Dryers: Dry But Important
In dire economic times like these, an inefficient operation is every processor's worst nightmare. Unfortunately, however, many companies are also finding their budgets constrained in leaner times, and...
In dire economic times like these, an inefficient operation is every processor’s worst nightmare. Unfortunately, however, many companies are also finding their budgets constrained in leaner times, and many have had to cut back on the amount they spend to maintain their plant’s equipment.
There was a time, and it’s still true today, where everybody had their own maintenance crews who would maintain their equipment,” noted technical support manager Bill Collis of Universal Dynamics Inc. “I think gradually we have been seeing a trend where people are getting rid of their maintenance crews.”
When it comes to dryers, suppliers note that downtime or inefficient drying often boils down to poor or improper maintenance. A few quick and easy preventative maintenance steps can help ensure that your drying system is running optimally, or help identify inefficiencies in your drying process.
“Typically, processors don’t even touch the dryer until they have a problem with a part, and then they start to investigate,” explained Joe Corturillo, engineering manager for Wittmann Canada.
Here are a few pointers to stay ahead of the curve, and avoid any unpleasant surprises when it comes to your dryers.
Check and replace your filters. Most suppliers identify poorly maintained filters as the number one culprit for drying inefficiencies. “This is often the primary cause of poor drying said Charles Sears, president of Dri-Air Industries, Inc. “Not only does it affect the dryer performance, but without adequate air flow, the material will not heat up to the proper drying temperature.”
Equipment manufacturers advise that you regularly inspect the process and regeneration filters, and clean or replace them if necessary. Suppliers note that some processors don’t even use regeneration filters on their machines.
“Some people think regeneration filters are not important, but in many of these plants you have dryers and grinders next to the machine, and sometimes these grinders generate a lot of dust,” said engineering manager Kalhan Tavakoli of Universal Dynamics. “When the plastic dust gets pulled into the regeneration system, the plastic dust melts and fuses itself to the desiccant.”
Maguire Canada’s Brian Davis explains that the regeneration filters on Novatech dryers are exposed to avoid this “out of sight, out of mind” mentality.
How often should you check your filters? It depends on who you ask, but it can also depend on the material you are running through the machine.
“If the material is dusty, has an additive in it, or has a plasticizer in it, you may have to clean the filter every shift,” said Dri-Air’s Sears.
Check your dew point. If your machine is not already equipped with a dew point meter, portable ones can be purchased for periodic checks of dew point levels. One supplier compared being without a dew point meter to operating an automobile without a speedometer.
“If you’ve got a bad dew point, your first line of defense is to check the desiccant,” said Maguire Canada’s Davis.
Davis also recommends that processors check their desiccant once a month, which is relatively easy to do with a beaker test.
Check for ambient air leaks. Suppliers also recommend that plant managers check their equipment for any leaks that may let ambient into the process, affecting the air flow and pressure in the system.
“It’s supposed to be a closed system, and if you’re bringing ambient air into it, you are reducing the efficiency,” said Maguire’s Davis.
Wipers and seals should be checked and not allowed to degrade. Brad Lemieux, sales manager at En-Plas Inc., also recommends that processors check for leaks at the hopper -most commonly the lid or access door of the hopper -or for leaks inside the dryer (bed seals, hoses and heater boxes) if the machine isn’t maintaining dew point.
Additionally, Jamie Jamison, product manager for dryers at The Conair Group, recommends that operators check all the hosing to ensure that there are no cracks or holes letting air into the process.
“Collapsed air hoses will reduce air flow and compromise dryer performance,” said Jamison. “Frayed or damaged hoses may draw wet ambient air into the closed-loop drying circuit, causing premature desiccant loading and resulting in high dew points.”
With larger dryers, Universal Dynamics also suggests that customers ensure they are using proper ducting made for the pressure the system will be under.
“Seamless ducting is important in large dryers for maintaining pressure,” said Collis “We find that people think that normal house ducting will be sufficient, but it doesn’t get you there.”
Check your air temperature. If you’ve made sure your filters and hoses are clean and in good shape, but notice that material is still not drying properly, check your drying air temperature. The drying air temperature should be monitored and controlled at the inlet of the hopper rather than at the dryer outlet, and the sensor should be positioned in the center of the air duct to prevent false readings.
“A low drying temperature at the hopper inlet may be caused by something as simple as an improperly adjusted controller, or something a little more sinister like failure of heater elements, heater contractor, thermocouple or controller,” said Conair’s Jamison.
Check your heaters. “When you check heaters, you are checking for continuity, to make sure you don’t have any breaks in the heating element,” said Wittmann’s Corturillo. “As long as the heater is producing the air temperature that is required for regeneration, you are usually fine.”
