Electric heated pavor screeds

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Electric heated pavor screeds

Post #1 by widget » Sun Jun 09, 2013 9:10 am

Hi all, :wave:
Hutch got me intrigued with another post so i thought i would start a new thread.

I have never worked with electrically heated pavor screeds so i went and did some research and found some interesting stuff.
Heres a link to a few bits that might be of interest to all the guys,

http://www.google.com/patents/US6981820

Because ive never used electric heating i could do with some feed back from you guys on the job, on maybe how electric heating compares to other methods of heating screeds. Like we have said before, theres nothing like hands :thumbup:
I want to rust out not wear out


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Re: Electric heated pavor screeds

Post #2 by Hutch » Mon Jun 10, 2013 1:25 pm

Hi Richard
Vogele were the first with electric heating around 1956 but it never seemed to catch on with other manufacturers maybe because on these early machines and upto the 90s the engine had to be reving flat out to heat the screed and so was not popular with operators also the cost of components may have stopped other manufacturers ,though back in the mid ninties Blaw Knox had a prototype screed that used a mat inside the screed like that used for underfloor heating in houses.Modern technology has allowed the heating system to control the engine speed and most warm up on fast tickover.The electrical power is supplied by a three phase alternator that may be belt driven off the crankshaft pulley or hydraulically driven (dynapac)with the hydraulic drive being engaged and disengaged by the heating control.The electical power is split 3 ways with a single phase supplying each of the main screed and left/right extensions,a temperature probe mounted on each screed section sole plate controls the heating through a control system and contactors.Side gates may also be heated by two extra heating elements.The elements are like long strips of steel with a electrical flex fitted in the end.Two or three of these depending on the width of the plate are clamped to each sole plate including bolt on extensions,there is also a single element in each tamper blade to allow the tampers to free off easily.Electric screed heating really took off in the early 2000s because of the dangers of transporting and storing propane along with propane burners being classed as enviromentally unfriendly (something that a few manufacturers are now starting to challenge as machines with electric heating consume more fuel thus producing more exhaust emmissions).From a maintenance point of view electric heating is more reliable and does not do the damage to the screed structure like burners but on the downside they are not as easy to do a quick fix to with some of the elements being a mornings work to change.Out of all the paver manufacturers Vogele seem to have the best elements lasting as long as the sole plate themselves.

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Re: Electric heated pavor screeds

Post #3 by widget » Mon Jun 10, 2013 10:01 pm

Hi Paul,
All interesting stuff, ive had a look on he web and thats where i found the patents.
Your post is very good and explains the system very well, It seems a very straightforward idea, i assume fairly large d/c is involved?
Is this system commonly used now by all manufacturers, and do many people choose the system over others?
I want to rust out not wear out


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Re: Electric heated pavor screeds

Post #4 by Hutch » Tue Jun 11, 2013 1:46 pm

Hi Richard
415 AC alternators are used. Vogele,s system used to run at 60htz with 110v take off via a transformer.When Tarmac took delivery of their Super 1800 pavers we were told never plug in power tools designed for the uk as the motors would destroy themselves due to the hertz rating.The Super 1800 that ran out of Snodland also proved the old saying "A little knowledge is dangerous" as regards the electric screed heating and the closest I have come to being electricuted.The workshop foreman and I had gone to fit extension boxes to this machine in Sompting West Sussex and all was going well until one of the boxes was plugged in by myself,the plug was damaged and could fit either way into the socket so I fitted it in the way that seemed correct, the wiring to the socket then started to burn so we shut the machine down disconnected the plug and rewired the socket.Upon restarting the machine the alternator bellowed out smoke so the machine was shut down again and we called the workshop manager to inform him what had happened.Next day I was down Sompting again with the Wirtgen fitter,a new alternator and some armoured wiring.After a long day we had the machine back as it should be but could still not understand why the tripping device had not tripped when the plug was inserted incorrectly .On close inspection we found that the trip had been bypassed.We decided to call it a day and investigate further in the morning due to it being dark.Next morning we discovered that the fuse for the 24v lights also supplied the heating system low voltage and because it kept blowing someone had bypassed the trip.An investigation was then carried out at Snodland and it was decided that the most likely culprit was a subbie fitter we used but it could not be proved and in a memo it was put sarcastically that once again " mr nobody was to blame " for the £11000 repair bill.From a personnel point of view if that plug had been connected to the live when I plugged it in 415 V would have continued to flow into me until that machine was shut down.Most companies now lock or bolt the heating control boxes shut safe from prying fingers but the modern systems are almost idiot proof with insulation failure alarms and very sensitive voltage breakers.All the main paver manufacturers offer electric heating, though Marini/Bomag and Ammann/Antec were late into it, along side their propane screeds but the large surfacing companies seem to prefer electric because they do not have to store and transport large numbers of propane bottles.

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Re: Electric heated pavor screeds

Post #5 by widget » Wed Jun 12, 2013 9:34 pm

Hi Paul,
Sounds like you were very lucky especially with a/c being involved, and i should think you would give "mr nobody" a bloody good arse kicking if you ever found out who they were :roll:

I wonder if you have to be a fully qualified electrician to work on these systems where health and safety is concerned? I now work in the electric vehicle industry and we are very tightly controlled when it comes to anything 240 a/c for the trucks(a/c charging) , but when it comes to the trucks themselves, they operate a/c motors of up to 5Kw using a d/c inverter systems of up to 1000amps from a d/c power source such as an 80volt d/c battery, so no electricians qualification is needed.

I can see the advantages of the electric heated screed, especially as you said, when it comes to the logistics of moving and handling propane or gas oil.

I have had in my operating days lost 2 of pavors (both Bitellis) to propane fires!! Due to gas pipes on the machine failing. These were total burn outs, and believe me these fires very quickly got out of control and got back to the cylinders themselves. Any fires on gas oil burner systems were much easier to control and extinguish.

It seems to me that if the electric systems heat the screed to the correct temps quickly and doesn't cause any sole plate warping etc, reasonably maintenance free and has a good safety system then it sounds like the system to go for :thumbup:
I want to rust out not wear out


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