Changing a diffusion pump from 704 to 705 and validating the fluid change-Iota

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News > Dynamic industry > Changing a diffusion pump from 704 to 705 and validating the fluid change

Changing a diffusion pump from 704 to 705 and validating the fluid change

Changing a diffusion pump from 704 to 705 and validating the fluid change

Do not treat direct topping-up and mixing as the default changeover method. First confirm the pump manufacturer’s permitted fluids, the existing fluid’s identity, maintenance condition and specified charge. Replace it according to the applicable manual. Acceptance must cover pumpdown, stable pressure, cooling and backing conditions, rather than the new fluid’s name or a single vacuum reading.

Start with the published information for IOTA 704 diffusion pump fluid. If considering a 705 route, compare IOTA 705 diffusion pump fluid. Both require selection against equipment conditions. This article does not promise any system ultimate pressure merely by switching to 705.

Why the fluid number does not justify topping up

The diffusion-pump manual states that fluids of different types and sources must not be mixed, and advises that old and new fluid should generally not be combined as one pump charge. These instructions apply to the equipment covered by that manual. For other equipment, consult its manufacturer’s documents; do not invent a universal mixing ratio.

A uniform-looking mixture does not validate evaporation under heating, pumping or residue behaviour. Adding fresh fluid to contaminated or degraded fluid also retains the existing contamination load. Even topping up the same grade requires identifying the loss mechanism and confirming permission and procedure in the equipment instructions.

Information to establish before changing fluid

Item	What to confirm	Effect on the change
Equipment	Manufacturer, model, permitted fluids and charge	Establish whether the candidate is approved
Existing fluid	Product, source, batch, maintenance and mixing history	Determine residue and cleaning needs
Backing system	Backing-pump condition, backing pressure and valves	Rule out causes unrelated to the fluid
Cooling and heating	Water circuit, flow requirements, interlocks and heater	Confirm manual-compliant operating conditions
Process load	Process gases, water vapour, solvents, load and outgassing	Define actual trial conditions
Measurement	Gauge type, location, condition and gas correction	Make before-and-after data comparable

If the existing fluid is unidentified, treat that as a maintenance anomaly; colour cannot identify 704 or 705. If the manual does not permit the candidate, consult the manufacturer before proceeding. A material supplier’s application statement is not equipment approval.

Follow the equipment manual for maintenance

1. Record the existing pumpdown curve, stable pressure, backing performance and process load. If a fault already exists, leak-test and check backing and cooling first. Retain an old-fluid sample.

2. Qualified or appropriately trained maintenance personnel must shut down, isolate energy and cool the equipment according to the manual. Do not independently vent, open or drain a pump while it is hot or operating with the heater on.

3. Drain according to the manual and inspect the body, jet assembly and residues. Use equipment-approved cleaning agents, seal-compatibility checks and drying procedures; do not copy another model’s solvent recipe.

4. After cleaning, drying and reassembly, add the confirmed fluid at the specified charge and record product and batch. Do not increase the charge to compensate for pumping faults.

5. Check cooling, backing, valves and interlocks, then follow the startup procedure. Maintenance temperatures, pressures and waiting times must come from the corresponding manual.

Evaluating results after the change

Stage	Records needed	Acceptance focus
First startup	Heating, cooling, backing and anomalies	Normal operating conditions established as prescribed
Unloaded pumpdown	Initial conditions and pressure over time	Leaks, outgassing or measurement differences
Steady operation	Stable pressure, backing pressure and cooling	Equipment criteria met under equivalent conditions
Actual process	Identical load, gases and production cycle	Production requirements and contamination limits
Subsequent maintenance	Level, appearance, residue and repeat-run trends	Persistent loss or abnormal degradation

One improved pressure reading does not prove long-term suitability. Keep gauge location, load, bakeout or degassing conditions consistent and use agreed equipment and application criteria. Material or test data in a product sheet do not directly represent an entire system with valves, pipework, baffles and process loads.

IOTA Silicone Oil (Anhui) Co., Ltd., a provider of solutions across the silicone value chain, can help review IOTA 704 and IOTA 705 candidate data. Provide pump model, existing fluid identity, approved fluids, process load, maintenance history and acceptance requirements before agreeing sampling and validation.

FAQ

Q1 Can similar-looking 704 and 705 be mixed directly

Appearance is insufficient. Check approved fluids and maintenance documents; without clear authorization, do not mix by topping up.

Q2 Does switching to 705 guarantee lower pressure

Pressure also depends on leaks, outgassing, backing, cooling and measurement. Make comparable trials only where the equipment permits the fluid.

Q3 Can some old fluid remain if its colour looks normal

Colour does not establish contamination or degradation. Drainage and cleaning requirements depend on maintenance documents and actual condition.

Q4 Does adding more fresh fluid improve pumping

Use the specified charge. Overfilling cannot remedy leaks or other pumping faults.

Q5 Does high pressure after a change prove the fluid is unsuitable

Check measurement, leaks, outgassing, backing, cooling, residues and reassembly before assessing the candidate. Do not attribute every issue to the fluid.

Q6 Can another pump’s cleaning procedure be copied

Check model, materials and manufacturer procedures first. Fluid, cleaning and reassembly requirements may differ.