Shell and tube side cleaning of a severely fouled u-tube exchanger Summary
This international petrochemical company shipped a severely fouled styrene polymer bundle to Tube Tech in order to minimise costs whilst swopping over with an identical replacement. A production upset led to cured blanket of styrene polymer fusing between all the tubes forming a very hard, brittle deposit on the shell side of the exchanger.
A UK based international petrochemical company shipped a severely fouled styrene polymer bundle to Tube Tech in order to minimise costs as they own an identical changeover replacement already. A production anomaly led to a thick, hard, brittle deposit forming on the shell side of the bundle and also severe bend blockages in tubes. Our challenge was develop a method to unblock polymer from the U Bends within a small 2m square footprint in front of the exchanger so in future it could be cleaned in-situ, saving on crane costs, scaffolding, damage, gaskets, bolts and third party costs. A triple lance feeding mechanism was modified to allow lances to negotiate and unblock the every U-Tube. The client correctly pointed out that it was a pointless exercise if only the straight section was cleaned and the hairpin bend left blocked. By using Tube Tech’s globally patented Plate and Shell Jet every last particle of fused polymer was removed, even from deep inside the bundle. All the tubes were unblocked, descaled and polished using the modified triple lancing method.
- Cured, Thick, hard, brittle polymer fouling located between the tubes as a solid mass and inside the tubes.
- Solid blockages within the tubes of horizontal styrene polymer bundle.
- 52% of the 530 square pitch tubes were blocked at the bends of the U-tube.
- Bundle transports polystyrene.
- The deposit on the shell side was brittle on the top and gooey/gummy at the base.
- The Rotary Shell Jet Lance was inserted between the 6mm tube space where an opening existed and the polymer that bridged the tubes was blasted away from the inside out using pressures up to 60,000 psi (4000 bar) with no damage to the tubes.
- The unique Twin Shell JeTT system was applied to remove the remaining 98% of fouling located between the tubes.
- A modified triple lance feeding method was deployed which was controlled remotely within a small 2 m2 area to simulate an in-situ working environment. All tubes straight and hairpin U bend legs of each tube were unblocked. This method is 3 times quicker than traditional jetting methods and is the only automated system that will negotiate every hair pin bend.
- Tube Tech designed tooling to negotiate the smallest radius bend using intelligent metals.
- Remote controlled technology ensured operators were kept a safe distance away from the polymer debris.
- Three quarters of a ton of deposit was removed from both tube and shell side.
Tube Tech Comment
Scott Donson, Technical Sales Manager: “Our client had contacted several national and international contractors who declined to attempt this project. Tube Tech was the only company who were up for this unique challenge. This was without doubt one of the toughest projects we had come across. Our ability to apply several unique and patented systems, meant we were able to remove this severe fouling and save our client the expense of a replacement bundle.”