Pumping & Compressing Gases

Using a liquid, steam or air to entrain gases

Using Liquid

Liquid Jet Exhausters

Liquid Jet Exhausters are simple, efficient and versatile devices for vacuum pumping or mixing liquids and gases. Using liquid under pressure as the only motive force, these units are ideal for handling mixtures or condensable and non-condensable gases.

Exhausters are manufactured in two varieties, a Single Nozzle Exhauster and a Multi Nozzle Exhauster. Single nozzle exhausters are standard units, and are similar in design to the Liquid Jet Eductor. Multi nozzle exhausters have much higher air or vapor handling capacities at lower pressures and are ideal where the motive liquid supply is limited.

Liquid jet exhausters are manufactured in a variety of materials however these are typically Carbon Steel, Stainless Steel and Bronze, special materials such as Hastelloy are also available. Unit sizes range from 3/4 Inch to 6 Inch for the Type 484 Single Nozzle Exhauster, and from 3 Inch to 10 Inch for the Type 488 Multi Nozzle Exhauster. Connections for all units can be either screwed or flanged depending up on size.

(Image - Type 484 Liquid Jet Exhauster)

Typical Exhauster Applications

Liquid Jet Exhausters have been used in many different industries for different purposes. Generally, their applications can be divided into three main categories, each of which can be seen below:

  • Pump priming
  • Pumping and mixing of liquids and gases, including entraining free air or vapours
  • Evacuating closed vessels

Priming a centrifugal pump

The exhauster is mounted on the pump casing in a manner similar to that shown and is used to exhaust air from the casing and suction line before starting the pump. In normal installations the vacuum required varies from that equivalent to 1.5 meters water lift to a 6 meter water lift.

Note - the motive liquid temperature is the primary limiting factor of operation, for very low suction pressures consideration must be given to the motive liquid vapour pressure to prevent it from flashing to a gas/vapour.

(Image - Priming centrifugal pumps)

Vacuum Pumping

This is a simple laboratory arrangement for obtaining low suction pressures with a Liquid Jet Exhauster using chilled water at about 2 degrees Celsius. Depending up on the available motive water temperatures, this system can provide suction pressures approaching 5mm HgA. Unlike other types of equipment, Liquid Jet Exhausters are compact, low in cost and require no lubrication or oil seals.

Note - the motive liquid temperature is the primary limiting factor of operation, for very low suction pressures consideration must be given to the motive liquid vapour pressure to prevent it from flashing to a gas/vapour.

(Image - Creating vacuum)

Evacuating a closed tank or vessel

This is a typical system for evacuating a closed vessel. In order to reduce overall evacuation time before operating the exhauster steam can be used to flush or purge air from the vessel as the exhauster will condense any steam remaining in the treating chamber. If a steam purge is not available, the exhauster will work equally well with any condensable or non-condensable gas.

Note - the motive liquid temperature is the primary limiting factor of operation, for very low suction pressures consideration must be given to the motive liquid vapour pressure to prevent it from flashing to a gas/vapour.

(Image - Evacuating closed vessels or tanks)

Using Steam

Steam Jet Syphons

Steam Jet Syphons operate on the steam jet principle utilising the energy of steam under pressure to pump, mix liquids and handle solids. In operation syphons use the kinetic energy of motive steam to entrain another liquid or slurry, completely mix the two, and then discharge the mixture against a head or counter pressure.

Syphons can be used for the handling of corrosive or abrasive liquids and solids because of their design simplicity and the absence of moving parts. They are also especially well suited for processes where heating is required in addition to pumping since the pumping is accomplished for the cost of the heating.

Steam Jet Syphons are used in large numbers throughout industry for pumping, mixing and heating operations, some of their uses can be seen below:

  • Intermittent pumping of liquids from tanks, pits, sumps and bunds
  • Pumping filtrate from vacuum vessels and condensate from surface condensers
  • Supplying heated water to the jackets of stills and graining bowls
  • Removing liquid from pickling baths, Extracting chemicals in reaction chambers
  • Moving powdered material or material in granular form, Filling and emptying gas holder tanks
  • Handling soap solutions in textile plants, Pumping sugar juice and various liquids in canning plants

Steam Jet Syphons consist of three basic components, namely a converging nozzle, a diffuser (or venturi) , and a body to hold these parts in their relative positions and to provide a suction (or mixing) chamber. In addition, they can be equipped with accessories such as regulating spindles, snap valves and floats to control operation.

Syphons offer numerous advantages over conventional pumps, within the syphon there are no moving parts to wear or break and therefore no parts to require extensive maintenance. Since the syphon is small in relation to the work it does, the cost unit is correspondingly low. Syphons are easy to install and they may be located in remote and inaccessible places without requiring constant attention.

Steam jet syphons can also be made from practically any workable material. Depending upon service conditions units can be made from Cast Iron, Bronze, Stainless Steel, Aluminium, Teflon, P.V.C., Kynar, Polyester Fibreglass, Hastelloy, Carbon Steel, or many other materials - this is a factor not available in most other pumping and mixing devices where special material prices are difficult to justify. Typical Syphon sizes range from 0.5 Inch to 3 Inch for the Type 217 and can be equipped with either flanged or screwed connections. The Type 219 Syphon is used where line sizes are 4 Inches and above and are typically equipped with flanged connections.

(Image - Type 217 Steam Jet Syphon)

Using Air

Air Jet Syphons

Air or Gas Jet Syphons operate on the same principle as Steam Jet Syphons by using the energy of a gas under pressure to pump liquids and handle solids. In operation syphons use the kinetic energy of motive gas to entrain another fluid, and then discharge the mixture against a head or counter pressure.

Unlike Steam Jet Syphons consideration must be given to the motive gas being used as gases that will not readily condense in to the suction liquid can limit the operating envelope. Practically any source of gas can be used to operate a Jet Syphon, such as bottled Nitrogen, Argon, or compressed air. This can give greater flexibility if the on-site motive supply resources are limited or the installation is in remote location.

Typically uses of Air or Gas Jet Syphons are:

  • Sampling liquids or granular solids when the suction fluid must not be contaminated
  • Intermittent pumping of liquids from tanks, pits, sumps and bunds
  • Applications where steam is not available

Air jet syphons can also be made from practically any workable material. Depending upon service conditions units can be made from Cast Iron, Bronze, Stainless Steel, Aluminium, Teflon, P.V.C., Kynar, Polyester Fibreglass, Hastelloy, Carbon Steel, or many other materials - this is a factor not available in most other pumping and mixing devices where special material prices are difficult to justify. Typical Syphon sizes range from 0.5 Inch to 3 Inch for the Type 217 and can be equipped with either flanged or screwed connections. The Type 219 Syphon is used where line sizes are 4 Inches and above and are typically equipped with flanged connections.

(Image - Type 217 Air Jet Syphon)