Vacuum Technology Simplified

Boiling Temperature of Diffusion Pump Oil Explained

A lot of confusion exists in the vacuum industry about certain things, for example-

· What should the optimum temperature be set in diffusion pump heaters so as to get maximum level of vacuum in shortest possible time?

· How can the temperature in diffusion pumps be set in such a way that the engineers are able to get maximum life from costly diffusion pump oil?

· Is boiling temperature of silicone diffusion pump oil different from hydrocarbon diffusion pump oil?

Before attempting to understand optimum boiling temperature of diffusion pump oil, let us take a brief look about working of diffusion pump.

http://supervacoils.com/rotary-vacuum-pumps-oils/

Since efficiency of diffusion pump depends solely on the working cycle of diffusion pump oil (diffusion pump has no moving parts) so this is evident that a higher diffusion pump temperature will mean a higher ultimate vacuum. Obviously a question comes to mind at this stage that why don’t we increase the boiling temperature to highest possible level. Answer to this is that increasing the temperature of diffusion pump oil involves financial implications (cost increase) because of the following reasons -

1. Diffusion pump oil works in very difficult environment where there is vacuum and high temperature. So to increase the boiling temperature, superior (obviously costlier) oil will be required which is capable of withstanding these adverse conditions.

2. At higher temperature O-rings and oil seals may give way so better quality sealing material is required (Costly again).

3. For handling higher temperature, construction of diffusion pump also has to be stronger.

4. For attaining higher temperature higher energy charges will be incurred.

5. For obtaining higher temperature longer time is required so vacuum time increases.

Decision about boiling temperature is basically a balance between level of vacuum required and cost incurred. Our guideline in line with the established practice in the industry is as below -

S. No.	Vacuum Required	Temperature in Diffusion Pump	Supervac Products	Equivalent Products
1.	10^-9to 10^-10 Torr	245^oC	SV-SIGMA+	DC-705
				Hivac F5
2.	10^-7to 10^-8 Torr	220^oC	SV-SIGMA	DC-704
				CVC4
				Hivac F4
				Ulvoil D31
3.	10^-5to 10^-6 Torr	180^oC	SV-SIGMA FAST	DC-702

Some myths are prevalent in the industry about diffusion pump oils. These are clarified as under-

Myth no.1: Boiling temperature of hydrocarbon diffusion pump oil is different from boiling temperature of silicone diffusion pump oil- This myth is baseless as boiling temperature of both hydrocarbon and silicone diffusion pump oil is same. For example- Well known hydrocarbon diffusion pump oils like Supervac SV-DELTA, Lion S, Ulvoil D11 and CVP300, all have boiling temperature of 220^oC.

Myth no.2: My diffusion pump has been designed for hydrocarbon/silicone diffusion pump oil only- This is also false. You can use any diffusion pump oil (hydrocarbon or silicone) in any diffusion pump based on your requirement. For details about merits of hydrocarbon and silicone diffusion pump oil please read my blog post-http://supervacindustries.blogspot.in/2013/04/silicone-diffusion-pump-oil-vs.html

diffusion pump fluid-silicone-hydrocarbon

Myth no.3: My equipment manufacturer asks me to use only a particular brand of diffusion pump oil which is exorbitantly priced- Your equipment manufacturer is trying to fleece you. For details about equivalent vacuum oils manufactured by reputed and established manufacturers anywhere in the world please read our blog post at- http://supervacindustries.blogspot.in/2014/03/vacuum-oil-equivalents.html. In case you don’t find it there then please contact us. We will help you find an equivalent product.

Myth no.4: There is no need of topping up- Absolutely false and dangerous myth prevailing in the industry. Topping up at regular intervals is of utmost importance to get proper vacuum and avoiding damage to the equipment.

Myth no.5: Charging less diffusion pump oil in diffusion pump reduces vacuum time- Absolutely false. Charging less oil than required will cause back streaming, burning of diffusion pump oil and damage to costly equipment.

Myth no.6: My diffusion pump oil works at 170^oC- Diffusion pumps do not work at temperature below 180^oC. Your oil supplier is supplying you cheaper vapor jet booster pump oil.

Conclusion:-

Based on the information given above I am sure that you will be able to choose the right diffusion pump oil as per your requirement. For example- if level of vacuum required is only up to 10^-5 Torr and equipment is old then hydrocarbon diffusion pump oil will work more economical. Similarly if vacuum level required is 10^-7 Torr then there is no point in using SV-SIGMA+. Furthermore by using simple precautions like frequent topping up you can get a much longer life and value for money from your diffusion pump oil.

manufacturers and suppliers of vacuum pump oil

For more helpful tips about how to get your money’s worth from your diffusion pump oil, you can read my blog post- http://supervacindustries.blogspot.in/2013/09/how-to-get-maximum-life-from-your.html

Written by: Anshuman Punj.

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Roots Blower Booster Vacuum Pump Oil

Roots Blower Booster Pumps

Roots Blower Booster Pump:

These pumps work on the principle of positive displacement of gas. The Roots pump consists of two impellers called roots in the shape of figure 8. These impellers are mounted on parallel shafts in a single cylinder having inlet and outlet openings on the sides. The impellers, through synchronized rotative timing, are maintained in a relative position to each other and rotated in opposite directions without any internal contact and at a very high speed measuring a couple thousand or more rpm. The operating clearances are very small, measuring just a few microns– only a few thousandths of an inch - in order to keep back leakage to a minimum.

