For efficient purifier operation, use of appropriate size gravity discs according to the density of the medium to be treated and throughput is necessary. The selection of gravity disc is carried out using nomograms given in the purifier manual. Nomograms are different for different types of purifier models from the same manufacturer. This article explains the procedure of selection of gravity disc size depending on the density and throughput of the oil to be purified on ships.

Example 1

The specific gravity of treated oil at 15℃ is known.

Treating condition

• Specific gravity of treated oil: 0.925 at 15℃
• Treating temperature: 70℃
• Feed rate: 3000 L/h

Selection method

1. Refer to the nomogram given in the figure above. Click on the figure to enlarge.
2. From an intersection between falling curve ① of specific gravity of 0.925 and the vertical line of 70℃, draw horizontal line ② to reach the vertical line of 100℃.
3. Connect between the right end of line ② and the point of 3000 L/h on the treating capacity scale using straight line ③.
4. Read within which section of gravity disc inside diameter scale the intersection made by line ③ falls.
5. For this [Example 1] select a gravity disc having an Inside diameter of φ79.

Example 2

The specific gravity of treated oil at a certain temperature is known.

Treating condition

• Specific gravity of treated oil: 0.944 at 50℃
• Treating temperature: 98℃
• Feed rate: 1250 L/h

Selection method

1. Refer to the nomogram given in the figure above. Click on the figure to enlarge.
2. From an intersection between rising curve ④ of specific gravity of 0.944 and the vertical line of 50℃ (being converted to a specific gravity at 15℃), draw curve ⑤ along the falling curve to reach the vertical line of 98℃, then draw a horizontal line to reach the vertical line of 100℃.
3. Connect between the right end of the horizontal line and the point of 1250 L/h on the treating capacity scale using straight line ⑥.
4. Read within which section of gravity disc inside diameter scale the intersection made by line ⑥ falls. For this [Example 2] select a gravity disc having an Inside diameter of φ71.5.

Reference:

SAMGONG -MITSUBISHI SELFJECTOR Operation Manual