Water Flow Problems / Unbalanced System Injection Moulding Shop

Although this illustration shows "chillers" there might be a clue here.

I think unredundant was showing you that all lines need regulation and balance. Whether you working Water Towers or filling a kids plastic pool in the back yard.

Whosever idea it was to 'save money' on the fourth line added in later by not adding the valves is going realize that it is more expensive to 'fix' after a bad 'spec.'

But maybe it is not that big of a deal and not worth fixing, that is something someone who makes more money than you will tell you.

So make sure the problems you keep finding are really problems that are worth the cost to fix otherwise you will become an expensive nuisance that some may prefer not to deal with.

Since the other lines are working fine with the correct valves, does not this indicate that the fourth line should have control valves also. I don't even know what color your Water Tower is and even I can see that from here.

Thanks Massey, almost time to kick the kids out of the plastic pool

There are no valve in the system, all three lines just dead end, the four has the supply connected straight into the return line. resulting in low water flow / pressure. After looking at the diagram again. I can now see the balance valves / two way control valves. Not the same monster. I am the highest paid here. I am here to fix all the mistakes made in the past. By past Managers and techs. that didn't have injection molding experience. It's what I do. the question was do I need to balance all four ends. My opinion they do, Just want a second opinion.

Thanks

Then there is the obvious problem with low flow on the fourth branch, in that there is no (or a lot less) impedance to flow direct return to sump. That will cause insufficient flow and pressure supplying whatever injection heads are being cooled on that branch. You might as well have a heat exchanger with the divider plate removed and see how well that cools things off.

Water analogy to electricity always helps. Think of the water flow path as a circuit, and then look for "open circuit" conditions (that might wipe a pump), and "short circuit" conditions that will overheat your process.

The first opinion may be found in the design documentation and the commissioning records.

I have the blueprints of the builds layout in 2003 problem is it doesn't show any pressure difference valves in the system. The print does show future machine locations. All water just dead ends on the prints. I'm dealing with problems that go way beyond past managers but with no one knowing what they were doing when this plant was setup. In 2009 two new machines were added then a third used machine added not long after that. that's where the last connection was made. That's when I believe the water problem started, to the records I am finding.

I thought I would get some help here but it seems Arrogance out ways knowledge....

Sorry, I was just trying to help.

If I understand correctly, your fourth unit has it's supply connection fed from the return line?

What is the pressure difference between your return line and the supply line from say Unit 1?

"Arrogance out ways knowledge"

It's "Arrogance outweighs knowledge", and I'm not sure who has more of either.

Right now, you're the one with the problem, not us.

What you haven't told us is what the passages in the tools look like. Straight drilled and capped? More complex? What size they are. What size are the tools? I assume you have drawings of them.

Are the passages clean? Flow rate through each tool and circuit. How many tools on each circuit?

Real schematic of the plumbing?

20 questions is not a popular game here.

Since the system was initially designed for "x" number of machines at a given flow rate I am sure that addition of the two new machines in 2009 and subsequently a third machine were severely disruptive to the process flow pattern as well as the total water flow required.

More than likely the initial mechanical design was budget driven for a balanced system without instrumentation intervention or balancing valves therefore it would not take into consideration sizing for future expansion and adding of equipment.

If the flow source equipment and piping size was not properly updated in 2009 for providing enough flow to accommodate the added equipment then I would perform a system flow requirement analysis to identify exactly what is needed to correct the flow issues.

I would be attentive to self-induced flow resistance dynamics from such items as improper pipe diameter size, valve diameter size & design type, added change-of-direction fittings, and overall added pipe length.

from the information I have gathered, the last connection was made by a plant plumber, who passed away this past Sunday. Where the new machines are located is still a short run in the system. The print shows all ends terminate as a dead end, also shows future machine location. this design forces water through the heat exchanger and water manifolds. a bad design from the start. We have a chiller system that also runs to each machine to manifolds that are used to displace heat during molding process, in my experience we never used tower water for process, it was only used for heat exchanger on the machines. All molding process was chilled water or thremolators for better circulation through the tooling, Not tower water. I not sure if there has ever been any one here in the past that has had injection molding experience. Bottom line is it's not correct, the supply line being diverted directly into the return line is wrong. Someone else's mistake, error or lack of experience.

