Silicone grease in CH

[omph]

Has anyone ever used silicone grease in the wet parts of a heating system? e.g. pump, diverter etc - I have on occasion come across valves that get a little sticky which could do with some cleaning and I would imagine some waterproof grease would do wonders but I am not sure about longevity of the product, esp. in closed systems.

 

[CBW]

Yep, use it all the time when replacing parts with an o-ring and apply to other parts where it’s needed too.

 

[omph]

Yep, use it all the time when replacing parts with an o-ring and apply to other parts where it’s needed too.

Do you use marine grade grease ? or anything as long as its silicone? My biggest concern is with pressurised systems which have a high flow rate (esp low temp) that the grease will just wear off. I am currently researching different types of greases and have found marine grade lithium grease tends to hold better.

 

[CBW]

No I use whatever TP can get hold of, but it’s usually high temperature rated. Currently using Arctic Hayes.

 

[omph]

Thanks. The Artic Hayes brand is water repellent so will probably break down in the short term in a wet system.

I have settled on Carlube Marine Waterproof Grease - waterproof and has low wash off so hoping it'll last for a few years.

 

[Madrab]

Carlube Marine Waterproof Grease

This isn't a silicone based grease, it is a mineral based paraffin based grease, not advisable to be used (edit spell) long term with synthetic seals/orings etc found in modern systems and components.

WRAS approved Silicone grease is classed as potable which means it will not breakdown in water and can be used with mains hot and cold water.

 

[omph]

This isn't a silicone based grease, it is a mineral based paraffin based grease, not advisable to be used ling term with synthetic seals/orings etc found in modern systems and components.

WRAS approved Silicone grease is classed as potable which means it will not breakdown in water and can be used with mains hot and cold water.

This is to be used on CH, not potable. The silicone grease I have used to fix some sticky diverter valves (plastic) always wash off 2-4 weeks post install, and before you mention, the issue is thermal expansion and not sludge. The part needs lubrication to prevent sticking/water hammer.

Also note the grease will be fully immersed so it needs to resist water penetration, pressurisation and wash off, a tall order for poor design choices.

 

[omph]

Looks like Silverhook do a diaelectric waterproof silicone-based grease with a max operating temp above 180c. That would be more appropriate with synthetic o-rings.

 

[Madrab]

This is to be used on CH, not potable.

I understand that but it's not really about where it's being used rather with it being potable then it wouldn't dissolve in water, I've yet to use a silicone grease that wasn't still in place the next time it was exposed.

Not sure where you are using it, but the synthetic components where the grease is being used shouldn't really be in full contact with water? It's the seals themselves that stop water ingress not really the lubrication?

 

[omph]

I understand that but it's not really about where it's being used rather with it being potable then it wouldn't dissolve in water, I've yet to use a silicone grease that wasn't still in place the next time it was exposed.

Not sure where you are using it, but the synthetic components where the grease is being used shouldn't really be in full contact with water? It's the seals themselves that stop water ingress not really the lubrication?

What grease brand do you use, and where do you use it?
I want to use it primarily in certain types of valves (inc. diverters) that get sticky and attract dirt which effects performance.

 

[Madrab]

that get sticky and attract dirt

I find that any grease will attract dirt, by it's very nature, if there is dirt in the vicinity if you see what I mean. I use silicone grease primarily as a lubricant to resist binding, reduce friction and help materials like silicone and nitrile rubber seal without twisting or turning. It is also inert when it comes to these newer materials and used in a potable setting.

What materials do you want to lubricate, is it seals or is it on metals to reduce binding and excessive wear?

I have 3 different tubs actually with one being dielectric, just acquire them and use whatever I have to hand - Arctic Hayes is my usual though as that's what my supplier had in stock, never failed me yet on whatever I use it on and it still seems to be there when I return to the job. Typical examples of where I use it are mag filter tops and pump seals/valves - others would be compression waste pipe seals, any O-rings I happen to come across in boiler/flues/fittings/valves etc, pushfit couplers, compression tap valve worms etc.

The only part of a zone valve that should get sticky is where the shaft seals meet the shaft housing and by that point the seals are goosed and it will need replaced.

 

[omph]

I find that any grease will attract dirt, by it's very nature, if there is dirt in the vicinity if you see what I mean. I use silicone grease primarily as a lubricant to resist binding, reduce friction and help materials like silicone and nitrile rubber seal without twisting or turning. It is also inert when it comes to these newer materials and used in a potable setting.

What materials do you want to lubricate, is it seals or is it on metals to reduce binding and excessive wear?

I have 3 different tubs actually with one being dielectric, just acquire them and use whatever I have to hand - Arctic Hayes is my usual though as that's what my supplier had in stock, never failed me yet on whatever I use it on and it still seems to be there when I return to the job. Typical examples of where I use it are mag filter tops and pump seals/valves - others would be compression waste pipe seals, any O-rings I happen to come across in boiler/flues/fittings/valves etc, pushfit couplers, compression tap valve worms etc.

The only part of a zone valve that should get sticky is where the shaft seals meet the shaft housing and by that point the seals are goosed and it will need replaced.

In terms of dirt, it depends on the type of grease. For example, water resistant/repellent grease is semi-permeable so will allow for eventual water/dirt ingress, but waterproof grease creates an impenetrable film so water and dirt will slide off.

Using it in pushfit couplers, non-moving o-rings etc is fine and I don't think you need to worry too much about technicalities and any silicone grease will work. The issue is with immersed moving parts. To give you one example, on certain Viessmann combi boilers the diverter use a piston action which pushes out to seal for heating and pulls in for dhw. The diverter's sealing o-rings when pushed out become very tight due to the thermal expansion of the pipe its sealing, so when the motor pulls out, it results in a very loud thud. Since it's a moving part, using water repellent type greases will work for 2-3 weeks and then I am back at sqaure one. I have ordered some of that waterproof Silverhook silicone-based grease and will be testing it soon enough.

 

[Madrab]

Ah right, I now see the application you are describing. In those circumstance I'd use a lithium based synthetic grease, again as it's synthetic it doesn't react badly with the new type synthetic rubbers but it can be more resilient than silicone based greases.

It is specifically suited to wet/immersed applications where mineral spec greases are not suitable. I do have to add though that I never found a grease, mineral or synthetic that is completely waterproof, no matter what they say. Even the turbulent and natural action of immersed moving items can 'remove' even the most 'waterproof' of greases.

BTW - Silverhook also do a lithium base synthetic grease, may be worth a try.