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Heat exchangers and the bolting of gaskets    

Heat exchangers and the bolting of gaskets

Bolt tensioning is now the preferred method of tightening bolts and studs on all critical applications. Bolt tensioners are designed for use on a wide range of applications including pipeline flanges, pressure vessels, compressor covers, boiler feed pumps and heat exchangers to name a few.

Shell and Tube, Air Cooled and the Plate-Type heat exchangers are the three most commonly used types of exchangers in the chemical and process industry. With an increasing effort in recent years to reduce both the weight and size of exchangers whilst increasing efficiency, other types of exchangers are frequently being used.

Gasketed plate heat exchangers use high quality gaskets to seal and clamp together plates and protect against leaks. The gasketed plates are assembled in a pack, mounted on upper and lower guide rails, and compressed between two end frames by compression bolts.

The gasket arrangement of each plate distributes the hot and cold media in a counter-flow arrangement into alternating flow channels through the plate pack. These heat exchangers are simple and relatively cheap to maintain since the plates can easily be removed to allow maintenance procedures to be carried out.

Heat transfer equipment may be selected for its type or for the function that it performs such as chiller, condenser, cooler reboiler, whereas the choice of a Shell and Tube type exchanger is determined primarily by factors such as the need for the provision for differential movement between shell and tubes, the design pressure, the design temperature, and the fouling nature of the fluids rather than the function.

Flanges

There are three types of flanges that are found in Shell and Tube exchangers, namely:

  • Girth flanges for the shell and channel barrels
  • Internal flanges in the floating head exchanger to allow disassembly of the internals and removal of the tube bundle
  • Nozzle flanges where the flange/gasket standards and the size/pressure rating will be set by the line specification.

Out of the three flange types, the weld neck flange type, which has a tapered hub with a smooth stress transition and accessibility for full nondestructive examination, provides the highest integrity.

A flange consists of three subcomponents: the flange ring, the gasket and the bolting. The successful operation of the flange depends on the correct choice, design and assembly of these subcomponents.

The external bolted joints will require re-tightening in a uniform, diametrically staggered pattern.

Heat exchangers and the bolting of gaskets

Challenge

On average heat exchangers tend to leak every eight months as a result of changing temperatures and pressures. This requires completely stripping the heat exchanger down to change the gaskets. They can also be stripped for inspection purposes every 3 years.

HTL’s solution

HTL’s Spring Return Tensioners produce the necessary pre-load force to properly load the studs and the sealing system. You can assured that the heat exchanger is secure and tightly sealed, preventing the likelihood of leaks.

Maintenance

Heat exchangers should be cleaned as they are subject to fouling, the build- up of unwanted waste such as scale, sludge, deposits etc. These deposits need to be cleaned from the system periodically as even a light buildup of deposit can greatly reduce the effectiveness of the tube. Neglecting regular maintenance of the tubes cleanliness can cause excessive heat or cooling, which then causes physical damage and leaking tubes as a result of the differential thermal expansion of metals.

Eliminate leakages and costly downtime

To eliminate the likelihood of leakages and to ensure correctly secured flanges are achieved, HTL’s Spring Return Tensioners are available in a range of sizes to suit every application.

Complete with CE Certification, the range of HTL Spring Return Tensioners offer significant advantages to traditional tightening methods:

  • No torsional loading of fasteners
  • Direct loading, no damage to the gasket
  • Simple and fast operation
  • High accuracy consistently

HTL-ST2 1-3/8” STUD, HEAT EXCHANGER BOLT TENSIONING APPLICATION.

HTL-ST2 1-3/8” STUD, HEAT EXCHANGER BOLT TENSIONING APPLICATION

To support essential regular maintenance, HTL can also provide premium quality Flushing Rigs and Particle Analyzers to detect and remove deposits, saving on maintenance costs and downtime. (See the below related articles for further information).

To find out more information or to get an instant quote contact us: call +44 (0) 1670 700 003 or email info@hiretorque.com / info@htl-australasia.com.

