This article relates a novel case study of the use of mechanical tube plugs by a Dutch contractor to solve a problem a gas production and distribution company was having with a heat exchanger in one of its process trains.
Heat exchanger tube plugs are often used to plug leaking or degraded tubes to prevent cross contamination of shell-side and tube-side media. A novel use of tube plugs was recently identified. The contractor was contacted by a large gas production company about a problem it was having with a heat exchanger in one of its process trains. The gas formation the company was drawing from was approaching the end of its production life. As the producing volume declined, feedstock flow rate and pressure to the processing plant also decreased. This decrease unbalanced the unit's efficiency and caused gas hydrates to form in their heat exchanger tubes, further reducing unit efficiency and increasing maintenance downtime, poor end-products, safety concerns and increased costs. These were costs the end-user could no longer tolerate. Working with the end-user, the contractor reviewed a number of solutions and ultimately settled on a tube plugging program that would reduce the number of available tubes in the heat exchanger, thereby increasing the flow rate of the production gas through the tubes.
The challenge was that the flow conditions at the heat exchanger changed and were no longer the same as the original design conditions.
Alternatives were evaluated including designing a new heat exchanger or tube bundle. Tube plugging was a distant alternative until a pro/con analysis was performed (Table 1).
Due to the speed with which it could be accomplished and the overall operating flexibility, tube plugging was selected. An analysis of tube plug technologies was performed and an engineered tube plugging solution, Pop- A-Plug Tube Plugs by Curtiss-Wright EST Group, was selected and implemented.
Critical attributes for engineered heat exchanger tube plugs
- Tube plugs provide a reliable, leak-tight seal across the full range of design conditions of the service in which the plugs will be installed.
- They can be installed without welding or damage to the tube end or tube-to-tubesheet joints. They also eliminate the need for hot work permits.
- Tube plugs provide a fast and simple installation.
- Plugs are easily removable to allow tubes to be returned to service, if operating conditions change again, or other tubes in service leak or are condemned by thinning/damage.
- Plug material should be selected to match the tube material. This minimizes galvanic corrosion concerns and differences in thermal coefficients of expansion.
- They comply with ASME PCC-2 (Article 312).
- They have a proven track record of service.
As a result, 1,200 plugs were received and installed, completing the work within a week. The contractor and the end-user have added this solution to their heat exchanger repair options in the future.
For more information, visit www.cw-estgroup.com/bic, call (281) 918-7830 or email est-sales@curtisswright.com.