The following diagram shows how the rotation of impellers traps and pushes the gas/air out. The positive displacement works in a continuous flow to create vacuum.

Choose the Right Type of Lubricant

Often, out of ignorance, cost-cutting or any other reason, people use ordinary machine oil, automotive lubricants, gear oils or even normal rotary pump oil in these booster pumps. Since these oils do not have properties required for safe running of Booster Pumps, this leads to serious damage to the pump. Repairing a booster pump is nearly impossible without a complete overhaul which costs a lot while a new pump too costs lakhs of rupees. Choosing the right lubricant for the booster pump is the best type of insurance one can bank upon. A suitable, high quality booster pump oil is the pump’s primary protection against wear, pitting, spalling, scoring and scuffing of moving metal parts. The following pictures demonstrate the type of damage that can occur due to –

1. Wrong choice of lubricant

2. Not topping up at the right time, so the metal parts are not well-oiled.

prevent pitting in your pump use Supervac Roots booster pump

Careful selection of lubricant goes a long way in saving the machinery thereby preventing loss of time and money.

When it comes to choice of lubricant – One size DOES NOT fit all

Different vacuum processes require different types and grades of vacuum oil.

Supervac Roots Blower Vacuum Lubricants:

After careful actual testing on Roots blower pumps, Supervac has formulated Roots blower vacuum oil in two grades-

1. Hydro-carbon based booster pump oil- SV-90H

http://supervacoils.com/organic-roots-blower-pump-oil-sv-90h/

2. Silicone based booster pump oil- SV-90S

http://supervacoils.com/silicone-roots-blower-pump-oil-sv-90s/

Both are suitable for all makes and sizes of Roots Booster pumps all over the world.

Specifications:

SV-90H (Hydrocarbon)		SV-90S (Silicone)
Property	Value	Property	Value
Vapor Pressure at 25⁰C	Below 1x10^-4 Torr	Vapor Pressure at 25⁰C	Below 1x10^-4 Torr
Flash Point	270⁰ C	Flash Point	300⁰ C
Viscosity at 40⁰ C	90 cst	Viscosity at 40⁰ C	90 cst
Pour Point	Below (-) 10⁰ C	Pour Point	Below (-) 15⁰ C
Appearance	Pale Yellow	Appearance	Water White
Packaging	(20 Ltrs.) (210 Ltrs.)	Packaging	(20 Ltrs.) (210 Ltrs.)
Equivalent	Edwards Stokes- V lube Grade H oil Lubricant	Equivalent	Roots Synthetic Lubricant ISO VG 320 LVO 210 GS 555 HE 600

Supervac Roots Blower vacuum pump oils have the following properties-

1. Excellent lubrication

2. Heat dissipation

3. Protection of the pump machinery

It carries damaging wear debris away from contact zones.

Offer extreme temperature and pressure protection in order to prevent wear, pitting, spalling, scoring, scuffing and other types of damage that result in equipment failure and downtime.

Protection against-

1. Oxidation

2. Thermal degradation

3. Rust

4. Copper corrosion and

5. Foaming.

Pump parts come in contact with different types of contaminants like water, corrosive chemicals and surface wear debris which can cause serious and irreparable equipment failure.

What is special about Supervac Roots Blower Vacuum Pump Oils?

Supervac Roots Blower lubricants have been formulated specially for Roots Booster vacuum pumps (also called positive displacement pumps) and are loaded with the following features –

Viscosity index improvers – Supervac brand Roots Blower pump oils have the viscosity - 90 cst at 40⁰ C which is ideal for functioning of the pump. Special viscosity index improver additives make them work superbly in hot as well as cold climates.

Anti-foam additives –Impellers inside the pump are moved by gears at a very high speed (2000 or more rpm) and oil on them is churning at that point. Ordinary gear oil is likely to form foam. Formation of foam in Roots Blower pump is absolutely unwanted in a vacuum system. Just a trace amount escaping into the chamber can wreak havoc to the entire process. Supervac Roots Blower oils have been specially formulated keeping this important property in mind.

Wear protection additives – Along with lubrication, Supervac Roots Blower oils protect the machinery against wear like pitting, spalling and scuffing thereby enhancing the machinery life.

Corrosion inhibitors – Special additives in these oils resist corrosion caused by strong toxic process gasses.

Extremely high film strength

Low co-efficient of friction

Warning:

1) Supervac DOES NOT recommend the use of automotive lubricants or gear oils for Roots Blower pumps as they DO NOT have the above mentioned properties which are absolutely necessary for vacuum booster pumps.

2) Topping up of Booster Pump oil is absolutely essential to prevent pump damage. If level of oil falls below required level, immediately make up the level by adding more oil.

As is evident from the above diagram, a whopping 89% of the problems related with booster pumps are lubricant related. Merely choosing a good pump is not enough. If money’s worth is to be taken out of that pump then it has to be run with the right oil and regular and timely topping up ensured.