The casing material on an AODD pump determines what it can handle and at what temperature. Getting this wrong means either buying a more expensive pump than you need, or buying one that fails in service. The Fluimac Phoenix range offers five casing materials — PP, PVDF, Aluminium, SS316, and POMc (Acetal) — and each has a distinct position in the selection matrix. Here’s how to choose.
Polypropylene (PP) — The Workhorse
PP is the default choice for most chemical applications in the mild-to-moderate range. It handles dilute acids, dilute caustics, many salts, and a range of aqueous process streams. It is lightweight, cost-effective, and well-understood in chemical processing environments.
Maximum fluid temperature for PP in the Phoenix range is 65°C. Above this temperature, PP begins to soften and lose dimensional stability — flange faces distort, gasket seats pull out of true, and leak paths develop. If your process operates at or near 65°C, allow margin: a pump body running at its material limit will drift out of specification faster than one operating well within its range.
PP is not suitable for aromatic hydrocarbons (toluene, xylene), chlorinated solvents, strong oxidisers (concentrated nitric acid, fuming sulphuric acid), or strong caustics at elevated temperature. For these, move to PVDF or SS316.
PVDF — Chemical Resistance at Higher Temperature
PVDF (polyvinylidene fluoride) is the step up from PP for aggressive chemistry and higher temperature. It handles concentrated acids including HF (at appropriate concentrations), chlorinated solvents, aromatic hydrocarbons, and strong oxidising agents that attack PP. Maximum fluid temperature in the Phoenix is 95°C — significantly higher than PP.
PVDF is heavier and more expensive than PP, but the chemical resistance justification is clear for the applications it’s designed for. In semiconductor, electroplating, and specialty chemical environments, PVDF is the standard choice.
Note that PVDF is not universally superior to PP. It does not handle strong caustics (NaOH, KOH at high concentration) as well as PP does, and it is attacked by ketones (acetone, MEK) and certain esters. Check the specific chemical and concentration against PVDF compatibility data — don’t assume it handles everything PP can’t.
SS316 — Metal When You Need It
SS316 is specified when operating pressure exceeds the limits of plastic casings, when mechanical robustness is required (high-vibration installations, impact risk), or when the fluid is incompatible with both PP and PVDF. Maximum fluid temperature is 95°C, matching PVDF.
SS316 is not universally chemically resistant. It is attacked by chloride-containing fluids (seawater, hydrochloric acid) at the concentrations and temperatures encountered in many process applications — a common mistake is specifying SS316 based on its general “stainless steel” reputation without checking compatibility with the specific process chemistry. For HCl, ferric chloride, or high-chloride brines, SS316 is typically the wrong choice; PVDF or Hastelloy are the alternatives.
SS316 Fluimac Phoenix pumps are also available with ATEX certification to the full range of zone and gas group options, which makes them useful in high-pressure or high-impact hazardous area applications where PVDF would be the chemical alternative.
POMc (Acetal) — The Niche Material
POMc (polyoxymethylene copolymer, trade names Delrin/Hostaform) is a semi-crystalline thermoplastic with good dimensional stability and low friction. In the Phoenix range, POMc provides the cleanest surfaces in the wetted path — it machines to very tight tolerances and has low porosity, which makes it useful in dosing and metering applications where consistent ball seat geometry matters.
Maximum fluid temperature for POMc is 80°C. Chemical resistance is intermediate — good for neutral to mildly acidic aqueous streams, but POMc is attacked by strong acids, oxidisers, and many organic solvents. POMc is not suitable for concentrated acid applications; it is typically found in water treatment dosing, food processing, and clean chemical applications.
Aluminium — Limited Chemical Applications
The Aluminium version of the Phoenix is primarily specified for solvents and hydrocarbons where a metallic casing is required but SS316 is overspecified or incompatible. Aluminium is attacked by strong acids and strong caustics, so it’s limited to near-neutral pH organic fluids — petroleum products, paints, adhesives, resins. Maximum temperature is 95°C.
For hazardous area applications involving aluminium-cased pumps, note that impact sparking from aluminium in certain gas atmospheres is a consideration — confirm ATEX compliance for the specific gas group before specifying aluminium in Zone 1.
The Temperature-Chemistry Matrix
To summarise the operating temperature limits from the Phoenix manual: PP and POMc (PC) are limited to 65°C fluid temperature in Zone 2 ATEX service. POMc (standard) is limited to 80°C. PVDF, SS316, and Aluminium are all rated to 95°C in Zone 2. For Zone 1 ATEX service, all materials are limited to 80°C regardless of the material’s individual temperature ceiling — this is set by the T4 temperature class calculation, not the material limit.
If you need help matching casing material to a specific chemical duty for a Fluimac Phoenix, contact us at info@autoflotechnology.com.