Why pressure relief valves should be checked & serviced

conikal

??? ???

derrilex

Fixer upper  :laugh: :laugh:

Koffee_Kosmo

That looks like an implosion in my small screen Like the egg sliding in the bottle neck science experiment If its an explosion then WATCH OUT KK

FreshCoffee2

Careful......someone will see that and think its a great looking project and probably vintage, and want to import it to restore...... :pan

Lacehim

That machine was at Sainsbury's in the UK, and I don't think it all came down to servicing.  By all accounts the coffee shop was only recently opened and I'm sure Sainsbury's would have regular services on their equipment.  Human error (training) also added to that accident, there would have been a pressure gauge on the machine somewhere and no one noticed or checked it.  People have to realised that a pressurised boiler is something to be taken seriously, especially when it's full of boiling water! Sadly (typical media) after the inital reporting of the incident there hasn't been any report by Rushmoor Borough Council who where said to be looking into the matter or any update as to how the injured are.

derrilex

Definitely looks like its sucked itself inside out. Ahhhh, atmospheric pressure, is there nothing you cant do :D

conikal

on 1353894477:

Definitely looks like its sucked itself inside out.,

???.. i hope you are not considering a career as an accident investigator.. :D Can you not see the heating element splayed out like a dry flower display ? ..not to mention the classic "burst" appearance of the boiler. Lacehim. .. ... Were there injuries ?..sorry to here that if so.  I had imagined it was the sort of accident that would happen overnight when not in use. As it was a commercial situation, the Health & Safety Exec would have been involved by default.

derrilex

on 1353900264:

i hope you are not considering a career as an accident investigator

Until its in front of me there is no definite cause. All that damage could be post mortem for all you know. 

UNM

http://m.bbc.co.uk/news/uk-england-hampshire-11320258 Apparently after the pressure valve failed, heat continued to be supplied to the unit, causing it to malfunction.

conikal

on 1353903144:

Apparently after the pressure valve failed, heat continued to be supplied to the unit, causing it to malfunction.

I would have to think that in order to burst the boiler there was more than one failure.. !) The boiler overheated/over pressurised..suggesting the pressurestat or temp controller , failed. 2) for the boiler to fail from over pressureisation, the pressure relief valve must have malfunctioned 3) I would have thought that a commercial m/c would have a secondary over temp cutout or alarm to back up the pressurestat ( as most domestic m/c ) ? Dual redundant safety valves would be a simple and cheap  way of avoiding this.

derrilex

on 1353904477:

Dual redundant safety valves would be a simple and cheap  way of avoiding this.

For sure. Big boilers need big safety features I reckon. I would have thought 3 or 4 pressure release devices would have been par for the course - obviously not

FreshCoffee2

Well, it depends on anyone's viewpoint really. There are already two cut off devices in the system and the Boiler Safety Valve IS the secondary cut off: a) pressurestat b) Pressure Relief / Boiler Safety / Over Pressure - Valve. Failures in the former are more commonly manifested as failure to pressurise, rather than to allow an over pressure situation, but they do occur one way or the other from time to time, which is why we have a Safety Valve. Failures in the latter are rare OR, the pressurestat is usually good enough that a situation of over pressure seldom occiurs, so the safety valve is rarely "tested". Either way, rare enough. I could be wrong but think you may find the failures were caused by one or other faulty parts, rather than through a "common service malfunction" in use if you get the distinction? Happy to be corrected if not. Incidentally, one does not (atleast in my neck of the woods), "check and service" a Boiler Safety Valve. If for some reason it's suspect (perhaps if its really old, or leaking,  OR like when someone who is not in the know has tried to remove or service it and we cant be sure the pre set manufacturer setting hasnt been tampered with),  we change it over for a new one. That is the extent of the check and service. Hope that helps.

conikal

on 1353927028:

I could be wrong but think you may find the failures were caused by one or other faulty parts, rather than through a "common service malfunction" in use if you get the distinction? Happy to be corrected if not.

