{"id":6989,"date":"2025-06-20T11:29:02","date_gmt":"2025-06-20T09:29:02","guid":{"rendered":"https:\/\/www.hws-mainz.de\/?p=6989"},"modified":"2026-08-23T20:19:07","modified_gmt":"2026-08-23T18:19:07","slug":"common-mistakes-glass-reactors","status":"publish","type":"post","link":"https:\/\/www.hws-mainz.de\/de\/common-mistakes-glass-reactors\/","title":{"rendered":"Common Mistakes When Using Glass Reactors (And How to Avoid Them)"},"content":{"rendered":"

Borosilicate glass reactors<\/a> are the default vessel for chemical synthesis, pharmaceutical R&D and pilot-scale development, because they combine visibility with chemical resistance that exceeds most metals. They are also more forgiving than their reputation suggests \u2014 borosilicate 3.3 is a genuinely robust material, not delicate laboratory ornament.<\/p>\n

Most failures in service are not material failures. They are specification and handling errors: a duty the vessel was never built for, a geometry mismatched to the process, or a seal chosen for the wrong medium. Here are the mistakes that actually cause damage, and how to avoid them.<\/p>\n

Treating a glass reactor as a pressure vessel<\/h2>\n

This is the most consequential misunderstanding, and it usually comes from experience with glass-lined steel \u2014 a different product entirely, where several bar of working pressure is routine.<\/p>\n

Unless a specific execution has been engineered and documented for it, an HWS flat-flange reactor is intended for operation without pressure, or with a slight overpressure of up to 0.1 bar<\/strong>. Using the standard execution as a pressurised reactor within the meaning of the relevant norms is not permissible.<\/p>\n

That is not a reason to avoid pressure work. It is a reason to declare it up front. Where a process genuinely requires pressure, state the maximum pressure and temperature in the enquiry: the reactor is then manufactured to the applicable standards as a special order and supplied with a material test certificate. HWS also supplies overpressure valves in defined ratings from 0.1 bar upward, so the protection can be matched to the declared duty rather than improvised.<\/p>\n

The failure mode to avoid is silent pressure \u2014 a blocked vent, an isolated reactor still under heat, or a gas regulator faulting open. None of these appear in a process description, and all of them can put a vessel well past 0.1 bar.<\/p>\n

Assuming any glass vessel handles vacuum equally<\/h2>\n

Vacuum loads act inward, so geometry decides the outcome more than wall thickness does.<\/p>\n

The HWS flat-flange reactor is well suited to vacuum because of its torispherical vessel shape and the profile of the flat-flange lid. But that suitability is not universal across the catalogue: vessels with a flat bottom<\/strong>, or with a fused disc of smaller radius, are only suitable for vacuum or slight overpressure in limited circumstances.<\/p>\n

If a vessel was specified for atmospheric work and is later pressed into a solvent-stripping role under deep vacuum, the geometry may simply not be right for the new duty. Check the execution before changing the process, not after.<\/p>\n

Believing borosilicate is inert to everything<\/h2>\n

Borosilicate 3.3 is rated hydrolytic class 1<\/strong> and acid class 1<\/strong> \u2014 it is highly resistant to water, neutral and acidic solutions, concentrated acids and their mixtures, chlorine, bromine and organic media, and holds that resistance through extended reactions above 100 \u00b0C.<\/p>\n

Its alkali rating is different: alkaline solution class 2<\/strong>. Three media attack the glass surface progressively:<\/p>\n