Pump technology that Keeps Producers in the FieldPump Technology that keeps
Producers in the Field
by Don Blaser
October 30, 2017
Recently at the Ag Spray Equipment National Sales Training Conference held in Columbus, Nebraska, Hypro Global Products Manager- Andy McNair had a session on PWM (Pulse Width Modulation) hydraulic driven centrifugal sprayer pumps and the new 9310 Series Forcefield wet seal technology pumps. Mr. McNair went into great detail about the technology, the features and the benefits.
Traditional hydraulically driven centrifugal pumps in conjunction with an automatic rate controller operate with the pump set at a constant rpm and the rate controller servo valve regulates the fluid flow. The downside to this setup is slow response time, potential pump over speeding and the opportunity for run dry.
Slow Response Time
The slow response time are a function of the plumbing system and motor speed on the regulating valve. The regulating valves have to have slower motor speeds otherwise they tend to overcompensate and as a result pressure and flow continually go up and down and the rate controller never locks on the target rate. This is magnified when speed adjustments are required while going through the field. Speed changes ranging from going up a hill to going down a hill to slowing down to go through a washout, regardless the reason, these speed changes cause the rate controller to send a signal to the servo valve to compensate and adjust the flow to maintain the desired application rate. Many producers have complained about the response times especially while turning around on the ends of the field. This issue has become more evident the last few years with the increased weed resistance.
Tractor manufacturers have improved hydraulic performance and output over the last decade allowing many models to have hydraulic oil output thirty pulse gallons per minute. Great for the increased hydraulic needs of the implements, but hard on orbit motors. The high output systems result in many pumps being supplied too much oil and as a result over-sped. This over speeding causes premature pump failure. Additionally, if operators were not careful when they shut the hydraulic pumps off, they could "hard stop" the motor as well. A "hard stop" is when the pump is disengaged and the hydraulic lever is placed in the neutral or off position rather than in the float position. The float position allows the hydraulic motor to come to a gradual stop. Placing the hydraulic lever in the neutral/off position closes both sides of the hydraulic ports simultaneously and as a result takes a motor running at 4000 plus rpm to zero immediately. This can cause a momentary pressure spike in the hydraulic hose lines causing the hydraulic pump motor seal to fail.
Additionally, the more sophisticated machinery of today requires the operator to monitor more things while going thru the field and increasing the opportunity for the pump to be run-dry when the tank or tanks get empty. Traditional mechanical seals function very well as long as there is fluid in the pump chamber to lubricate and keep the seal cool. But because of the high rpm these pumps operate at, if run-dry, the seals can fail very quickly causing untimely down time. According to Jason Hake, Service Manager for Ag Spray Equipment, "We generally see two things when we see a mechanical seal failure. 1. The pump was run dry for a period of time and the seal actually melts. And 2. probably more common, the seal cracks, and this generally happens when the tank gets about empty and the pump sucks some air due to terrain or other factors that cause no fluid to be present in the outlet of the tank. When this happens, the seal faces are spinning at such a high rate, it doesn't take very long for them to heat up. And then fluid comes back to the tank outlet and the pump gets a burst of cool liquid, boom, the seal cracks."
PWM (Pulse Width Modulation) Technology
PWM Technology allows the hydraulically driven pump to be directly controlled by the automatic rate controller. As a result, response times are markedly improved, over speeding is not possible and the rate controller shuts the pump down when flow is not detected so run dry is nearly impossible. The PWM hydraulic flow control valve is incorporated into the hydraulic motor. A low voltage signal is sent from the rate controller to the PWM control valve which controls the hydraulic oil flow which dictates how much oil actually goes thru the hydraulic motor controlling motor rpm and output.
McNair, in his presentation, highlighted some of the benefits:
·Precise and fast response for pump control, compared to standard flow control valves.
·Proportional flow control for tractors with close center hydraulic systems.
- Open center/fixed displacement systems will also work with additional plumbing components.
·Reduces system cost by decreasing plumbing components, and removing potential leak points.
·Decrease overall footprint for the pump and control valves system.
·Prevent abuse conditions from damaging pump and motor:
- Motor over-speed prevention
- Reverse flow prevention prevents potential seal damage
- Hard stop (neutral vs float) prevention allows pump gradually stop
·Eliminates the need for a separate control valve.
