Aqueous cleaning in heat treatment

Oil separation is a significant issue in heat treat applications.

Heat treatment normally involves quenching, which is done with oil. Removing this oil from the parts and cleaning them adequately for the following production step is a hot issue. Loads of waste from cleaning baths and smoking oven stacks, due to residue oil on the parts, are common in this industry.

Better oil control is the answer and Suparator® has proven to be the solution in many applications already.

The normal practice.

Basically there is only one way to clean the parts, coming out of the quencher, and that is to wash them with aqueous cleaners. High loads of heavy oil on the parts present a big problem and cleaning solutions need changing frequently. The results are large amounts of aqueous waste and parts that are still not clean enough, causing the tempering oven to start smoking.
Sometimes centrifuges are used to spin the parts, to get excess oil off, in an attempt to reduce the problems with the cleaning process.

Oil removal.

There are a number of issues involved in controlling the oil in the cleaning process:

• The amount of oil.
  Depending on the geometry of the parts there may be a whole lot of quench oil on them when they get into the washers.
• The nature of the oil.
  Quench oil is often heavy and thick and would absorb cleaning solution
• The chemistry.
  Quench oil often contains additives that may react with the cleaner.

The amount of oil.

The amount of oil will make any oil/water separation technology look good initially. Because there is a lot of it, any separation device will remove quite a bit of oil and appears to function great. The problem is that they don't get enough oil out fast enough; the oil concentration is allowed to build up.

Adhesion skimmers.

Adhesion skimmers like disk, hose or belt skimmers should not even be considered for heat treat applications. They can only remove a fair amount of oil once there is a thick oil layer in the washer!

Gravity and coalescer separators.

Gravity separators and coalescer separators seem to do a great job and they certainly get a lot of oil out, but the problem is in the nature of their operating principle. They need the build up of a floating layer for the oil to be pushed out over the oil weir or funnel. The more oil in the process, the more oil needs to be pushed over the oil weir and the thicker the oil layer has to be.

Quickly this oil layer will start to develop a gradient. The nice, light oil goes to the top but the thick, heavy material builds a layer at the bottom, quickly becoming a serious barrier for the oil to pass through.
The system that seemed to perform so great initially, quickly starts to fail and the oil concentration gets out of hands, all in a matter of days or weeks.

Suparator®.

The Suparator® thin film technology is of great significance here. In stead of allowing oil to build up and form a layer, and a barrier for the oil itself, the technology concentrates and separates the oil from the process in a matter of minutes.

The amount of oil is no issue at all; the largest amount of oil being separated by a Suparator®, that was ever measured, was 1500 liter/hour(oil!!).

Suparator® handles heavy oils very well. If the quench oils react with the cleaner chemistry and build a sticky, scum-like floating layer, rake skimmers can be fitted to remove this material also, with the oils.

Suparator® is insensitive to dirt. First of all, oil, with most of the dirt, is removed continuously and quickly, keeping the fluid, the washer and the Suparator® itself a lot cleaner. Secondly the passive construction, without any moving parts or controls, is insensitive to accumulated dirt. Finally, if desired, the units can be fitted with flush headers that will make them require less cleaning than the washer itself.