No, i dont think servicing was an issue here ..( I understand the M/c was less than a year old) .. and that Electra  ( the manufacturer)  have stated there was a design fault (  ???) .. But,  would it not still require the boiler to go over temp" ( temp control failure ?),  AND the safety pressure relief  valve to malfunction, for a boiler failure to occur  ? Dont commercial m/c's have the back up "over temp" thermostat that many domestic m/c's have ?? Sorry to go on about this, but i thought it was a timely reminder to those of us who may have "commercial",  or "semi commercial" espresso m/c's in their homes.

beanflying

This shot was all over Twitter last year when it happened but I don't remember seeing anything about the follow up investigations. With Pressure Relief Valves I have seen plenty fail in industry with some nasty results (much higher pressures than Espresso machines including chemicals brews). The recommendation was to crack the relief valves once in a while to make sure they are not frozen or stuck. ** Extreme care with hot boilers with steam pressure behind them so do it cold. If I have the top off my machines they get lifted a few times just in case. We also used to fit up burst or rupture discs into some systems which are a one hit over pressure safety device normally these were rated above the relief valves but below pipe or vessel pressure ratings. Mass produced at say 2 Bar they would be a minimal price add for commercial machines but as Attilio mentions very unlikely to ever be needed due to expected failure mode of the P/Stat. Having both sets of contacts on a P/Stat remain closed would mean a failure of the spring or mechanism inside, the only case of a failure I have seen like this was extreme corrosion of that spring in a chemical environment.

UNM

According to the various articles I read. Elektra said there was a design CHANGE as and that older machines could not fail in the same way. Not the same as a design fault. One article suggested a fault in the water supply line. Haven't seen any definitive diagnosis in the two  years since it happened though. FYI, my machine has a pair of of pressure relief valves at different pressures and runs standalone not plumbed.

conikal

due to expected failure mode of the P/Stat. Having both sets of contacts on a P/Stat remain closed would mean a failure of the spring or mechanism inside

Not all pressure stats are the same. I recently had a pressurestat ( CEME) fail on my domestic Isomac...it failed closed,..heater on. Fortunately i was nearby and the relief valve worked. That failure was due to the switch contacts arcing and welding together..so it does happen.

Elektra said there was a design CHANGE as and that older machines could not fail in the same way. Not the same as a design fault.

Electra made a design CHANGE and introduced a FAULT into the design ! ..to me , that sounds a lot like a design fault, ..or maybe,  more correctly a REDESIGN  Fault  :-* Its difficult to imagine an experienced m/c designer/maker missing that , or it getting through factory testing ....or tests by the installation tech ? It actually sound as if there must have been a combination of errors and ultimate component malfunctions for this to happen.

beanflying

Not a fan of the little CEME/Mater ones and they are known to fail more often, microswitches or small contacts like in them do fail open or closed. I did mean generally the larger ones used in commercial machines which are a very different device. Also a thought with the increased use of PID's programming safeties into them in case of Thermocouple failure.

FreshCoffee2

Still talking commercial amchines here. The manufacturer is never going to tell anybody nuttin about the real reason behind the failures, and it could have been as simple as a faulty batch of Boiler Safety Valves (that would not open if a pressurestat failed and continued to power the elements) delivered by the manufacturer of the valves. On machines where the pressurestat has never failed in that way, you would never know about a faulty boiler safety valve.... OR, there could be some kind of mechanical design change in the machine that stops the "flow' of pressure to the safety valve so that in the event that a pressurestat fails, effectively there is no safety valve present. I would think this would be extrememly unlikely given the safety valve screws directly into the top of the boiler, but you never know your luck in a big country. Some machines in the past have also had resettable (clickson type) thermostats fitted up against the boiler but they have their own little foibles. After that, its anybody's guess. The machine makes a great pirce of art that many modern artists could never hope to duplicate if they tried, and I especially like the elements fanning out at the top.

conikal

But surely there would be pressure tests and safety checks done an any new commercial machine before it is dispatched from the factory or passes off for use in a restaurant !   That would be like someone selling a new public transport bus and not checking the brakes work !

FreshCoffee2

Dont get me wrong, I am not going in to bat for these people. With any manufacturers I deal with, all machines are run & checked by a dedicated staff member that only does QA at the end of the production line before they are packed up. That is in the way they work, and electrically. But I dont know that they would deliberately overpressurise a boiler to see if the safety valve works. That would be the domain of the manufacturer of the safety valves before they are delivered to the esp machine manufacturer who in the case of something like the safety valve, is assekbling something that was made elsewhere. The manufacturers have various certifications for their boilers.....and if I remember rightly, I think (from memory) our manufacturer BFC also supplies the certificate for the safety valve as supplied by BFC's  supplier/manufacturer..... I have no idea what these other people do.....but i dont think you can expect an esp machine manufacturer to test their machine in that way (to see if they can make the safety valve blow off)..... Would they also be expected to try and make the CPU fail to see if the fuses in the CPU will blow before irrepairable damage is done to the electronics? As to fitting more and more safety devices one after the other in case the immediately preceding one fails.....what happens when you fit 2 safety valves and they are both from the same batch which could be faulty? Fit 3 or 4 from different batches? Where do you stop/. I understand where you are coming from but as already stated (in a roundabout way) I think there is more to this instance than meets the eye. Hope that helps.

conikal

... I think there is more to this instance than meets the eye.

