Pump Solutions Group Neptune Series 500 MODEL 481 THRU 547 - Manual (Page 32)

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APPENDIX
INTRODUCTION
A special version of the Neptune Series 500 Pump is the Model 481. This pump is different than the standard
pump due to the unique Low-Flow design, which involves a smaller Piston and Metering Device with extremely
close tolerances. (Correct installation is critical for proper pump operation.) The valves used in this pump also
contain smaller ball checks and seats. Refer to Parts Drawing S00091 for cross-sectional details. This drawing
also indicates each part of the Model 481 that is not common to the other pumps within the Series 500.
Generally, the maintenance and repair procedures for the Model 481 are the same as those shown in the
Operating and Instruction Manual for the Series 500 and 500-A Pumps. Failure to follow these instructions
could cause pump output to become erratic, or stop altogether.
PUMP CALIBRATION
Each pump is tested at the factory prior to shipment to assure proper operation without leakage at the
maximum capacity and discharge pressure specified, with a constant flooded suction of 2 feet of water. For
precise capacity control in the field, a calibration test under actual operating conditions with the actual piping
arrangements is frequently desirable. Use a calibration drawdown cylinder in the suction line.
After the suction and discharge lines are piped with a convenient sampling point in the suction line, and the
pump has been suitably primed, test samples are collected at 25%, 50% 75% and 100% capacity settings. A
straight line results when these points are plotted on graph paper. This graph can be used as a calibration
curve for an intermediate setting as long as suction and discharge conditions remain constant.
It is important to realize that the sample at 50% will not necessarily be 1/2 that of 100%, nor will any other
sample points be to a specific percentage of the 100% value, but the pump will give repetitive samples at the
same setting. This is due to the extremely low volume of the pump which results in a shifting zero flow point as
pressure increases and can be seen in the curve below.
RECOMMENDED SPARE PARTS
1. Diaphragm,
P/N 000231, Qty. – (1)
2. “O” Ring, P/N 106997, Qty. – (1)
3. “O” Ring, P/N 105079, Qty. – (1)
4. “O” Ring, P/N 100204, Qty. – (2)
5. “O” Ring, P/N 100200, Qty. - (2)
6. Suction Valve, P/N 002439, Qty. – (1)
7. Discharge Valve, P/N 002440, Qty. – (1)
Spare Parts Kit P/N 003624 contains all parts
Above in the quantity shown.
THIS MODEL MUST BE INSTALLED
WITH FLOODED SUCTION.
The hydraulic fluid for “481” Pump supplied by Neptune is EP SAE 90.
Common sources for hydraulic fluid are listed on page 5.
PARTS ORDERING INSTRUCTIONS
Note: For prompt entry of parts orders; your order must include
both model numbers and serial number.
MODEL 481
LOW VOLUME PUMP
PERFORMANCE CURVE