Liquid jet liquid ejector

Liquid jet liquid ejector or eductors are designed for liquid pumping and mixing operations and for the handling of some solids. In operation, pressure liquid enters the eductor through the pressure nozzle and produces a high velocity jet. This jet action creates a vacuum in the line which causes the suction liquid to flow up into the body of the eductor where it is entrained by the pressure liquid. Both liquids are thoroughly mixed in the throat of the eductor and are discharged against back pressure. The streamlined body permits the pressure liquid to move straight through the eductor and reduces the possibility of solids in the suction material from collecting and clogging. In eductors high turbulence achieves a homogeneous intermixture of both flows.

Advantages

Water Jet Eductors have a low initial cost, are self-priming, have no moving parts, are easy to install, require little or no maintenance, and pump as well as mix liquids.

• Low Cost – Units are small in relation to the work they do and cost is correspondingly low.
• Self Priming – Eductors are self-priming. They operate equally well in continuous or intermittent service.
• No Moving Parts – Eductors are exceedingly simple and reliable. There are no moving parts to wear or break in a basic eductor. Even when equipped with accessories such as regulating spindles, snap valves, float mechanisms, they require little attention, only periodic inspection and maintenance.
• Corrosion and Erosion Resistant – Because they can be made of practically any workable material, or coated with corrosion-resistant materials, eductors can be made highly resistant to the actions of the liquids handled or the environment in which located.
• Safe – Eductors can be used in hazardous locations where electrically operated alternates would require explosion proofing at considerable cost.
• Versatile – Various piping arrangements permit adapting to environmental conditions. Eductors of various types can handle granular solids, semi-solids, and slurries without contamination.
• Automatically Controlled – Units can be adapted for automatic control by means of a pressure liquid regulating spindle or a snap-valve and float arrangement.
• Perform Double Duty – Eductors mix motive and suction liquids intimately while pumping against a counter pressure.
• Easy to Install – Connections can be made to suit your piping requirements. Little space is required to accommodate units and they are normally so light in weight they can be supported by the piping to which they are attached.

Applications

General

A few of the primary applications where eductors are used can be seen below, this list is by no means exhaustive as their uses are numerous.

Pumping & Lifting

Water jet eductors are often used to empty tanks or to pump out sumps, bunds and cellars. The motive line should be fitted with a regulating valve and a pressure gauge while the suction line should be fitted with an strainer or mesh to prevent large particles entering the unit and causing blockages. Care should also be taken to ensure the discharge lines are always sealed to prevent air leaking back towards the eductor. To accomplish this either fit a U-bend to the discharge line, or always keep the open end of the discharge pipe submerged as this will allow stable and rapid entrainment of the suction liquid.

Where possible it is recommended that the eductor be installed a short distance above the liquid to be entrained and that short suction lines be used, however eductors will operate equally well with long suction lines. Care should be taken with suction lifts greater than 4.5 meters as operating capacities are considerably reduced.

Pumping Additives in to Liquids

This diagram above shows an Eductor being used to introduce an additive into boiler feed water. A percentage of the water flowing from the pump is bypassed into the eductor where it acts as the motive force to draw in and entrain the additive. This is the preferred method of introducing additives as it does not reduce pressure in the main line downstream of the pump, and also allows the eductor to be kept to a much more economical size.

Ship-building

• pumping and cargo out bilges, chain lockers, holds ballast tanks

Water treatment

• dilution of lyes and acids

Foodstuffs- and chemical industry

• pumping and mixing of diverse liquids

Synthetic fertilizer plants (UREA plants)

• pumping “carbamate”-solution back to the Urea-reactor

Hydroelectric power stations

• emergency drainage of pump pits

Sea-water evaporators

• conveying concentrated sea-water (brine)