Liquid Controls Gear Plate Selection Guide - Manual (Page 6)

6
Formulas for Computing Gear Plate Ratios
Nb x Rc Dn
Pg x W x Ra Dr
= R1 R2=
11. The % difference of the actual ratio (R2) cannot be
greater than or less than 1% of the desired ratio.
NOTE: To convert specific gravity to pounds, use the
following example.
For a specific gravity of 0.893:
0.893 x 8.3453 = 7.452 pounds per gallon.
Water weighs 8.3453 pounds per gallon and has a
specific gravity of 1.000.
Nb x Rc x .98
= R1
∆R = = % difference in ratios
100 (R1-R2)
R1
1. Nb = Revolutions per gallon of the blocking rotor.
Meter Model Nb Value
M-5 (old style) ------------- 4.0790
M-5 (new style) ---------- 12.2370
MS-5 ----------------------- 12.2370
M-7 --------------------------- 5.555
MS-7 ------------------------- 5.555
M-10 ------------------------- 5.555
M-15 ------------------------- 2.058
MS-15 ----------------------- 2.058
*M-20 ------------------------ 2.058
M-25 ------------------------- 2.058
M-30 ------------------------- 0.742
MS-30 ----------------------- 0.742
M-40 ------------------------- 0.742
M-60 (new style) ---------- 0.3983
M-60 (old style) ----------- 0.2545
M-70 ------------------------- 0.4024
MS-75 ----------------------- 0.2545
M-120 ------------------------ 0.1579
MS-120 ---------------------- 0.1579
*M-20 uses only 2:1 packing glands. Consult the
Customer Service Department at the factory for proper
gear plate selection.
2. Rc = Number of units per revolution of the right-hand
wheel of the counter. For a counter to read in 10th
gallons, the unit per revolution of the right-hand wheel
is 1 gallon. For a counter to read in pounds, the unit
per revolution of the right-hand wheel is 10 pounds.
Refer to the units per revolution on page 5.
3. Pg = Packing gland ratio; 1:1, 2:1, or 3:1.
4. W = Units per gallon. For example; pounds per gallon
or kilograms per gallon. If the counter reads in
gallons, this value is 1.
5. Ra = Adjuster ratio = 3.997.
6. R1 = Gear plate ration desired.
7. R2 = Dn divided by Dr, which is the actual ratio.
8. Dn = Driven gear.
9. Dr = Driving gear
10. For 20% correction, multiply the gear plate ratio, R1,
by .98 as in the following example: