grundfos redi-flo 2 pump preventive maintenance

7/22/2019 Grundfos Redi-Flo 2 Pump Preventive Maintenance

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Inspection & Preventive Maintenance Procedures for the

Grundfos Redi-Flo 2 Submersible Pump

The Grundfos Redi-Flo 2 Submersible Pumps provides optimal performance when

used to pump crystal-clear groundwater from a 2” monitoring well with the pump

placed well off the bottom of the well and within the screened interval of the wellcasing. Say what? How many times is the pump actually used in the environmental

consulting arena under all, or even any, of these conditions? That’s right – rarely.

That’s why proper use, care, and maintenance of the pump are vital to ensure a

reasonable service life from a significant capital investment.

The Grundfos Redi-Flo 2 Submersible Pump depends upon water flowing past the

pump stator housing and water within the pump stator housing to keep the bearings

cool and the motor windings from swelling due to heat build-up. Routine

performance of the following procedures will help prolong the life of the pump and

provide for optimum performance.

We have provided the following photographs and procedures to assist you in either

the care and maintenance of your pump or of one of EEI’s rental pumps that you may

use on a long-term project.

If necessary, refer to the pump schematic provided at the end of these procedures

for part name or assembly order.

Use a small blade screwdriver to remove the

pump screen set screw.

Grasp the pump firmly and gently slide the

screen up and off of the pump. Be careful

not to cut or score the pump motor lead in

the process. If necessary, create a little

slack in the motor lead by pushing the motor

lead down behind the screen.



Remove the pump housing by turning it

counter-clockwise. Note that the impellers,

wear plates, and spacer rings may not stay

in place on the pump, as shown in the

photo.

Remove the impellers, wear plates, and

spacer rings from the rotor shaft.

Grasp the rotor and rotate it back and forth.

It should turn effortlessly in the statorhousing.

Invert the pump and use a large stainlesssteel flat washer to remove the filling screw

on the bottom of the stator. A large blade

screwdriver will tend to slip within the recess

in the head of the screw.



Use a 2.5 mm hex-head driver bit or Allen®

wrench to remove the three short motor

screws from the bearing housing in the

bottom of the stator housing.

While still holding the pump inverted, gently

tap the rotor shaft, at the top of the pump on

a hard surface to push the bearing housing

up and out of the stator housing.

Push the rotor up and out of the stator

housing. The water that is in the stator

housing will flow out of the pump once the

rotor shaft clears the seal in the upperbearing housing.

The rotor has a bearing and Teflon® motor thrust

washer at each end. The motor thrust washers arecaptive when new, but will wear over time to where

they will come off the bearing. When removing the

rotor from the stator housing, ensure that the

upper motor thrust washer does not stay lodged in

the upper bearing housing. If so, a gentle tap on a

hard surface will make it fall out. Inspect the

bearing for cracks. It is normal for the surface of



the bearing to look mottled over time. It is also normal for the end of the bearing to

have a bubbled, gold-colored appearance. If either bearing is cracked, the pump is

damaged beyond repair.

Inspect the body of the rotor for rotational

wear due to abrasion against the inside of

the stator housing. Under normal

circumstances, the surface of the rotor body

will be smooth, shiny, and abrasion-free. If

there are signs of rotational wear, this

indicates that there may be swelling of the

coils inside the stator housing. This occurs

due to over-heating of the pump.

Inspect the bearing housing for cracks in the

bushing. If a crack occurs, a semi-circularpiece will usually break away from the

bushing. If this occurs, the pump is


Insert your index finger into the bottom of

the stator housing and feel around the inside

of the stator housing for swelling of the

motor coils. This occurs due to over-heating

of the pump. This can occur gradually over

time or very suddenly if the pump is run dry.

Eventually, the swelling of the coils will

cause the rotor to bind within the stator

housing and either inhibit the performance

of the pump or render it unusable.

