RetubeCo

08/23/2022

We couldn’t be more excited to be a part of this years Duke TechX. Stop by booth 67 to meet Alex, one of our in-house Engineers, and learn about some of our other capabilities!

07/15/2022

Plate fin hydrogen cooler designs are fabricated using a ‘core’ design. In this, the tubes pass through and expand into many thin layers of plate fins. Unfortunately, this design cannot be refurbished without replacing the entire core.
The tubes found in hydrogen cooler bundles are straight, bare tubes that have a thin fin applied to the tube OD. Some designs include one end of the base tube to be belled or swaged as shown in image A to allow removal of individual tubes from the bundle (through one of the tubesheets). The majority of hydrogen cooler bundles are designed to use individually finned tubes as shown in image B. Thin strips of metal are spirally wound on the tube OD and soldered to adherence. Protective collars are strategically placed along the length of the finned area at the cooler frame support plate locations to reduce tube vibration, as shown in the last 2 images. These collars can differ depending on the manufacturer and are commonly made from carbon steel, zinc, rubber, or comprised of closely packed fins to mock a solid mass.

07/13/2022

Tubes found in l**e oil cooler bundles are primarily straight and have a bare (smooth) OD. Some designs include enhancement of the OD surface known as integral fins, best described as small machined / formed fins much like threads on a bolt. Other designs have u-bend bundles to return the cooling water flow (2 pass) instead of the conventional tubesheet and cover.
**eoilcooler

07/11/2022

Tubes should be the primary concern regarding the l**e oil cooler or heat exchanger unit itself. The performance of both cooler types revolves around the bundle design, simply comprised of a “bundle of tubes”. You need to know what you are working with so start by determining the existing tube detail. Do your research first and be thorough with this, you will want to get it right. Locate the OEM (Original Equipment Manufacturer) data sheets, specifications, and drawings if they are available. Gather all maintenance and inspection documents. Compare and don’t make any assumptions. It is not unusual to find that the tube specifications do match the existing tubes. It is in this vane that the following should be considered:
• Root Cause Clearly identify the reasons behind the failure mechanism of the tubes to be replaced. While the most logical source is commonly the Eddy Current Reports, the most definitive would be the laboratory analysis of a sample pull.
• Material Are the replacement tubes to be ‘like for like’ (same) tube material as that removed? Either way, investigate how the old tube failure mechanism might apply to the new tube. Was it a one-time event caused by improper lay-up? Was it a long-term failure due to wall thinning (old age)? In most cases, knowledgeable plant personnel in the Water Chemistry and Metallurgical departments enjoy discussing the subject. Is it advantageous to replace the failed tubes with a different material? Again, investigate and determine the advantages and disadvantages. What are the consequences/effects regarding cooler performance? The cooler’s mechanical design? How do the price and lead times compare?
• Country of Origin In today’s global market, the tube manufacturers are vastly different than when the original unit was manufactured. Where once the tubes were manufactured in USA based mills using ASTM / ASME standards, today there are only foreign sources for seamless copper alloy tubes. It is important to know the country of origin for the metallurgy. Research the qualifications and experience of the tube mill. Has your utility, or another utility, audited the mill’s quality control program? Be aware that there are some mills that make the billets and tubes and others that ‘draw’ tubes from billets acquired from mills foreign to their own country.
• Fabrication If the tube is to be fabricated (i.e., bent, finned, etc.) there are experienced, knowledgeable tube fabricators available domestically (USA). Research them and be careful to verify their qualifications and references. If they are providing the base tube, ensure that their source meets your approval. L**e oil cooler bundles often have u-bend tubes or tubes with low fin (integral fins) machined on the exterior to enhance surface area. All hydrogen cooler bundles, except for plate fin designs, have applied copper alloy fins (application of spiral fin stock to tube OD) and the fins are secured with a solder coating (to applied fin and tube OD). Make sure to request no-lead solder.
• Quality Not all testing methods and certifications are the same. Confirm that tubes will be supplied with a Certified Mill Test Report (CMTR) from the tube mill, not rewritten or transferred through a distributor. Verify that the CMTR includes an English translation (or that of your country’s primary language), as all qualify mills provide this service. If possible, schedule a Quality Assurance Audit. If special or additional testing is desired, ensure that the results will be included on the CMTR. Examples of such testing include Residual Stress Tests performed on actual lost samples and Hydrostatic Testing or Air-Under-Water Testing.
Most l**e oil and hydrogen coolers in service today were originally designed to have non-ferrous, seamless copper alloy tubes manufactured to ASTM B111. The primary copper alloys still in use today are:
• C443 Admiralty Brass – Arsenic inhibited
• C706 90-10 Cupro-Nickel
• C687 Aluminum Brass
**eoilcooler

07/08/2022

A l**e oil or hydrogen cooler prior to refurbishment is a daunting sight. The imagination can run wild with “what if’s”, “oh no’s”, and “there’s no way”. Its best to reign in those fears and take a more rational approach that considers less obvious but more immediate concerns such as:
• Details of the unit’s original construction and present condition
• Defining the scope of the necessary repairs
• Researching options for cooler component replacement (primarily tubes)
• Determining material lead times
• Determining how long the refurbishment will take
• Identifying qualified refurbishment contractors
In most cases, the engineer responsible for the refurbishment must also consider:
• Developing and maintaining a budget
• Creating specifications
• Coordinating an RFQ with the Purchasing Department
• Coordinating removal from the generator (hydrogen cooler) or oil reservoir (l**e oil cooler) with Plant Maintenance
• Ensuring all refurbishment work will be completed within the time allotted by Operations
An experienced, qualified refurbishment contractor can be a valuable asset in overcoming most of these challenges. Understanding relevant considerations and what options are available to effectively refurbish l**e oil and hydrogen coolers is paramount.
Generally speaking, most considerations are common for both l**e oil and hydrogen cooler bundles. These are related to the primary components: tubes, tubesheets, sealing surfaces, covers, and frame/tube supports. Both units use plant cooling water for cooling. Both usually include copper alloy tubes and tubesheets. Both usually have floating return-end tubesheets. And both are designed so that the tube bundle is inserted/immersed in an open reservoir instead of a shell. While l**e oil and hydrogen cooler bundles are functionally similar, the key design details are actually quite different.
**eoilcooler

07/06/2022

Today’s power plants are plagued with aging balance-of-plant heat exchangers, particularly l**e oil coolers and hydrogen coolers nearing the end of their useful lives. This lifespan can be drastically expanded with proper refurbishing. Refurbishment requires Plant Engineers and Maintenance personnel to carefully evaluate the extent of damage, research available solutions, and develop a plan of action. A better understanding of important considerations and available options will allow them to prepare more effectively.
More often than not, refurbishing l**e oil and hydrogen coolers is far less costly than full replacement. This is due largely in part to the ability to clean most major components to functionally new condition. In the event of a failure, tubes can no longer perform as designed. Thankfully a unit’s tubes can effectively be replaced using a process commonly known as retubing.
A retube, or refurbishment, requires a greater level of expertise than replacement or rebundling because of the countless components to be evaluated and subsequent decisions to be made. L**e oil and hydrogen coolers are highly specialized exchangers and their refurbishment requires careful consideration.
**eoil

07/04/2022

Happy Birthday America!!

05/30/2022

05/23/2022

It’s finally here! Come by booth 5161 and see what we’ve been up to, and grab a few goodies while you’re at it.