When it comes to the pharmaceutical industry – whether it is concerning clinical trials, pharmaceutical manufacturing, or pharmaceutical waste management – two things are paramount: safety and efficacy. Either one without the other is pointless; an effective drug or machine which is not safe will only add to health concerns, while safe substances which cannot achieve the desired effect are simply a waste of resources. While assessing the types of pressure vessels used in pharma, too, safety and efficacy are of utmost importance.
Biopharmaceutical reactions must be carried out under controlled conditions of temperature and pressure if they are to achieve the desired results. This means that pressure vessels should be of extremely high quality for you to be assured of efficacy. As for safety, that is even more important when it comes to the different pressure vessel types. This is because, by their very nature and function, pressure vessels present risks to the people who operate them. If there is even a small crack, error in design, or vulnerability in construction, the consequences for the personnel working with different types of pressure vessels can be catastrophic.
So, what is a pressure vessel anyway?
Before we get into any technical details, let’s answer the fundamental question of what a pressure vessel is and what pressure vessels manufacturers in India have on offer.
Pressure vessels are not unique to the pharmaceutical industry. In fact, they have applications in power plants, petrochemical processing, petrochemical refining, oil and gas industries, and beyond. The term ‘pressure vessel’ refers to any closed, leak-proof container which is designed and engineered to hold substances usually in liquid or gaseous state; but pressure vessels are not like any other storage or holding tank – they are special in that they can hold substances at pressures extremely different (usually higher) than ambient pressure.
Generally designed by pressure vessels manufacturers in India to operate at pressures greater than 15 psig, they may be constructed with any robust high quality metal which is proven to be able to withstand extremely high pressures and temperatures. Stainless steel and carbon steel are the go-to options for pressure vessels of all kinds in pharma. But aluminium, copper, and some non-metallic substances may also be used in certain situations.
Pressure vessels comprise a shell, nozzles, flanges, gaskets, a skirt, a baseplate, internals, as well as ladders and platforms for easy access. Pressure vessel types can be differentiated based on industry, application, installation or orientation, shape, and construction – we will explore some of these pressure vessel types in this article. Irrespective of types of pressure vessels, however, they are generally equipped with heat removal or introduction mechanisms because temperature and pressure control go hand-in-hand. Different types of pressure vessels also share another common feature: they are always closed containers because even a tiny leak or damage can be dangerous, affecting the safety of people and the efficacy of the machine itself.
Classifying different types of pressure vessels
On the basis of shape: Cylindrical pressure vessels with flat or dished heads are the most commonly found design; storage tanks and compounding vessels are usually constructed in this shape. Spherical pressure vessels are used when uniform stress distribution is required; such design enables pressure vessels to withstand higher pressures, with applications ranging from aerospace to LPG storage. Rectangular pressure vessels are the rarest shape, but are used to ensure optimal space usage.
On the basis of construction techniques: Since pressure vessels have to be absolutely leak-proof, their construction must be robust and completely error-free. This may be achieved via welded construction, in which different metallic components are welded together for economical construction of pressure vessels which only need to withstand medium pressure. On the other hand, forged pressure vessels are constructed from one single piece of metal which is forced into its final shape under high pressure – this method is indispensable while constructing pressurized vessels which are used in high-pressure situations and use cases. Finally, applications like air conditioning and refrigeration call for brazing techniques to join metallic pieces in the construction of pressure vessels.
Types of pressure vessels used in pharma
You know now that pressure vessels manufacturers in India supply not only the pharmaceutical industry, but also the petrochemical industry, among several others. Across industries and even within, the design and construction of the vessel differs based on use case. In pharma, tubular heat exchangers, boilers, chemical reactors, bioreactors, compounding vessels, storage vessels, and distillation columns can all be pressurized vessels (though they don’t always have to be – for instance, atmospheric holding vessels which store raw materials or finished products at ambient pressures are not considered types of pressure vessels).
Your essential guide to different types of pressure vessels must include at least a brief look at the following pharmaceutical pressure vessels which have wide-ranging applications:
Heat exchangers are used at multiple stages of pharma and biopharma production. Not all heat exchangers are pressure vessels, but double sheet tubular heat exchangers sure are as they depend on the transfer of heat between fluids (sometimes gases) to transfer heat. The fluids running through them are usually at high temperatures and pressures, and with the transfer of energy that they are responsible for, they are subject to high temperature and pressure differentials. All of these factors result in excess stress being exerted on heat exchangers. So like all other pressure vessels, heat exchangers, too, must be extremely resilient.
Boilers depend on either fuel or electricity to heat mainly liquids. To prevent loss of energy, boilers are often closed containers, a feature which makes them pressurized vessels. Heating liquids naturally results in some amount of phase change, like boiling water giving rise to vapours. To withstand the pressure generated in such situations, pressure vessels manufacturers in India use thermostable, corrosion-resistant materials which can tolerate high pressures as well.
As we’ve mentioned earlier, not all storage vessels are pressure vessels. But sometimes, storage or holding vessels are pressurized depending on the stability and properties of the products they hold. Often, to prevent the inflow of air and the contaminants it brings, raw materials and finished pharma products are even stored under positive nitrogen pressure.
Compounding vessels (also called manufacturing vessels), ultimately, may also need to be constructed to be one of the types of pressure vessels. This is because biochemical reactions in pharma needed to be carried out under controlled temperature and pressure conditions. In fact, this is the case during not just chemical reactions, but also during distillation, mixing and agitation. So pressure vessels are actually quite crucial to the pharmaceutical manufacturing process.
Standards followed by pressure vessels manufacturers in India
Ultimately, given the high risks involved in different types of pressure vessels’ construction and use, there are high standards applicable to these processes. The ASME or the American Society of Mechanical Engineers have a Boiler and Pressure Vessel Code which is widely regarded as an important standard in pressure vessel manufacturing. Sections II, V, VIII, and IX are particularly useful to gain a holistic understanding of the expected standards in the design, engineering, welding, and materials used to make pressure vessels. The API 510, EN 13445, and AD Merkblätter all serve as important resources for safe pressure vessel construction, inspection, rating, repair, design, piping, and durability. There you have it – your essential guide to understanding different pressure vessel types. If you still have questions, the experts at TSA are only a chat away. If you have any high purity or process challenge plaguing your operations, we’re all ears.