There are many things in life that are just not worth fixing. Your old or damaged glass-lined reactor doesn’t have to be one of them. Depending on the service conditions, some vessels can last for years and years without any issues of erosion to the glass lining. Other, more corrosive services can erode their way through a reactor’s glass-lining in six months while others can destroy the glass lining in a year or two, leaving a virtually new vessel unusable. Mechanical and thermal shock can also account for damage that could render a vessel unusable.
The immediate solution is to perform various field repairs on the glass. There comes a point, however, when field repairs are uneconomical or impractical. At this point, reglassing should be considered. For those of you who aren’t well versed on the subject of reglass, this post is for you.
What is Reglassing?
Reglassing is a complex process that provides efficient, economical repair to old, damaged or worn glass-lined vessels and their accessories, such as agitators, baffles and covers. Once a vessel or ancillary part is reglassed it is equivalent in quality to a new item. The reglassing procedure involves the following steps:
1. Removal of the old glass lining from a vessel or part by grit-blasting
2. Repair of the steel substrate by welding (e.g. stud holes from plugs and corrosion-damaged areas are ground out and patch welded, severely corroded sections may be trepanned and a new section welded in.)
3. Addition or removal of nozzles or other changes (such as replacement of jacket closure rings or addition of diaphragms)
4. Application and firing of numerous coats of glass
5. Testing before and after glassing
6. Application of external protective coatings
For more detailed information about the glassing process read last week's post about how glass-lined vessels are made.
When is Reglassing Needed?
Reglassing may not be practical for an older vessel if there is significant corrosion of the non-glass-lined steel surfaces. It is often the solution when problems unexpectedly arise with newer equipment. For example, nascent hydrogen attack can cause sudden failure. Here, acid spillage on the exterior surfaces of the vessel generates nascent hydrogen. This nascent hydrogen passes into the steel substrate, forming molecular hydrogen that results in spalling of the glass underneath.
Occasionally the use of dissimilar metals in the reactor, like dip pipes, valves and/or repair plugs can cause galvanic corrosion. The loss of a repair plug can cause substantial damage, necessitating reglassing of the vessel. Batch type operations and pilot operations can lead to temporary buildup of extremely corrosive or erosive products, greatly shortening the life of the glass lining. Other serious problems that arise include contamination of jacket heating and cooling media (which can accelerate corrosion at the bottom closure ring) and lack of venting, which can allow corrosion-producing air pockets at the top jacket closure ring. Additionally, whenever a component that is welded to the substrate has to be replaced, damage to the glass lining is probable, requiring the vessel to be reglassed.
Other reasons for reglassing usually involve some accidental damage to the lining of the vessel. This can be in the form of mechanical damage, like that time when a workman dropped a tool or other object he shouldn’t have had in his pocket (big oops), poor workmanship on a repair, or thermal shock or stress beyond the safe limits of the glass. While many of these problems are not common every day occurrences, any or all of them may damage the glass lining, making the reactor a good candidate for repair and reglassing.
Advantages of Reglassing
Why do so many knowledgeable process people opt for reglassing? Here’s a rundown on the advantages behind this technology:
- Delivery - Turnaround time to reglass is within weeks versus months to fabricate a new vessel.
- Cost Savings – Considering today’s common reactor sizes, reglassing can provide a 4000-gallon vessel at approximately the cost of a new 2000-gallon vessel. That is nearly 50% of the list price of new.
- Cash Flow – Many companies find reglassing, which is considered a maintenance budget expenditure, preferable to a new capital expenditure.
- Warranty – Most companies (including DDPS) provide a warranty that all reglassed vessels come with the same standard warranty as new vessels.
How do you know if your Vessel is a Candidate for Reglassing?
Before you go to the expense of shipping, it’s best to “pre-qualify” the vessel on-site. A representative from the reglassing vendor of your choice should inspect the vessel with you. First you’ll need to remove accessories and disassemble the vessel as required to inspect the glass, and make a preliminary evaluation as to the possibility of reglassing. If the vessel seems in “reglassable” condition, you can follow the steps outlined by the vendor to prepare and ship the vessel.
De Dietrich Process Systems offers an affordable reglass service on our own vessels as well as on competitors’ equipment. Even if you’re unsure if your equipment qualifies for reglassing, it’s an affordable solution worth looking into. For a complimentary quote, fill out our Return Equipment Questionnaire to provide us with more information about your equipment so we can better assess if this is an economical choice for you to consider.