Solving Oil Water Separator Problems

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How oil water separators work and how to use them

How Oil Water Separators Work

The MSR HE-Plate ™ coalescing module – see how oil water separators work and how to use them.

The MSR HE Plate coalescing modules remove oil using only gravity as the motive force. Permanent separator modules require little to no maintenance, no absorbents or other consumable items (such as filter cartridges), more often than not producing separated recyclable oil. No pumping or other utility costs are usually required (although pumped systems can be designed if necessary to meet certain site conditions).

How Oil Water Separators Work

Oil water separators operate under a great range of operating conditions and handle input oil contents up to 100%. Underground oil water separator systems minimize the waste of valuable space on the surface, allowing an inlet flow by gravity. The preferred gravity inlet flow advantage is greater average droplet size. This allows for better removal because oil water separators using gravity as the operating principle. Their design is more complex and requires more knowledge as opposed to the design of filtration or other systems that operate under pressure.

The ongoing benefits of low operating and low maintenance costs and the sale of recyclable oil, usually outweigh the slight added expense of the initial designs of the separator systems. As stated earlier, no absorbents required limits disposal costs to the disposal of the recovered oil.

Stokes’ Law

Oil-water separators operate as an application of Stokes’ Law. In 1845, an English mathematician named George Stokes first described the physical relationship that governs the settling solid particles in a liquid. This same relationship also governs the rising of light liquid droplets within a different, heavier liquid. The function iin the form of an equation obtains the particle rising or settling velocity.

The other variables of the equation include the viscosity of the continuous liquid, The specific gravity difference between the continuous liquid and the particle, and the particle size. Stokes also made three important assumptions in the calculation:

  1. Particles are spherical
  2. Particles are the same size
  3. Flow is laminar, both horizontally and vertically. Laminar flow in this context means flowing gently, smoothly, and without turbulence.

Stokes’ law also governs the rise rate of oil droplets. Knowing the droplet size, specific gravity, and viscosity of the continuous liquid allows the rise rate calculation.

Calculation of rise rate by this method is a gross simplification of actual field conditions. Oil droplets are not all the same size, and they tend to coalesce into larger droplets. Unavoidable turbulence within a separator makes an orderly rise of very small droplets impossible. Droplets will rise following Stokes’ Law as long as laminar flow conditions prevail.

How Oil Water Separators Worl Using Stokes’ Law

There are several types of separators that utilize the principle of Stokes’ law. These systems range from very simple tanks to very internally intricate structures. For most applications in removing oil, the simplest systems are inadequate (although often used) and the most complicated are either too expensive or too maintenance-intensive, or a combination of both. The most often used separator methods include API Separators, enhanced gravity separators and MSR HE-Plate ™ multiple angle separators, which are the most efficient and most predictable of these systems.

How Oil Water Separators Work – Multiple Angle Plate Separators

Multiple angle plate separators take full advantage of the effects of gravity for oil removal, while still resistant to plugging by solid particles. Most, if not all, of the oil and water separation occurs when the wastewater flows through the separator plates. Corrugated in both directions, multiple angle plate separator systems utilize coalescing separator plates, making a sort of “egg- carton” shape.

Spacers built into the plates and constructed have two spacings (nominal 8 and 16 mm). Narrower spacings are more efficient and wider spacings are more resistant to plugging by any solids that might be present. Oil droplets rise up and meet the undersides of the plates. They separate and eventually migrate to the surface of the water. Solid particles fall onto the top surfaces of the plates. They go to the bottom of the separator through holes provided for that purpose.

How Oil Water Separators Work – Contaminated Waste Water Removal

Removal of contaminated wastewater continues to be a problem both environmentally and economically. The use of coalescing plate module type oil-water separators has a number of benefits from both economic and environmental standpoints. These separator systems are highly efficient, reliable, and require little to no maintenance. Being gravity operated, they require no utilities and recovered oil is usually recyclable. The complex designed systems also meet the requirements of environmental regulations. In addition, it is often possible to retrofit existing equipment with more sophisticated internals to enhance separation quality.

Meet environmental requirement with MSR HE-Plate ™ coalescing module oil water separators. From stormwater to industrial stream applications, they are the best long term choice. Request a free quote.