Ask The Brewmasters

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

Mix proof valves can be difficult.  I know breweries often use butterfly valves, but they are not allowed in most food plants and shouldn't be needed on an automated system.  There should never be a true dead leg that is not CIPed or allows "mixtures" of anything.  Typically, product or sanitizer is pushed out.  Product can be pushed with water, sanitizer can be pushed with product.  Breweries typically use De-oxygenated water to push.  This can be wasteful, so you want to look at ways to minimize.  A yogurt company I work with uses a "pig" or pipe sized hockey puck to push product out with air.  And air to return the pig "home".  Hope this answers your question.

Original Message:
Sent: 09-13-2023 15:20
From: A Z
Subject: Dead-legs in mixproof valve networks

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

Or, see something similar in this product video, starting about 20 seconds in:

(I do get that these examples are simplified demonstrations only and don't reflect actual practice, but I suppose those possible differences are what I'm wondering about)

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

But, here's another valve matrix from the same manufacturer, with only mixproof valves aligned in rows (this seems closer to what I'd expect given what I've read):

Even many piping and instrumentation diagrams seem to show it's common-place to just have grids of mixproof valves butted directly up against one another:

I can guess the practical ways of dealing with this without additional shut-off valves between the mixproof valves (clever sequencing of valves, flushing all pipes pre- and post-run, &c). And I can imagine CIP isn't an issue, given that a whole pipe must be flushed and cleaned after use. I'm more trying to wrap my head around what happens at changeovers, such as between sanitizer and product. Would the product be flushed out to fill both sanitized pipes, even "upstream" of the destination? Is there a reliance on very little mixing occurring at the interface, as the product simply bypasses that path? What if you're talking about a fully-drained pipe? Are these dead-legs not even an issue in practice, since the valves seem to be packed quite close together? Or is it all taken care of in the design and sequencing of process steps?

There's just something about this that's never quite aligned with my intuition and experience, and so I'd appreciate anyone who's able to chime in.

------------------------------
Zandy Zeiser
Brewer-at-large
------------------------------

Hi Zandy,

Having done controls on several large matrix installation over the years, they only use a limited number of butterfly valve as block valves mostly on CIP inlets and outlets.

Packing a lineup of valves is a multi-step process, I have utilized packing through the seat lifter on the end valve to eliminate the product water interface.

Typically, at 12 PSI counter pressure seat lifters flow at 10 to 12 GPM making a good drain point for packing but not a great drain.

Let me know if you have any additional questions.

Original Message:
Sent: 09-13-2023 15:20
From: A Z
Subject: Dead-legs in mixproof valve networks

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

Or, see something similar in this product video, starting about 20 seconds in:

(I do get that these examples are simplified demonstrations only and don't reflect actual practice, but I suppose those possible differences are what I'm wondering about)

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

But, here's another valve matrix from the same manufacturer, with only mixproof valves aligned in rows (this seems closer to what I'd expect given what I've read):

Even many piping and instrumentation diagrams seem to show it's common-place to just have grids of mixproof valves butted directly up against one another:

I can guess the practical ways of dealing with this without additional shut-off valves between the mixproof valves (clever sequencing of valves, flushing all pipes pre- and post-run, &c). And I can imagine CIP isn't an issue, given that a whole pipe must be flushed and cleaned after use. I'm more trying to wrap my head around what happens at changeovers, such as between sanitizer and product. Would the product be flushed out to fill both sanitized pipes, even "upstream" of the destination? Is there a reliance on very little mixing occurring at the interface, as the product simply bypasses that path? What if you're talking about a fully-drained pipe? Are these dead-legs not even an issue in practice, since the valves seem to be packed quite close together? Or is it all taken care of in the design and sequencing of process steps?

There's just something about this that's never quite aligned with my intuition and experience, and so I'd appreciate anyone who's able to chime in.

