Home : Products : Screw Plug  

Heat Exchangers - Screw Plug - (Breech Lock) Products

SCREW-PLUG (Breech-Lock)
After the catastrophic failure that occurred in a high-pressure Screw Plug enclosure in Japan and subsequent failures that were witnessed time and again in several parts of the world, the Screw-Plug design lost its significance to a large extent. Tema India Ltd. a Licensor of M/s. Struthers at one time, decided to conduct an extensive research program to bring about key changes to make this design safe and free of maintenance problems.
Screw-Plug Heat Exchangers
Extensive structural analysis was carried out and a need for added steel on the threaded portion of the enclosure was realized. This technology was acquired from its parent company, Leo Engineering Works, a manufacturer of high pressure sampling bombs for all refineries in India.
Typ. Channel Closure Assembly   3D View    
FEA analysis carried out on standard units at Tema India Ltd. has revealed that due to the uneven thermal expansions undue/unaccounted stresses are developed. This causes bell mouthing in the threaded region reducing the shear area of the threads, i.e. resulting in some part of the threads not being fully engaged. This results in expelling the plug in an extreme circumstance thus causing an explosion.

The other condition that is often experienced is known as thread "galling" or seizing. Given the large amount of clearance in the threads, there is an increased chance of the plug being displaced or shifted which causes thread galling. Galling occurs when surfaces of mating parts are of the same metallurgy and when there is loss in lubrication due to the plug displacement. Thread galling can become severe enough that the mating parts seize, making it virtually impossible to separate them and when tried to pry open, a seal lock is created.

Tema India Ltd. has conducted several experiments and has done destructive testing on prototype to ensure that the added steel in fact restricts any such distortion by creating positive stresses and results in easy removal of the plug.

It can be seen by analysis that the magnitude of bending stress can amount to three times the average longitudinal stress in the undercut area.

This phenomenon can be logically understood and supported by calculations to show that the combined bending and longitudinal stresses on the undercut surface of the threads produces a wedging action that results in radial displacement causing dilation of the channel.

Therefore this dilation that is a cause of reduction in shear area has to be restricted by using higher wall thickness in the threaded region. This higher wall thickness of the channel barrel immensely shoots up the cost of the forging.

Tema India Ltd. has thus adopted their own technology of added steel to overcome this phenomenon of bell mouthing or galling of threads.
Finish Threaded lock ring   Strip Cladding   Tube Bundle Insertion
DEU Screw-Plug High - High Type Heat Exchanger
In service at Fluor Ultramar - Jean Gaulin Refinery Canada
Copyright © 2010 TEMA INDIA LTD Home | Contact Us
Breech Lock Heat Exchangers High Pressure Heat Exchangers Power Sector Equipment Helixchanger
Screw Plug Screw Plug Heat Exchanger Heat exchanger manufacturer in india Gas to Gas Heat Exchanger Solar Power