Heat Exchanger Anti-Vibration

ExxonMobil Research and Engineering Company (EMRE) has developed and patented a suite of anti-vibration technologies, DTSTM, STSTM and SBXTM, that can be retrofitted into existing heat exchangers or used in new applications.

Potential applications include:

• Tubechattereliminationbystiffeningbundles(verticalandU-bend bundles as well) with DTS or STS technology • FailedbundleretrofitreplacementusingDTSorSTStechnology while reusing existing shell • Lowershellsidepressuredropbydecreasingthenumberof baffles and including DTS or STS technology to avoid vibration problems in conventional exchanger • Eliminateapotentialvibrationproblemduetocapacityincreasesby retrofitting an existing exchanger with DTS or STS technology • RetrofitSBXtechnologyintoexistingshelltoreduceshellside pressure drop

Expect these advantages:

• Improvedreliabilitybyeliminationoftubevibrationproblems • Increasedenergysavingsbyreducedpressuredropin compressor circuit • Increasedthroughputatsamepressuredropinexisting exchanger

DTS technology

DTS technology consists of dimpled and corrugated straight metal strips that are inserted into a heat exchanger bundle to reduce vibration by stiffening the bundle. As figure 1 shows, the corrugations on each strip act as a wedge to slightly deflect the tubes. The dimples on one end of each thin strip provide a locking mechanism to hold the strip in place. DTS strips are inserted in alternate lanes, only in the regions of the bundle where the tubes are vulnerable or where a vibration analysis calculation predicts a high risk for damage.

The strips can be used in all common tube layouts and can be fabricated from many different metals. Strips have been successfully fabricated from SS304, Titanium, Duplex, Carbon Steel, Monel and Brass. DTS is typically applied in bare tube bundles and can be applied to any common tube layout.

STS technology

STS technology (figure 3), consists of a corrugated pair of identical thin metal strips that are welded together and inserted into alternate lanes in a heat exchanger bundle. The “saddle” portion of the STS provides a wide contact area against the tubes instead of a point contact. A locking device on each strip keeps it in position in the bundle. STS is typically applied in finned tube bundles with a square tube layout.

figure 1: DTS strip installed in bundle

figure 3:STS strips inserted in

tube bundle

figure 2:DTS strips applied as U-bend stiffener

SBX technology

SBX technology consists of an axial-flow exchanger in which a relatively small number of hori-zontal and vertical tube support stations (slotted baffles), along with a number of strategically placed DTS or STS strips, provides low shell side pressure drop with vibration-free operation.

Figure4illustratesanSBXbundlethatwasdesignedforagas-compressioncircuitinachem-ical plant. By retrofitting the existing shell with an SBX bundle containing integral-fin tubes, the plant was able to reduce pressure drop from 16 to 4 psi (110 to 28 kPa) while maintaining theexistingfeedpreheatduty.Inthiscase,thesavingscapturedfromreducedoperatingex-pense (reduced pressure drop) and capital avoidance (used existing shell/foundation/piping) more than offset the cost of the finned tubes.

figure 4:SBX bundle designed for compressor circuit

The HTRI Xvib ® software includes DTS and STS options for evaluating vibration in shell and tube heat exchangers. This modification is available to all Xvib ® users beginning with Version 6

www.HTRI.net

For information on software contact: