Variable Speed Pumping Pays Off for Soft Fruit Grower
January 26, 2007
A major UK producer of soft fruit under glass recently upgraded its pumping equipment for irrigation and overhead moisture. In addition to new pumps from ITT Lowara, all the main pumps at the site have now been equipped with ITT Industries’ computer-controlled variable speed drive. This much finer control of pumping operations has contributed to higher yields and quality, and has eliminated damaging pipe bursts.
S & A Produce Ltd. is the largest privately owned soft fruit grower/packer in the UK, producing 8,000 tons to 10,000 tons annually, and employing around 2,000 pickers. Its main site is an open-air market garden where the bulk of the company’s crop is produced during the UK’s growing season. In 2002, S & A purchased Hernhill Nursery to produce winter and spring crops under glass.
Jason Lewis, general manager of Hernhill Nursery explains, “We took over 15 hectares of greenhousing here, which was originally used to produce tomatoes. We now use it to grow 1,600 tons to 1,800 tons of strawberries and raspberries per year, and employ around 400 pickers. We have two annual crops – one running from end of September to January and the other from mid-March to end of June/July.”
Computer-controlled EnvironmentThe plants are grown hydroponically in raised troughs containing peat. “We try to control the growing environment as much as possible,” says Lewis. “The temperature is kept between 57 degrees F and 64 degrees F, additional carbon-dioxide is pumped in when needed, overhead moisture is provided by sprayers, sprinklers and misters, and we have nearly 500,000 feet of piping supplying irrigation. The entire system is monitored and controlled by computer.”
“We took over the basic equipment from the nursery’s tomato-growing days,” says John Fuller, maintenance manager, “except for the growing troughs and over-head moisture system, which S & A installed and we’ve now recently upgraded the irrigation system. This upgrade consisted mainly of installing new pumping equipment. We originally had four, 11-Kw, ITT Lowara pumps in the irrigation pump station. We’ve now moved these to the ‘overhead’ pump station (which supplies the sprayers, sprinklers and misters) and equipped them with pump-top Hydrovar units. The irrigation pump station is now equipped with seven new 18.5-Kw, Lowara pumps, also with pump-top Hydrovar units.”
Increased Irrigation Capacity“The irrigation pipes are 41⁄2 inches in diameter,” comments Roger Burt of Autometric Pumps who sold the new pumping equipment to Hernhill Nursery. “The new set up in the irrigation pump station increase capacity by 30 percent to 50 percent, and also increases reliability. The seven pumps share and rotate pump duties and should one of them fail, a valve system enables it to be by-passed until it’s fixed or replaced. In addition, the pressure in the pipes varied from 7 bar to 10 bar. Hydrovar now limits it to 4.5 bar, making their problem with pipe burst a thing of the past."
The Variable Speed System“Hydrovar is a variable speed drive whose software has been pre-programmed for the sole purpose of centrifugal pump operation,” explains ITT Lowara’s Ian Dure. “Its single-purpose programming results in simplified installation and set-up, while at the same time, provides greater pump control capabilities, resulting in improved pumping system reliability and decreased maintenance costs.
”The software can be set-up to protect the pump from operating under unfavorable conditions. It can be provided with minimum and maximum set points, which are used to maintain pump performance within the recommended operating range of the pump. If conditions prevail where demand requires pump operation outside these limits, Hydrovar will automatically shut down the pump and send an alarm. This capability prevents the pump from ‘dead heading’ or being run off the curve. Similarly, if changes in suction conditions (e.g., draining of a vessel, etc.) were to result in cavitation or dry-running, the system will shut down and alarm, thereby protecting both the pump and its shaft seal from failure.”
Lewis emphasizes the elimination of pipes bursts: “In addition to the obvious inconvenience of having to go in and replace an underground pipe, such bursts also had the potential to cause major production losses – we could lose a whole bay of fruit. We now feel a lot more confident about our pumping system – both in the sense that we now have the capability to water what we want, when we want and in the greater levels of reliability and control which the new system gives us.”