Nova-Tech LMI Series G - SG Metering Pump - Manual (Page 7)

1
SECTION 1
DESCRIPTION
1.1 GENERAL INFORMATION
The Series G Model G is a reciprocating, chemical
dosing pump capable of producing controlled flows
up to 310 gallons per hour (1175 L/H) at pressures
up to 150 psi (10 BAR) (depending on the model).
These pumps feature a mechanically actuated dia-
phragm liquid end, which eliminates the need for
flow-restricting contour plates, and a stroke adjust-
ment mechanism based on the variable eccentric
principle instead of the traditional lost-motion
design. This design substantially reduces pressure
and flow pulsations contributing to an increase in
the life of system components and more continu-
ous chemical injection. It is designed for industrial
service and offers an accuracy of ±2% of 100%
rated flow between 10% and 100% of its flow
range.
1.2 PRINCIPLES OF OPERATION
The pump consists of two major assemblies; the
drive and the liquid end. Pump delivery is a func-
tion of the drive’s stroke rate, liquid end size and
stroke length. Stroke length can be adjusted while
the pump is running or stopped by turning the
stroke adjusting knob.
The drive motor transmits rotary motion to a worm
gear speed reduction unit which in turn drives the
variable eccentric crank. The adjustable crank
imparts reciprocating motion to the diaphragm
through an interposing connecting rod. The stroke
length is adjusted by changing the position of the
variable eccentric crank in the connecting rod
assembly.
As the diaphragm starts back on the suction stroke,
the pressure immediately drops inside the liquid
end. When the liquid end pressure drops below the
suction line pressure, the suction ball check is
“pushed” upward and the process fluid in the suc-
tion line flows into the liquid end chamber. When
the suction stroke ends, the diaphragm movement
momentarily stops. The pressure in the liquid end
equalizes with the pressure in the suction line and
the suction ball check seats.
NOTE: It is important that the pressure in the
liquid end remain above the vapor pressure of
the process fluid during the suction stroke. If
the fluid pressure drops below the vapor pres-
sure, cavitation will occur, negatively impacting
the performance of the pump. If you suspect
the possibility of cavitation, contact your LMI
Distributor for assistance.
As the diaphragm starts forward on the discharge
stroke the pressure immediately rises inside the
liquid end. When the liquid end pressure rises
above the discharge line pressure, the discharge
ball check is “pushed” upward and the process fluid
in the liquid end flows into the discharge line. When
the discharge stroke ends, the diaphragm momen-
tarily stops again. The pressure in the liquid end
equalizes with the discharge line pressure and the
discharge ball check reset. The cycle then starts
again.
1.3 GENERAL SPECIFICATIONS
FLOW RATE:
Up to 300 GPH (1175 L/H)
PRESSURE:
Up to 150 PSIG (10 BAR)
DESIGN:
Mechanically Actuated Diaphragm
DRIVE:
Variable Eccentric
ACCURACY:
±2% of 100% rated flow between 10% and 100%
of rated flow
ADJUSTMENT:
Lockable micrometer is adjustable from 0% to
100% while pump is running or stopped
LUBRICATION:
Oil bath Over 50ºF (10ºC), Zurn EP 95, 3 1/2
qt.(3.3 liter). Below 50ºF (10ºC), Zurn EP 35
WEIGHT:
90 lb (40.8kg)