7 replies to this topic

[The Prof]

Hello

 

I am working at a food manufacturer where steam jacket kettles with rotating scrapers are used. I have today seen a scraper that has melted at the tip. The temperature at the kettle wall is approximately 170 deg C. I suspect the wrong scraper has been used. Does anyone know of scraper options with a higher temperature tolerance? I'd very much appreciate your help. 

[GMO]

The kettles I've always rated are made by DC Norris. Never had a problem with a paddle melting. 

 

Ready-2-Cook Industrial Kettle | Commercial Cooking Kettle UK

 

Not sure who made your kettles in the first place but I'd go back to them first. Ask them for a spec for the material if you want to go generic but honestly, why? It won't save you that much 

[The Prof]

Thank you GMO. They are DC Norris vessels. The scraper melted when it was left in direct contact with the vessel wall (at 170 deg C). I guess the scrapers need to keep moving and when stationary, mustn’t remain in direct contact with the vessel wall.

[GMO]

It was one of their scrapers? I'm surprised. I'd go back to them and ask them about it. I'd expect their material to be more robust. I suppose the other thing is why was it stationary when on? Again I'm kind of surprised their programming doesn't protect against that. Unless it had emptied.

From memory though I don't think ours would touch the sides even when they were inside the pans, I mean apart from as they were turning but only a minimal amount because otherwise you'd get tonnes of plastic shredded into your product.  Is it the kind where the paddles lift out the top (god, DC Norris get on my nerves for some of the things they do but I love that design). I don't work with one now but I can't remember a point where they'd be touching the side apart from at the tips as they turned. Could it be a set up issue?

[The Prof]

It was one of their scrapers? I'm surprised. I'd go back to them and ask them about it. I'd expect their material to be more robust. I suppose the other thing is why was it stationary when on? Again I'm kind of surprised their programming doesn't protect against that. Unless it had emptied.

From memory though I don't think ours would touch the sides even when they were inside the pans, I mean apart from as they were turning but only a minimal amount because otherwise you'd get tonnes of plastic shredded into your product.  Is it the kind where the paddles lift out the top (god, DC Norris get on my nerves for some of the things they do but I love that design). I don't work with one now but I can't remember a point where they'd be touching the side apart from at the tips as they turned. Could it be a set up issue?

 

Yes, it was one of their scrapers. I am waiting for the specification. The paddles do lift out from the top. It would appear the motor should not have allowed the blades to stop in direct contact with the kettle wall.......many thanks for your input with this.  

[GMO]

Ah no problem. Thought it sounded weird. 

Hope you get it set up properly. It would be interesting to see if you had any excessive wear before that point indicating it was hitting the side or anything. It would be good to understand how it got there so it doesn't happen again.

[The Prof]

It would seem that steam jacket vessel blades are typically made from acetal copolymer. This material can withstand temperatures up to 105 deg C. Above that, the material softens and will melt if left in contact with a hot steam jacket vessel surface. When stationary, the blade must not remain in direct contact with the vessel surface. In our case, we discovered that the blade stirrer phasing was not operating as it should, leaving some blades in contact with the hot surface. The problem has been solved by ensuring the stirrer blade motor phasing prevents exposed contact with a hot surface.

[GMO]

It would seem that steam jacket vessel blades are typically made from acetal copolymer. This material can withstand temperatures up to 105 deg C. Above that, the material softens and will melt if left in contact with a hot steam jacket vessel surface. When stationary, the blade must not remain in direct contact with the vessel surface. In our case, we discovered that the blade stirrer phasing was not operating as it should, leaving some blades in contact with the hot surface. The problem has been solved by ensuring the stirrer blade motor phasing prevents exposed contact with a hot surface.

 

Brilliant. I've learned something from that. I really appreciate you following up with the update. Considering how close that is to sauce temperatures (considering solutes within water) that does seem a bit close. But glad you fixed the root cause too.