------------------------------
Zandy Zeiser
Brewer-at-large
------------------------------

Butterfly valves are sometimes used on the perimeter of mix-proof valve matrices, such as with CIP send and return piping as was mentioned. Typically there are no butterfly valves between the mix-proof valves themselves as the valves are close coupled to save space and piping.  As the top diagram shows,  an entire header is filled/packed with whatever fluid it is handling so there are no dead legs. For example, after tank #1 is filled, there might be a water/DAW pressout to the tank and then the tank header could be flushed to drain. The entire tank inlet/outlet header would be cleaned when the tank is CIP'd and could also be designed to enable cleaning after the tank is filled. Hope that helps...

Original Message:
Sent: 09-14-2023 13:21
From: David Sleboda
Subject: Dead-legs in mixproof valve networks

Hi Zandy,

Having done controls on several large matrix installation over the years, they only use a limited number of butterfly valve as block valves mostly on CIP inlets and outlets.

Packing a lineup of valves is a multi-step process, I have utilized packing through the seat lifter on the end valve to eliminate the product water interface.

Typically, at 12 PSI counter pressure seat lifters flow at 10 to 12 GPM making a good drain point for packing but not a great drain.

Let me know if you have any additional questions.

------------------------------
David Sleboda
F & B Engineering Services
Milwaukee WI
(414) 704-7291

Original Message:
Sent: 09-13-2023 15:20
From: A Z
Subject: Dead-legs in mixproof valve networks

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

Or, see something similar in this product video, starting about 20 seconds in:

(I do get that these examples are simplified demonstrations only and don't reflect actual practice, but I suppose those possible differences are what I'm wondering about)

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

But, here's another valve matrix from the same manufacturer, with only mixproof valves aligned in rows (this seems closer to what I'd expect given what I've read):

Even many piping and instrumentation diagrams seem to show it's common-place to just have grids of mixproof valves butted directly up against one another:

I can guess the practical ways of dealing with this without additional shut-off valves between the mixproof valves (clever sequencing of valves, flushing all pipes pre- and post-run, &c). And I can imagine CIP isn't an issue, given that a whole pipe must be flushed and cleaned after use. I'm more trying to wrap my head around what happens at changeovers, such as between sanitizer and product. Would the product be flushed out to fill both sanitized pipes, even "upstream" of the destination? Is there a reliance on very little mixing occurring at the interface, as the product simply bypasses that path? What if you're talking about a fully-drained pipe? Are these dead-legs not even an issue in practice, since the valves seem to be packed quite close together? Or is it all taken care of in the design and sequencing of process steps?

There's just something about this that's never quite aligned with my intuition and experience, and so I'd appreciate anyone who's able to chime in.

------------------------------
Zandy Zeiser
Brewer-at-large
------------------------------

Hi Randy,

What appears to be a dead-leg in mixproof valve matrices is an extension of the tank inlet/outlet on the tank side of the valve, and the other side of the valve is a pipeline either supplying or draining the tank.  In the case of the tank extension, that portion of the tank should be cleaned during vessel CIP and the CIP return valve is the last mixproof valve in the valves service any particular tank.  This position ensures that the tank inlet/outlet is cleaned without any deadlegs. In some cases where the inlet/outlet line is very large, backward cleaning into the tank is used, and in other cases CIP solution is allowed to intermittently collect in the tank and the inlet/outlet line.

The beauty of mixproof valve matrices is that they allow for lots of flexibility and prevent liquids from leaking across the valve seats by design. Prior to mixproof valves, double block and bleed valves were common.  One mixproof valve replaces three double block and bleed sets, makes installations much cleaner and compact, reduces I/O, and makes programming easier. The downside for smaller breweries is that they are relatively expensive when installed to service small tanks.  Careful design is also critical to allow for all normal cellar activities without having to drag in pumps and hoses to allow for things not considered during the design phase.

The best way to learn about these valves is to talk to someone who works with mixproof design or to visit a brewery with a nice installation and ask questions.  If you are planning on attending the MBAA Conference in Seattle in October, this would make for great bierstube fodder!  Just be sure to bring a pencil and notepad for sketching.

Cheers, Ashton

------------------------------
Ashton Lewis
Manager of Training and Technical Support
BSG Craftbrewing
MBAA District Great Plains, Technical Chair
Springfield, Missouri
(417) 830-2337
------------------------------

Original Message:
Sent: 09-14-2023 13:21
From: David Sleboda
Subject: Dead-legs in mixproof valve networks

Hi Zandy,

Having done controls on several large matrix installation over the years, they only use a limited number of butterfly valve as block valves mostly on CIP inlets and outlets.

