Promoting coffee discussion.
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coffee-forum.com Promoting coffee discussion. |
> One more thing, in my business I've used adjustable brass pressure > reducing valves to cap the pressure and send extra liquid back to the > tank. I couldn't find such an animal on the EPNW web site. But it seems > this could be an easy approach. They don't cost much and it seems > there's room by the pump. Then just add a pressure guage if desired. > Thus adjustable and visual. Anyone done this? > > David F. Ask Greg Scace to send you pictures of the Bride of Frankensilvia |
>"David F" >> One more thing, in my business I've used adjustable brass pressure >> reducing valves to cap the pressure and send extra liquid back to the >> tank. I couldn't find such an animal on the EPNW web site. But it seems >> this could be an easy approach. They don't cost much and it seems >> there's room by the pump. Then just add a pressure guage if desired. >> Thus adjustable and visual. Anyone done this? >> >> David F. > >Ask Greg Scace to send you pictures of the Bride of Frankensilvia > That thing is UNBELIEVABLE! Randy "It's alive... ALIVE!" G. http://www.quiknet.com/~frcn/Coffee/Coffee.html |
Marzocco triple basket. It only makes sense that if all the other factors are correct then using more coffee creates a richer extraction. The second was to grind fine and tamp lighter. A finer grind exposes more coffee to the water and this aids in extraction as well. FWIW, I have not done the pressure mod. As Matt mentioned, Greg has done a pressure mod by putting an adjustable, inline pressure regulator (an expensive part by all reports) in the bypass return line (also replaced with stainless tubing) which has an external adjustment knob as well as installing a pressure gauge in Silvia. It is an impressive installation and one that (IMO) should be featured on a website as with Pepe's installation. Randy "He doesn't call it 'Frankensilvia' for nothing" G. http://www.quiknet.com/~frcn/Coffee/Coffee.html "David F" <david@precision_no_spam_landscape.com > wrote: > >In search of the perfect pour. Is it attainable on Silvia? Mine don't >look like these. Well, maybe close to Randy's on rare occasion. It is >important to realize that color on a PC can be misleading. In particular >the first clip looks dark from the getgo. And Randy says his is darker >than the clip shows. >http://www.coffeeresearch.org/espresso/extraction.htm >http://www.lucidcafe.com/cafeforum/schomertable19.html >http://www.quiknet.com/~frcn/Coffee/SilviaPour.html >Using a stepless grinder (Innova); paying attention to packing technique >(tried lots of options); fresh beans, etc. The shake, bang, and pack >routine seems to have stopped most pinholes. Still the pour gets >significantly lighter near the end. I'm pulling 1 - 1 1/4 oz in about 20 >seconds. If I pull a bigger shot, it gets more pale. So? > >So does the pressure mod magically solve the problem or not? Ok, maybe >not magically, but significantly help? > >Many pressure modders don't seem to really feel like there's a taste >difference, so why bother. Am I missing something here? Since the PID, >the espresso tastes really good, well as a milk drink anyway. > >Oh, by the way, is the gasket a "standard 3/8 copper crunch washer" or >not? Can anyone tell me the exact diameter of the gasket inside and out? > >One more thing, in my business I've used adjustable brass pressure >reducing valves to cap the pressure and send extra liquid back to the >tank. I couldn't find such an animal on the EPNW web site. But it seems >this could be an easy approach. They don't cost much and it seems >there's room by the pump. Then just add a pressure guage if desired. >Thus adjustable and visual. Anyone done this? > >David F. > |
> Many pressure modders don't seem to really feel like there's a taste > difference, so why bother. Am I missing something here? Since the PID, > the espresso tastes really good, well as a milk drink anyway. If I remember correctly, given the pressure/flow characteristics of unregulated vibe pump machines, only a relatively "long" shot (around 2oz or 2.5oz) will be extracted in 25 sec shot at ~9 bar. If you want to pull a ristretto (say 1oz or 1.25oz), your 25 sec shot will inevitably be extracted somewhere around 12 or 13 bar. The higher pressure from the vibe pump will compel you to adjust your grind finer than you would on a machine with good pressure regulation. This may result in the harsh flavors that some people report from their unregulated vibe machines. > One more thing, in my business I've used adjustable brass pressure > reducing valves to cap the pressure and send extra liquid back to the > tank. I couldn't find such an animal on the EPNW web site. But it > seems this could be an easy approach. They don't cost much and it > seems there's room by the pump. Then just add a pressure guage if > desired. Thus adjustable and visual. Anyone done this? As Matt said, that's exactly what Greg Scace and others have done. Many of the higher end home machines have vibe pumps with adjustable pressure bypass valves, which people can tweak to their heart's content. -- -Andy S. picture page: http://tinyurl.com/eh0x |
