This month you will learn how to identify and repair the other common cause of
pressure, excessive clearance between the impeller and raceway in the Burks 5
and 7 CT family
of turbine pumps.
These pumps are used on most
of the return systems found in the
drycleaning and laundry industry.
Unlike problems caused by
excessively high water temperature
in the return tank (see
Troubleshooting Boilers Gone Bad
in the August issue), the water
temperature in the return tank and
outlet of the return pump will not
be excessive. (The pipe at the inlet side of the check valve nearest the boiler
will be hot but will
hardly evaporate spit).
The culprit here is likely pump wear, easily fixed with a simple pump impeller
which will have you up and running in no time.
Here’s the reason this happens. As the pump is used, the impeller and raceway are
eroded away which increases the physical clearance or distance between them.
This results in
the lowering the pressure that the pump can push against (“dead head pressure”).
Eventually, you will notice that the return pump is always running and the
burner is being
controlled by the low water level cut off. By this time you will wish that the
low water level
alarm would just shut up while making frequent trips to the boiler room to press
the water level
At this point we need to be careful to check that there is a sufficient water
level in the return
tank and the strainer between the return tank and condensate return pump is
water to get to the pump. These conditions will mimic the symptoms of a pump
I know I repeat myself but you must shut off the boiler and blow down until
there is no boiler
pressure! Do not do any repairs on a boiler under pressure under any
Here’s a list of tools you’ll need for this job:
Large flat blade screw driver; small hammer; spanner wrench for impeller
adjustment nut (it
is well worth investing in this tool instead of trying to use a punch); vise
grip pliers (needle nose
type if possible); and a 5/16" combination open end/box wrench; and spray can of
WD-40 or a
good penetrating oil.
Be sure the electrical power to the boiler and pump is off!
Once the boiler is no longer under pressure, get some decent lighting on the
area of the
return pump and wipe it down, removing dust and debris.
As long as you’re down there, make sure the ventilation louvers (for our non-French speaking
readers these are the cut outs at the end/ends of the motor) are free of
Adjust the vise grips to gently grab the impeller shaft near the motor. Rotate
the shaft. If the
pliers swings easily up and down you will need to adjust the pump impeller.
On the older types of Burks pumps, there is a plastic cap or metal plug covering
the rear shaft
bearing at the center in the rear of the pump. Take the screw driver and pry out
the cap or plug
if there is one present (the latest pumps do not have this access cap).
Spray a shot of WD-40 into the opening covered by this cap or plug, NOT into the
On the pump end of the motor is a round impeller adjustment nut about two inches
diameter that has six blind holes drilled around its circumference. The impeller
through the center of this impeller adjustment nut, through the inboard wall of
housing then through a rotating seal.
The pump impeller (not visible because it is enclosed in the pump housing) is
pressed on the
end of this shaft. Spray some WD-40 over the shaft and on this nut as well where
shaft enters the inboard wall of the pump housing.
Allow 10 to 15 minutes for the WD-40 to penetrate the parts.
On the face of the pump that has the impeller adjustment nut is an adjustment
small flat slotted piece of metal with a right angled tab at the end which goes
into a hole in the
impeller adjustment nut) held in place by a bolt with a 5/16" head.
Use the 5/16" wrench to unscrew the small adjustment retainer bolt from the pump
remove the adjustment retainer. Take the screwdriver, push it through the hole
in the rear of
the pump from which you removed the cap, or plug if one is present.
Place the screwdriver against the end of the impeller shaft (it will have a
screw on the end,
you don’t have to put the screwdriver into the screw slot; we are using the screw driver
handy punch) and gently tap the shaft end.
Now you’re ready to make the adjustment.
To better understand the object of this exercise, let’s take a moment and visualize what we’re
Remember that the cause of our problem is too much distance between the impeller
rotating part on the end of the motor shaft) and the raceway (the stationary
part that also is the
outboard end of the pump housing where the inlet and outlet pipes are screwed
We are going to adjust the pump by moving the impeller closer to the raceway.
Take your spanner and adjust it so the protrusions at the ends fit into holes in
adjustment nut. Rotate the impeller adjustment nut in a clockwise direction
facing the nut (I use
the mnemonic “clockwise is closer” to recall the effect of rotating the impeller adjustment nut).
After about every 45 degrees of rotation on the impeller adjustment nut, tap the
against the impeller shaft and try rotating the impeller shaft using the vise
Continue the adjusting until it becomes difficult to rotate the impeller shaft.
One final tap of
the screw driver against the impeller shaft and the impeller is then resting
against the raceway
with no clearance and you are ready to make the clearance adjustment.
Turn the impeller adjustment nut in a counter clock-wise direction about 10
degrees at a time
and try to rotate the impeller shaft after each adjustment.
When the impeller shaft just drags slightly, you have reached the proper
Voila! You’re done.
Turn on the power and switch the pump on while listening to be sure the motor
smooth without straining. If there is an indication of a problem, immediately
turn off the power,
check to make sure the valves between the return tank and pump and the pump and
If all valves were correct, readjust the impeller for slightly more clearance.
Place the tab end
of the impeller adjustment retainer into a hole in the impeller adjustment nut
and bolt it in place
with the impeller adjustment retainer bolt and replace the cap or plug at the
rear of the motor.
That’s it for this issue. Don’t know what I’ll be writing about next month. If you have any
suggestions, let me know.