Pumping World News Blog

Is Your Trailer Pump Impeller Installed Correctly?

Posted by Elizabeth Kaiser on Wed, Feb 08, 2012 @ 08:02 AM

By Travis Stroh, SRS Crisafulli Applications Specialist

Over the years trailer pumps get modified, parts get replaced and sometimes one of those parts is a new impeller. Here are some tips for inspection, removal and installation to make sure your impeller gets installed correctly.

IMPELLER ROTATION AND ASSEMBLY INSPECTION
To avoid expensive repairs and downtime, take a minute and verify that your impeller is rotating in the right direction. Problems you might see if your impeller is installed backwards:

  • Pump does not deliver water
  • Insufficient flow delivered
  • Insufficient pressure developed
  • Pump requires excessive power

backwards impeller resized 600An impeller installed backwards

The impeller in this picture was installed backwards. When looking at the impeller from the back of the pump, make sure the blades are backhanding the water and not cupping it.

Operation of the pump with the impeller rotating in the wrong direction will result in greatly reduced performance and increased wear.  Check the impeller assembly to make sure the vanes curve backward from the hub out in direction of rotation as shown in the figure below.  If incorrect, the impeller is installed backwards and must be reversed on the shaft. 

impeller drawing resized 600

Warning: Before performing maintenance, disconnect the power source and take any necessary precautions to assure that power to the pump will not be engaged while work is being done.

Note:  Ridding the shaft of paint with paint remover, cleaning and sanding the shaft with an emery cloth, and oiling the shaft may assist in impeller removal and installation.

IMPELLER REMOVAL

  1. Remove the nuts from the bolts on the casing back door (6-18 nuts depending on pump size).
  2. If water-lubricated bearings are used, no loosening of set screws on the bearing eccentric collar is necessary prior to back door removal.  This type of bearing is assembled to slide over the shaft.  However, if sealed bearings are used, loosening of the set screws on the bearing eccentric collar is necessary to allow the bearing to slide over the shaft.  (See note below.)
  3. Remove the casing back door.  Mark the casing and casing back door so reassembly will be to the same bolt pattern.  Tapping the back door around the bolts may be necessary for removal due to adhesive glue or gasket holding the back door to the casing.
  4. Loosen the impeller hub set screws.
  5. Slide the impeller off of the shaft.
  6. Remove key stock from shaft and inspect for wear or damage.

IMPELLER INSTALLATION

  1. Clean the impeller hub and shaft to assure both surfaces are clean, smooth, and free of paint, burrs, sharp gouges, etc.
  2. Place key stock in the shaft keyway
  3. Apply anti-seize lubricant to shaft and key.
  4. Slide impeller onto the shaft and over the keyway.  Check the impeller for correct vane curvature as discussed above.
  5. Center the impeller in the volute. The impeller is set equally spaced between front and back cases of pump to allow it to spin free.  The tolerance between inside the pump case and impeller is generally about 1/8".
  6. Block the impeller to prevent rotation.
  7. Tighten the impeller set screws which hold the impeller to the shaft.  Do not lubricate the set screws.
  8. Slide the back door and bearing over the shaft.  Align the back door to the proper bolt holes and install two or three nuts.  Turn the shaft and check the
  9. If the impeller is rubbing the casing, remove back door, adjust the impeller, reassemble and recheck for proper clearances.
  10. Once the impeller is centered properly, slide the back door a few inches away from the casing and spread gasket cement around the back door where contact is made with the casing.  This will prevent leakage from the pump and will improve overall performance.
  11. Bolt the back door to the casing.
  12. If water lubricated bearings are used, no set screw adjustment is needed.  Tighten the eccentric lock collar to the bearing by use of a punch and then tightened to the shaft by set screws.
  13. Remove any impeller blocking devices.  Turn the shaft to check alignment; shaft should turn freely by hand.  If binding of the shaft occurs, adjust bearings and recheck alignment.

