Steam filtration is a vital part of any industrial application that requires steam as an energy source, whether it is to drive mechanical processes, heating, or sterilization. Steam is an inherently dirty resource, commonly contaminated with rust, scale, and other particles. The maintenance program for any steam based system should always include a filtration component to protect every aspect of your system from contamination.
In industry, steam is commonly used in processes for a variety of applications. Broadly speaking, you can divide the industrial use of steam in its various forms into several categories, each with specific process requirements:
-
Process steam for power transfer for applications such as pressure and thermostatic controls, or power to drive mechanical processes;
-
Culinary steam as used for food and beverage processing;
-
Superheated steam is typically found in mechanical applications that depend on its considerable energy, such as electrical power production and other mechanical processes, as well as antimicrobial applications;
-
Saturated steam, like superheated steam, drives mechanical processes and provides heat energy for thermostatic processes, such as cleaning and sterilization;
-
In situ sterilization is based on steam to sterilize in situ the components of a sterile system without having to change or disassemble the system afterwards, thus maintaining absolute sterility;
-
Clean-in-place is similar to sterilization-in-place without the absolute purification requirement.
Regardless of the application, there is a great need for contaminant-free steam to protect equipment or downstream processes from scale, rust, and other particles. One important application is sterilization. By design, sterile filters for compressed air or gas systems remove bacterial and viral contaminants from the compressed air source prior to application. To perform this function effectively, you must first sterilize the sterile filter and its element before use. Also, you should re-sterilize the filter every day, as well as every time you shut down the system, whether for maintenance or otherwise. An effective way to sterilize filters in situ is to use steam to prepare the units. However, the introduction of steam also creates contaminants commonly found in steam sources, such as dirt particles, rust, and scale; contaminants that will drastically reduce the life and efficiency of the sterile filter element, as its design serves to remove the aforementioned biological contaminants and not the larger coarse contaminants found in the source steam. Steam filters will effectively remove those coarse particles before the steam is introduced into the sterile filters for sterilization in place, thus increasing their useful life.
Steam filter housings are necessarily made of stainless steel to ensure housing integrity when operating in the harsh environmental conditions of compressed steam sources. Lesser materials, such as aluminum or polycarbonate, are generally not suitable for steamy environments. Steam filters are often available with NPT, flanged, sanitary, or short end connections with line sizes ranging from 1/2″ to 12″. Additionally, steam filter elements are available in stainless steel by combining stainless steel end caps with a sintered stainless steel porous filter media. The sintered stainless steel filter element is available in a variety of pore sizes, typically ranging from 1, 2, 5, 10, 15, 25, 40, and 50 microns, depending on your filtration requirements.
Key factors for sizing filters for your application
When determining the proper steam filter size and its micron retention rating, you must gather specific details related to your application:
-
Determine the maximum pore size allowed. Please note that selecting a smaller pore size than required will reduce the life of the steam filter element, as well as create a higher pressure drop. A larger pore size than required will effectively reduce the life and efficiency of your post-installed sterile filter;
-
Steam flow rate of your system in lb/hr or kg/hr;
-
Vapor pressure measured in psi or bar;
-
Allowable pressure drop for a new/clean element measured in psi or bar. For this specification, we recommend a pressure drop of no more than 1.0 psi or 0.07 bar, as a higher pressure drop will reduce the effective life of the steam filter element;
-
Nominal pipe size (NPS) for the inlet and discharge of the installed filter, as well as the type of connection (ie, NPT, flange, sanitary connection, or short end).
Cleaning the steam filter elements
Depending on the type of contaminant, you can safely and effectively clean sintered stainless steel steam filter elements with a dilute hydrochloric acid solution, an ultrasonic bath, water, or air. Typically, it will clean the installed steam filter element when the differential pressure reaches 15 psi or 1.0 bar. A vapor filter element will have reached the end of its effective useful life when the “clean” unit can only sustain a pressure drop that meets or exceeds 10 psi or 0.7 bar.
Regardless of your system application or steam requirements, steam filters protect your equipment and downstream processes, as well as your end product in some cases, and are critical to maintaining system viability and maximizing performance at the lowest cost. possible. Their role is invaluable, and properly selected, applied, and maintained will greatly extend the life of downstream equipment components, as well as protect your final product from unwanted contamination.