Technical Answers
The questions engineers actually send us, answered at the length they deserve — with the reasoning, the numbers to check, and what to do when the answer is “this is the wrong pump for the job”.
On clean, dry air duty: every 3,000 to 6,000 running hours. But that number is a starting point, not a rule — what actually sets the interval is what …
Rotary Vane Pumps · Read →What size vacuum pump do I need for my chamber?Size on three numbers, not one: chamber volume, the pressure you need to reach, and the pump-down time you can accept. Pumping speed alone will mislea…
Rotary Vane Pumps · Read →What backing pump does a turbomolecular pump need?A turbo pump cannot start against atmosphere — it needs a backing pump to bring the foreline into the low mbar range first, and to keep it there while…
Turbo Molecular Pumps · Read →Why is my turbomolecular pump not reaching its rated ultimate pressure?Work through it in this order — foreline pressure, then leak, then outgassing, then the gauge, then the pump itself. The order matters because the fir…
Turbo Molecular Pumps · Read →Can a rotary vane pump handle water vapour?Yes — but only with the gas ballast valve open, and only within the pump's stated water-vapour tolerance. Run it without gas ballast and the vapour co…
Rotary Vane Pumps · Read →Why does the helium background stay high after pumping down?Four causes, and they are distinguishable by how the signal behaves over time rather than by how high it is: helium dissolved in elastomer seals, heli…
Helium Leak Detectors · Read →How do I choose the ratio between Roots pump and backing pump?A speed ratio of roughly 4:1 to 6:1 — Roots to backing pump — is the common industrial range. Going wider raises the differential pressure across the …
Roots Pumps · Read →Diaphragm, scroll or rotary vane — which should I choose?Choose on two questions, in this order: what pressure do you actually need, and can your process tolerate oil? Everything else — price, noise, service…
Diaphragm Pumps · Read →Gate, angle, butterfly or pendulum — which vacuum valve do I need?Pick on two things first: whether the valve has to isolate against full differential pressure, and whether it has to get out of the gas path when open…
Vacuum Valves · Read →Pneumatic, electric or manual actuation — how do I choose?Choose on cycle count and on what utilities you already have at the machine. A valve that opens twice a shift and a valve that cycles with every wafer…
Vacuum Valves · Read →What leak rate should a vacuum valve have, and when do I need an all-metal one?Read two numbers, not one: the leak rate across the closed seat, and the leak rate of the valve body to atmosphere. They are different specifications …
Vacuum Valves · Read →KF, CF or ISO — which vacuum flange should I use?Pressure range decides it, and size decides the rest. KF for rough and high vacuum up to small sizes, ISO for the same pressure range in larger bores,…
Vacuum Fittings & Flanges · Read →FKM, EPDM or copper — which vacuum seal material should I specify?FKM (Viton) is the default and covers most industrial vacuum work. Move off it for a specific reason: EPDM when your process fluid attacks FKM, and me…
Vacuum Fittings & Flanges · Read →When do I need a vacuum bellows, and how do I size one?Fit a bellows when two rigid parts of the system must move relative to each other — thermal growth, pump vibration, or an alignment mismatch you canno…
Vacuum Fittings & Flanges · Read →Which ion source filament does my helium leak detector take?Find your detector in the table below and read off the part number. The ion source filament is the electron emitter of the mass-spectrometer cell: it …
Helium Leak Detectors · Read →My vacuum pump oil has turned milky white — what does it mean and can I save the pump?Milky oil is water in the oil. The oil and the water have been whipped into an emulsion inside the pump chamber, and the pump is now running without a…
Rotary Vane Pumps · Read →The oil has gone black (or thick) — is that normal wear or a warning?Black and thick are two different faults with two different causes, and they are worth telling apart before you order anything. Black means the oil ha…
Vacuum Pump Oil & Grease · Read →When should I change the tip seals on a dry scroll pump, and what happens if I wait?Change them on hours, not on symptoms. Most manufacturers put the interval between 8,000 and 16,000 running hours on clean duty — Edwards nXDS is 16,0…
Dry Scroll Pumps · Read →Vacuum has got worse but the pump sounds and draws current exactly as before — where do I look?Look for internal clearance, not for a leak. A failure that changes noise or current is mechanical; a failure that changes only the pressure is almost…
Vacuum Parts & Components · Read →My liquid ring pump will not pull the vacuum it used to — what do I check first?Measure the seal-liquid temperature before you touch the pump. On seven or eight cases out of ten that is the whole answer, and it costs nothing to ch…
Liquid Ring Pumps · Read →The motor current on my dry pump keeps creeping up — what is happening inside?Powder is building up in the stages and closing the clearances. Rising power draw at the same duty point is the earliest signal a dry pump gives, and …
Dry Screw Pumps · Read →Shimadzu TMP-V2304LM: when do the bearings need replacing, and what does it cost you to wait?The TMP-V2304LM is a magnetically levitated turbomolecular pump, so the bearings people ask us about are almost always the touch-down bearings, not ru…
Turbo Molecular Pumps · Read →Pfeiffer / Adixen ASM leak detectors: which 3G analyzer cell filament do I need, and why do they keep failing?For the 3G analyzer cell used in ASM 310, ASM 340, ASM 380 and ASM 390, the filament part numbers you will see are 129108S and 114864S. The ASM 142 / …
Helium Leak Detectors · Read →Pfeiffer HiPace 80: when does the operating fluid reservoir need changing, and what happens if you skip it?Pfeiffer schedules it as Level 1 maintenance, typically every four years or at the interval the controller reports, whichever comes first. The part is…
Turbo Molecular Pumps · Read →Internal calibrated leak on an ASM detector: how often does it need recertifying, and can I keep using an expired one?Once a year is the normal recertification interval, and the reason is physical rather than bureaucratic: a permeation-type calibrated leak empties. Th…
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