Culinary steam distribution system: the separator, filter and sanitary piping that carry plant steam to direct food contact

01

The 3-A 609-03 sequence from steam main to food: separator, filter, differential pressure, sampling, sanitary check valve

3-A Accepted Practice 609-03, A Method of Producing Culinary Steam, was adopted on 21 November 2004 by 3-A Sanitary Standards, Inc. with the US Public Health Service and FDA, USDA Dairy Programs and EHEDG. It defines steam of culinary quality as steam free of entrained contaminants, relatively free of liquid water and suitable for direct contact with food or product-contact surfaces, and its scope begins at the steam inlet of the entrainment separator and ends at the steam inlet of the process equipment. [1]

The practice requires the following components, installed in this order: an entrainment separator capable of removing particles 10 µm and larger, with its own condensate trap; a filter capable of removing 95% of particles 2 µm or larger, also with a condensate trap; a means of measuring differential pressure across the filter medium to show when it needs replacing or, for reusable filters, cleaning; a means of sampling the steam or condensate downstream of the filter; and a sanitary check valve to 3-A Standard 58, whose steam-supply side may be threaded. Disposable filter media may not be cleaned and reused. Valves, orifices, strainers, gauges and control piping are optional. [1]

The practice's piping diagram for direct steam injection lists fifteen items from the steam main: stop valve, strainer, entrainment separator, condensate trap, pressure gauge, pressure-reducing valve, throttling valve or orifice, differential-pressure device, filter, then stainless steel from that point, sanitary piping and fittings from the next, a spring-loaded sanitary check valve, sanitary piping to the process equipment and a sampling means. [1]

Material rules change along the line. Product-contact surfaces, defined as those from the inlet of the sanitary check valve to the equipment connection, must be AISI 300-series stainless steel excluding types 301 and 302, or an equally corrosion-resistant non-toxic metal; stainless pipe, fittings and valves are required downstream of the filter, and tubing, fittings, valves and instrument connections downstream of the check valve must be of sanitary type. Where welding is involved, the appendix says carbon content should not exceed 0.08%. [1]

For each point of use, state whether the steam is injected into product, sparged into a vessel or used on product-contact surfaces, the steam flow and pressure at the inlet, and where the sampling point and differential-pressure gauge will be read.

02

Separator and filter ratings: 10 µm, 95% at 2 µm, and how a separator-filter is sized for flow

Filter makers translate the 3-A ratings into element choices. Donaldson writes that its P-EG housing with a 25 µm P-GS element serves as the entrainment separator and pre-filter, separating condensate and keeping larger contaminants off the culinary element, and that its 1 µm P-GS or 5 µm P-GSL N elements meet the requirement of 95% efficiency at 2 µm and larger. [3]

Donaldson also recommends pressure gauges upstream and downstream of the steam filter element, since differential pressure rises as the element loads, and states that its steam filters can be cleaned and regenerated in an ultrasonic bath up to six times within a year. [3] That applies to its reusable elements; 3-A 609-03 bars cleaning and reusing disposable media. [1]

TLV's SF1 combines both stages in one stainless body: a built-in cyclone separator, which TLV says separates condensate at efficiencies as high as 98%, ahead of a five-layer sintered wire-mesh filter offered at nominal ratings of 0.5, 2 and 5 µm. Body and separator are cast CF8 stainless, gaskets are fluorine resin, and TLV states that the unit conforms to the recommendations of 3-A Accepted Practice 609-03. Sizes run from ½ to 2 in, with a maximum operating pressure of 150 psig and maximum operating temperature of 365 °F. [4]

TLV's pressure-loss charts are drawn for steam at 15 psig; for other pressures the flow is multiplied by a correction factor, ranging from 1.14 at 10 psig to 0.45 at 150 psig, before reading the chart. Its flow-capacity chart assumes a steam velocity in the piping of 100 ft/s, which TLV recommends not to exceed. [4] Editorial calculation: at 100 psig the factor is 0.52, so 1,000 lb/h of steam is read on the 15 psig chart as 520 lb/h; 100 ft/s is about 30 m/s. [4]

Nominal micron ratings differ between makers that all cite 609-03 (Donaldson 1 or 5 µm, TLV 0.5, 2 or 5 µm); ask for the element's tested efficiency at 2 µm in steam, its clean pressure drop at your flow and pressure, and whether it is disposable or cleanable.

03

What the boiler puts into culinary steam: 21 CFR 173.310 amine limits and the stricter 3-A advice

Filters remove particles, not dissolved chemicals carried over from the boiler. In the United States, 21 CFR 173.310 lists the boiler water additives that may be used to prepare steam that will contact food, requires that no more additive be used than its function needs, and caps volatile amines by their concentration in the steam. [2]

3-A 609-03 is stricter than the regulation for the dairy plants it was written with. Its boiler-operation appendix states that compounds containing cyclohexylamine, diethylaminoethanol, hydrazine, morpholine, octadecylamine or trisodium nitrilotriacetate are not permitted, prefers ion exchange or similar pretreatment of feed water over adding conditioning compounds, asks that the water-treatment firm be told the steam is for culinary use, and warns that tannin, although on the approved list, has been reported to cause odour problems. [1] The regulation itself already excludes the four amines and NTA from steam that contacts milk and milk products. [2] Where the two differ, the buyer has to decide which applies to the plant; a dairy line following 3-A practice would avoid the amines entirely.

The practice also asks that boilers be run to prevent foaming, priming and carry-over, noting that carried-over additives can cause off-flavours, and recommends periodic analysis of condensate samples taken from the outlet of the final separating equipment or the line between it and the process equipment. [1]

Ask the boiler water-treatment supplier for the additive programme in writing, with each chemical's 21 CFR 173.310 listing, and set a condensate sampling schedule at the culinary train's sampling point.

04

Point-of-use, steam and compliance data for a culinary steam train

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Use: [direct injection, sparging, kettle, sterilising product-contact surfaces]
Steam at use: [flow lb/h or kg/h; pressure; temperature]
Supply: [main pressure; pressure-reducing station needed]
Separator: [particle duty 10 µm and larger; trap type]
Filter: [efficiency at 2 µm; disposable or cleanable element; housing 3-A authorisation]
Piping: [stainless from filter; sanitary from check valve; tube standard]
Instruments: [differential-pressure gauge; sampling point]
Boiler: [feed-water source; additive programme; dairy or non-dairy use]

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