Many oil separators are termed coalescing plate interceptors. Encouraging coalescence of oil droplets improves the performance as the effective droplet sizes are increased. The AJM EnviroSEP uses either a pack of specially designed tubes or stainless steel plates in the larger versions, which promote this coalescing effect whilst also providing adequate surface area and retention time for 20 micron droplets to be removed.

The AJM EnviroSEP is a gravity separation device.

Gravity separation relies on there being a difference in the density of the oil and water.

When oil is present in water in an unemulsified or free state it exists as thousands, maybe millions of droplets ranging in size from a few microns to several centimetres.
 

A curve showing how these droplets are distributed can be seen on the chart below. In this example, the area underneath the curve (number of droplets x droplet size) defines the concentration of oil in the solution. It can therefore be predicted that if all droplets greater than approximately 20 microns are removed from the water phase then the concentration of oil left in the water will be of negligible proportions.

The basis of oil separator design relies on applying the principals of Stokes law and calculating the rise rate of a 20 micron droplet.
 

Many oil separators are termed coalescing plate interceptors. Encouraging coalescence of oil droplets improves the performance as the effective droplet sizes are increased. The AJM EnviroSEP uses a pack of specially designed tubes which promote this coalescing effect whilst also providing adequate surface area and retention time for 20 micron droplets to be removed.

Other essential considerations when designing oil separators are;

• The ensurance of near laminar flow conditions which is achieved by inlet distribution baffles.
• Equal distribution throughout the oil separator plate pack.
• Materials that attract oil and encourage coalescing.
• A plate pack angle of at least 60 degrees to maximise solids removal.
• The use of a non emulsifying pump.

Key:

The rise rate of the oil droplet =
Density of oil =
Density of water =
Droplet size =
Viscosity of water =