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Petrochemical | Flange management

Critical shell and tube heat exchanger flange sealing


Two heat exchangers critical to this refinery's Hydrocracker unit operation had a long history of leakages. Given the nature and temperature of the fluids (H2S & H2) handled by these heat exchangers any leaks were a serious safety concern, and on occasion forced the unit to be shut down - at considerable economic expense.

Several attempts were made to resolve the leaks by existing sealing & bolting partners, without much success. The plant owner took the decision to invest in replacement heat exchangers to resolve this issue. Investing a considerable amount of money in the design & manufacture of new heat exchangers, the plant owner needed to be sure that the new heat exchangers would not leak and that is where James Walker came into the picture.


Bolted flange connections in Shell & Tube Heat Exchanger

Pressure (Channel): 116.7 Bar
Pressure (Shell): 16.7 bar
Ptest (Channel): 166.9 bar
Ptest (Shell): 23.9 bar
Tdesign (Channel): 355°C
Tdesign (Shell): 250°C

Existing solution

Standard Kammprofile type gasket from a James Walker competitor

James Walker solution

James Walker was involved in the project when the construction of heat exchangers was already well advanced. Our Flange Management Solutions team performed an analysis of the bolted joint in accordance with EN-1591, and shortcomings in the new design were quickly identified. 
James Walker proposed easily implemented solutions/improvements and these were accepted by the plant operator; These included a Metakamm ActiVate gasket with modified dimensions together with Rotabolt RB1 Touch calibrated to the optimum bolt load (as determined by our flange analysis). 
The high recovery characteristics pf Metakamm ActiVate counteract relaxation as it occurs in the bolted joints helping maintain leak-free operation of the vessels over time. 
The Rotabolt RB1 Touch allows the bolting technicians to install the desired bolt load precisely & simply during flange assembly. Equally important, Rotabolt allows the bolting technician to detect & correct losses in bolt load as the bolted joint relaxes. 
This is simply not possible with traditional studs/bolts & traditional bolting methods and was critical in ensuring reliable leak-free performance on these heat exchangers.

Results and benefits

The heat exchangers passed the hydrotest in the workshop with no leaks. Inevitably there was relaxation in the bolted joint, however, with the Rotabolt RB1 Touch this was easily detected - with just a fingertip check. Quickly the Rotabolts were re-tightened precisely to achieve the optimum bolt load again. 
The heat exchangers entered service, were leak-free on start-up and have been ever since.

ncreased Health & Safety through bolting calculation validation and reliable gasket characterisation data
Reduced downtime product loss and cost
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