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2.20  Operation and System Optimization

2.21  High Pressure Operation

 

DUOSEAL two-stage pumps are designed to be most efficient when operated at or near their ultimate blanked off 

 

pressure.  The pump is designed to remove air from a vacuum system at atmospheric pressure to a deep vacuum. 

 

When the pump is operated at elevated pressures up to about 10 Torr for long periods of time, the pump will run 

 

hotter.  At elevated ambient temperatures under these conditions, the thermal protection switch on single phase 

 

motors may cut out.  Use of an exhaust filter with coalescing element is required.

 

Leaky vacuum systems, too large a vacuum chamber for pump size or high gas loads to the vacuum systems 

 

are causes for extended runs of the pump at elevated pressure.  If you need additional information, please contact 

 

Welch Vacuum at 847-676-8800, extension 1, for further information and precautions.

2.22  Principle of Gas Ballast

2.221  Effects of Unwanted Vapor

 

Systems which contain undesirable vapors cause difficulty both from the standpoint of attaining desirable ultimate

  

pressures as well as contamination of the lubricating medium.  A vapor is defined as the gaseous form of any 

 

substance which is usually a liquid or a solid.  Water, oil and a mercury vapors are three of the more common 

 

vapors encountered in typical vacuum systems.  When such vapors exist in a system, the vapors or mixtures of 

 

gas and vapor are subject to condensation within the pump; the precipitated liquid may thus ultimately dissolve 

 

or become emulsified with the lubricating medium.  This emulsion is recirculated to the chambers of the pump 

 

where it is again volatilized causing increased pressure within the system.

2.222  Presence and Removal of Condensate

 

Condensation takes place particularly in the compression stroke of the backing or second stage of a two-stage 

 

pump.  The compression stroke is that portion of the cycle during which the gas drawn from the intake port is 

 

compresses to the pressure necessary to expel it past the exhaust valve.  Condensation takes place when the ratio 

 

between the initial pressure and the end pressure of the compression is high, that is, when the mixture of vapor 

 

and gas drawn from the intake port is compressed from a low pressure to high pressure.  By adding air though the

  

gas ballast valve to the mixture of vapor and gas being compressed, the pressure required for delivery past the 

 

exhaust valve is reached with a considerably smaller reduction of the volume of the mixture; this, depending upon 

 

the amount of air added, condensation of the vapor is wither entirely avoided or substantial reduced.

2.223  Pump Function With Gas Ballast

 

In a pump functioning on a contaminated system and operating without the gas ballast, compression within the 

 

stage takes place in the normal manner until the saturation pressure of the contaminating vapor contained within

 

the mixture of gas and vapor is reached.  The saturation pressure of water vapor is that pressure and corresponding 

 

temperature at which the dew point of the vapor is reached and condensation occurs.  The saturation pressure of 

 

water vapor at an ambient temperature of 20°C is 17.5 Torr, while at 60°C, the approximate operating temperature

 

of a pump, the saturation pressure is 149 Torr.  The external side of the exhaust valve is subjected to atmospheric 

 

pressure.  Consequently a compressive force somewhat greater than atmospheric pressure is required to open the 

 

valve and permit expulsion of the gas.  Sometime during increased compression of the mixture of gas and vapors, 

 

the saturation pressure of 149 Torr for the water vapor is reached and the vapor condenses.  The condensate is 

 

then allowed to emulsify with the oil which is recirculated within the pump stages this providing continued 

 

contamination of the system.

2.224  Pump Function With Gas Ballast

 

On the other hand, when ballast air at atmospheric pressure is supplied to the compression stroke by means of the

 

gas ballast, the partial pressure of the unwanted vapor becomes a very small part of the total pressure of the 

 

mixture of gas, vapor and newly supplied air.  The vapor is thus prevented from reaching its saturation pressure 

 

corresponding to the temperature of the pump and is finally expelled form the pump as a vapor.

2.225  Controlled Ballast Flow

 

Some degree of variation in ballast flow may be obtained by the amount of opening applied tot he gas ballast.  

 

Two or more turns of the gas ballast are sufficient to open it wide.  With the gas ballast open, the sound of the 

 

exhaust is similar to that of a pump operating against a large leak.  Because of the increased pressure introduced 

 

into the compression stroke, the pump must work a little hard to function, thus resulting in an increased 

 

operating temperature of approximately 8°C over a prolonged period of time.  Tests have shown that continuous 

 

and prolonged operation for several weeks under these conditions is not injurious to the pump.

CAUTION

Do not run this pump for prolonged periods of time at or above

10 Torr.  The  pump will overheat, excessive oil mist will be 

emitted from the exhaust and the pump will eventually seize.

Summary of Contents for Welch Duoseal 1402C-46

Page 1: ...pump body bursting and causing possible injury to personnel in the area Gardner Denver Inc Welch Vacuum Technology 5621 W Howard Street Niles IL 60714 Phone 847 676 8800 Fax 847 677 8606 Technical Su...

Page 2: ...ons are found where failure to observe the instruction could result in damage to the equipment associated equipment and process These units confirm to the SI International system of units of measureme...

Page 3: ...vel 10 3 30 Shaft Seal Replacement 10 3 40 Repairing Oil Leaks 11 3 50 Repairing Vacuum Leaks 11 3 60 Drive Problems 11 Section 04 Trouble Shooting Guide 4 10 Poor Vacuum Readings 12 4 20 Noisy Pump 1...

