Replacing AX Series pumps on elevated-temperature duty

The AX Series uses a grease-lubricated bearing frame and a single cartridge seal with FKM secondary elastomers. Both are limited by the elastomer, not the casing: FKM loses compression set above approximately 200 °C, and the grease film breaks down well before that at the bearing temperatures reached by a close-coupled hot duty. The published 120 °C continuous limit carries margin for a hot-standby excursion. It is not a conservative number that can be exceeded on advice.

For an AX-220 duty moving into the 150–205 °C band, the PX-440 is the standard selection. It shares the DN50 ANSI 150# suction and discharge connections, so existing pipework lands without modification, and the PX-440 overall length of 880 mm sits within 5% of the AX-220's 840 mm — inside the tolerance for reusing an existing grouted baseplate, subject to a site check of the coupling gap. The PX-440 carries a finned bearing housing with oil lubrication and a SiC/SiC cartridge seal with flexible graphite secondaries, which is what buys the temperature headroom.

Above 205 °C continuous, step to the PX-460 (230 °C) or PX-480 (300 °C). Be aware that the PX-460 is a longer frame at 1010 mm and will not reuse an AX-220 baseplate. Below 55 m³/h the PX-400 is the cheaper selection, but it will not cover an AX-220 duty point at full flow. The PX-420 is hydraulically adequate for most AX-220 duties but carries a DN40 suction, which means either an adapter kit or a re-pipe on a DN50 line — quote the PX-422 instead where the pipework is DN50.

Confirm NPSH available at the site. The PX-440 requires 3.1 m against the AX-220's 2.8 m, and a suction-limited installation that was marginal with the AX-220 will cavitate with the PX-440. Confirm the coupling and guard are rated for the PX frame — the AX spacer coupling CP-100 fits, but the guard bracket differs. Confirm insulation and personnel protection: a 180 °C casing is a burn hazard the AX installation did not present.