American stainless pumps – Schreiber Chillers MC75AC User Manual

Page 14

American Stainless Pumps

Stainless Steel Pumps for the Commercial Marketplace

www.aspumps.com

14032 S. Avalon Blvd. Los Angeles, CA 90061

Phone: (310) 630-8089 Fax: (310) 630-8095

Page 5

Setting Impeller Clearance: Model SSP Only

See

SSP Performance Notes for impeller shimming discussion.

Properly setting the impeller to case clearance is the most critical factor in determining the SSP’s perfor-
mance. You will get maximum performance and efficiency (and maximum amp draw) with near to zero clearance.
Factory standard clearance is 8 to 12 mil. Spacer/Washers to adjust clearances are available in 10 mil and 15-mil
thickness.

You can have more or less than normal flow and head by changing the clearance. To increase clearance, remove
impeller spacer/washers. To decrease clearance, add impeller spacer/washers. Be aware that if you set the
impeller at near to zero clearance, and operate near maximum flow rates, you may overload the standard
motor. Also be aware that impeller clearances near zero greatly increase the risk of the impeller grinding
against the casing.

Standard factory settings for spacers are 30 to 90 mils of spacer/washers to obtain 10-mil clearance. Since the
tolerances of the motor shaft and pump parts can stack up, some pumps may need more or less than this standard.
Some special OEM assemblies will not have any spacers when the customer elects to accept reduced performance
in return for ease of assembly.

American Stainless Pumps provides special feeler gauges for impeller shimming. Call and order our feeler gauge set,
part number K200. Our standard shim pack set is also available. It contains ten each of the 0.010” and 0.015” shims.

Use the following impeller shimming method when building a new pump:

Place the pump (as assembled through step 4 on page 47) on the workbench, positioned vertically.

Place 0.050” shims onto the motor shaft (two 0.015” shims and two 0.010” shims).

Thread the impeller onto the shaft, compressing the seal and shims. You will need to hold the motor shaft from the

rear of the motor with a large screwdriver, wrench or vise grips while tightening the impeller.

Place case o-ring (item 500) onto seal plate. Make sure o-ring is laying flat against the seal plate flange.

Place case onto pump assembly, and install case screws (item 7CS). Tighten case screws in a cross-bolting

fashion.

Rotate the impeller from the back of the motor, or with your finger through the suction or discharge nozzles. Listen

and feel for any scraping noises from the impeller hitting the casing. If a scraping noise is heard, remove the
case and impeller, and then remove either one 10 or one 15 mil shim. Repeat step 5 & 6. If no noise is heard,
proceed to step 7.

Use the pink feeler gauge (0.015”), and slide it in between the impeller and the casing through the discharge nozzle.

If the pink feeler gauge does not fit, go back to step 6 and remove shims as necessary to make pink gauge
slide in between impeller and casing. When done correctly, the feeler gauge will become visible through the
suction nozzle. Continue pushing the feeler gauge into the casing until it is all the way in, and centered across
the face of the impeller. Rotate the feeler gauge using a pair of needle nose pliers, and feel for tight spots. If
gauge encounters only a slight pinching resistance, you probably have a good impeller clearance. Remove the
pink feeler gauge, and check to see that the brown feeler gauge (0.010”) does not bind when used in the same
way. If it does not, go to step 9. If it does, remove 0.010 mils of shims from behind impeller and repeat step 7.
If the pink feeler gauge is free to rotate 360 degrees across the face of the impeller without binding or resis-
tance, go to step 8.

If the pink gauge is capable of rotating 360 degrees without binding, then there is a greater impeller/casing clear-

ance than 0.015”. Determine this clearance by repeating step 7 with the thicker gauges. Yellow=0.020”,
White=0.025”, Orange=0.030”. If clearance is larger than 0.030”, stack the various gauge thickness and repeat
procedure until clearance is known. When clearance is determined, add shims behind the impeller to close
clearance as desired. Repeat step 7.

Proper clearance has been established. Return to step 5 on the previous page.