Recycle Asymmectrical Time Switch

[gtownspark]

I'm working on a job where I need to make a pump switch ON for 15 seconds then OFF for 45 seconds then repeat ON for 15 seconds and OFF for 45 seconds etc...At the moment the pump is switched on by a contactor that is permanently energised while ever the plant is operational. Can anyone recommend a din rail mounted asymmetrical time switch with recycle function that I can use to switch the pumps contactor on and off? or any other device that might be better suit to the task

 

[snowhead]

Buy Time Delay Relays | RS Components

 

[Marvo]

There's lots of them available are they're mostly as good as each other if they're a recognised brand name.

You do realise you'll possibly destroy the pump by frequent cycling it at 30 or 45 second intervals? Check the manufacturers data to see the maximum number of cycles per hour permitted for that particular motor or pump before you install any asymmetrical time switches. There's very few motors capable of that kind of duty cycle.

 

[Leesparkykent]

http://www.timeguard.com/products/t...ingle-channel-3-module-16a-digital-timeswitch

 

[gtownspark]

Thanks Marvo, I hadn't considered the maximum number of cycles per hour of the pump....I'll have to raise this with the customer, at the moment the pump is constantly running so maybe they can compromise on the timing to meet the maximum cycle requirements of the pump.

 

[HandySparks]

here's lots of them available are they're mostly as good as each other if they're a recognised brand name.

You do realise you'll possibly destroy the pump by frequent cycling it at 30 or 45 second intervals? Check the manufacturers data to see the maximum number of cycles per hour permitted for that particular motor or pump before you install any asymmetrical time switches. There's very few motors capable of that kind of duty cycle.

Quite agree. Sounds like a lower power / lower capacity pump running continuously would be a better bet.

 

[Marvo]

Some more info about the actual pump and the overall system it's operating in would be handy. If it's a centrif pump then artificially raising the head pressure using a hand operated or even a modulated valve would possibly work to reduce the flow and, depending on the pump, could reduce the run current and hence the running costs as well. Setting up a bypass system around the pump with a PRV or similar to ensure the minimum head presssure requirements are met might also work. Short cycling the pump electrically is a really bad idea, there's a good chance the heat that will develop in the rotor will cause catastrophic failure.

 

[gtownspark]

Some more info about the actual pump and the overall system it's operating in would be handy. If it's a centrif pump then artificially raising the head pressure using a hand operated or even a modulated valve would possibly work to reduce the flow and, depending on the pump, could reduce the run current and hence the running costs as well. Setting up a bypass system around the pump with a PRV or similar to ensure the minimum head presssure requirements are met might also work. Short cycling the pump electrically is a really bad idea, there's a good chance the heat that will develop in the rotor will cause catastrophic failure.

Thanks mate, I'm back on site on Tuesday so I'll have to see what I can find out.

 

[rapparee]

Is it a interlube pump you are using by any chance. We use them and they duty cycle with no bother. We actually have the lower spec pump (lubeplus e) which we control from the PLC of the main machine. You can also get the pumps with their own intregal microprocessor (lubeplus gx) to set the duty cycle which suits you. We use these on basic machines where no PLC/HMI is present.

 

[Knobhead]

Interlube are very good, considering some of the places we used them I don’t know how they kept on going. The cycle time was nowhere near as rapid as the OP suggests but the duty was arduous to say the least.

 

[Marvo]

Most lube pumps come with a built-in timer so I was thinking it's more likely to be a pump for water or another fluid. Unless the OP comes back with more info I guess we'll never know

 

[Knobhead]

Fair point Marvo but I can’t see any reason to pulse a water pump, I don’t know about you but I’d use an automatic shut off valve and a constantly running pump.
[SUP] [/SUP]
A positive displacement pump would be a different matter as the delivery can’t be valved.

There are ways around it but I suppose we’ll have to wait for the OP to get back with what he finds, if he comes back.

 

[SheffSimon]

There's lots of them available are they're mostly as good as each other if they're a recognised brand name.

You do realise you'll possibly destroy the pump by frequent cycling it at 30 or 45 second intervals? Check the manufacturers data to see the maximum number of cycles per hour permitted for that particular motor or pump before you install any asymmetrical time switches. There's very few motors capable of that kind of duty cycle.

A bit OT, but that's not an unusual duty cycle for packaging machine motors, palletisers and the like, using bog standard SEW induction motors. Only small kW motors though.

As has been said, more process info required. I've used a lot of pumps, big and small, and don't ever recall pulsing them on and off.

 

[Darkwood]

Any chance of keeping pump running and switching a return valve on required setting with a solenoid a very robust solution... again info is needed.