Why Raider?
| Ideas from PPC's Senior Engineer: On a regular basis we have people shaking their heads and asking, “Why haven’t other manufactures built a product like the Raider?” and “How can it perform so well, with such simplistic operational controls? ” The answer is engineering. The Raider is not a remanufactured paint pump. It has been designed from the ground up with only a plural component dispenser in mind. No old designs carried over from extinct technologies, no shared parts from something we thought would work, the only thing PPC focused on was, and is, simplistic dispensing operation of plural components. We began the evolution by researching all of the problems associated with processing of plural component materials, not only under high pressure but low pressure as well. While conducting further research and development for our line of High Shear in-plant machinery, we experienced similar problematic handling patterns and characteristics, and set out to solve them. Under even low-pressure conditions, the issue of what is commonly referred to as lead-lag is a problem. Lead-lag is when the A material dispenses before B material, or vise-versa. Lead-lag causes problems across the spectrum of the plural component processing with ratio, crossovers, and poor mix. The answer to the Lead-lag problem lies in the rheology of polymers themselves, understanding the processing parameters and handling characteristics of each material separately. These include:
You will find each material A and B to be drastically different in properties; however, that is what makes it work - two liquids to form a solid. They have to be different in just about every facet of handling. On top of that, we then compound the problem with a variety of materials, from foams, elastomers, polyureas and epoxies, each different in chemistry and A to B handling. In the past, we (as an industry) attempted to mitigate rheology indifferences by adding more heat to one side, different orifices, hose sizes and anything else to make A and B “match” on mix and exit. The truth is that in the past ten years chemicals companies have done their part in providing more one to one systems with a viscosity match, requiring minor set-up changes from A and B. The other issues come from equipment manufactures. When we review a piston type pump to understand how it works, we realize that there is a gauge bouncing, similar to an engine, the piston reaches top dead center and is reversed. Each ball must be reseated and, with it, the fluid in the opposite direction, showing as the gauge bounces or dips. If gauges could read fast enough, you would see pressure go to zero at the top and bottom of each stroke if not for the hose expansion, check valves, and fluid reservoirs. We have all attempted to minimize this effect by using larger-than-output rigid size pumps, larger hoses, restricting devices, etc. One way to view this is in pressurized hose under a microscope, watching it pulse like a beating heart. To this, most say, “As long as ratio and volume is on, I’m o.k.” True… to a point of understanding how each material compresses in center of power stroke and relaxes top and bottom of stroke. Most A sides of systems (ISO) have a higher specific gravity and do not compress as well a B side (Polyall). This lends itself to sporadic ISO flow and steady B-side flow. The B-side of most foams behave like a lubricating fluid, they are an oil base and have the ability to act as a surge-suppressor by compression alone. The A-side of a foam system is drastically different: it runs like water, doesn’t compress well, and drops dead at top and bottom of stroke. Each system requires different heat settings, tips, chambers, and hoses to minimize the effect of lead-lag. Now add one hundred fifty feet of hose to a piston pump machine, understanding that A and B each have different frictional loss formulas. For example, five hundred cps-B side (lubris) has 1/3 psi per ft. pressure loss, and two hundred seventy five cps. A side only has 1/5 psi pressure loss, what does this do? You know that sound when you’re spraying at high pressure, that shhh……shhh, that is center of the power stroke. When it falls off, so does the ratio at the point of mix. Chemical companies usually formulate at above 100 index to minimize the effects of this, generally spray systems have a 105 to 108 index, 100 meaning matched ISO to Poly, one 105 more ISO to compensate reactivity and mix. Many of the difficulties in processing plural component materials with piston pumps can be associated with Lead-lag, some you may be familiar with include:
Lead-lag is one of many problems the Raider was built to solve, and to emphasize that point we perform a demo at all Raider trainings, which includes starting spray with zero ISO pressure and full Poly pressure to show the resilience of the Raider product. We have eliminated open packing and stems on all pumps, utilizing close coupled rotary pumps, with seal side submerged in lubricating bath. We have solved massive power and/or air consumption with counter rotating pumps and helical gear transmission. Raider machines use under fifty amps of two hundred twenty volt, single-phase power. We also incorporated large dwell time heaters, where others have gone to direct contact type. PPC heaters all possess stainless steel interiors and one hundred fifty fluid inches of heating path. Heating liquids is a direct correlation of wattage and dwell time, utilizing only wattage and direct contact can cause hot spots and uneven distribution, not to mention thermal shock on heater and controllers inability to make rapid changes, all leading to ware. The Raider is built on a rock steady welded steel frame; you will find the electric system box at the highest point of the cage, for safety and durability. All controls are large and well labeled with circuit breakers for each function, and a minimalistic approach to functionally. What does all this mean to the end user?
The Raider has shown improved physical properties at lower application pressures because it is reading actual pressure, not a spiked or stalled pressure. With on-the-ratio accuracy the Raider yields a better mix, better fan, and better product at all pressures and volumes. |