Fan or PD?
I'd like to know the thoughts out there about what people prefer...fan or pd systems? Is there a time where one is needed over the other based on situation or what??
Thanks.
Tags: Fan, PD, Preference
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Permalink Reply by Scott Krupinski on -
With very few exceptions, I strongly prefer a fan machine. In my previous life as a contractor, we dealt with several industrial customers which required 300'+ horizontal pulls of heavy liquids and sludge. The PD performed very well, but the restriction of the suction tube from 8" to 6" or even 4" in some applications SEVERELY impacted the life of the blowers. (overheating lobes, blow-by, etc.) once the blower was overheated once (first job) warranty was out the window... so there was a price to pay for the PD beyond the initial purchase cost increase. Additionally, you do not get the full efficiency of a PD until the vacuum is fully loaded, so for sewer work in particular, any slight performance enhancements would only be enjoyed when the tube is buried, and I can think of no good reason to do that.
But all PDs are not created equal. I recently sold a refurbished 2004 Vac-Con with a Roots 827 that sucked iinfinitely harder than other brand trucks I have worked with the identical blower... its about airflow, and how that flow is directed cleanly throughout the entire system to minimize drag. The design does not stop at the blower.
The fan conveys air better for sewer work. I have yet to find, in the real world, a manhole or a lift station which required anything more than a properly operated 3 stage fan to clean it. Greater tolerances on the fan also are much more forgiving for any residual blow-by (let's face it... we dont work in the cleanest environment). Reducing the airflow to a smaller diameter hose will not cause irrepairable harm to the system, and a first party warranty is worth its weight in gold.
But all fans are not created equal either... Welded steel vs. aluminum rivets.... 2 stage vs. 3 stage... and again the clean flow of air...
A fan will act as an excellent air induction system to ventilate a chamber for safe confined space entry; and can operater on less horsepower, leaving more in reserve.
I will say that I am a bit biased, but biased based of real world experience with both systems. and just because I am biased does not mean I am not right! :)
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