KOSA Filter · Application Engineering
Filter Housing Material Selection: 304 vs 316L vs PP/PVC-Coated
Choose a filter housing by the fluid chemistry, temperature, pressure and budget: 304 SS for mild duty, 316L SS for chlorides and CIP/SIP, polypropylene for corrosive non-metallic service, PVC-coated for low-cost chemical resistance. Compare before specifying.
Key Takeaways
- 304 SS housings suit mild, non-aggressive or dry duty at the lowest metal cost.
- 316L SS adds molybdenum — the default for chlorides, CIP/SIP and high-purity loops.
- Polypropylene (PP) housings resist many acids/alkalis and are non-metallic for ultrapure or plating duty.
- PVC-coated steel housings add chemical resistance cheaply for aggressive ambient service.
- Decide on fluid chemistry + temperature + pressure + budget, not the catalogue headline.
Match material to the fluid
The housing wall sees the full fluid, temperature and cleaning regime, so material choice is a corrosion and pressure decision first, then a budget one.
| Material | Fluid chemistry | Temperature / pressure | Budget & use |
|---|---|---|---|
| 304 SS | Mild, non-chloride, neutral | Good pressure; moderate temp | Lowest cost; utility/dry duty |
| 316L SS | Chlorides, CIP, acids | Higher temp/pressure | Default hygienic & pharma |
| Polypropylene | Acids, alkalis, non-metallic | Lower temp/pressure | Ultrapure, plating, corrosion |
| PVC-coated | Chemical-resistant coating | Ambient–moderate | Cheap corrosion upgrade |
How to decide
Start from chemistry. Chlorides and oxidizing cleaners pit 304 quickly, so any CIP/SIP or high-purity loop should specify 316L. For strong acids or where metal pickup is forbidden, a PP housing removes the corrosion and ion-leaching problem entirely — at lower temperature and pressure ratings.
- Pressure & temperature: metal housings carry higher ratings; PP and coated housings are limited — confirm the ASME / design pressure.
- Budget: 304 is cheapest metal; PP is mid; 316L and PVC-coated sit above 304 but avoid early failure.
- Validation: hygienic loops need 316L with a documented finish and material certs.
Selection checklist
1. Does the fluid contain chlorides or see CIP/SIP?
Specify 316L SS; 304 will pit in chloride or oxidizing-cleaner service.
2. Is the fluid strongly acidic/alkaline or metal-sensitive?
Choose polypropylene (or PTFE-lined) for non-metallic, corrosion-free duty.
3. What are the temperature, pressure and budget limits?
Metal for high ratings; PVC-coated or PP for low-cost chemical resistance within their limits.
Material guidance above is general engineering practice. Always verify against the exact fluid, concentration, temperature and pressure, and request material certs for validated lines.
Need a specification for your line?
Send your fluid, flow and hygiene class — we return a documented recommendation.
Contact KOSA KosafilterSuZhou KoSa · +86 512 57501864 · [email protected]
Frequently asked questions
When should I specify 316L instead of 304 for a filter housing?
Specify 316L whenever the fluid contains chlorides, sees CIP/SIP or oxidizing cleaners, or is a high-purity loop. The molybdenum in 316L resists pitting and crevice corrosion that quickly attacks 304, so it is the safe default for hygienic and pharmaceutical duty.
What is polypropylene used for in filter housings?
Polypropylene housings resist many acids and alkalis and are non-metallic, so they suit corrosive chemical service, plating, and ultrapure or metal-sensitive applications where stainless would corrode or leach ions. They carry lower temperature and pressure ratings than metal.
What does a PVC-coated housing give me?
A PVC-coated steel housing adds a chemical-resistant barrier over a low-cost metal shell, useful for aggressive ambient-to-moderate service where you want corrosion resistance without the cost of 316L or a full plastic moulding.
How do I choose housing material on a budget?
Start from chemistry and ratings, not price: 304 is cheapest for mild duty; 316L or PP prevent early failure in chloride/acid service; PVC-coated is a low-cost corrosion upgrade within its limits. Premature corrosion almost always costs more than the right grade upfront.