Page 4: ...SEAL pumps should be mounted in a horizontal plane 1 122 Unmounted Pumps If you have purchased an unmounted pump refer to parts list for information concerning the motor motor pulley and belt necessar...

Page 5: ...e gas flow is substantially molecular in character The gas flow is then dependent upon the kinetic activity of the molecules to bring it to the intake of the pump 1 162 The Effects of Conductance It h...

Page 6: ...e yourself with the function and action of the pump which you have now required Remove the intake and exhaust port plugs and temporarily provide a stopper for the intake and a dust cap for the exhaust...

Page 7: ...f the volume of the mixture this depending upon the amount of air added condensation of the vapor is wither entirely avoided or substantial reduced 2 223 Pump Function With Gas Ballast In a pump funct...

Page 8: ...rich in hydrogen and observing a sudden change in pressure on an electrical gauge The difference in calibration of these gauges for air and other gases will produce a distinct change in the pressure...

Page 9: ...a system must be thoroughly clean If the system is completely clean and free from leaks and unwarranted vacuum problems still exist the pump should be checked A simple criterion for the condition of a...

Page 10: ...rubber stopper Turn the pump on and run the pump for 10 minutes Close the gas ballast 8 Check the vacuum reading of the pump by connecting a thermocouple gauge tube to the pump s intake If the pump is...

Page 11: ...ng surfaces cleaned of any nicks 3 50 Repairing Vacuum Leaks 3 501 Surface Preparation Good Vacuum seals are an essential and important attribute of a good mechanical pump A good seal is dependent upo...

Page 12: ...t a forced oil flush 5 If noise level is still unsatisfactory consult with WELCH Technical Service at 847 676 8800 Ext 1 4 30 Excessive Oil Mist 1 Check oil level Maintain the level between the two li...

Page 13: ...l Requirements 3 1 Phase Replacement Parts Shaft Seal Lip Seal 1401D 01 Shaft Seal Mechanical Seal 1401D Air Filter Screen 41 0660 Intake Chamber Cover Gasket 41 0234 Oil Case Gasket 41 0403 Drain Plu...

Page 14: ...14 Section 6 DIMENSIONAL DRAWING...

Page 15: ...ange High RPM direct drive vacuum pumps on the other hand experience a rapid fall off of pumping speed below 100 microns A comparison of the DuoSeal pumping speed curves shown below versus high RPM pu...

Page 16: ...tion 8 EXPLODED VIEW 1 46 34 5 24 31 52 53 15 27 46 5 24 51 25 49 30 6 28 12 8 39 29 40 44 35 54 41 42 11 43 45 10 12 50 9 26 28 36 25 33 23 7 55 22 57 56 4 2 16 47 3 32 59 14 13 20 18 17 38 48 58 19...

Page 17: ...5 1 41 2175 SETSCREW 1 4 20 x 2 25 LG 16 1 41 0234 1 1 GASKET INTAKE CHAMBER COVER 46 6 41 2363 WASHER 5 16 ID x 1 2 OD 17 1 41 0403 1 1 GASKET OIL CASE 47 1 41 2757 LOCK NUT 18 1 41 0508 1 1 WASHER T...

Page 18: ...101 Parts List for Model 61 8101 Item Qty P N Description 1 2 61 2229A Oil Window Glass 2 1 61 2278 Drain Valve 3 2 61 2370 Oil Window Cover 4 1 61 8833 Oil Case Machined 5 4 62 1014 Screw 8 32x3 8 Fl...

Page 19: ...onnection kit Cat No 141601 for models1400 1405 1376 1380 1402 Standard Exhaust Filter Use with pump model Dimension Catalog Number Diameter Height Filter Replacement Element 1392 1399 1400 1376 1380...

Page 20: ...Height A2 Cat No 1 NW16 to 4 CFM 140 L min 3 75 5 25 8 25 541001 Stainless Steel Element for ISO NW 16 Trap 1 541921 Stainless Steel Element for ISO NW 25 and NW 40 Traps1 541922 Removable 3 quarter...

Page 21: ...significant adverse health effects are expected to occur upon short term exposure to this product Aspiration of liquid into the lungs can cause severe lung damage or death Eye Contact Minimal eye irri...

Page 22: ...ir Eye Contact Check for and remove contact lenses Flush eyes with cool clean low pressure water while occasionally lifting and lowering eyelids Seek medical attention if excessive tearing redness or...

Page 23: ...ct recovery or disposal Prevent entry into waterways or sewers In urban area cleanup spill as soon as possible In natural environments seek cleanup advice from specialists to minimize physical habitat...

Page 24: ...c vapor respirator equipped with a dust mist prefilter should be used Protection factors vary depending upon the type of respirator used Respirators should be usedin accordance with OSHA requirements...

Page 25: ...product However if spilled this product and any contaminated soil or water may be harmful to human animal and aquatic life Also the coating action associated with petroleum and petroleum products can...

Page 26: ...rd categories No SARA 311 312 Hazard categories identified SARA 313 This product contains the following components in concentrations above the minimis levels that are listed as toxic chemicals in 40 C...

Page 27: ...for Research on Cancer NTP National Toxicology ProgramNIOSH National Institute of Occupational Safety and Health OSHA Occupational Safety and Health Administration NPCA National Paint and Coating Man...

Page 28: ...um Technology and receipt or possession does not convey any rights to loan sell or otherwise disclose said information reproduction or use of said information for any purpose other than that in connec...

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