Rubber or High Chrome? When and Why?
The guidelines for how to specify or review your slurry pump MOC.
In industrial processes involving slurry pumps a range of options for MOC (materials of construction) is critical to ensure an acceptable wear life with abrasive and often corrosive fluids.
Manufacturers typically offer rubber (SlurryPro 360) or high chrome hardened steel (SlurryPro 331) wear parts as a standard offering with more exotic materials for especially corrosive applications. Both rubber and metal have a part to play in slurry pump applications and an experienced pump supplier will work with the customer to determine what material is the most appropriate for the application.
However, there is often confusion over what material is the better choice and a change in duty point can have a negative impact on the life of the wear parts and pump reliability.
Some broad guidelines to consider when selecting or reviewing wear part materials for slurry pumps are:
|Fluid / application property||Rubber compounds||High chrome - HC (hardened metal alloy)||Exotic alloys|
|Temperatures above 100°C||Not appropriate||Recommended||When required (ie no rubber/HC alternative)|
|Large course/sharp particles||Not appropriate||Recommended||With care, typically softer than HC|
|Fines, silica sand, sand etc||Recommended||High wear||High wear, rarely recommended|
|Hydrocarbon/oils content||With care, review compatibility||Recommended||When required (ie no rubber/HC alternative)|
|Corrosive media||Recommended, review compatibility chart||With care – often not compatible||Recommended, review compatibility chart|
|High speeds/high impeller tip speed (larger pumps)||Not appropriate||Recommended||When required (ie no rubber/HC alternative)|
High head applications (>70m head)
|Not appropriate||Recommended||When required (ie no rubber/HC alternative)|
SlurryPro pumps are available with metal (high chrome hardened) or rubber liner and impeller.
There are applications that justify a hybrid approach such as a metal impeller and rubber liners. One example of this is for applications where the discharge head required demands that the pump operate at a speed too fast for a rubber impeller. For these applications, a metal impeller is used with rubber liners.
SlurryPro pumps have interchangeable rubber/metal liners allowing for ultimate flexibility at site level if a change in duty or fluid properties require a change in impeller or liner material.
In summary, rubber wear parts as a lower cost and lighter option are first choice for pump slurries with small, smooth and light weight particles that “bounce” off the rubber wear parts. However for applications where higher temperatures, pump speed or slurry characteristics such as sharp mineral solids are present the recommendation is generally to use high chrome metal wear parts.