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It uses
water as the motive force. The induced fluid is entrained and
condensibles are condensed. The non condensible gases are then
compressed in the diffuser and discharged into a constant level water
sea tank against atmospheric pressure. Maximum absolute pressure
obtained by these types mainly depends on the temperature of water or
motivating fluid. These units with water at 30 C can attain an absolute
pressure of 32 – 40 mm Hg at shut off and with chilled water at 3 C as
motivating fluid it can attain 5 – 10 mm Hg. Generally absolute pressure
at shut off nearly equals the vapour pressure of the operating liquid
at operating temp. These units are most economical where condensible
vapours are to be handled. |
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Single jet low level |
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Single jet barometric |
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Multi jet low level |
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Multi jet barometric |
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Accessory equipment |
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Design standards and codes |
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Laboratory water jet ejector |
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| Material of Construction |
| Generally they are
constructed from C I with gun metal nozzles, carbon stel, stainless
steel, F R P , carbon, P V C, Poly Propylene and rubber lined. |
| Low Level Steam + Water Ejector |
They are used in
various industries like food processing; petrolium and others to produce
low suction pressure as required by many production operations and
laboratories. |
| Water Ejector |
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One Stage Steam + Water Ejector |
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Two Stage Steam + Water Ejector |
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Three Stage Steam + Water Ejector |
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Four Stage Steam + Water Ejector |
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| Steam Jet Ejectors |
| Single Stage and Multistage Steam Jet
Ejectors |
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| Single stage steam jet ejectors are used to create vacuum covering 40 mm Hg. Absolute. |
| Material of Construction For Ejectors |
| Vacuum Up to 40 MM Hg Absolute |
| Two stage Ejector with Condenser |
The system is the
assembly of two units whose construction is similar to single stage
with inter condenser (direct contact type or surface type).
Steam of the first stage is
expanded through nozzle entrains the air or other gases and discharges
them to diffusers at a higher pressure in the condenser. The discharge
from the first stage will then directed to condenser which reduces
volume of discharge gases. These gases turn discharged with the help of
second stage ejector. The ejector is required to be placed at sufficient
height to drain the ejector condenser barometrically. If barometric
installation is not possible then an extraction pump is provided to
drain the condenser in vacuum. The discharge of exhaust steam and
entrained gases is directed to the atmosphere or can be condensed by an
after condenser or lead to a water tank if required. |
| Absolute Pressure Range |
| Vacuum from 100 MM HG Absolute to 10 MM HG Absolute |
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Three Stage
Ejector is similar in construction as of Single Stage Ejector, but
having intermediate condensers. Three Stage Ejector comprises of Booster
Ejector, Booster condenser and a Two Stage Ejector. And Two Stage
Ejector consists of a high vacuum ejector, a inter condenser and a low
vacuum ejector.
This system will give higher vacuum and can handles larger quantity of condensable vapors.
Gas or Gas vapor mixture is
discharged from the first stage into the condenser where the operating
steam is condensed and gases are cooled. The cooled gases are then
entrained by the second stage and discharged into the second inter
condenser. Here, the steam used in the second stage is condensed. The
gases are finally entrained by the third stage and discharged to
atmosphere. |
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| Absolute Pressure Range |
| Vacuum from 5 MM HG Absolute to 15 MM HG Absolute |
| Four Stage Ejector with Condenser |
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Four Stage
Ejector is having construction and working similar to Single Stage, Two
Stage & Three Stage Ejector. When ejector is to be installed at low
ambient temperature area, primary booster should be steam jacketed to
prevent building up of ice on the diffuser internal bore. Sometimes both
primary and secondary boosters are completely jacked to avoid
deposition of product inside the ejector.
The Four Stage Ejector consists of following components:
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Primary Booster Ejector |
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Secondary Booster Ejector |
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Booster Condenser |
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Vacuum Ejector |
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Inter Condenser |
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Low vacuum Ejector |
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| Absolute Pressure Range |
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| Vacuum from 0.5 MM HG Absolute to 5 MM
HG Absolute |
| Five Stage and Six stage Steam Jet Ejectors
With Condensor |
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Five stage and
six stage ejectors are designed for absolute pressure in Micron Range.
The arrangement of these ejectors is similar to the four stage ejector
with additional one or two non condensing stages.
Absolute Pressure Range
In Micron as per customer requirement. |
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| Special Precautions while measuring low
Absolute Pressures |
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Do not use spring type vacuum Gauges |
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Ensure that the guage tubes are clean and free from contamination |
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Ensure that the guage liquid is clean and free from contamination |
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Barometer should be located near mercury manometer |
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Use a suitable macleod gauge with dry mercury and clean ice freezing trap to measure absolute pressure below 1 mm Hg. |
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