new water wall and or super heater tubes in and rolling in the tubes into the steam and mud drums. However, this will vary from boiler to boiler and should be specified in the project scope.
When it comes to tube rolling, Elliott Tool has an excellent range of boiler tube expanders and rolling motors for this water tube boiler application. Elliott is a USA-manufactured and owned business that manufactures their 3300 and 1500 series boiler tube expanders specifically for this application. The 1500 series boiler expanders from Elliott Tool offer unmatched tool life and create a well-transitioned flared roll. What we mean when we say a well-transitioned roll is that the rolls in the expander overlap and taper in such a way as to create a smooth bend outward as opposed to some expanders which create a jagged edged flare roll. This jagged edge decreases the surface area of the tube making contact with the drum, resulting in a less quality roll which creates more opportunity for leakage and splitting.
Once the initial flared roll is created on the inside of the drum, it is highly recommended to follow this up with the 3300 series straight rolled expander to ensure a leak-free seal against the drum. It will be important that we discuss the tube OD, wall thickness (or gauge if you know it), tube material and drum thickness to determine the correct size expander and the best rolling motor to use for the application. Torque is an important consideration when choosing a rolling motor as you do not want to risk under-rolling or over-rolling the tube into the drum. If under-rolled you can risk leaky tubes and if over-rolled you can risk cracks or splits in the tubes at the rolled joint. Typically for this application we recommend renting our 445 series pneumatic right angle roll motors as they will be able to fit into the mud or steam drum you'll be working in while rolling and these motors offer adjustable torque control. The 445 series pneumatic right angle roll motors come in 2 variable speeds, 90 rpm and 190 rpm both with roll-style and trigger-style throttles. For applications that require more torque, we recommend using the 90 rpm motors.
Another important consideration when ordering tube expanders for your project is the length of straight run before the tube bends. We recommend ordering short mandrels for the expanders when working with a limited straight run after the drum.
The tubes being installed at the water wall will need to be welded in. While we do not rent or sell
welding machines as they are readily available at your local welding supply store, we do have tube fit-up tools to help assist you in lining the tubes up to be welded. Pulling together and lining up tubes to be welded can be difficult especially in a water tube boiler application. We typically recommend the Esco Tool "Hog Tie" line of boiler alignment clamps for most water tube boiler applications. These simple-to-use clamps align the tubes and hold them in-place for tack welding. Once the tubes are tacked together the Hog Tie can be removed so that the tubes can we welded together. The Hog Tie is quick and simple to use with an impact gun providing most of the clamping power.
Whether you are a large crew with experienced boiler makers or a small crew just getting started in the industry, Gulf States Industrial is here to provide you equipment rentals, expert service and 24/7 support and tool availability for your most critical projects.
When considering vendors for your boiler retube jobs, we urge you to consider more than just rental or purchase price alone. Even for our largest most experienced clients, there comes a time where 24-hour service and availability saves the day. With all of our tools being manufactured domestically, we are able to stock large quantities of spares, rentals and
consumables locally for quick response on critical jobs. Having a vendor that can respond in the middle of night to an emergency need can make all the difference, especially when your reputation is on the line with a new client.
Call us for your next water tube boiler retube project and get everything quoted correctly so you know your cost going into the job and experience our "next level" 24/7 customer support.
Gulf States Industrial Inc.