Vietnamese flat-bed dryers SGH4 and SGH8

flatbed-dryer-picWhat is a flat-bed dryer?

A dryer is a machine that removes the water from wet grains by forcing heated air through the grain bulk. In a flat-bed dryer, the same quantity of grain is kept stationary in a holding bin until drying is completed.

What is the capacity of a flat-bed dryer?

In Southern Vietnam, 3 t/batch is the minimum capacity for economies of scale. On the other hand, 10 t/batch is the maximum size in terms of labor management. Size is selected on the basis of harvest season duration. On average, drying time is 7 h depending on the initial moisture content. Thus, an x t/batch dryer can dry 2.5x t/d, or 100x t per drying season of about 40 days. For example, the 8 t/batch dryer can dry 20 t/d or 800 t per drying season.

Why do we use a flat-bed dryer?

The flat-bed dryer has these features:

  • Easy to operate
  • Can be used for rice and corn
  • Gives better quality grain compared with sun drying
  • Simple design allows local production and ensures easy maintenance and repair
  • Can be operated with an engine if electricity is not available or is very expensive

How do we operate a flat bed dryer?

  • Check oil and fuel levels of the engine, the pulley tension and make sure the dryer is operational. Consult your manual.
  • Load the drying bin evenly. If the grain contains lots with different moisture content, mix these well before drying.
  • Start the motor or engine.
  • For very wet grain, aerating the grains for 30-60 min before drying will improve quality but increase drying time and fuel consumption.
  • Start the heater.
  • Monitor moisture content and temperature every hour. Stop drying when the moisture content in the middle of the bulk (half grain depth) reaches the desired final moisture content.
To check whether a flat-bed dryer has a sufficient and even air flow: A sheet of letter-sized paper placed on top of the grain must float atop the grain at all locations of the drying bin.


Thu-Duc District, Ho Chi Minh City, Vietnam

  • For seeds drying air temperature should not exceed 43°C
  • Increasing the temperature reduces drying time but results in uneven drying.
  • Increasing the airflow shortens drying time and reduces moisture content but increases energy cost.
  • Mixing during drying reduces the moisture gradient.

Technical specifications

Drying performance
Capacity  4 (SHG4) - 8 (SHG8) t/batch
Grain depth 0.25m
Drying air temperature 43 - 45 oC
Drying rate 1.5 % h-1
Drying bin  
Usually made of bricks or concrete
Grain floor
  • 2.38 mm-diameter perforated steel sheet 0.76 mm thick or nylon net nailed over a slatted wood frame
Fan and heater options
Fan Axial vane type
Air delivery 1 + 0.1 m3 s-1 t-1
Pressure creation 300 Pa
Rice hull consumption 6.25 kg h-1 t-1 capacity
(One ton of paddy contains approx. 200 kg of rice hull)  
Drive options
Diesel engine 3 hp
Fuel consumption 0.2-0.4 l diesel h-1 t-1 capacity
Electric motor 2 hp

With information from:

Center for Agricultural Energy and Machinery Nong Lam University, NLU Thu-Duc District, Ho Chi Minh City, Vietnam. Email:

For more information:

email; or call +63 2 580 5600

Prepared by M Gummert with inputs from JF Rickman (2004); updated by M Gummert (2010)