Advantages of Half Pipe Reactors in High Pressure Service

Specifying the right type of jacket to use for your reactor vessel can make all the difference between long-lasting, trouble-free equipment and frequent unplanned maintenance. Getting it wrong can prove costly. Working with the Ward Vessel & Exchanger team to select the best design for your new unit can save on initial material and fabrication costs, improve your heat transfer efficiency and, thus, the performance of your equipment, and spare you downtime for repair or replacement of premature failures. “We are one of the leading experts in jacketed pressure vessels, and we will provide you with the best option for your process,” says Jon Ward, President at Ward.

There are three options to choose from for jacketed vessels: (1) conventional, (2) dimpled, and (3) half-pipe. Each has its advantages and disadvantages, depending on processing conditions. Conventional jackets are best suited for containment of dangerous chemicals and high media flows; however, they often require the added expense of increased inner wall thickness to handle high pressure environments. Dimpled jackets are often ideal for smaller vessels in lower pressure environments, but the numerous welds on this type of reactor jacket can be labor intensive and may be more susceptible to leaking. Half-pipe jackets are ideal for cooling water, steam, hot oil and heat transfer fluid applications in high pressure/high media flow environments, and they allow for a thinner inner shell wall due to their design. The thinner shell allows for superior heat transfer properties. But they can also be susceptible to condensate or weld failures if not properly designed by an experienced fabricator.

Of these three alternatives, half-pipe jackets offer the most cost-effective “sweet spot” between cost, amount of heat transfer, and overall reliability. For example, with a 90-in. OD, 316 stainless steel reactor vessel, a conventional jacket would cost about 30% more than a half pipe jacket. A dimpled jacket would cost approximately 10% less than half pipe, but would also only be viable at lower pressures and temperatures than the other two types, while introducing a lot of welds that are more susceptible to failure. For these reasons, the half pipe option is preferred by most clients.

Ward Vessel and Exchanger is a leading manufacturer of half pipe reactors, having invested in custom fit-up/welding equipment and developed its own proprietary fabrication process. “Our experienced engineers, designers, and technicians along with state-of-the-art proprietary equipment have propelled Ward far ahead of the competition,” explains Jon Ward. “Our automated process enables us to fabricate the highest quality half-pipe units in the industry.” In fact, Ward has a perfect track record when it comes to half pipe reactors, with no premature failures.

What makes Ward’s reactor fabrication process unique is its application of half pipe to the vessel. The automated system loads whole coils of 2-, 3-, or 4-in. width pipe onto the shell at a pitch that yields optimal heat transfer efficiency. The continuous coils allow Ward to fabricate entire jacket zones with a minimal number of butt welds, which are only introduced when coiling runs out. Minimizing and/or eliminating butt joints, which are the number one failure points, is a critical factor in the reactor’s reliability. 

“Without this equipment and our process, you would have to install by hand, resulting in butt joints every 1 ½ to 2 turns of half pipe,” points out Jon Ward. “when fitting and welding by hand, a fabricator can’t safely and successfully handle the entire coil, which is why the coil is then cut and installed in smaller sections.” Adding to the challenge, most fabricators have to tack weld the half pipe to the shell manually, which can be very time-consuming. “They typically put on a turn and a half, tack weld it, then put another turn and a half on it and repeat the process until the fabrication is complete ? instead of loading it all at once.”

Ward’s twin sub-arc welding process greatly reduces or eliminates the need for tack welds during fit up. Not only does this cut out costly labor and speed up the reactor fabrication process, but it reduces or eliminates stress risers through tack welds along with the stops and starts during the welding process, which ultimately enhances the overall weld quality and reliability. Weld penetration and heat input are consistent throughout the process, resulting in weld quality that is uniform throughout the vessel. That level of consistency becomes much more difficult to achieve when equipment is fabricated manually.

There is also a perception in the industry that full penetration welds are the most reliable and must be used for ALL top-quality half pipe welds, according to Bill Huffman, Director of Engineering at Ward. “We provide full-pen welded half pipe jackets all the time, but it is much more labor intensive and much more expensive,” he reports. “Our process provides very reliable, high quality half pipe welds without needing full-pen welds. Our process can be 60% the cost of a full penetration unit, so it becomes a true cost of ownership, type of service, and expected-life discussion with our client.” 

In addition, the half-pipe specialists at Ward have figured out how to install half pipe onto dished heads in a more uniform way, with less stresses than the industry standard. Automated cutting equipment in the company’s Charlotte, North Carolina facility provides a precise fit-up of head half pipe in 180-degree segments, with each concentric ring requiring a different cut angle. The more precise rolling and cutting results in a product that can then be installed manually onto each head with perfect gapping with minimal stresses to achieve the exact weld joint to meet customer welding requirements. This attention to detail helps ensure dependable equipment, from top to bottom.

It’s just one more innovative way that Ward Vessel and Exchanger goes the extra mile for its customers in the Petrochemical and Chemical Processing Industries. For more information about Ward’s capabilities and experience building long-lasting half pipe reactors and other jacketed pressure vessels, contact our shop at (704) 568-3001 or