Rules for Drycode programming

1.  Dryer Step Types 

• The dryer programmer uses Step "types" to set the initiation point for the countdown of a step. 
• Time only starts counting as soon as the step starts. 
• Outlet + starts after an outlet temp is first achieved. 
• Inlet - starts on a declining inlet temp.  This uses a second inlet temp as a trigger temp.  
• We usually lower air flow or basket speed to prevent plastering as the goods get drier and lighter.  
• Multiple steps give us breakpoints in which to make these changes.   

2.  The Dryer is a beast.  

• The dryer has a lot of power, and that power must be tamed to match the goods.  
• You can program too much air flow or too high a basket speed and plaster the goods to the cylinder.  Plastered goods do not dry properly and obviously do not tumble.  So, part of your mission is to prevent plastering through the entire dry cycle.  

3.  Watch the tumbling goods inside

• The air flows from the upper rear side to the lower bottom front of the dryer.  There is a seal that separates the front and back of the dryer housing to force the hot inlet air though the cylinder into the tumbling goods. 
• The ideal dry code will have the goods completely cover the exit air suction hole.  Look at the pics.  If the goods do not cover the entire area of the suction inlet then bypass occurs and dry times extend.  So, fine tuning is about getting the goods to cover the exit air suction hole without plastering.  
• The pics show a dryer shell...outside the basket.  Air flows from the rear, upper left to the front, lower right.  The air pushes the goods toward the right wall when we turn Clockwise. But, when we turn CCW the air pushes the goods away from the cylinder. Plastering is more likely in the CW direction.  So, the dryer dynamically slows the cylinder speed using the "retard" programming in a dry code. This is usually set at 9%.  If programmed, the cylinder turns 9% slower in the CW direction.  This helps prevent plastering.  
• Note that the dryers are Siamese twins.  So, a left dryer will be just the opposite air flow of a right dryer.  A right dryer turns CW when commanded CW.  A left dryer is modified (at the inverter CW and CCW command) to turn CCW when commanded CW.  This keeps the retard function working properly.  
• The ideal speed for the cylinder causes the goods to hit the cylinder side and completely cover the suction outlet hole.  Too fast and you plaster.  Too slow and you flow air over the goods and through the opening in the suction hole. Bypassing air is less effective than air flowing through the goods. 
• Watch your goods tumbling through a dry cycle. Design a dry code to keep the goods covering the suction hole and not starting to plaster to the dryer cylinder.      

4.  Pick an inlet and outlet temp and stay with it.  

• Goods are sensitive to overheat.  In some cases, you can make a wrinkled mess by over-drying and also by using too much heat (too high an outlet temp).  A properly dried cotton towel will hang better (and have less wrinkles) if lower outlet temps are used.  So, even though you can program high outlet temps to speed up the drying process, goods need time to wick moisture out of the deepest part of the fabric.  If you dry the outside faster than the fabric wicking capability, you will end up with a crispy outside and damp inside.  This problem is witnessed on high quality cotton toweling more than lower quality toweling due to the density of the warp and weft thread count. 
• Do not program a lower outlet temp in subsequent dry code steps.  Stick with the outlet temp in step 00.  If you decrease the outlet temp, you may false trigger the next step parameters. The gas valve will shut down when you change to a lower outlet and possibly lower the inlet temp so that you trip the 2nd inlet temp initiation to start the count down timer.  
• The inlet temp is only in play at the beginning of a cycle when outlet temps are not reached yet. Set it and leave it the same through all heating steps.  If drying delicate goods, restrict the inlet to protect goods that may melt or singe in high heat.   

5.  Cooldown temps - a few considerations

• Cooldown temps are set to allow operators to handle goods without burning their hands.  But, very low cooldown temps waste valuable production time.  So, find the right temp for the operator's comfort and production goals. 
• Some goods may be prone to spontaneous combustion if not cooled down enough.  Bar mops, grease towels and some massage towels are great examples. If any combustible oil is not washed completely out, then this stuff is prone to combust.   
• If the outside temperature is hot, then your cooldown capacity is limited.  So, using low cooldown temp is futile and unproductive.   
• Poly goods need to be cooled enough to not set wrinkles in fabric, usually below 140 degrees. Cotton goods don't care, but the operators will.  

5.  Don't waste time unloading.  

• The dryer can probably unload in 20 seconds or less.  If you program a basket on-time that is too long the goods will start tumbling, stay in the basket longer and not fall out as quickly as a soft jog with just a couple to 3 seconds in each direction.  
• You can use a custom discharge that slowly decrements the basket speeds while unloading and lets goods fall out the bottom basket lip quickly.  Goods that are spinning at high speed tend to go up in the cylinder and fall back onto the bottom of the cylinder and not out of the cylinder. 
• You might consider a custom discharge in one direction for small goods like face towels and wash rags that do not tangle.  
• Too long an "on-time" will tend to rope sheets.  Sheets and other long goods should always reverse when discharging.  

6. Roping of sheets in a conditioning dry code

• Some sheets tend to cling to themselves more than others.  We had extreme roping problem with high end sheeting of this clingy material.  The goods were tumbling fine, just like we thought they should.  But, the sheets were roping as they fell through the air flow in the dryer.  We could see a twist induced by the air moving through the center of the ball of tumbling sheets. The solution was to slow the basket to prevent normal tumbling and let the air blow over the ball of sheets rather than through the tumbling sheets.  This is counterintuitive but it worked!