boilers, pumps & valves
same reaction
compaTibiliTy for conTrol valves Whatever chemicals they are exposed to, control valves need to operate over extended periods of time and prevent contamination of the media they come into contact with. For valve manufacturers, there is also increasing demand to demonstrate the composition of the valve’s construction materials. In this article, Kieran Bennett, field segment manager for Hygienic - Food & Beverage applications at Bürkert, explains how control valves should be properly matched to the chemicals they come into contact with.
The increasing imporTance of chemical
chemical composition of the materials used in valve construction. Today, perhaps half of all users of process valves require a materials certificate, while nearly all diaphragm valve users consider it a necessity. In some cases, such as the pharmaceutical sector, every valve that comes into contact with the media requires full documentation and traceability. This increased requirement is unsurprising: not only does it give the customer
A
significant change increasingly seen in the valve market, particularly for hygienic applications, is the focus on the
reassurance, but it answers increasingly strong regulatory compliance. In sectors such as food and beverage and pharmaceutical, whether for an on-site check or for compliance with FDA regulations, a valve user needs to be able to prove the chemical composition. For the manufacturer of a PTFE diaphragm valve for example, this means proving traceability to the original batch of manufacture of the chemicals and the quantity used. The chemical composition of the valve,
mainly consisting of its body, seal and potentially the diaphragm that creates a barrier with the
media, is an important factor for the quality and safety of the end product. Food and beverage manufacturers, for example, need to prove that there’s no shedding of traces of valve components, which can contaminate or impact the taste or odour of the end product. This means that clarification of the valve’s chemical composition is fundamental, as well as its suitability for long-term use with the media it comes into contact with. The other main concern in valve material
specification is resilience to the chemicals it comes into contact with in order to achieve the expected lifetime. For this reason, proving origin is also an important factor for customers to validate valve quality. For example, a manufacturer can be asked to provide a 3.1 material certificate, which could trace the composition of a stainless steel valve body to clarify carbon content. Lower quality valves can use stainless steel with a higher carbon content, generally making it more brittle and less robust, so validation is a sensible request. Traceability is vital, but ensuring chemical
compatibility can also be a matter of application experience. For example, in many dairies, nitric acid is used as part of the CIP (clean in place) process. Within a ball valve, typically two carbon graphite seals are used in the end caps, however the material isn’t suitable for long-term use with nitric acid, which will degrade the seals, reducing the number of cycles the valve can perform in its lifetime. This is a commonly overlooked
Summer 2021 UKManufacturing
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