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What is the Best Type of Base for a Sanitary PD Pump?

November 27, 2013
Waukesha U2 Pumps Mounted on Polished Round Tube Bases with Adjustable Feet

Waukesha U2 Pumps Mounted on Polished Round Tube Bases with Adjustable Feet

We sell a lot of sanitary rotary PD pumps.  Sometimes we ship customers standalone pumps.  But the majority of our sanitary PD pumps leave here mounted on a base with a motor/gear reducer and coupling assembly.  Over the years we have fabricated all types of bases depending upon the client’s specifications, including flat stainless steel plates, rolled stainless steel plates, and fabricated square tube frames and fabricated round tube frames.  We have built frames with all types of mounting arrangements: casters, adjustable feet, leveling feet, feet with mounting plates and bases with no feet at all.

So which type of base construction is the best for sanitary PD pumps?  Our customer’s opinions are like noses…everyone has one but they are all different.  We tried polling some of our engineers here at Holland, certainly an interesting exercise if you have the time.  Of course there was no consensus, but it did get us moving in the right direction.  After a lot of internal discussion we have put together what we feel the key criteria to consider when making a decision on what type of base you want with your sanitary PD pump.

Waukesha U1 Pumps Mounted on Square Tube Frames with Casters

Waukesha U1 Pumps Mounted on Square Tube Frames with Casters

 Structural Integrity

Many sanitary PD pumps are used in high pressure applications.  Higher pressures at the pump head can produce quite a bit of torque on the entire pump/drive assembly.  We also regularly see pumps in applications where there is a lot of line vibration.  These types of applications require as rigid a base assembly as possible.  Constant torquing and vibration can lead to shaft misalignment, as well as premature seal and bearing failures.  Flat plate bases are the least rigid of the bases.  Rolled plates are sturdier, but round and square tube fabricated bases are the best for rigidity. Complete assembly construction also should be considered. Square and round tube bases, with their open centers, often allow the motor to be dropped into the frame making alignment of the motor and pump drive shafts simpler. Flat plate bases often require stanchions or spacers to mount the motor and allow for proper alignment. This is especially true with side mounted pumps that require a pedestal for clearance.

 Installation/Serviceability Issues

You can attach foot pads, adjustable feet or casters to all of the bases.  Our recommendation for casters would be to buy as large a wheel as you can dimensionally fit for you application.  Sanitary PD pump assemblies can get very heavy and larger wheels will make them easier to roll.  Also make sure the caster assemblies have floor locks.  You don’t want your pump taking off on you.

As far as servicing, at some point you will probably want to remove the pump or drive for service.  The fabricated tubular base assemblies provide much easier access to remove the mounting bolts than a plate type base.

Cleanliness

The flat and rolled plate bases are the least clean of the sanitary PD pump bases.  The large flat areas hold water and or cleaning solution.  The surface finish on these plates is often less than required by good sanitary piping standards.  This type of equipment gets wet a lot in process plants.  The rough surface finishes can become bacterial entrapment areas.

The fabricated tube bases are cleaner than the plates.  But square tube or round tube, which should I use?  The round tube in cleaner as the flat surfaces on the square tubes trap more liquids than the round tube.  So if you want the cleanest base available go with the fabricated round tube.

Waukesha U1 Pumps mounted on Stainless Steel Channel Bases

Waukesha U1 Pumps mounted on Stainless Steel Channel Bases

Cost

If you buy into what we have written so far you are convinced that the best way to mount your sanitary PD pump is use a round tube fabricated base.  Of the four types of bases we have addressed, guess which is the most expensive?  Of course, it is the fabricated round tube one.  You get what you pay for.  The cheapest is the flat plate, followed by the rolled plate, the square tube with the round tube the costliest.

Why does the round tube base cost more that the square tube?  The material prices are similar.  But there is more welding a polishing required to make the good round tube type base.  The piping has to be coped to make good clean joints.

Carbon Steel

This is something we wanted to touch on.   95% of all the bases we sell with our pumps are stainless steel. While many people find carbon steel is cheapest base material possible, we try and dissuade our customers from using it. Carbon steel must be painted and is prone to corrosion. Initial material savings are often offset by additional labor. In high purity, washdown applications, it shouldn’t even be considered. That being said, it is something we get requests for and can offer, but try to discourage our customers from using. The upfront cost savings are not worth the back end headaches.

Conclusion

Sanitary PD pump assemblies are expensive.  Often when we quote customers a pump assembly they question how we can take cost out of the assembly.  One of the first things that comes up is why don’t we use a cheaper base.  You are going to spend a lot of money for this pump and you expect it to run relatively trouble free for a long time.  That being the case, why would you not want as high quality base as possible?  Would you buy a Mercedes and in order to save money put retread tires on it?

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