Vermorel electric sprayer reliability - Page 1
Forum section: electronics / projects

author: cheeseit
author_rank: Regular Contributor
timestamp: January 18, 2021, 09:53:38 pm
content: I've just been tasked with trying to improve the reliability of some electric sprayers used for de-icing during winter, and repairing them from now on. Our issue is that the sprayers break down constantly and repairing and buying new ones each year is somewhat costly. We have 7 at the moment and 5 of them are non-functional right now. This is unacceptable as they are somewhat mission critical. Functional and reliable sprayers are primary, cost is secondary but each sprayer cost around €750 ex. VAT and we replace around 3 each winter. I don't know the combined cost of parts and labour each year but that's no doubt the largest expense.Sometimes the sprayers go without use for weeks, sometimes every day for prolonged periods. Two are used at a time and and we cycle through them as they break down. Usually one or two tanks of 18L are used in each when in use but it peaks at 200L, though this happens rarely. They are used and stored in somewhat harsh environments, that are cold, wet and with salts in the air, and they get wet from time to time, from both water and the liquids used. A rinsing solution is pumped through after each use.The sprayers used are Berthoud Vermorel 3000 Comfort Electric 18L and are supposed to be the duck's guts - I dunno about that.. The tech that's repaired them until now is a general repair tech and not particularly into electronics.Two products are used, primarily Viaform Liquid (50 wt% potassium formate with <0.5 wt% corrosion inhibitor of some kind. pH 10.9-11.4) and urea in liquid form (35 wt%, pH 9-10). I think Viaform is the one causing trouble but we have to use this product.I have a brand new sprayer I'm going to try to modify before putting it to use.Four areas that needs to be improved: PCB/connectors/switches, pressure sensor, pump, batteries and chargers.PCB/connectors/switchesPCB appears to be conformally coated but they still fail from time to time, likely due to corrosion as Viaform is incompatible with solder, zinc and galvanized steel. The PCB has four common type spade connectors, tin/nickel plated? A pair of SH E80 toggle switches are mounted to the board and these appear to corrode too. From what I've found they are supposed to be sealed waterproof IP67. The board only features a PIC16F685 microcontroller, a power MOSFET (IRFR9024N), two SOT23's and a bunch of passives. Simple stuff I think.Some traces appears corroded beneath the solder mask.The board conveniently has an ICSP connector if needed and I can read and write to flash. One board has what appears to be one or two blown resistors but I haven't traced anything.The repair tech has tried doing a few things, including potting the board, which all failed. The potting attempt may have failed due to the MOSFET overheating, or due to moisture trapped on the board before potting it. I have access to two boards that, according to the tech, has failed.My planReplace connectors with gold plated connectors - gold must be better suited, right?Mount a heat sink on the MOSFET, just to be certain it's not overheatingSwitches (SH E80) apparently are IP67 rated but I'm not confident they're good enough. Two removed measure fine though with visible corrosion on the outside, on the pins and beneath the switches.Bake the board at low temp and thoroughly coat it with conformal coating - I have some Kontakt Chemie PLASTIK 70, is this good enough?Pressure sensorThese apparently fail regularly and are quite expensive from to buy from the distributor at about €135 ex. VAT. I not sure about Viaform compatibility with brass but the sensor inlet appears to have a thick coating of what looks like salts with a green-ish tint to it so I'm guessing it's not good. Anyone with a better understanding of chemistry that can chime in on this?Only IP00 rated, which to me is surprising and could likely explain why it fails. The sensors connection is a board edge connector that appears to be tin/nickel plated which, again, the Viaform is incompatible with so simple corrosion could be the issue but I'm thinking the internal salt deposits are worse.No matter what, if it fails regularly I'll have to try something else. I don't know how the MCU uses the input from this sensor but I guess it is used as feedback for the pump for regulating the pressure as these sprayers have three settings for flow. Only one setting is ever used, which is the max setting, so the sensor can perhaps be removed by faking the output from it via a fixed value. Some investigation is needed.My planFind a suitable replacement that can handle the liquids - suggestions are very welcomeSeal the connector using siliconePumpI don't have one yet but it's a 12V diaphragm pump and they fail from time to time. I'll update when I know more about it.Batteries/chargersLi-ion batteries where the batteries themself don't fail per se but the connectors very much do due to corrosion, both the charging port and the connector. The plugs on the chargers them self also fails, again with corrosion. The tech replaces the factory plugs, a kind of Molex I think, with something waterproof but this does little as it's still exposed to moisture and gets attacked.My planReplace connectors with gold plated connectors - gold againLong post but I wanted to be thorough. Hope someone has some input and suggestions.

author: Terry Bites
author_rank: Super Contributor
timestamp: January 19, 2021, 11:13:11 am
content: When you get aid for this work will we get a %?

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 19, 2021, 01:56:22 pm
content: Put automotive dielectric grease in all the connectors, that will greatly reduce corrosion from moisture.

author: cheeseit
author_rank: Regular Contributor
timestamp: January 23, 2021, 10:54:29 am
content: Quote from: Terry Bites on January 19, 2021, 11:13:11 amDo you have anything to contribute that warrents payment?Quote from: NiHaoMike on January 19, 2021, 01:56:22 pmExcellent suggestion, thanks!