>If I remember correctly, given the pressure/flow characteristics of unregulated >vibe pump machines, only a relatively "long" shot (around 2oz or 2.5oz) will be >extracted in 25 sec shot at ~9 bar. If you want to pull a ristretto (say 1oz or >1.25oz), your 25 sec shot will inevitably be extracted somewhere around 12 or 13 >bar. You are right. I have been trying to grind too fine for my ristrettos (using a Rocky) Do you mean I should grind much coarser? For a ristretto what times shpuld I be aiming for? Instead of 25-30 seconds perhaps 15-20 seconds? (using a Silvia)? Is the 25-30 second shot only for cappacinnos etc.? I draw 1 ounce shots Ken |
> I have been trying to grind too fine for my ristrettos (using a Rocky) > Do you mean I should grind much coarser? For a ristretto what times > should I be aiming for? Instead of 25-30 seconds perhaps 15-20 > seconds? (using a Silvia)? > Is the 25-30 second shot only for cappacinnos etc.? > I draw 1 ounce shots Hi Ken: Sorry if these concepts are hard to understand, but this stuff gets a little complicated. As I understand the theory, when going from a standard pour to a ristretto pour you grind FINER so that the shot time will be several seconds LONGER. Since the amount of liquid is "restricted," it needs a little more time in contact with the grounds to perform a proper ristretto extraction. This is the theory; hopefully you will experiment and your tastebuds will lead you to the extraction timing that you prefer. Complicating the matter, though, is the fact that an unmodified vibe pump machine will produce a higher pressure at a lower ristretto flow rate. This higher pressure will in turn require you to grind even FINER than otherwise necessary. And this fine, fine, finer grind may make it more difficult to get a good-tasting ristretto. The advantage of machines that have pressure regulation (eg, high-end consumer machines and commercial machines with rotary pumps) is that the pump pressure is relatively consistent irrespective of flow rate. -- -Andy S. picture page: http://tinyurl.com/eh0x |
> > The advantage of machines that have pressure regulation (eg, high-end consumer > machines and commercial machines with rotary pumps) is that the pump pressure > is relatively consistent irrespective of flow rate. So Andy, am I right in inferring that a Silvia, that has been pressure modded in the somewhat simple way of the addition of a washer, so that the overpressure valve opens at just over 9bar, is then acting in somewhat the same way as a machine with the adjustable pressure regulator, at least in that a ristretto is still going to only extract at 9bar, rather than the 12-13 bar that an unregulated vibe pump would? I.e., that pump pressure doesn't increase beyond that 9bar? Chris Staley |
> So Andy, am I right in inferring that a Silvia, that has been pressure > modded in the somewhat simple way of the addition of a washer, so that > the overpressure valve opens at just over 9bar, is then acting in > somewhat the same way as a machine with the adjustable pressure > regulator, at least in that a ristretto is still going to only extract > at 9bar, rather than the 12-13 bar that an unregulated vibe pump > would? I.e., that pump pressure doesn't increase beyond that 9bar? I haven't done this pressure mod on Silvia, but from what I understand, that's pretty much the way it works. Pressure regulation is never perfect, and you usually see a small drop in pressure as the flow rate increases. But the system pressure should stay right in the 9 bar neighborhood (hmmm...sounds like an blue-collar area in Boston). -- -Andy S. picture page: http://tinyurl.com/eh0x |
A couple of days ago I opened up the over pressure valve. I was pleased to see the length of the spring, since I assumed it would be much shorter. This design is very similar to the pressure regulating valves we use for pesticide applications. It is much simpler in operation than a design that must stop excess flow. In this case it simply diverts excess flow. A typical Watts regulator has two opposing springs that work in tandem. It is more complex to regulate flow when it begins from a zero flow situation. Espresso extraction is very close to a zero flow, when compared with typical water flows in such devices. So it is much harder to regulate such a flow when there is just two holes: One in and one out. The Silvia over pressure regulator has three hole: One in and two out. Much simpler to regulate. I expect the result will be plenty accurate enough for our purposes. Note: This is totally opposite my preliminary conjecture. As a result I myself am doing this mod. I was close to opting for an additional valve. Greg Scace has used a very expensive two hole valve. It is suitable for metering gases. Hence it is very accurate. One potential down side of using the over pressure valve as a pressure regulating valve: It will affect boiler temperature somewhat. In