..agreed, ..Certainly more than we are aware of.   But i am surprised that you would not expect a boiler safety to be checked after assembly ? Obviously you would not do any destructive type tests, but safety systems should (must ? for liability?)  be checked on any new equipment after assy and during initial set up. Its not like a full boiler test,.. only 2 + bar and a pretty fundamental safety function. The valve manufacturer could not be held responsible for a wrongly installed valve. Its  simple to test these valves ( on a domestic)  using a bicycle pump via the steam wand. ( cold m/c obviously )

FreshCoffee2

Re: :"....Obviously you would not do any destructive type tests, but safety systems should..........be checked on any new equipment after assy and during initial set up...." Interesting point I'll put the question!

FreshCoffee2

FYI, the usual prompt and helpful reply from our manufacturer BFC in northern Italy: The Boiler Safety Valves used by BFC are tared and certified directly by their manufacturer and therefore they are not tested at assembly of the espresso machines. Additionally, BFC employs an independent lab that checks the components they use (all the components have to be certified). What anyone else does is.............? Hope that helps.

conikal

::) Ha , i can just see those Italian hands waving, eyes rolling, and the shoulder shrugging...at the question !  :D     :rofl: :rofl:       You have to admire their approach to life. ! :thumb:

FreshCoffee2

I can tell you, BFC is much easier to deal with, more accommodating and transparent than the other.... ;D....in fact, than many others......

UNM

Is there any Australian requirement for  boilers to be periodically pressure tested? I know gas cylinders need a test every few years. Just wondering.

FreshCoffee2

In terms of espresso machine boilers....not that I know of. Having said that, I dont know what it would prove because I dont think the boiler itself would ever be an issue. Also, just off the top of the head    if you hydrostatically pressure test & measure the expansion of steel gas cylinders (to see if they remain within a certain range of expansion to either pass or fail), where the gas cylinders will return to their nominal size after the test (because of the elasticity of the steel), it may be a different kettle of fish to where you hydrostatically pressurise a copper boiler and it stays stretched and is therefore rendered useless for reassembly ie if you test it, you may actually be making it fail, ergo.....what for the test?  And it may be that what you really want to test is the safety valve to see if it still works at its rated blow off pressure ??? OR.....at that point you may give up and decide its simply cheaper and quicker to replace the old safety valve with a new CERTIFIED rated safety valve, at pre determined iintervals during the working life of a coffee machine. 

conikal

on 1354067231:

.. it may be a different kettle of fish to where you hydrostatically pressurise a copper boiler and it stays stretched and is therefore rendered useless for reassembly ie if you test it, you may actually be making it fail,...

No, that would be testing it beyond its designed safe pressure.

on 1354067231:

....at that point you may give up and decide its simply cheaper and quicker to replace the old safety valve with a new CERTIFIED rated safety valve, at pre determined iintervals during the working life of a coffee machine.

  Assuming  a functional relief valve makes the boiler itself safe is dangerous. What if the valve pot on the boiler gets plugged with scale ?  Individual component checks do not ensure the safe function of the assembled system. To use the car analogy again,..its like the mechanic fitting new brake pads , and not road testing afterwards to ensure they work correctly.   "Simpler" , "quicker", and "cheaper"  are not words you would want to have to use  in an accident investigation such as the one for this machine. I assume the installation /service technicians have a check sheet for start ups and service  inspections that would be reviewed in this type of accident. I would bet Electra have revised theirs since this event  :thumb:

FreshCoffee2

When you change out a boiler safety valve, you can tell if the path is safe or not (blocked) because there is nothing there but a sizeable hole. If its clear its clear, and if its blocked you can take appropriate action/s. If a boiler fails BEFORE a correctly working safety valve blows off, *I dont believe* (my opinion) the result will be anywhere near as dramatic as what happened in the photo, and I have (once or twice but no more in decades of my own experience) seen a boiler that has "popped" and become mis-shapen. *In my view* if a boiler fails because (after) the safety valve fails, then the issue is with the safety valve not the boiler so I cant see the point in testing a boiler and for all we know (another guess), the working pressurisation of an espresso machine boiler could / may be below a certain limit as to any "testing" rules and regulations....perhaps that is why there is no requirement that I know of, to periodically test esp machine boilers......who knows? Incidentally, the ORIGINAL "safety valve" as fitted to early espresso machines was virtually not much more than a hole in the top of the boiler with a weight on top. Rudimentary, but effective and probably less prone to "failure" than a modern valve....not that failures are common :thumb:  After that I am not an engineer nor a legislator, and cant comment any further because we are all only getting into what ifs and wherefors.