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Commercial Trench Drain in Warehouses

Calculate load tolerance and expected flow for smooth operations and risk management

September 11, 2019

A warehouse full of stacked palettes of beer of kegs, with forklifts and industrial lighting
Warehouses that store liquid should have trench drains as part of their risk management plan.

Industrial trench drains are installed to help manage run-off in parking lots, warehouses, and factories. Cast iron is the most common type of metal used in trench grate and trench drain in commercial installations. It is low-maintenance and can stand up under the load of heavy machinery.

Why install commercial trench drains?

Warehouses that store liquid should install trench drains as part of their risk management plan. If one or more storage containers break, how will the liquid be managed? Loading bays often need drains to manage the run-off of rain or snow from trucks or other vehicles. Water used for cleaning—either inventory, vehicles, or the floor—can also be managed with trench drains. Depending on the installation and expected run-off, drains can go to ground or be captured for processing.

Consistent and reliable grating that will not crater under strain is often made from ASTM-48a, Class 35B Cast Gray iron.

Properties of ASTM-48a class 35b Cast Gray Iron (Standard Test Bars)

English

Metric

Hardness, Brinell

212

212

Hardness, Vickers

223

223

Tensile Strength, Ultimate

36500 psi

252 MPa

Modulus of Elasticity

14500 – 17300 ksi

100-119 GPa

Ultimate Compressive Strength

124000 psi

855 MPa

Fatigue Strength

16000 psi

110 MPa

Shear Modulus

5800 – 6960 ksi

40-48 GPa

Shear Strength

48400 psi

334 MPa

An airplane is pulled up to a gate while airport trucks move across hardscape with airport trench grates
Airport trench drain and airport trench grates must be rated ASTM special duty or DIN Class F.

Heavy duty, extra heavy duty, and airport rated grates

Trench drain often does not have to support an entire wheel, as the width of trench is generally smaller than wheel application area. Since warehouses often deal with heavily-loaded vehicles, heavy-duty or extra heavy-duty drains are standard.

Specifying load ratings for trench drain

Two main standards are used in the US for trench drain: ANSI A112.21.1M and DIN 19580.

ANSI A112.21.1M

Light Duty

Pedestrian traffic only: safe load < 2000 lbs.

Medium Duty

Sidewalks and residential parking: safe load 2,000 – 4,000 lbs.

Heavy Duty

Commercial tires and tractor trailers: safe load 5,000 – 7,499 lbs.

Extra Heavy Duty

Roads and highways: safe load 7,500 – 10,000 lbs.

Special Duty

Airports and shipping ports: safe load > 10,000 lbs.

The ANSI specification calculates a safe live load by pressing a 3.5in test plate into the center of a grate and increasing pressure until the grate fails. The plate is loaded slowly so the failure point can be recorded. For gray cast iron, failure is seen when the grating fractures. (Ductile irons fail when the grates warp past a certain tolerance.)

The load that causes failure is divided in two, to provide the appropriate safety factor.

DIN standards are tested differently and have one extra category for precise tolerances.

DIN 19580

Class A

Pedestrian and bicycle traffic: load up to 3,372 lbs per foot.

Class B

Sidewalks and small passenger vehicles only: load of at least 28,100 lbs per foot.

Class C

Commercial applications and trucks: load of at least 56,200 lbs per foot.

Class D

Roads and highways: load of at least 89,920 lbs per foot.

Class E

For industrial applications, solid tires, places that expect impact: load of at least 134,800 lbs per foot.

Class F

For airport and shipping ports: load of at least 202,320 lbs per foot.

DIN standards are internationally recognized for trench drain and have different testing methods depending on the width.

  • For drain less than 8″ wide DIN testing uses a test block is 10″ long by 3″ wide.
  • Drains 8″ – 12″ wide use a test block 10″ long by 6″ wide.
  • Drains wider than 12″ use a test block 10″ in diameter.
Water gushes through a shining trench drain
To choose trench, calculate expected flow and consider the porosity of the surrounding ground.

How much trench drain is necessary?

The Federal Highway Administration offers “Hydraulic Toolbox” software to help calculate the required surface area for drainage in a given installation. The width and length of the drain must respond to the peak possible flow the drain is expected to manage.

The drain’s eventual endpoint matters in the calculation of needed drain size. Is the drain managing water that can be returned to ground? If so, what is the hardscape and softscape like in the environs of the warehouse? If there’s a lot of non-porous asphalt or concrete, the absorption rate from the drain may be much slower. Construction in a developing area should consider what the built environment may become in the next decade.

If the drain will send spilled fluid for processing, then the flow rate of the processing facility is important to calculate.

Warehouse trench drains for cleanup

Installing commercial trench drain is often an important part of risk management or disaster recovery planning, but it can also be a way to help keep a warehouse clean by giving the option of hosing down a floor space. It also allows the option to wash vehicles or other items within the space.

Taking the time to consider warehouse build-out plans and the hardscape surrounding the site, as well as considering maximum flow and required load, means confidently installing trench drain and trench grates that require very little maintenance, and cause no challenges, for years to come.

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