*Lateral Move irrigator on the turf farm*

May 2014 Tallemenco was contracted by NSW Dept Primary Industries to conduct a detailed pumping energy efficiency audit on a well-managed turf farm in the Hawkesbury District.

A new 666’ long Lateral Move (LM) irrigator had recently been installed on the privately owned farm. A belt driven 60HP electric pump delivered 444 gpm from the Hawkesbury River to the LM approx. 3300’ away via a 6” PVC pipe plus 426’ of lay flat hose.

The audit measured pump efficiency plus friction losses across each major pipe and irrigation equipment sector. The system pumped 113.5 AF /yr, $13,700/yr electricity cost at an ave 24c/kWh and pumped head was 276 ft.

Findings

It was found that the pump was running left of BEP at 65% and the 6’’ PVC rising main was fouled with iron hydroxide unbeknown to the farmer, causing the extra 118’ (51psi) of friction loss greater than new pipe friction.

The pump losses accounted for 13% or $1,800pa.

The hydraulic losses accounted for 43% or $5,900pa.

This table summarises the findings in terms of $$/AF attributed to deficiencies in the irrigation system..

Restoring the pipeline was attempted with pigging, but the iron hydroxide has crusted in the 15 yr old pipe and little improvement was made.

Replacing the 3,330’ of pipe with new 6” PVC and replacing the pump with a lower head direct drive 40HP pump with correct BEP would have saved $7,700pa, or 56% of present pumping costs.

Remedial costs of pump and 6” pipe replacement amounted to $45,000, with a ROI of 5.9 years.

However, the farmer chose to upgrade the rising main with an 8” poly pipe to facilitate additional irrigation capacity.

If a simple pump test only had been carried out on this property, $5,900 (43%) of recoverable annual energy savings due to the high friction losses in the rising main would have been overlooked.

Indeed, two previous audits by local irrigation consultants did just that, conducted a pump test only, gave the pump a tick of approval, but failed to identify the larger hydraulic losses.

Quantifying pumping energy efficiency in an irrigation system has long been achieved with a simple pump test. Ignored was the significant additional potential energy efficiency savings available in irrigation system pipelines due to poor hydraulics.

The WATER PUMPING INSTITUTE’s aim is to educate water engineers in the art and science of identifying hydraulic in-efficiencies in irrigation (and other water) systems. This is achieved through its training course “Pumping System Master Class (US)” with “Fit for Purpose” software which comes with the 4 session training course.

These case studies have been compiled as living proof of the feasibility and practicality of identifying (or incorporating into new system) up to 50% hydraulic savings into pumping system energy audits. These case studies demonstrate the importance and savings advantages of quantifying hydraulic efficiencies when conducting pumping energy audits.