Why Irrigation Craft Uses
Mechanical Pipe Systems
Pump station manufacturers typically use "welded painted", or "threaded galvanized". These two methods of fabrication are explained as follows:
WELDED PAINTED - Fabricated by welding steel pipe to steel weld fittings. After welding the manifold is painted, sometimes a primer coat is applied. Problems that may occur with this method are: Internally the pipe may receive no paint, heat from welding may stress the pipe and electrolyses may occur if welding rod does not match pipe material closely. Welding is superior to threaded systems in one important point - there are no threads cut into the pipe reducing the thickness of the metal.
GALVANIZED THREADED - Hot dip galvanized pipe is cut and threaded. Fabrication consists of cutting pipe to length, then cutting threads into the pipe, which is then threaded into fittings which are also hot dip galvanized. Two main problems with this system are: thread cutting process reduces pipe thickness by about 1/2 at leading edge of threads, and thread cutting must be done after galvanizing, so the cutting process removes the galvanizing, and removes that galvanizing at the weakest part of the system, where thread cutting has reduced metal thickness.
In the 1980s Irrigation Craft observed that "Welded Painted" and "Galvanized Threaded" manifolds had frequent problems with corrosion and leakage.
Irrigation Craft improved the welding system by first welding the manifolds together, and then the welded assembly was sent out to be sand blasted, chemically cleaned, and then dipped in a hot bath of molten zinc, otherwise known as "Hot Dip Galvanizing". Galvanizing is superior to most or all paint systems. We call this the "Weld and Dip System". The major drawbacks are high cost and the process is time consuming. Irrigation Craft was and still is unique in the industry for this feature as we are unaware of any competitor using the process at this time.
In 1991 Irrigation Craft also implemented the "Mechanical Pipe System", known also as the "Roll Grooved System". Our systems now include some "Weld and Dip" fittings, but the majority of the pipe and fittings in our systems today are "Mechanical".
In field piping fluid velocities are kept low to reduce pressure losses and pressure surges (water hammer). Field pipe velocities typically range from 1-5 feet per second. But in pump stations fluid velocities are higher and can reach 10 feet per second. High fluid velocity accelerates the aging rate due to turbulence and abrasion. Velocities are higher in pump stations for various reasons such as flow meter runs and pump intake runs. Flow meters often have higher accuracy and linearity at higher velocities. Pump intakes require straight runs of connection size pipe to produce an even flow of fluid into the impeller eye.
High fluid velocities are death to threaded galvanized fittings because of the accelerated aging rated caused by high velocities combined with the reduced wall thickness where threads are cut, and also because the galvanizing is removed in the thread cutting process.
Irrigation Craft uses pumps with either grooved or flanged connections almost exclusively. All Irrigation Craft pumps have flanged or grooved connections except:
All turbine pumps have one threaded connection at the discharge.
Self Priming Pumps - Irrigation Craft may supply small self priming pumps with threads because there may not be any pumps available without threaded connections.
JOCKEY PUMPS - Except for turbine jockey pumps, Irrigation Craft never allows threaded jockey pumps, regardless of size or horsepower. Jockey pumps must be flange or roll groove connected because of the severe duty expected of jockey pumps.
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