When you operate and maintain a purifier, you should refer to the detailed instructions that come with each purifier. These manufacturers' technical manuals contain information on the construction, operation, and maintenance of the specific purifier. You need to follow these instructions carefully. This section of the TRAMAN contains a discussion and general information on the methods of purification and the

principles of operation of centrifugal purifiers. Centrifugal purifiers are used to purify both lube oil and fuel. However, we will discuss lube oil only since the principles are the same for both.

A purifier may remove both water and sediment, or it may remove sediment only. When water is involved in the purification process, the purifier is usually called a SEPARATOR. When the principal contaminant is dirt or sediment, the purifier is used as a CLARIFIER. Purifiers are generally used as separators for the purification of fuel. When used for purification of a lube oil, a purifier may be used as either a separator or a clarifier. Whether a purifier is used as a separator or a clarifier depends on the water content of the oil that is being purified.

The following general information will help you understand the purification process, the purposes and principles of purifier operation, and the basic types of centrifugal purifiers used by the Navy.

PURIFIER OPERATION

Centrifugal force is the fundamental operating principle used in the purification of fluid. Centrifugal force is that force exerted on a body or substance by rotation. Centrifugal force impels the body or substance out ward from the axis of rotation.

Essentially, a centrifugal purifier is a container rotated at high speed. As it rotates, contaminated lube oil is forced through, and rotates with, the container. Only materials that are in the lube oil are separated by centrifugal force. For example, water is separated from lube oil because water and lube oil are immiscible, which means they are incapable of being mixed. Also, there must be a difference in the specific gravities of the materials before they can be separated by centrifugal force. You cannot use a centrifugal purifier to separate JP-5 or naval distillate from lube oil because it is capable of being mixed; likewise, you cannot remove salt from seawater by centrifugal force.

When a mixture of lube oil, water, and sediment stands undisturbed, gravity tends to form an upper layer of lube oil, an intermediate layer of water, and a lower layer of sediment. The layers form because of the specific gravities of the materials in the mixture. If the lube oil, water, and sediment are placed in a container that is revolving rapidly around a vertical axis, the effect of gravity is negligible in comparison with that of the centrifugal force. Since centrifugal force acts at right angles to the axis of rotation of the container, the sediment with its greater specific gravity assumes the outermost position, forming a layer on the inner surface of the container. Water, being heavier than lube oil, forms an intermediate layer between the layer of sediment and the lube oil, which forms the innermost layer. The separated water is discharged as waste, and

Figure 10-33.-Disc-type centrifugal purifier.

the lube oil is discharged to the sump. The solids remain in the rotating unit.

Other factors that affect separation by centrifugal force include the size of the particles, the viscosity of the fluids, and the length of time the materials are subjected to centrifugal force. Generally, the greater the difference in specific gravity between the substances to be separated and the lower the viscosity of the lube oil, the greater the rate of separation.