What makes our pumps special? After an all-round hydraulic test, here’s another aspect that explains Calpeda’s special approach to its products.
This time our concentration is on pump casings, in particular those of the NM series centrifugal pumps.
The starting point is the UNI-EN 12162 Standard, namely the standard that specifies the hydrostatic test procedure to be applied to the pressurised parts of all types of pumps for liquids.
This standard demands that pumps pass a hydrostatic test, at a pressure that is 1.4 times greater than the maximum limit declared by the product.
Our enthusiasm for research and care during production constantly leads us to demand an increasingly higher level of quality; in this specific case it drove us to go beyond the requisites of the standard.
While developing our NM series single-block centrifugal pumps, we determined that the hydrostatic test set by the standard was not enough to guarantee maximum pump casing reliability; in fact, a centrifugal pump restarts continually, therefore the casing undergoes stress caused by variations in the speed of the liquid and its pressure.
Calpeda pump casings = 100% reliability: this is the simple equation behind development of the new PN16 pump.
In substance, we studied a new control protocol, additional to the one indicated by the standard, on the basis of which all the casings of Calpeda NM centrifugal pumps are tested using pressure cycles from 0 to 16 bar for a minimum of two years of life.
To satisfy the new protocol, we concentrated mainly on the casing material. We replaced the grey cast iron with spheroidal cast iron which has better mechanical characteristics and which, being ductile, can deform plastically under loads before breaking. This translates into an advantageous resistance/weight ratio, something that allows us to reach our objective of resistance to pressure without increasing the product weight.