With 50 years of intake screen experience and thousands of installations covering a variety of conditions, application engineers
from Aqseptence Group can provide design and application assistance.
From shallow rivers to deep oceans from coastal to offshore installations JOIS™ can meet site requirements anywhere in the
world. JOIS™ comprises two parts: one or more original Johnson Screens® passive intake screen(s) and the corresponding Hydroburst™ air-powered cleaning unit.
- Highly efficient
- Custom-designed and engineered
- Low operating costs
- Low capital costs
- EPA Rule 316b-compliant and also compliant with UK fish protection laws
- Easy and quick to install
- Low head loss
- Proven technology for shallow water resources
- No waste stream – there is no debris brought to the surface to be handled or disposed of
- Compact design
- Fully automated cleaning
- Submerged and offshore
Johnson Screens® Passive Intake Screens
To provide maximum efficiency, Johnson Screens® passive intake screens are designed and engineered to each unique environment,
resulting in a system which costs less to install, operate and requires less maintenance. Johnson Screens® high capacity passive intake screens are constructed using non-plugging Vee-Wire® with a patented internal dual flow modifier that creates a nearly uniform low flow velocity through the entire screen surface. This significantly reduces impingement and entrainment of debris while protecting aquatic life.
Passive screens are designed to meet regulatory requirements for a maximum slot velocity for both entrainment and impingement.
This velocity is typically 0.15 m/s which is the maximum velocity at which a juvenile fish can turn around, swim away and not be
impinged onto a passive screen but the screens can be designed to the velocity requirements of the application. This, combined with a
wide range of slot sizes (typically between 2 - 10 mm) determines our screen sizing. Furthermore, the large open area and low velocities
result in a very low head loss in all applications, providing low overall operating costs.
- Low capital costs and no moving parts, and low maintenance needs
- Easy cleaning – with a periodic blast of compressed air using our Hydroburst™ system
- Non-plugging Vee-Wire®
- Three standard configurations – drum, tee and half screens
- Patented internal dual-flow modifier – provides low and even slot velocity (CFD modelling is available on demand)
- Selection of materials – from 304 stainless steel for fresh water to Super Duplex for seawater; Z-alloy (CuNi) for repelling zebra mussel attachment and anti-bio fouling in fresh water
Internal Dual Flow Modifier
In early development, Johnson looked at modifier designs, which included restrictive pipes using slots and holes, they were rejected due to potential plugging and a very high pressure drop across the screen surface area was experienced.
The Johnson Screens® passive intake screen systems have an open pipe design that is highly effective, and is based on the industry
standard. The key component of a Johnson® intake screen system is the patented internal dual flow modifier. The even flow raises the
overall efficiency of the screen to over 90 percent, which means more compact screen cylinders than with a single pipe modifier.
The low pressure drop across the screen surface and through the screen body (lower head loss) reduces the amount of energy required to pull water through the screen, creating significant savings on operating costs.
Half Intake Screens for Shallow Water
As water demands increase for cities, towns and industry, shallow water resources previously hard to withdraw from due to their lack of
depth, have become a more viable option. Our patented half screen has all the same attributes (low slot velocity, Hydroburst™ option, Vee-Wire®, dual flow modifier, etc.) as the standard passive intake screens but can operate in a much lower depth of water. Our standard passive screens require approximately half a diameter clearance around the screen. The half screen sits flat on the bottom and only needs the top clearance.
Aqseptence Group GmbH developed the Hydroburst™ backwash system to ensure a reliable submerged intake system. The Hydroburst™ cleans the Johnson® passive intake screen efficiently from debris using compressed air.
The process flushes the debris away from the screen surface by releasing an appropriate volume of compressed air through the bottom
of the screen within a few seconds. The typical backwash procedure cleans each water intake sequentially, at regular intervals.
Hydroburst™ Air-Backwash System: Mode of Operation
With time, general debris will gather on the outer screen surface and will need periodic cleaning to keep the screen functioning continuously and properly. Our Hydroburst™ system offers an efficient method of regular cleaning without having to send divers in to
clean the screens. Our Hydroburst™ system is designed to deliver a sufficient volume of air in 3 - 5 seconds time – a real solid blast of air that has proven to work in a wide variety of types of applications and conditions.
This volume of air comes out from the bottom of the screen, and as it rises and expands, grabs and carries impinged debris away from
the screen surface, returning the screen to a clean and efficient operating condition. Our application engineers evaluate screen size,
depth and distance away in order to deliver the correct amount of air.
Using a programmable timer system and automated PLC system that is able to communicate to a central data control system / SCADA
system for control, it is is possible to clean the screens in automatic and/or manual mode.