Single and Multi Stage Ejectors

Jet Flow Technologies Vacuum Division

Basic Principle :

A steam jet ejector produces a vacuum by means of a venturi-effect. The motive steam fluid is expanded, after passing through a motive nozzle, where the pressure energy is transformed into kinetic energy. This energy stream impinges with and withdraws gases, air and water vapour from an application where a sub-atmospheric pressure (vacuum) must be established or maintained.

Steam jet ejectors are especially used for wet processes that require vacuum levels ranging from 15 mbar down to 0.1 mbar vacuum absolute. Water ring pumps are not capable to generate such a high vacuum. Vacuum is widely applied in the chemical and food processing industry, because it permits to perform processes that cannot otherwise be done under atmospheric conditions.

Type of Ejectors :

Ejector is a device for producing vacuum which is achieved by using high pressure motive. The ejectors are static devices in which the energy provided by the release of pressurized fluid (steam, gas, liquid ....) can:

  • Aspire, compress or mix fluids
  • Put vacuum or pressurized enclosures
  • Transfer fluids, powders or sludge
  • Transfer of heat

According to the features described above, Ejectors carry different names: Thermocompressors, eductors, mixers, heaters, ejector, scrubber, hydroejectors etc.

Type of Ejectors in terms of number of nozzles :

Single Nozzle Ejectors
Single-nozzle ejectors are used for either critical or non-critical flow, but usually for only one set of design conditions. It is generally used where very large compression ratios are required.

Multi Nozzle Ejectors
Based on the process requirement, a Multi Nozzle Ejectors can be designed five or seven nozzles type. Generally has one nozzle in centre and the remaining of the nozzles are evenly circled around it. Multi-Nozzle Ejectors which can reduce steam consumption by 10% to 20% as compared to Single Nozzle Ejectors when designed for the same conditions and it is more efficient compared to single nozzle ejectors. At times it is also considerably shorter in length when compared with same rated single nozzle ejectors.

Variable Flow Ejectors
A Variable Flow Erectors are pneumatically / Electrically operated single nozzle ejectors, used to handle the variable suction and discharge conditions wherein pneumatically / Electrically operated Needle goes in and out for precise controlling the flow rate based on pressure requirement. It is very useful when a low pressure steam is compressed to a higher pressure level.

Multi Stage Ejector System
A single stage steam ejector can produce only a limited vacuum. Multi-stage steam ejectors are used when an application requires a pressure lower than what single-stage ejectors can develop, as the first can develop a greater suction pressure. With more stages added to the system, the pressure of the first stage becomes lesser and lesser, generating a deeper vacuum. The ejector which the entrained gases enter first is called the first stage and subsequent stages are numbered in succession.

It is desirable to connect a condenser to the discharge of each steam jet ejector to bring all steam and condensable gases to the liquid state, reducing the load to the succeeding ejector stage and thus imposing on subsequent stages the work of compressing only those gases that are non-condensable. The condensers so employed are known as inter-condensers. A condenser connected to the diffuser discharge of the final stage is known as an after-condenser, that is used to prevent the discharge of motive steam and condensable process vapours into atmosphere.

Materials: All materials can be used. Among the most common steel, carbon, stainless steels (304L, 316L…), Special Alloys (Uranus, Monel, Hastelloy …), graphite, plastics (PVC, PPH, PVDF, PTFE …)
Codes and design guidelines: JFT’s standard, ANSI, ASME VIII, Normes CE, TEMA
Connection: On demand, flanges (as ISO, DIN or ANSI), threaded connections, threaded or welded.

Benefits :

CUSTOM DESIGN AND MANUFACTURING: Thank to our resources which have been validated by thousands of achievements, we provide well sized ejectors for each specific application, ensuring optimum performance (and security) at competitive prices.
HIGH PERFORMANCE: The specific profiles of our ejectors guarantee maximum efficiency for a reduced operating cost.
EXCEPTIONAL RELIABILITY: due to the lack of moving parts, no breakdowns, no decrease in performance, a low maintenance cost.
WIDE RANGE OF RATES: An unlimited suction capacity.
WIDE RANGE OF PRESSURE: Our ejectors can also be used to make a vacuum within a chamber (up to 10 -2 mbar abs.) or use as compressors for several dozens of bars.
CORROSION RESISTANCE: Ability to aspirate any fluids, even abrasive or corrosive thanks to the diversity of building materials that we offer.

In association with Jet Flow India