Steam Types for Process Applications
Types of Steam
Steam is used in processing applications where purity and efficiency is important, including blanching or rehydrating products, sterilizing equipment, and steam-in-place cleaning of process equipment. But not all steam is created equal.
The type of steam selected has direct implications for product quality, safety, and regulatory compliance, particularly when it comes into direct contact with food or product-contact surfaces. As the steam moves from plant steam to culinary, clean, and pure steam, the level of purity increases, along with system design and requirements.
Choosing between plant, culinary, clean, and pure steam ultimately comes down to application requirements & risk. Culinary steam can minimize the risk of contaminants entering the product and is widely used due to its cost efficiency. Clean steam eliminates chemical additives and provides a higher level of control. Pure steam removes virtually all contamination risks but at a higher cost based on equipment, components, and piping needs.
For operators, the key is to evaluate the level of risk acceptable for the application and the expectations of regulators and end users. This includes consideration of product type, process conditions, and applicable standards such as FDA and USDA requirements for food safety, 3-A sanitary standards for equipment design, and clean steam guidelines such as HTM 2031 or EN 285 for regulated sterilization applications.
Plant steam is the lowest-grade steam. Sometimes called utility steam, it is used for general, indirect heating purposes in process plants. It is commonly used in industries such as paper, petrochemicals, laundries, and HVAC systems. Plant steam may contain a range of contaminants, including solids, liquid droplets, and chemical additives used in boiler treatment. Because of this, it is not safe for human consumption and is not advisable for applications involving direct contact with food or beverage products. Instead, plant steam is limited to indirect heating applications. A barrier separates the steam from the product so that impurities do not affect product quality. Plant steam should be filtered (10-100 µm) to help keep system components in good working order and avoid premature breakdown. Filters with 10 µm elements or steam separators are good options to purify steam supplies to keep equipment in working order and avoiding costly component breakdown.
More Information about Micron Rated steam filters at Micropure Steam Filters
Common indirect heating applications include steam jacket heating, non-critical area humidification or temperature control and the cooking of alcohol products prior to fermentation.
Culinary Steam
To make steam suitable for direct food contact, plant steam must be treated to remove contaminants. Culinary grade steam, also referred to as filtered steam or food grade steam is the most commonly used steam in the food industry because it represents the safe level for direct food contact. Culinary steam is produced by passing plant steam through a high efficiency filtration system designed to remove both particulate matter and entrained liquid. A typical specification requires removal of 99.99+% particles greater than 5 microns or 95% of particles greater than 2 micron, including both solids and liquid droplets. These filters must be changed or cleaned on a regular schedule; neglect can result in increased pressure differential or reduced steam flow due to filter fouling or clogging.
Producing culinary steam requires more than filtration alone. Systems typically include a steam separator to remove excess water content. Condensate removal beneath the filter is necessary to prevent re-entrainment of contaminants, and downstream piping is typically constructed of stainless steel to minimize corrosion and particulate generation. Boiler chemicals used upstream must also meet FDA requirements, with non-volatile formulations preferred, as chemicals remain in the boiler and are removed through blowdown.
The FDA and 3A Dairy have specific requirements for culinary steam production systems. Those requirements beyond just the filter micron level can include pipe material and connection types along with specific ancillary equipment in support of the complete steam filtration line. The 3A steam standard 609-03 has a detailed list of the steam filtration line requirements and a process diagram.
More information about Culinary steam filters can be found at Culinary Steam Filters
Clean Steam
Clean steam is purer than both plant and culinary steam and contains no boiler additives or treatment chemicals. It is typically generated in a dedicated clean steam generator using treated feedwater such as softened potable water, de-ionized water, or reverse osmosis water. The choice of feedwater has a significant impact on system design and materials of construction. For example, systems using potable water may incorporate mild steel or copper components, while systems using de-ionized (DI) or reverse osmosis (RO) feedwater require 316L stainless steel to withstand the more aggressive nature of the water.
The design of the clean steam distribution system is critical to maintaining purity. Systems must be crevice-free and self-draining to prevent microbial growth, and stainless-steel construction is used to eliminate corrosion risks. Although clean steam is used in some food and beverage applications, it is more commonly found in higher-risk environments such as pharmaceutical support processes, cosmetics manufacturing, and applications involving sensitive consumer populations such as baby food and hospital patients. Non-critical humidification within the biopharmaceutical industry is another example where clean steam may be used.
Even in clean steam systems, filtration may still be recommended as an added safeguard. Low micron steam filters can be used to capture any residual contamination present in the water or introduced through the system. This extra filtration helps protect the steam supply from any potential upstream or system-related contamination issues.
Find More information about our low micron filters here: Culinary Steam Filters & Micropure Steam Filters
Pure Steam
At the highest level of purity, pure steam is used in pharmaceutical and biotechnology applications where contamination cannot be tolerated. It is often considered the most safe option available to processors. It is generated using a dedicated pure steam generator or multiple effect still. The resulting condensate must meet USP Water for Injection (WFI) standards and contain no bacteria or pyrogens. Like clean steam, pure steam contains no additives or chemicals, but it is subject to far more stringent quality requirements.
There are two primary methods of generating pure steam. One method uses a steam heating coil to heat water in an open or vented system, while the other uses a sealed steam generator that operates under pressure. The sealed system is generally more efficient because it prevents steam loss. Open systems may allow steam to escape, which increases humidity and potentially contributes to issues such as mold growth or equipment corrosion if not properly managed.
Pure steam generators can be used across a wide range of applications but require regular maintenance and represent a higher upfront cost. In general, higher flow rates improve the cost-effectiveness of these systems.
Pure steam offers the highest level of safety and is often required for pharmaceutical production and for certain organic food applications where chemical additives are not permitted. The majority of food processors that utilize pure steam do so to meet standards required for labeling products as organic. However, this level of purity comes with tradeoffs. Pure steam systems require higher capital investment, increased energy consumption, and more complex equipment. As a result, facilities may choose to use pure steam selectively, applying it only to specific processes while relying on culinary or clean steam elsewhere. Similar to clean steam, Pure stream applications can also install low micron filters as extra protection from upstream equipment breakdown or contamination.
Find More information about our low micron filters here: Culinary Steam Filters & Micropure Steam Filters