 

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Trailer Pump Operation and Performance (Part 3 of 3)

Posted by Elizabeth Kaiser on Wed, Dec 28, 2011 @ 09:12 AM

By Isaiah Helm, SRS Crisafulli Applications Engineer

SYSTEM CURVES

Just as a plot can be made of pump performance, a graph can be made of the resistance to flow of the piping system through which the pump must drive the fluid.  Using the same head-flow coordinates as the pump performance curve, the figures below can be created.  The curve in Figure 1 represents a system in which there is no static head.  The curve in Figure 2 shows the loss curve displaced upward an amount equal to the static head.

System Curve 1Figure 1: a system in which there is no static head

System Curve 2Figure 2:  the loss curve displaced upward an amount equal to the static head

After a pump is installed on the basis of a certain head and capacity requirement, it may be desired to vary the pump's performance.  A controllable restriction such as a valve can be placed in the discharge line to vary the system friction loss (dynamic head).  The operating point of the pump may then be moved along its performance curve by opening or closing the valve.  Figure 3 below demonstrates the response to changes in head.

System Curve 3
Figure 3: the response to changes in head

In most systems, the static head will vary as a pond is drained or a river level rises and falls.  As the vertical distance from intake to discharge increases, the static head also increases, effectively raising the system curve.  The system head is then represented as a pair of parallel curves intercepting the performance curve, as shown in the figure 4 below.  These two curves determine through what range of capacity and total head the pump will be expected to operate.

System Curve 4
Figure 4:  parallel curves intercepting the performance curve

An example system curve is shown below for a 4-inch L-series pump.  The static head (lift) is 7 feet, and it is pumping through 50 feet of rubber discharge tubing.  The TDH increases from the base value of 7 feet as the flow increases and more energy is lost to friction between the water and discharge tubing.  If the impeller is spun at 540 RPM, the intersection of the 540 RPM curve and the system curve designates the expected operating point.  In this example situation, the pump  will produce nearly 600 gallons per minute out the end of the 50 foot discharge hose.

System Curve 5

 

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Trailer Pump Operation and Performance (Part 2 of 3)

Posted by Elizabeth Kaiser on Wed, Dec 21, 2011 @ 11:12 AM

By Isaiah Helm, SRS Crisafulli Applications Engineer

PERFORMANCE CURVES

Performance curves are used to predict a pump's flow as a function of total dynamic head, impeller diameter, and rotational speed.

Total dynamic head (TDH) is measured in feet and equals the total of a system's static and dynamic heads.  Static head is the vertical distance the fluid is lifted, and does not change the flow.  Dynamic head represents the potential head that is lost to friction between the fluid and the piping system, and increases with flow.

pump performance curve

Head is equivalent to pressure, in that head in feet divided by 2.3114 equals the pressure at the pump in pounds per square inch. 

The red lines on the performance curve above show that a 4 inch L-series trailer pump with a 16 inch diameter impeller spinning at 540 RPM will produce 600 GPM at a system TDH of 19 feet.

 

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Trailer Pump Operation and Performance (Part 1 of 3)

Posted by Elizabeth Kaiser on Thu, Dec 15, 2011 @ 10:12 AM

By Isaiah Helm, SRS Crisafulli Applications Engineer

Crisafulli pumps are naturally robust, and capable of handling a variety of unscreened water-borne debris and slurry mixtures.  The following table lists the maximum sizes of spherical solids each model can pass without clogging.

 

Impeller (in)

Solid Size (in)

4

1-1/4

6

1-3/4

8

2-1/4

10

3

12

3-3/4

16

5-1/4

24

7-1/2

 

Occasionally the pump's speed will have to be changed to get more or less flow and pressure.  A small change in speed can result in a large change in power required.  Increasing the speed by a factor of 2 increases the horsepower requirement by a factor of 8 (2 cubed).  This can be estimated with the Affinity Laws below, taken from the Cameron Hydraulic Data Book (Flowserve Corporation):

Crisafulli Pump Curve 

H = Heads in feet

Q = Capacities in gallons per minute

S = Speeds in revolutions per minute

BHP = Brake Horsepower

Subscript 1 is for original design conditions.

Subscript 2 is for new design conditions.

Note: The Affinity Laws lose accuracy with larger speed variations.  Consult with the factory when considering speed changes of more than 20%.

