Sodium Hydroxide (NaOH), or more commonly known as caustic soda, is one of the most widely used chemicals in manufacturing processes. We come across pumping applications for caustic quite often and the primary concentration we see is a 50% solution. I am not saying this is the most common around the world, but this is just what we see more regularly.
In our part of the country, we find mechanically sealed centrifugal pumps in the caustic transfer applications, and of those pumps the Goulds 3196 and Flowserve Mark III are the two most common. When looking at these pumps, what is the common safety and reliability issue? MECHANICAL SEALS! My goal here is to provide a couple of other options to these that have proven to be far more reliable and safe than a traditionally sealed pump in a caustic application.
Teikoku LE Series Pump
This pump has proven to be one of the most reliable pumps for this application. The LE series is ANSI/ASME B73.3M compliant and requires NO mechanical seal. If you are not familiar with canned motor pumps you can see on the video below how this pump achieves it’s seal-less leak proof design.
As you can see in the video, the process fluid flows between the Hastelloy C lined stator and rotor of the “canned” motor, into the rear bearing housing, and back through the hollow shaft and into the suction of the pump. The shaft rides on two carbon graphite helical grooved sleeve bearings that are lubricated by the process fluid. Seeing as how caustic is a good lubricator, the bearings have a long life cycle for this application. The continuous circulation path and the heat from the motor keeps the Caustic from forming crystals. The primary benefit of this pump is true dual containment, which, even in a catastrophic failure, the fluid remains contained within the pump which drastically reduces the safety hazards to operators that mechanical seals have always presented. Here are a some other benefits to consider:
- Small Footprint
- No Alignment Required
- No Mechanical Seals
- Ease of Maintenance
For more information click here: Teikoku LE Series Brochure
Wilfley Model A9
I mentioned this pump in my previous post: Dynamically Sealed Pump Overview. This technology is something that other manufacturers have attempted but nobody does quite as well as Wilfley. With the use of an expeller and seal faces that are separated when the pump is running, the WIlfley Model A9 has proven to be a work horse in Caustic loading/unloading applications. Due to the design of the dynamic seal, the WIlfley pump is capable of dry running which is a result of the loading/unloading process. I have a short video to show how this pump operates so you can get a better idea of how this is possible.
Model A9 pumps are ANSI dimensioned and are offered in a wide range of materials, such as:
- CD4MCuN & WCD4
- Alloy 20
- 304L & 316L SS
- to see more materials, click here
To learn more about the Wilfley Model A9 pump, click here
Many pump users I come across live by the old “If it ain’t broke, don’t fix it” mentality. However, a 6-month (or however long) Preventative Maintenance schedule doesn’t qualify as not broken and, more importantly, the potential dangers of traditional seals in chemical pumps should be enough to make any engineer, operator, team leader, or whoever take some time to consider some safer and potentially more reliable options!
This post is in no way, shape, or form a comprehensive look at either of these technologies, nor is it a detailed look at the many different types of caustic applications and the pumps that are used in those applications. But it is enough to shine a glimmer of light on the different options and what they bring to the table.
Please do not hesitate to get in touch if you have any questions or would like to dig a little deeper into your own application. Contact Us