The PWM technology has dramatically improved pump performance as well as longevity. Many of the issues that cause down time and inefficiencies have been eliminated. Ag Spray Equipment has made the PWM pump standard on all 6000, 7000 & 8000 Series Pull-Type Sprayers and LA5000, LA7000 & LA9000 Liquid Applicators if equipped with hydraulic pump option.
ForceField Wet Seal
Hypro's Andy McNair continued his presentation moving on to the new 9310 Series ForceField Wet Seal Pumps. He stated, "The biggest complaint we get at tradeshows is that the seal went out on my pump. "The typical conversation goes something like, "Pump leaks, so I had to stop what I was doing. Take it off. Run and get a seal. Take the pump apart. Replace the seal. Put it back together. Put it back on. And then hope I fixed it correctly. The whole time, I'm not turning a wheel and getting nothing done." "Producers understand that time is money", McNair stated. It's this Feedback that drove Hypro to develop the ForceField Series of pumps.
A traditional centrifugal pump has a spring incorporated black and white viton/ceramic mechanical seal. It's duty is to seal off the shaft so no product can escape the pump, leak and contaminate the hydraulic motor. The biggest enemies of this type of seal is excessive heating caused by running dry and sticking together caused by chemical bonding. A potential answer to this problem is isolating the mechanical seal in what is called a "wet seal".
A wet seal pump has a separate chamber that the mechanical seal is housed in. This chamber is filled with a barrier fluid (propylene glycol mixture) that lubricates and cools the seal. The seal itself is a double faced seal. Doing the traditional duty of sealing the application product, but also sealing the wet seal cavity holding the barrier fluid in. Conventional wet seal pump technology has been around for a long time and has been limited to low pressure applications like transfer pumps. Transfer type pumps normally operate at pressures less than 50 PSI. Whereas sprayer pumps can see pressure spikes in excess of 120 PSI. These higher pressures were causing seal challenges. Mr. McNair explained that the barrier chamber operates at basically zero pressure and the sprayer chamber can exceed 100 PSI. The resulting pressure differential resulted in the seal blowing out into the wet seal chamber. The challenge was developing a way to equalize the chamber pressures within the pump to maintain seal integrity.
What is ForceField Technology
To address these issues, Hypro launched the ForceField Series pumps in October, 2016. The ForceField pumps come standard with a wet seal that utilize a barrier fluid to keep the mechanical seal cool and lubricated. The wet seal protects against common failures, like dry run and chemical bonding. Addressing the pressure chamber deviations, a self-regulating diaphragm membrane was added. The membrane actively maintains a pressure differential between the barrier fluid and the pumping solution. Pressure is transferred by the diaphragm, balancing the two chambers. This provides longer life, worry free operation and safe serviceability.
·ForceField wet seal technology protects seals by using a barrier fluid to keep them cool and lubricated, even while the pump is running dry.
·ForceField technology actively maintains a positive pressure differential between the chamber barrier fluid and the pumping solution, which prevents chemical bonding of the seal faces. The result is increased life and maintenance free operation.
·Eliminates dry run failure.
·Prevents chemical and fertilizer bonding failures (slip-stick).
·2,000 hour minimum pump life.
·Maintenance free operation, barrier fluid top-off required at 1,000 hours.
·One year "bumper to bumper" warranty covering all parts.
- Current standard pump warranty does not cover wear items (mechanical seal).
Bruce Bode, Vice-President of Business Development, Fimco Inc. stated that the ForceField series would be a great fit for all applications, but especially on planters. "Planter installations intuitively present challenges for centrifugal pumps with mechanical seals." Between multiple tank setups and the hose routing, there is a lot of opportunity for air to be trapped in the system. This trapped air is hard on seals. "Farmers can't afford downtime anytime of the year, but especially during planting." "Looking at the economics, if you replace one seal on a standard pump, you would be money ahead to invest in a ForceField", Mr. Bode added.
Hydraulic Motor Updates
In addition to the ForceField Technology, Hypro has upgraded the hydraulic motor on the 9310 Series pumps. These upgrades enhance the durability of the motors for todays hydraulic systems.
These updates include:
·Larger ball bearings for longer life
- Motors have been tested to over 7,600 hours, no failure (testing stopped)
·New hydraulic seal runs at lower temperatures, extending life.
In conclusion, whether you are looking to improve accuracy, decrease maintenance or eliminate downtime, PWM Technology or ForceField can keep you in the field. For more information contact your nearest Ag Spray Equipment store. Be sure and have your Ag Spray Sales Team member share more about what they learned at the recent National Ag Spray Sales Training.