Related Articles: https://www.hiretorque.co.uk/subsea-and-topside-tensioning/

https://www.hiretorque.co.uk/advantages-of-controlled-bolting-techniques/

https://www.hiretorque.co.uk/bolt-preloading/

https://www.hiretorque.co.uk/the-ultimate-portable-service-tool/

https://www.linkedin.com/pulse/oil-flushing-rigs-troublesome-systems-contamination-issues-arnold?trk=mp-author-card


4 responses to “Heat exchangers and the bolting of gaskets”

  1. Parag Amratia says:

    We are State Government Ferlitizer and Chemcial company , M/s Gujarat Narmada Valley Fertilizers & Chemicals Ltd., situated at Bharuch, Gujarat. India.

    In our Ammonia Plant, we have floating head heat exchanger in which we want to know the torque value to be applied on the Stud bolts which are of size : 4″ x 8 UN x 1000 mm long of MOC : ASTM A194 Gr 8M for Nut and ASTM A193 Gr B8M Cl1 for Stud : Qty. 20 nos.

    Kindly inform us the details at the earliest.

  2. Yk says:

    Hi

    I had minor safety incident because of rupture of gasket used in heat exchanger .

    What could have been reason

    • georgie says:

      Hi Khalad,

      Thank you for your comment.

      There can be many reasons why the gasket ruptured, but i’m glad to hear that it was only a minor safety incident.

      Causes of them rupturing can be down to multiple factors, equipment manufacturers, engineering personnel. You would have to look at the heat exchanger design as each design has it’s own purpose. Also, whether it was fixed-tube, floating head or a u-tube heat exchanger.

      There are also considerations to the way the gasket was inserted. In order to ensure the maintenance of the seal throughout the life expectancy of the assembly, sufficient stress must remain on the gasket surface to prevent leakage. The residual bolt load on the gasket should at all times be greater than the hydrostatic end force acting against it.

      Many factors should be considered when selecting a gasket to ensure its suitability for the intended application. Gasket properties as well as flange configuration and application details are part of the selection process.

      This is just a brief overview of the many reasons, but should you like to discuss your incident and find out the root cause send me more details to georgie.arnold@htlgroup.com and we can review.

      Best Regards,
      Georgie

      +44 (0)1670 700 003

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Parag Amratia says:

We are State Government Ferlitizer and Chemcial company , M/s Gujarat Narmada Valley Fertilizers & Chemicals Ltd., situated at Bharuch, Gujarat. India.

In our Ammonia Plant, we have floating head heat exchanger in which we want to know the torque value to be applied on the Stud bolts which are of size : 4″ x 8 UN x 1000 mm long of MOC : ASTM A194 Gr 8M for Nut and ASTM A193 Gr B8M Cl1 for Stud : Qty. 20 nos.

Kindly inform us the details at the earliest.

georgie says:

Hi Parag,
Thank you for your comment and I have emailed you some information.
Kind Regards,
Georgie

Yk says:

Hi

I had minor safety incident because of rupture of gasket used in heat exchanger .

What could have been reason

georgie says:

Hi Khalad,

Thank you for your comment.

There can be many reasons why the gasket ruptured, but i’m glad to hear that it was only a minor safety incident.

Causes of them rupturing can be down to multiple factors, equipment manufacturers, engineering personnel. You would have to look at the heat exchanger design as each design has it’s own purpose. Also, whether it was fixed-tube, floating head or a u-tube heat exchanger.

There are also considerations to the way the gasket was inserted. In order to ensure the maintenance of the seal throughout the life expectancy of the assembly, sufficient stress must remain on the gasket surface to prevent leakage. The residual bolt load on the gasket should at all times be greater than the hydrostatic end force acting against it.

Many factors should be considered when selecting a gasket to ensure its suitability for the intended application. Gasket properties as well as flange configuration and application details are part of the selection process.

This is just a brief overview of the many reasons, but should you like to discuss your incident and find out the root cause send me more details to georgie.arnold@htlgroup.com and we can review.

Best Regards,
Georgie

+44 (0)1670 700 003

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