Packing a lineup of valves is a multi-step process, I have utilized packing through the seat lifter on the end valve to eliminate the product water interface.

Typically, at 12 PSI counter pressure seat lifters flow at 10 to 12 GPM making a good drain point for packing but not a great drain.

Let me know if you have any additional questions.

------------------------------
David Sleboda
F & B Engineering Services
Milwaukee WI
(414) 704-7291

Original Message:
Sent: 09-13-2023 15:20
From: A Z
Subject: Dead-legs in mixproof valve networks

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

Or, see something similar in this product video, starting about 20 seconds in:

(I do get that these examples are simplified demonstrations only and don't reflect actual practice, but I suppose those possible differences are what I'm wondering about)

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

But, here's another valve matrix from the same manufacturer, with only mixproof valves aligned in rows (this seems closer to what I'd expect given what I've read):

Even many piping and instrumentation diagrams seem to show it's common-place to just have grids of mixproof valves butted directly up against one another:

I can guess the practical ways of dealing with this without additional shut-off valves between the mixproof valves (clever sequencing of valves, flushing all pipes pre- and post-run, &c). And I can imagine CIP isn't an issue, given that a whole pipe must be flushed and cleaned after use. I'm more trying to wrap my head around what happens at changeovers, such as between sanitizer and product. Would the product be flushed out to fill both sanitized pipes, even "upstream" of the destination? Is there a reliance on very little mixing occurring at the interface, as the product simply bypasses that path? What if you're talking about a fully-drained pipe? Are these dead-legs not even an issue in practice, since the valves seem to be packed quite close together? Or is it all taken care of in the design and sequencing of process steps?

There's just something about this that's never quite aligned with my intuition and experience, and so I'd appreciate anyone who's able to chime in.

------------------------------
Zandy Zeiser
Brewer-at-large
------------------------------

Hello Zandy.

Thanks for the thoughtful question on mixproofs!  Although written in a previous reply, a good designer/integrator/programmer can certainly minimize product/CIP losses.  The "pushes" are fairly contained on the fluid transitions, and the transitions can be anticipated. Yes, mixproofs(double seats) manifolds, combined with butterflies(sometimes block & bleed) makes for a very efficient process.  By efficient, I mean we can save footprint in the facility, labor of product or CIP changes, swing panel connection errors, and general safety of stepping over a maze of hoses.  I think the major factor in determining if mixproofs are right for you is really a matter of capital costs.  For a small to medium size brewery, any product losses are frowned upon.  At a medium-large facility, that product loss percentage goes way down.  It's a matter of scale.  We have many thousands of mixproofs in larger brewery manifolds across the USA and globe.  On the larger scale, product losses become minimal, where errors, labor and safety go way up.  Although it would seem like a win-win for any brewery, you also must consider investment costs.  The ROI for smaller breweries can be a struggle to justify.  Double Seat valves and manifolds need programming/integrating, so there are significant dollars up front and maintenance as well.  I would be happy to discuss in more detail with you at any time. (uploaded a few videos, as well)

Original Message:
Sent: 09-13-2023 15:20
From: A Z
Subject: Dead-legs in mixproof valve networks

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

Or, see something similar in this product video, starting about 20 seconds in:

(I do get that these examples are simplified demonstrations only and don't reflect actual practice, but I suppose those possible differences are what I'm wondering about)

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

But, here's another valve matrix from the same manufacturer, with only mixproof valves aligned in rows (this seems closer to what I'd expect given what I've read):

Even many piping and instrumentation diagrams seem to show it's common-place to just have grids of mixproof valves butted directly up against one another:

I can guess the practical ways of dealing with this without additional shut-off valves between the mixproof valves (clever sequencing of valves, flushing all pipes pre- and post-run, &c). And I can imagine CIP isn't an issue, given that a whole pipe must be flushed and cleaned after use. I'm more trying to wrap my head around what happens at changeovers, such as between sanitizer and product. Would the product be flushed out to fill both sanitized pipes, even "upstream" of the destination? Is there a reliance on very little mixing occurring at the interface, as the product simply bypasses that path? What if you're talking about a fully-drained pipe? Are these dead-legs not even an issue in practice, since the valves seem to be packed quite close together? Or is it all taken care of in the design and sequencing of process steps?

