30 | IM-112 DECEMBER 2019
Vertical Turbine Pumps
2001299 - VTP- IOM
30 | IM-112 DECEMBER 2019
Vertical Turbine Pumps
2001299 - VTP- IOM
30 | IM-112 DECEMBER 2019
Vertical Turbine Pumps
2001299 - VTP- IOM
Vertical Turbine Pumps
Installation
Document Name: 2001299-VTP-IOM-EN Page 30 of 67
Revision 3 Copyright © 2014, Weir Floway, Inc. All Rights Reserved. Issue Date: December 12, 2014
Figure 5-6: Types of Impellers
1. Enclosed Impellers: for proper impeller adjustment refer to the pump nameplate on the discharge head.
2. Semi-open Impellers: the adjustment of semi-open impellers is more critical than that of enclosed
impellers. A small change in the impeller setting impacts the pump performance considerably (refer to
Figure 7-1 on page 43).
If after making the below adjustment the pump does not deliver its rated capacity, the impellers can be
lowered one step at a time until the lowest possible adjustment is achieved without the impellers
dragging.
On the other hand, if the impellers appear to be dragging after the initial adjustment the unit must be
stopped and the impellers raised one step. Dragging the impellers will increase the pump power
considerably and can usually be heard and felt as increased vibration.
• For optimum performance the impeller must run within a few thousandths of an inch of the bowl seat.
The exact shaft adjustment varies according to variables of each installation.
• For close coupled units, a general rule of 0.015" plus 0.005" of adjustment for each 100 feet of
discharge head produced by the pump, plus 0.005" adjustment for each 10 feet of column assembly
will provide close to ideal adjustment.
CAUTION
EQUIPMENT DAMAGE
The impellers must be completely down against the bowl seat when starting the impeller
adjustment. All dimensions and instructions given above are based on the assumption that
the impellers are seated. When pumps are subjected to suction pressure, the pressure
acting against the shaft tends to raise it. If the suction pressure is great enough it can raise
the shaft. Make sure the shaft is down when starting to adjust the impellers.
CAUTION
EQUIPMENT DAMAGE
Excessively dragging impellers during operation will result in equipment damage. If
dragging occurs, stop the pump and increase the impeller setting.
NOTICE
If semi-open impellers are raised and then adjusted down, a slight increase in the power
required will be noted due to the increased delivery of the pump. Do not confuse this with
the marked power increase when impellers are lowered enough to drag.
Semi-open Type Impeller
Enclosed Type Impeller
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