Rotational wear of the rotor body is causedby contact with swollen motor coils. In severe cases, the swelling will be so bad that

the rotor cannot be removed from the stator housing. If this occurs, the pump is




Inspect the motor lead connections at the

pump. Look for exposed wire strands where

contact with the suction inter-connector,

pump housing, or inlet screen have worn

through the Teflon® jacket of the motor

lead. Use a clean soldering iron to meltTeflon® back over the exposed wire strands

to repair minor nicks or worn spots. In

severe cases of jacket damage, or in the

case of complete wire separation, the pump

will have to be re-wired.

Re-insert the rotor into the stator housing.

Ensure that the top motor thrust washer

stays in place on the upper rotor bearing.

Fill the water cavity of the stator housing with

distilled water until the cavity is over-flowing.

After doing so, observe the top of the pumpwhile holding it inverted. If more than the

occasional drop of water is dripping from the

top of the pump, the lip seal needs to be

replaced.

Photo 16: Hold the pump firmly with an index finger on eachend of the rotor shaft. Slowly move the rotor shaft up and

down approximately 3/4" to displace air that is trapped in the

water cavity of the stator housing. Top off the level in the

water cavity with distilled water and repeat these steps until

all air is displaced from the water cavity, as evidenced by the

water level not going down when the rotor shaft is moved up

and down.



Line up the three holes in the bearing

housing with the corresponding three holes

in the stator housing. Gently insert the

bearing housing into the stator housing until

it is almost flush with the bottom of the

stator housing. Allow the bearing housing to

displace the excess water from the water

cavity of the stator housing.

Replace the three short motor screws.

Gently tighten them, using a 2.5 mm hex-

head driver bit or Allen® wrench, until you

begin to feel resistance and then move to

the next screw. Repeat this procedure,

working around to each screw, until the

screws are tight. Do not over-tighten these

screws! The softer stainless steel of the hex

head screw cap or stator housing threads

can easily strip! This step will continue to

displace excess water from the water cavity

of the stator housing.

Observe that the water level within the watercavity of the stator housing is to the top of

the bearing housing. If not, top off the level

with distilled water. Insert the filling screw

and gently tighten it with a large stainless

steel flat washer until it is flush with the

bearing housing.



Inspect the Teflon® wear plates and wear

rings for excessive wear. When new, the

wear plates and wear rings are

approximately 1/8” thick. They should be

replaced once you are able to see through

them.

Inspect the stainless steel impellers and

guide vanes for excessive wear and/or the

presence of coarse sand particles and PVC

shavings lodged inside the impellers or

guide vanes. New impellers and guide

vanes have sharp, square machined edges.

Pumping of water containing coarse fines

will “sand blast” these parts and lower the

performance of the pump. They should be

replaced when the square edges become

rounded or when the bottom contact

surfaces of the impellers and guide vanes become razor thin.

There are two stages to the pump. Assemble them one at a time on the pump to

ensure proper alignment. Replace the wear plate, impeller, wear ring, spacer ring,

and guide vane in the order shown. Ensure that the tabs on the lower edge of the



spacer ring engage the corresponding slots on the edge of the wear plate. Each

stage should be a perfect cylinder when properly assembled.

Replace the pump housing, turning it

clockwise until finger-tight only.

Gently slide the inlet screen back down over

the pump housing being careful to not

damage the Teflon®motor lead jacket.

Use a small blade screwdriver to replace the

pump screen set screw.

Test the pump for proper rotation and flow in a 5 gallon bucket that is 3/4 full of

clean water. Start the pump at the minimum speed of 25 Hz. Quickly run the pump

up to the full 400 Hz capacity of the Variable Speed Drive, and then quickly drop the

speed back down to the minimum speed of 25 Hz.



Please see an article in our on-line newsletter for more information about the proper

use of the Grundfos Redi-Flo 2 Submersible Pump.

Pump Schematic

grundfos redi-flo 2 pump preventive maintenance

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