Wainui Golf Club

The original system consisted of three vertical turbine main irrigation pumps and a bore pump for the jockey pump. Because the jockey pump had to have a minimum water level above the intake to prevent it cavitating, a very large % of the stored water wasn’t accessible for irrigation use. This wasn’t practical and with no low level cut out in the system, the main pumps lowered the water level to a point that when the jockey pump was called for it would cavitate. Overtime this resulted in the jockey pump failing. There was also some corrosion noted on the columns of the main irrigation pumps, so these were to be extracted for assessment/service. Because the main irrigation pumps were vertical turbines, the only way to extract them was to lift them out through the pump house roof. This meant sections of the roof had to be removed to extract them.

To fix the problems with the jockey pump it was proposed that a new Grundfos CRI20-07 7.5 kW all stainless steel vertical multistage surface pump, sized to match the performance of the exiting bore pump, be installed. Then a suction line would be fitted to allow the water level in the wet well be lowered, meaning more of the stored water could be used without compromising the pump system integrity. The main pumps were extracted and assessed for service. Once these were stripped it was clear that the corrosion was not just limited to the columns. The pump wet ends were also badly affected. However, the motors were still in good condition. Based on this the most economical option was to supply and install 3 x Grundfos CRN95-5 all stainless steel vertical multistage surface pumps. The existing motors were to be serviced and fitted to the new pumps. Being surface mount pumps the manifolds and pipework needed to be modified and the pumps fitted with new suction lines and foot-valves. The existing VFD’s and control system was to be reused.

How did the implementation work, did it solve the problem? After the confirmation to proceed with our proposal was received the existing base frame was rotated and the discharge manifold relocated. Minor pipe work modifications were required to reconnect to the discharge line. The base frame was modified to accommodate the new pump footprints. In the meantime, the main irrigation pump motors were refurbished with new bearings. Once the new pumps arrived, the pumps and motors were installed on site. The first advantage of the new system configuration became apparent – the new pumps could be installed and extracted without the need to remove sections of the roof! The new suction lines were installed, and each pump was fitted with temperature sensors to provide protection against overheating. A sensor was fitted in the wet well to provide low water level shut down as further protection. The motors were reconnected to the existing VFD’s and the system commissioned. The critical system equipment is now easily accessible for service and inspections. All of the pumps are all stainless steel meaning the risk of damage from corrosion is greatly reduced. However, most importantly the irrigation system is able to utilise as much of the water stored in the lake as possible, meaning more access to water for irrigation.