What is the procedure to be followed for plate heat exchanger (packinox) pressure test in Continuous catalytic reforming unit.
Answers
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02/04/2009
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A:
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Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
DP between the fluid being heated and the reactor effluent should be in the prescribed limit.
The bundles can withstand reasonable positive DP from feed to reactor effluent The mechanical design is such that plate deflection is computed to be acceptable value of 0.01mm for DP of even 20 to 30 bar
The reverse DP (effluent > feed) beyond certain margin value can damage the bundles. Plant design must take these considerations even in emergency depressurizing.
The potential harmful reverse DP may not occur unless shell is rapidly depressurized below bundle pressure due to mal-operation or hardware failure. The bundle may rupture with development of weld crack. In-situ re-welding may be done to repair the crack.
Sufficient expansion bellows provided for differential thermal expansion between hot plate bundles and cooler pressure shell.
Man holes are provided at the top and bottom ends for access and maintenance
Strainers may be provided for protection from solid fines. It prevents DP build up.
To prevent corrosion by condensation of acidic regeneration gas in the bundle, the bundle outlet temperature can be safely regulated above acid dew point.
Scales may invariably plug the spray bars. The scales could enter due to failure of the upstream filter or the unflushed / leftover debris in the pipe between the filters and spray bar during initial commissioning. The mesh in the filter is finer than spray bar. The holes in the spray bars be properly designed
The reasons for filter not working effectively are improper filter mesh micron, improper installation resulting in bypassing filter element, excessive DP across uncleaned filter element.
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