THE “NOT SO SIMPLE TRUTH” ABOUT HOW YOUR MILNOR PBW (PulseFlow Batch washer) WORKS.
This document will be best understood when used with the “The Simple Truth of How Your Milnor PBW Works.” You will use this document with a PBW that includes:
- Drain valves on every module (or at least most)
- A drain in the Pulse Flow Tank (PFT).
- There would also be a way to redirect press water to the sewer so it does not contaminate the Pulse Flow Tank. (see LDI valve set described below).
- Optionally: some machine have Alternate Pulse Flow which allows 2 pulse flow zones fed by the Pulse Flow tank. We will discuss this here, too.
There are a number of features that must work together to prevent “nasty” water from contacting “nice” goods.
The big idea is to
- insert a purge pocket which drains the module of the nasty water from nasty goods.
- stop the water from the press from getting to the Pulse Flow Tank,
- drain the PFT before the “nice” goods enter the PBW.
Purges cost water and energy. The best practice is to make a few radical changes in goods class to use the least amount of water in a given shift. Otherwise, water consumption will run very high. Each purged module will take about 100 gallons (in a 76039 module) to purge. Multiply this times the number of modules with drains and you get a lot of water usage for employing 1 purge module. So, keep these changeups limited during a shift. Our recommendation is to make a change once in a shift by stepping up the soil or color level until a purge resets the schedule back to a light soil and no color start point. Then build soil class and color through the schedule.
Using the drain…
First note that these machines do not have a way to stop the counterflow of rinse and wash water. So, if you open a drain for a short period, and then close it, the machine refills and counterflow “nasty” water will contaminate the module.
Make sure you program the drain valves for each mod at the “D” init. Otherwise, they won’t close again after the purge leaves the module.
So, we want to open the drain and leave it open for the whole cycle time…and ignore the level switch when it is time to transfer. And we can. In hardware config, set the “empty formula level” at 2. This indicates that you allow a formula coded “empty module” to be empty at transfer time.
The result is that any water flowing forward goes to sewer. And, the “nice” goods coming next will fall into an empty module and refill with fresh water. At the exact same time the drain in the next module opens preventing counterflow from coming forward.
Draining the Pulse Flow Tank (PFT)
Since the PFT is fed by the press water you need to decide if it is contaminated with enough color to not use the water on “nice” goods. If you need to get rid of the PFT water, you must drain the tank when a purge formula is in module 1. You need to give the drain enough time to clear the tank and allow time for refill before the next transfer.
Don’t re-contaminate the PFT! Long Distance Incompatibility
You must stop colored water from being pumped to the PFT. Do this with the outputs called LDI1 and LDI2. I usually rename these to “Nice” and “Nasty”.
“Nice” is assigned in module 1 to op code -1 (and the D init) so it turns on when nice goods are above module 1. You program “Nice” to 255 in very formula that is “Nice”.
“Nasty” is assigned to the last module and Op Code +1 (and the D init). Program the “nasty” output to 255 in every formula that is “nasty”.
When the Nice and Nasty relays are both on, water from the press will be redirected to the sewer. Fresh water will then make up the PFT.
Schedule is important!
If you run intermixed loads…like 3 nice loads and then a load that is not Nice or Nasty, then the water from the press starts flowing to the PFT. The PFT feed the main pulse flow water into nice goods in the rinse zone and possibly contaminate those goods with color. For this reason I would recommend all goods either get coded Nice or Nasty to help prevent this issue.
What happens after a Purge formula runs?
Normally we wash in water that is used by goods going before. But after a purge there is no chemical residual in the bath. And as such, you need to build a residual. We would recommend using “first dosing” in the Mentor controller to help reach this residual faster.
In addition, there will be no counter flow for a number of transfers while the purge formula is in the PBW. Remember that the purge formula has an open drain and the Pulse Flow is going to sewer at the Purge pocket.
In practice, this has proved to work well to wash and rinse goods due to the fact that we start with fresh water. Essentially each bath is a standing bath and the goods go to a cleaner bath each transfer. When the purge goes to the last module, Pulse Flow (counterflow) starts again through the whole machine.
So, what if you want to reestablish counter flow before the purge pocket in a machine while the purge formula is still in the machine? You would use an optional feature called “Alternate Pulse Flow”.
Alternate Pulse Flow
This feature allows the machine to Pulse Flow water before and after a purge. This is an optional feature and the alternate pulse flow purge is “inserted” using the table of “auto empty and purge pockets” just like a purge formula. A number of features happen automatically and the fast fill valve on the module following the purge is used to supply modulated flow from the alternate pulse flow pump.
The details are found in the programming book and through documents the Alternate Pulse Flow programming elsewhere.
If you have any comments or questions, contact Gary Lazarre at
glazarre@milnor.com.
“Cheat sheet” on Implementing Purges and LDI
- Program the following attributes in the Purge Formula.
- Set every drain in every module 255. This leaves the drain open for the duration of the entire formula allowing no contaminated water to be in the "purged" module.
- Program temps at 50 degrees F to prevent an overtime error on temp after the drain opens.
- Program the PFT tank to drain. 70 Seconds should be enough, but check that the tank is empty after the drain expires.
- The purge formula is neither Nasty or Nice as far as LDI is concerned. Program a 000 in the nice and nasty outputs for the Purge formula. You can rename the LDI relays to Nice and Nasty. Nice is in mod 1 and Nasty is assigned in mod last +1.
- Set the "Empty Formula Level" in the hardware configuration at a 2. This will allow you to transfer an empty pocket with no water if the formula in the module is a purge or empty.
- Go to the functions page. You will probably find the fast fill valve in the mid mod pump suction coded as a op code 2. We need to move the bit code to the fast fill op code 07 row. This is probably called the standing bath fast fill.
- Whatever module the mid mod pump sucks from is the mod to program as a fast fill code 07. Record the bit code for that module fast fill, then clear the row on the Op code 02. Set the fast fill valve in the mid mod pump module at an op code of 07. This allows it to refill as needed to supply the mid mod pump when we have a purge downstream of the mid mod suction.
- You need to program the Auto Purge table to insert a purge when goods are incompatible.
Obviously you need to program every formula with a goods class to make the Auto Empty and Purge table work.
- Only insert 1 Purge formula, never more.
- Confirm that the "Purge Formula" in hardware configure matches your actual Purge formula.
- Make sure the weir plates are set at 8 inches in the modules with a drain. This prevents over dumping when an adjacent module's drain is open. Never higher than 8 inches so that we don't impede the Pulse Flow from working normally. If the mods do not have weir plates the result will be lower levels. So, mods with drains should have a weir plate.