There's just something about this that's never quite aligned with my intuition and experience, and so I'd appreciate anyone who's able to chime in.

------------------------------
Zandy Zeiser
Brewer-at-large
------------------------------

Hi Zandy!

With respect to the diagram, "Matrix Piping with Tank Bottom Valve", it is common that each of the functions of the tank (filling, emptying, cleaning) would go to completion, and that product would not be left behind to stagnate in the pipes between the tank and matrix.  You are correct that the diagram is a simplified example to show how non-compatible processes (2 products filling into two separate tanks, 1 product emptying, 1 tank holding and 1 tank in CIP) can occur while maintaining an air-gap between the double-seats.

There are matrix layouts that minimize and mitigate the dead-legs that might occur if you activating the valve closest to your source vs. the furthest valve.

I hope this helps!

------------------------------
Stephen Pappas
Regional Sales Manager - Flow Components
GEA Canada - GEA Tuchenhagen Div.
Mississauga ON
(289) 288-5521
------------------------------

Original Message:
Sent: 09-13-2023 15:20
From: Z Z
Subject: Dead-legs in mixproof valve networks

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

Or, see something similar in this product video, starting about 20 seconds in:

(I do get that these examples are simplified demonstrations only and don't reflect actual practice, but I suppose those possible differences are what I'm wondering about)

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

But, here's another valve matrix from the same manufacturer, with only mixproof valves aligned in rows (this seems closer to what I'd expect given what I've read):

Even many piping and instrumentation diagrams seem to show it's common-place to just have grids of mixproof valves butted directly up against one another:

I can guess the practical ways of dealing with this without additional shut-off valves between the mixproof valves (clever sequencing of valves, flushing all pipes pre- and post-run, &c). And I can imagine CIP isn't an issue, given that a whole pipe must be flushed and cleaned after use. I'm more trying to wrap my head around what happens at changeovers, such as between sanitizer and product. Would the product be flushed out to fill both sanitized pipes, even "upstream" of the destination? Is there a reliance on very little mixing occurring at the interface, as the product simply bypasses that path? What if you're talking about a fully-drained pipe? Are these dead-legs not even an issue in practice, since the valves seem to be packed quite close together? Or is it all taken care of in the design and sequencing of process steps?

There's just something about this that's never quite aligned with my intuition and experience, and so I'd appreciate anyone who's able to chime in.

------------------------------
Zandy Zeiser
Brewer-at-large
------------------------------

The key is that the CIP supply and return valves for every path are located at the extreme ends of the matrix. You are right in noticing that dead-legs are created during various operations (filling, emptying, yeast/hop removal), depending on the location of the valve used for the operation. However, it is most important to eliminate dead-legs during CIP. As long as you can clean and sanitize through the entire row or column once the operation is finished, then you can ensure the whole pipe is clean. If you see any dead-legs in a path during a cleaning cycle in a matrix design, that is definitely cause for concern. This is something we had a lot of similar questions about when we started using valve matrices at Deschutes Brewery, and it look some discussion and careful path tracing to make us comfortable. Post matrix installation, years of clean lab results added to that level of comfort!

Original Message:
Sent: 09-13-2023 15:20
From: Z Z
Subject: Dead-legs in mixproof valve networks

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

Or, see something similar in this product video, starting about 20 seconds in:

(I do get that these examples are simplified demonstrations only and don't reflect actual practice, but I suppose those possible differences are what I'm wondering about)

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

But, here's another valve matrix from the same manufacturer, with only mixproof valves aligned in rows (this seems closer to what I'd expect given what I've read):

Even many piping and instrumentation diagrams seem to show it's common-place to just have grids of mixproof valves butted directly up against one another:

I can guess the practical ways of dealing with this without additional shut-off valves between the mixproof valves (clever sequencing of valves, flushing all pipes pre- and post-run, &c). And I can imagine CIP isn't an issue, given that a whole pipe must be flushed and cleaned after use. I'm more trying to wrap my head around what happens at changeovers, such as between sanitizer and product. Would the product be flushed out to fill both sanitized pipes, even "upstream" of the destination? Is there a reliance on very little mixing occurring at the interface, as the product simply bypasses that path? What if you're talking about a fully-drained pipe? Are these dead-legs not even an issue in practice, since the valves seem to be packed quite close together? Or is it all taken care of in the design and sequencing of process steps?

