Heat Exchanger & Pressure Vessel Solutions

Background

The failure rates heat exchanger (HX) and pressure vessel (PV) flanges is the worst/highest of all joints in the Oil, Gas and Petrochemical industries. Our aim is to eliminate these and provide faster bolt tightening tooling & methods.

Cause

The codes that these items adhere too (ASME VIII, AS1210, PD5500, EN13445 etc..) allow Engineers to design bespoke flanges. These items (particularly girth flanges) are one of the most costly parts, consequently they are designed to minimum diameters and thicknesses allowed by the codes. One of the ways to do this is to use high numbers of small bolts rather than fewer of a larger diameter. ASME VIII/AS1210 are the most conservative and consequently flanges tend to be stiffer but still failures are common.

This is compliant and cost saving however the interaction between adjacent and opposite bolting is extremely high. Every time any bolt is tightened those alongside and opposite loosen.

Many procedures exist to minimise this effect but it is impractical to eliminate it using standard methods.

Solution

The cornerstone of our solution is to measure the tension achieved by the tightening method, this way we have hard evidence, not assumed figures from either Torque or Tensioner calculations.

This chart shows actual results achieved using the standard lubrication and star pattern procedures as per the codes. This example is only a 24 bolt flange, the results become significantly worse as the bolt numbers increase. Typically a flange with 48 or more bolts will have at least one with zero tension.

Solution

The use of ultrasonic tension measurement brings significant improvements, namely:

  • 1. Leaks are eliminated, preventing un-planned shutdowns & costly, dangerous on-line sealing techniques.
  • 2. By identifying which bolts are low we focus on adjusting those, not re-tightening every bolt on the joint. This saves a significant amount of time.
  • 3. Once the data is collected the results can be analysed, allowing intelligent informed improvements to procedures to be made. This reduces time and improves accuracy.

This chart compares the original 4 pass torque tightened method with the readings taken after ultrasonic measurement and adjustments are made.

Clearly the variation s significantly reduced, as a result no leakage occurs.

Avoid using the wrong socket. Download our free Bolt to Nut comparison chart.

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