Choosing the Right System
When selecting a stainless steel drainage system, the following issues must be considered:
Ensure the correct grade of stainless steel is chosen for adequate chemical and temperature protection.
Refer to Chemical Resistance Chart. The corrosion resistance information contained within this table is indicative only.
All data is based on reactions noted at an ambient temperature of 20°C. Higher temperatures will generally reduce the corrosion resistance of the materials.
Typical factors that affect material selection:
- type(s) of chemical(s) and % composition in the liquid
- concentration percentages
- contact time with trough system
- temperatures of liquid flowing into the trough
- flushing system employed to clear liquids from the system
- type of cleaning agent
- grate, locking mechnism and trash basket materials
- sealant for compatibility, if applicable
Test samples should be used for final determination of chemical resistance, contact ACO.
|Suitable, contact ACO for further advice
|No data available
|Stainless Steel 304
|Stainless Steel 316
|Acetic Acid 20%
|Acetic Acid 80%
|Alcohol (Methyl or Ethyl)
|Ammonia Gas (Dry)
|Barium Hydroxide 10%
|Beet Sugar Liquors
|Bleach -12.5%Active C1
|Cane Sugar Liquors
|Chrome Acid 50%
|Chromic Acid 10%
|Fluorene Gas (Wet)
|Formic Acid (90%)
|Fruit Juices and Pulp
|Hydrobromic Acid (20%)
|Hydrochloric Acid (40%)
|Hydrogen Peroxide (90%)
|Lactic Acid 25%
|Methyl Ethyl Ketone
|Oils and Fats
|Palmitic Acid 10%
|Perchloric Acid 10%
|Perchloric Acid 70%
|Petroleum Oils (Sour)
|Sulphur Dioxide (Dry)
|Sulphur Dioxide (Wet)
|Sulphuric Acid 50%
|Sulphuric Acid 70%
|Sulphuric Acid 93%
Ensure the correct edge profile, grate and installation is selected to suit the load requirements of the project.
ACO recommends that grates are secured for heavy duty applications.
AS 3996 Clause 1.1 Scope
“This standard specifies requirements for access covers and grates for use in vehicular and pedestrian areas. It applies to access covers & grates having a clear opening of up to 1300mm…”
ACO believes that EN 1433: Drainage Channels for Vehicular and Pedestrian Areas, also provides a good measure of performance.
The load classes of both codes are shown in the table below.
Ensure the widths, invert depths, grate types and any falls within the trough meet the hydraulic and installation requirements of the project
ACO has an established Technical Services Department, with many years experience advising on surface drainage. Services include advice at the initial design stage through to on-site support, where required.
If you’d like assistance with trench and grate hydraulics to help select the correct size drain for your application, please contact us here.
A channel’s hydraulic capacity is calculated by the amount of liquid the channel is able to collect and drain in a given time period. This determines the size of channel required.
One way to alter a channels capacity is by changing its physical cross sectional size (width x depth). The other is by changing its hydraulic run length. This is defined as the distance water needs to travel before being discharged through an outlet. Changing this can dramatically alter a channel’s run capacity. With all other factors equal, the shorter a hydraulic run length, the higher a channels capacity to drain.
The volume of liquid a channel system needs to collect and remove in a given time period determines its size. Slab restrictions may limit the depth of the channel leaving its width as the usual variable for correct sizing.
Typical factors that affect the size of a channel:
- number of, and discharge rate (generally measured in litres per second) of wash down hoses in a room
- volume of spill containment
- hydraulic capacity of waste pipe beneath the floor connecting to the channel (for liquid evacuation)
- quantity, size(s) and location (along its length) of trough outlet(s)
- desired trough invert fall along the length of the system
- speed of liquid across the floor during service and/or wash down operations. In this instance the selection of the grate must also be considered
- for external areas: rainfall intensity,size of catchment, ground falls etc
A grate fails hydraulically when liquid bypass occurs. Consideration must also be given to the inlet size of the grate to ensure it adequately removes surface liquid, but not at the expense of introducing litter/waste into the drainage system, or compromise the heel safety of users.
A grate’s hydraulic capacity is calculated by the amount of liquid it will allow to pass through it in a given time period. Failure to allow passage of liquid into the underlying channel will result in bypass, regardless of how much capacity the channel has.
There are three factors that affect the hydraulic capacity of a grate, its size, its collective intake area and the design of its inlets.
For instance, a longitudinal grate (slots parallel to the channel) can have a large cumulative intake area. Between the bars, each slot acts as an individual elongated orifice and the grate will only reach its capacity once each slot has ﬂooded. The bars also have the effect of slowing down the speed of the liquid, ensuring gravity has enough time to maximise the evacuation of the water between the bars.
In comparison, the intake areas (and therefore capacity) of only single or double slotted grates are much smaller than multi slotted design. A double slotted grate has only two openings along the length of the drain. There are fewer opportunities for the liquid to be evacuated through the design.
Where there is a substantial amount of surface liquid on the floor or where there is a heavy concentrated pour, water bridging is common. This can result in liquid not entering the channel and splashing back. This should be avoided in vulnerable areas.
Furthermore, single slotted grates are the most compromised design as there is only one slot for water to be interrupted and slowed.
Ensure the correct size and location of outlet is selected to meet the underground pipework requirements
Ensure the correct grate and edge profile meet the aesthetic and safety requirements of the project.
AS1428.2-1992 Design for access and mobility – Part 2, clause 9(c) states:
If gratings are located in a walking surface, they shall have spaces not more than 13mm wide and not more than 150mm long. If grates have elongated openings, they shall be placed so that the long dimension is transverse to the dominant direction of travel.
ACO offers a range of Heelsafe® grates that have openings of less or equal to 7mm.
A range of rated Heelsafe® Anti-Slip grates are available from ACO and are certified to AS/NZS 4586: Slip Resistance Classification.
ACO Technical Services will give specifiers and installers advice on choosing the correct drainage system for the application.