There's just something about this that's never quite aligned with my intuition and experience, and so I'd appreciate anyone who's able to chime in.

------------------------------
Zandy Zeiser
Brewer-at-large
------------------------------

Thanks very much to everyone who responded, hearing this feedback really reinforces how indispensable practical experience is when trying to understand these things.

Pretty much every post offered me something good to consider, in particular:

• Using the seat-lifter/cavity CIP path of the end-of-the-line valve as a drain to flush and pack the piping, rather than (presumably) designing it with a dedicated drain at that same location
• Thinking of rows or columns as extensions of what they're connected to (especially the tank in/outlets) that will remain isolated and be cleaned when appropriate
• The utility of deaerated water to displace sanitizer and eliminate product contamination, even if some slight mixing were still to occur
• Losses, and how minimal they become as the volume being handled increases. It's definitely the smaller-scale brewer in me that worries about these losses but looking at it now, it seems like it probably wouldn't take much more than a gallon or two to pack even a fairly large pipe with 5 connections, and even that could be recovered with a thoughtful push-out.
• Taking care to "design out" any issues, most importantly by having all CIP operations supply or return from the extremeties of the matrix and be appropriately interconnected. Presumably a good design would be well-informed by the processes it's designed to handle and weigh the importance of minimizing losses from each.

Again, thanks to everyone for taking their time to help me understand this problem, it's greatly appreciated.

Original Message:
Sent: 09-13-2023 15:20
From: Z Z
Subject: Dead-legs in mixproof valve networks

I've never personally worked with mixproof valve matricies, but have spent a fair bit of time recently researching them and was hoping for some insight from anyone who has experience working with or designing these.

My question is, how are unacceptably long dead-legs avoided when using a matrix of mixproof valves? A lot of what I'm reading or seeing either glosses over this entirely or seems to indicate dead-legs are acceptable.

For example, in this illustration of a five-tank valve matrix allowing multiple concurrent operations (filling, CIP, emptying &c), it's indicated by the colored flow paths that any process fluid basically spreads out to occupy the whole volume of both pipes to which it's connected, despite being connected at a single point.

Or, see something similar in this product video, starting about 20 seconds in:

(I do get that these examples are simplified demonstrations only and don't reflect actual practice, but I suppose those possible differences are what I'm wondering about)

I've definitely seen evidence of well-placed shut-off valves that would solve this issue, for example this image of mixproof valves flanked by butterfly valves (though it strikes me that doing this would add a lot of complexity and cost):

But, here's another valve matrix from the same manufacturer, with only mixproof valves aligned in rows (this seems closer to what I'd expect given what I've read):

Even many piping and instrumentation diagrams seem to show it's common-place to just have grids of mixproof valves butted directly up against one another:

I can guess the practical ways of dealing with this without additional shut-off valves between the mixproof valves (clever sequencing of valves, flushing all pipes pre- and post-run, &c). And I can imagine CIP isn't an issue, given that a whole pipe must be flushed and cleaned after use. I'm more trying to wrap my head around what happens at changeovers, such as between sanitizer and product. Would the product be flushed out to fill both sanitized pipes, even "upstream" of the destination? Is there a reliance on very little mixing occurring at the interface, as the product simply bypasses that path? What if you're talking about a fully-drained pipe? Are these dead-legs not even an issue in practice, since the valves seem to be packed quite close together? Or is it all taken care of in the design and sequencing of process steps?

There's just something about this that's never quite aligned with my intuition and experience, and so I'd appreciate anyone who's able to chime in.

------------------------------
Zandy Zeiser
Brewer-at-large
------------------------------