Vacuum engineering is by no means a mainstream engineering discipline and vacuum systems do not crop up often enough to warrant a project engineer becoming familiar with vacuum technology. This results in companies, be they end users or contractors, tending to regard vacuum systems as black boxes - as yet uncharted regions of the process waiting to be mapped by third parties and herein lies the danger.
All too often, the firms called in to design the vacuum system are really only interested in just one thing - selling vacuum pumps. Furthermore, their personnel tends to consist of salesmen backed up solely by mechanical and electrical engineers.
The consequence is that the supplier pays insufficient attention to the process to which the vacuum system is to be connected and the customers pays insufficient attention to technical details of what he is being offered.
A few choice examples illustrate the potential pitfalls:
· No less than twenty vacuum systems at the same site, all rotting away from the inside out simply because the manufacturer had failed to appreciate just how much hydrochloric acid was passing though the reflux system. The systems were all closed-loop, liquid-ring employing seal water containing 20 wt% caustic soda (to neutralised the hydrochloric acid). Calculations showed that the alkali would be neutralised after just 5½ hrs of service!
· A three-stage vacuum system was installed having as the final stage, a liquid-ring vacuum pump using glycol at 105°C as sealing liquid? Why 105°C? Simply because it was supposed to pump water vapour and, as we all know, water vapour does not condense at 105°C and atmospheric pressure. Water is, however, infinitely soluble in glycol with the result that the glycol absorbed ever increasing quantities of water vapour (in an effort to move towards equilibrium) resulting in increasing vapour pressure of the sealing liquid, leading to poorer vacuum from the liquid-ring vacuum pump, in turn giving poorer process vacuum, longer cycle times and ultimately an inferior finished product.
· One man tried pumping styrene monomer vapour in a dry vacuum pump with PTFE seals (but not for long!).
Quicksilver Engineering Ltd.can help you bridge the knowledge gap. Quicksilver Engineering Ltd. can ensure that the requirements of the process dovetail with the capabilities of the vacuum equipment. Quicksilver Engineering Ltd. can offer you truly independent advice on which vacuum pump technology to use and why. Quicksilver Engineering Ltd. can also take care of the rest of the project management process for you: flowsheeting, tender dossiers, evaluation, pre-commissioning, commissioning and, if needs be, even trouble-shooting. If required, Quicksilver Engineering Ltd. can also coordinate acquisition and construction activities on your behalf.
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