Introduction: Process lines above 65°C need a wound cartridge whose media and core are selected together for the actual temperature and chemistry.
An 80°C or 100°C line often inherits a cartridge chosen for a cooler duty. It may fit the housing and meet the flow rate, yet the plastic core can soften or the media can age faster than expected. The practical question is whether a higher-temperature material combination is needed and whether the fluid chemistry permits it. Cotton fiber with a stainless steel core offers a 120°C option. PP with a plastic core is limited to 65°C, and PP with a galvanized iron core to 100°C. The right choice depends on the whole operating envelope.
Why High-Temperature Process Lines Need the Media and Core Matched Together
The fiber and core are exposed to the same hot fluid, and the weaker component determines the service limit. In cartridge filter manufacture, the core carries the wound fiber under pressure and keeps the cartridge straight inside the housing. A core that softens can relax the yarn, alter the pore path, or affect the end connections. For that reason, a temperature limit applies only to the exact material combination. The listed combinations are PP fiber with a plastic core at 65°C, PP fiber with a galvanized iron core at 100°C, and cotton fiber with a stainless steel core at 120°C.
1. Polypropylene and Plastic Cores Stop at a Lower Temperature Band
Polypropylene is a common choice for many water and process fluids, and a PP string wound filter cartridge with a plastic core covers many ambient and warm duties. The 65°C limit applies to that combination. Below it, PP provides predictable depth loading and is used across many water and process-fluid applications. Above it, the plastic core becomes the limiting component. A line running at 70°C to 80°C therefore needs a core-material check, because a standard PP cartridge with a plastic core is outside its listed band even when the housing is rated for a higher temperature. If the chemistry permits PP, the next option is PP fiber with a galvanized iron core at 100°C. That change provides more temperature headroom and changes the core material in contact with the fluid.
2. Cotton with Stainless Steel Reaches a Different Service Limit
Cotton fiber with a stainless steel core is the 120°C combination for high-temperature process lines. Cotton is a natural fiber, so it raises different handling and compatibility questions from PP, while providing a useful temperature step above the PP and galvanized iron option. The stainless steel core keeps the cartridge structure stable in hot service. SUS 316 is available as a corrosion-resistant core grade. SUS 403 is also listed; include the exact core grade in the RFQ so the supplier can confirm it for the intended duty. For food and beverage lines, review the media and wetted materials against the fluid and the applicable food-contact requirements.
How Fluid Chemistry Changes the Choice Beyond Temperature Resistance
Temperature resistance and chemical resistance are separate selection criteria. A cartridge can hold its shape at 120°C and still be unsuitable for a solvent, acid, caustic, oxidizing cleaner, or oil-rich stream. The cotton fiber, stainless steel core, and other wetted components all contact the fluid, so compatibility review must cover the whole wetted path. Stainless steel 316 is a corrosion-resistant core material, but its performance in a specific acid or chloride service depends on concentration, temperature, and oxygen level. Cotton suits many aqueous and food-related duties; strong chemical streams need their own compatibility review. Give the supplier the fluid name and concentration as well as the line temperature. Include cleaning and shutdown conditions. A line that runs at 90°C with a mild product may see a 60°C caustic wash or an acidic rinse that is more aggressive to the cartridge than the normal process fluid. Continuous temperature, peak temperature, cleaning chemicals, and contact time all belong in the selection discussion. If the fluid is a solvent or strong acid, a PP cartridge may be the better chemical fit at a lower temperature, or a different media may be needed. The 1 to 300 micron range is nominal depth filtration. Select the micron rating for particle loading and downstream protection, and select the media and core for temperature and chemistry. Those decisions must agree.
What to Send a Supplier Before Selecting a High-Temperature Wound Cartridge
The fastest way to get a useful response from filter cartridge suppliers is to send the operating data in one package. Start with the fluid name, concentration, pH, and any solvents, oils, oxidizers, or cleaning agents. Add the normal continuous temperature and the peak temperature during startup, cleaning, or upset conditions. State the flow rate, allowable pressure drop, and current changeout interval. Then give the housing details: 10, 20, 30, or 40 inch length; 63 mm or 114 mm outer diameter; 28 mm or 30 mm inner diameter; and end connection. DOE, 222, and 226 connections each require the matching housing, so a photo of the housing and the old cartridge helps. For a high-temperature line, ask for the media and core as a named pair: “cotton fiber with a stainless steel core, 120°C” or “PP fiber with a galvanized iron core, 100°C” rather than “a high-temperature cartridge” in general. Give the required micron rating and the nominal depth filtration you expect. Ask how the supplier handles chemical compatibility review and what data they need to respond. If the line is in food and beverage service, raise food-contact requirements early; food-contact polymer compliance under 21 CFR 177 is a separate review from the temperature rating. Once the fluid, temperature, and connection are defined, a sample request can match the real installation.
Conclusion
The listed combinations are straightforward: PP with a plastic core at 65°C, PP with a galvanized iron core at 100°C, and cotton with a stainless steel core at 120°C. Chemistry makes the selection more specific. Match the core and media to the actual continuous and peak temperatures, then check the wetted materials against the fluid and cleaning regime. For a high-temperature process line, cotton with a stainless steel core is the combination that reaches the 120°C band. Send the fluid data, temperature profile, housing dimensions, micron rating, and connection type to EAST Filtration, and request a material-combination review, a sample, and a quote for the exact cartridge.
FAQ
Q: What is the maximum temperature for a cotton string wound filter cartridge with a stainless steel core?
A: Cotton fiber with a stainless steel core has a maximum working temperature of 120°C. This is the highest listed combination for the string wound filter cartridge family. Use the 120°C figure with the exact core grade named in the specification and with the fluid chemistry reviewed for the line. For a continuous 110°C process with occasional 120°C peaks, select the cartridge for the peak condition as well, and include the housing in the same review.
Q: Is a 120°C limit enough to confirm a wound filter cartridge for every chemical fluid?
A: No. The 120°C figure is a thermal limit for the cotton and stainless steel combination. Chemical compatibility is a separate review. A fluid can be within the temperature limit and still attack the cotton fiber, the stainless steel core, or other wetted components. Send the fluid name, concentration, pH, cleaning chemicals, and peak temperature to the supplier. The answer should be specific to that chemistry and wetted material set; a general acid or alkali statement is too broad for a real process line.
Q: When should a process line use polypropylene instead of cotton wound cartridges?
A: Use polypropylene when the line stays within the PP temperature band and the chemistry favors PP. PP fiber with a plastic core is rated to 65°C; PP fiber with a galvanized iron core is rated to 100°C. PP is often practical for water, many aqueous process fluids, and food-related pre-filtration where temperature is controlled. Move to cotton with a stainless steel core when the line needs the 120°C band and the fluid chemistry suits cotton. Base the decision on both temperature and chemical compatibility.
Sources / References
Polypropylene Polymer Reference
Stainless Steel - Grade 316 (UNS S31600)
CFR - Code of Federal Regulations Title 21