A pump's impeller may need to be changed in order to get more flow and pressure or to require less horsepower with resulting less flow and pressure.  SRS Crisafulli offers up to three different impeller styles for each pump size.  They are referred to as Regular Lift, Intermediate Lift, and High Lift impellers.  The difference is their diameter.  For a change from a 16 inch Regular Lift impeller to a 21 inch High Lift impeller, the flow would increase by a factor of 1.3, the pressure by a factor of 1.7, and the power by a factor of 2.2.  This effectively doubles the horsepower requirements without changing the pump speed.

While Affinity Laws exist for diameter changes, they are only accurate for small changes of 5%-10%.  The best way to understand this relationship is to view the pump performance curves for the various impellers offered by SRS Crisafulli.

 

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Topics: crisafulli, srs crisafulli, Product Information, agriculture, slurry trailer pumps, Equipment Dealers, pumps and power units, mining, Replacement Part

5 Tips - SRS Crisafulli Temporary Discharge Tubing

Posted by Elizabeth Kaiser on Wed, Sep 14, 2011 @ 09:09 AM

By Isaiah Helm, SRS Crisafulli Applications Engineer

The 2011 battle against the flooding Missouri, Mississippi, and Souris Rivers has been in the news.  The Souris River winds its way down from Canada into the Minot, North Dakota area and then back to Canada.

Flooded home resized 600Photo Source:  The Washington Post.  Minot home flooded by Souris River

Spring and Summer of 2011 saw real flooding problems creating high demand for flood management PTO powered trailer pumps and accompanying discharge tubing.  Demand for SRS Crisafulli's heavy duty tubing quickly outpaced supplies.  As an SRS Crisafulli Applications Engineer I found myself searching for discharge tubing alternatives.

A co-worker visited the Minot, North Dakota area in July and witnessed some SRS Crisafulli Trailer Pumps in flood management action.

Crisafulli trailer pumps1SRS Crisafulli PTO Trailer Pump with lightweight vinyl discharge tubing in Minot, North Dakota

You'll notice the pumps are not using our standard black industrial duty discharge tubing.  My search for discharge tubing alternatives resulted in the light-duty tubing pictured above.

This alternative tubing was custom manufactured for the standard hose ring discharge on our 12" and 16" pumps.  The ends are folded over and sewn down to combat fraying.  Some advantages to this option:

  • Costs are about a quarter of the heavy-duty tubing price, and are more affordable when storage conditions and usage frequency result in buying new hose every time the pump is used.
  • Very light in weight - less than 50 lbs, compared to 150 or 200 lbs. Easily handled by one person and can be shipped rapidly via UPS rather than by a freight carrier.
  • Good alternative when heavy-duty tubing options are not available.

For those who use this light-weight tubing, using the following 5 tips will improve the experience:

  1. Crisafulli trailer pumps2As demonstrated in the photo above, support the hose as it exits the pump to decrease the chance of the weight and pressure pulling it off the pump.

  2. Our standard hose clamps are designed for thicker industrial tubing and will not hold the light weight tubing without help.  Solve the problem by increasing the hose thickness under the clamp by wrapping the hose at the location with thick, flexible material.  Old belts or a piece from old hose work well.  The light-duty tubing does have a small rope sewn into each end, but that alone is not enough.

  3. Make sure the tubing isn't rubbing against anything hard or sharp.  This applies to our standard industrial strength tubing as well, but thinner, more flexible hose will rub through faster.

  4. Crisafulli trailer pumps3Avoid letting the hose flutter as the water goes through it, which causes premature wear by being flexed back and forth rapidly.  It's recommended to put some kind of restriction on the end of the hose to keep it tight and stiff as shown above.

  5. Multiple hoses are connected by clamping each to a short section of pipe.  They cannot connect to each other without pipe as is used in our standard industrial tubing.

We are pleased to now have a "Plan B" when heavy-duty industrial tubing is too heavy, too expensive, or unavailable. 

Our best wishes go out to all the resilient residents of Minot - Isaiah Helm, SRS Crisafulli Applications Engineer.

Read The Washington Post Article: "Souris river flooding forces thousands of Minot, North Dakota residents to evacuate"

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