You'll get no more help from me!!

You are rude and arrogant. You failed to properly define the problem and what you were, or were not, doing.

I'm sure that at least three of us responding here have more experience than you have demonstrated.

I ran a captive molding shop that made parts for military and government aerospace projects for 7 years. That's satellites to you.

So long!!!!!!

Apologies.

I misread you comments.

But, I'm still done here.

Good luck.

Even though the distance to the new machines is short, the added resistance pressure drops across the added valves, fittings, and machines may be more than the system design can handle.

It could well be that you have scaling buildup inside all of the old system components from the cooling tower and/or the pumps have too much wear which is limiting the available amount of flow through the CW system.

If the cooling water system does not already have an inline filter system I would suggest you install a self-cleaning filter that cleans the water down to 500 microns or smaller.

Rather than fighting with balancing valves you might want to consider installing a simple mechanical operated TXV (Temperature Controlled Valve) on each machine to modulate the flow based on machine temperature so that no machine is starved for cooling during high cycle production time.

If the CW supply system is capable of providing enough flow then installing the TXV's will balance the flow to maximum efficiency.

If adding the TXV units do not solve your issues, I would identify where the root-cause of flow deficiency is then act accordingly.

It would be best to have chillers and a closed-loop system however the cost of installation, maintenance, and added electrical consumption is often considered too high by management so they will not opt for it.

We have six machines running at one of our facilities that used to have a cooling tower system then management decided to eliminate the cooling tower but not to install the recommended chilled closed loop CW system.

We instead opted for a once-through CW system using filtered domestic water with the waste water getting recycled in a different part of the process.

While the solution solves the monetary issues for the short term the scaling that will occur inside the machines and piping system will eventually take it's toll at a much higher cost in maintenance and loss of production due to poor machine performance.

When you say the supply is piped into the return line are you referencing the makeup water supply line? If so, this would not be abnormal.

Please clarify your layout:

1. The lines run out from the tower and feed through the machines to a second line that then returns to the tower (all coolant must pass through a machine),
2. The lines loop back to the tower and return excess flow without passing through a machine. This should have a form of flow control at the process end point.
3. Are these branches fed with a common pump?

Whenever I've built a piping loop like #2, I always use a diaphragm valve at the end of process point to build pressure/maintain flow. Ball valves are a bad choice for this as they cause turbulence when partly closed that can erode the valve under certain conditions, leading to a drift from the set parameters and eventual failure to operate.

If the other branches are working fine, they don't necessarily need them. Should you wish to change machine parameters in the future though, this will allow you to adjust the operating conditions. Keep in mind that if they are fed from a common pump, adjusting one branch will affect flow in the others as well.

the system has a common pump with a 6" main, four 4" runs that tee off and branch out from the main, than step down to 3" it is the second tee, that branches out is where the problem begins. the far side of the injection molding shop, which is where the supply is connected to the return ( 3" ) is where I have very little flow. To balance this I will install 4 Pressure differential valves to balance out this problem. I have already completed a cost analysis. Reduced cycle time form 12 /13 sec down to 8 /9 second will be the key player on this one.

Thanks for the help everyone.

Depending on what type of machines you have, their temp dissipation needs, and how critical your process is, you should evaluate to get rid of the towers and install one or more chillers. As the heat dissipation a tower can provide depends (among other factors) on the air temperature and it´s moisture content, they tend to be more efficient in winter than during summer months. We have had a problem alike at our plant. I bless the day we went for a couple of chillers, cause now we have the right operating temperature by just turning a knob!

If the last machine is close to the location of where the supply line connects to the return line, there will likely not be enough pressure difference to achieve adequate flow to the machine. There should be some kind of restriction in any supply-to-return bypass.

Your description isn't very clear; a piping schematic would help, including flows, pipe sizes, distances, and any pressure data available.