operation this could be totally irrelevant. I don't know. However, the cold water flowing through the opv will transmit into the boiler top. David F. "Chris" <rcs914@yahoo.com > wrote in message news:403d3a8d.0401140129.158db682@posting.google.com... > "Andy Schecter" <schecter@rochester.rr.com> wrote in message news:<eIJMb.145174$JW3.65026@twister.nyroc.rr.com >... > > > > The advantage of machines that have pressure regulation (eg, high-end consumer > > machines and commercial machines with rotary pumps) is that the pump pressure > > is relatively consistent irrespective of flow rate. > > So Andy, am I right in inferring that a Silvia, that has been pressure > modded in the somewhat simple way of the addition of a washer, so that > the overpressure valve opens at just over 9bar, is then acting in > somewhat the same way as a machine with the adjustable pressure > regulator, at least in that a ristretto is still going to only extract > at 9bar, rather than the 12-13 bar that an unregulated vibe pump > would? I.e., that pump pressure doesn't increase beyond that 9bar? > > Chris Staley |
One comments and two corrections imbedded: > > So it is much harder to regulate such a flow when there is just two > holes: One in and one out. The Silvia over pressure regulator has three > hole: One in and two out. Much simpler to regulate. I expect the result > will be plenty accurate enough for our purposes. Absolutely correct. The static pressure assumption is plunny valid for our case since the flow rate thru the puck is so low and we aren't interested in very small deviations in pressure from the static pressure assumption (See Andy's very good recent post on pressure effects). > > Note: This is totally opposite my preliminary conjecture. As a result I > myself am doing this mod. I was close to opting for an additional valve. > Greg Scace has used a very expensive two hole valve. It is suitable for > metering gases. Hence it is very accurate. No. The valve I used (Swagelok RL3) is a three hole valve, similar to the overpressure protection valve, but made of stainless steel and with adjustable pressure. The reason that i chose to use it is that I was developing the scheme and I wanted the adjustable pressure capability. I hadn't yet disassembled the OPV and I hadn't yet tested the feasibility of modifying it. On my system, the excess flow is diverted to the drip tray. In the over-pressure mod, the excess flow goes back to the tank. > > One potential down side of using the over pressure valve as a pressure > regulating valve: It will affect boiler temperature somewhat. Wrong, wrong, wrongity wrong. The over-pressure valve is mounted immediately upstream of the boiler. Diverting flow through it has virtually no effect on boiler temp at all. I say virtually because while the local temperature of the opv will drop due to water flow through it when brewing, the temperature drop will be only slightly larger than the stock case, and occurs during brewing. This is important because Andy and I have both shown that the water temperature entering the standpoint inside the boiler is largely independent of the incoming water temperature during a normal double shot brew cycle. In short, there is NO effect of boiler temperature. In > operation this could be totally irrelevant. I don't know. However, the > cold water flowing through the opv will transmit into the boiler top. See above. -Greg (do the simple pressure mod. It's easy!) Scace > David F. > |
Apparently my wording was unclear... See response near end. > > One potential down side of using the over pressure valve as a pressure > > regulating valve: It will affect boiler temperature somewhat. Notice that I said "boiler temperature." I did not say "brew temperature." > Wrong, wrong, wrongity wrong. The over-pressure valve is mounted > immediately upstream of the boiler. Upstream, yes. But it is physically connected. This results in conduction heat loss. Brass conducts heat pretty well. > Diverting flow through it has > virtually no effect on boiler temp at all. I say virtually because > while the local temperature of the opv will drop due to water flow > through it when brewing, the temperature drop will be only slightly > larger than the stock case, and occurs during brewing. This is > important because Andy and I have both shown that the water > temperature entering the standpoint inside the boiler is largely > independent of the incoming water temperature during a normal double > shot brew cycle. In short, there is NO effect of boiler temperature. > > In > > operation this could be totally irrelevant. I don't know. However, the > > cold water flowing through the opv will transmit into the boiler top. > > See above. Running cool water through the opb will cool it. In turn it will *conduct* this heat loss to the boiler. Yes, this is a distance from where the brew water is actually drawn into the pf. Which is why I suggested it could be totally irrelevant. I was thinking of simple physics. David F. > > -Greg (do the simple pressure mod. It's easy!) Scace > > > David F. |