According to Sears at Dri-Air, heaters can fail at any time and greatly affect the operation of the dryer.
“Also, fuses and relays to control the heaters can fail, making the dryer ineffective,” said Sears. “It is easy to spot a failed process heater but the failure of regeneration heaters are not apparent until the dew point is affected and defective parts are molded.”
Sears adds that some newer dryer models include circuitry to check the status of the heaters, but circuitry is not easy to add to an existing dryer.
Although these steps seem simple enough, they will go a long way in helping you ensure that your dryer runs efficiently and provide early warning signs if problems do arise. You should also follow your manufacturer’s specifications, contact a representative and use the maintenance schedule checklist on pg. 10.
Conair (Cranberry Township, Penn.); www.conairnet.com;800-654-6661
Hamilton Avtec Inc.(Mississauga, Ont.); www.hamiltonavtec.com;905-568-1133
Dri-Air Industries, Inc. (Windsor, Conn.); www.dri-air.com;860-627-5110
Plastics Machinery Inc. (Newmarket, Ont.); www.pmiplastics.com;905-895-5054
Maguire Canada Inc. (Vaughan, Ont.); www.maguirecanada.com;866-441-8409
Motan Inc. (Plainwell, Mich.); www.motan.com;269-685-1050
Dier International Plastics Inc. (Unionville, Ont.);
Thoreson-McCosh Inc. (Troy, Mich.); www.thoresonmccosh.com;248-362-0960
Universal Dynamics, Inc. (Woodbridge, Va.); www.unadyn.com;703-490-7000
Resource Polytec Inc. (Vancouver, B. C.); www.resourcepolytec.com;604-454-1295
Wittmann Canada Inc. (Richmond Hill, Ont.); www.wittmann-canada.com;888-466-8266
Anplast Inc. (Anjou, Que.); 1-800-387-4590
With the recent wave of consolidation in the industry, there has been a glut of used equipment in the market, with new auctions taking place on an almost weekly basis. But according to major suppliers, buying a dryer off the auction block may be more trouble than it’s worth.
Buying a dryer on auction is not the same as buying a second-hand dryer, because you can’t test auctioned equipment before buying it.
“At an auction, you can’t plug the dryer in,” noted Brian Davis at Maguire Canada. “Also, you don’t know how well it’s been maintained.”
Davis points to one major processor that went under last year and had its capital equipment auctioned off. He notes, however, that the company had had to cut its entire maintenance budgets eight months before it went under.
When a processor purchases a piece of used equipment from a supplier or distributor, the “buyer beware” is often taken out of the equation.
“We completely check over every used piece of equipment we sell and either completely refurbish the unit so it runs and looks like new or at the very minimum give the customer a checklist of potential concerns,” noted Brad Lemieux at En-Plas Inc.
If purchasing drying equipment at an auction, customers should try to check seals, filters and hoses to get a sense of the dryer’s maintenance record. Additionally, make sure that the cabinet control wiring is intact, and look for warning signs like rusted out boxes.
“The very least a person can do at an auction is check the quality of the steel,” said Davis. “That way, you will at least get a good shell.”
Suppliers also advise potential buyers to do their research before going to the auction, noting that dryers are often sized and engineered for a very specific application.
Once the equipment has been purchased, you want to clean up the dryer, including the hopper, and replace the filters and the desiccant.
“With the seals, go through and check if they are pliable and soft because you don’t want to start with air leaks,” said Corturillo.
Additionally, manufacturers also warn that equipment on the auction block can often be older, and savings on the sticker price may be lost when running the equipment at your plant.
“When you are buying an older product, you know it’s not the newest technology,” said Corturillo. “So odds are it’s not as efficient as the technology available today.”
Maintenance Schedule Checklist
Desiccant Bead Dryers
– A. Inspect air filters. Clean or replace as required.
– B. Check system for air leaks and correct as required. Every 3 Months
– A. Units equipped with sleeve bearing motors should be lubricated with SAE 20 oil.
– B. Units equipped with ball bearing motors are factory greased and should be re-lubricated with high-grade ball bearing grease.
WHEN ADDING LUBRICANT
– 1. Remove filters plugs at the bearings and install grease fittings suitable to your grease guns. Also, remove the drain plugs at the bearings.
– 2. Add ball bearing grease until all of the old grease is expelled through the drain hole.
– 3. Run motor with drain plug removed to eliminate excess grease.
– 4. Clean and replace drain plug.
– C. Check heater amperage
– D. Check Motor(s) amperage
NOTE: Most units are equipped with permanently lubricated bearings and no lubrication is required. All motors should be examined on an individual basis. Once Every Year
– A. Check dehumidifier valve linkage and operation of valve.
– B. Check wiper blades for wear and replace, if necessary – In general this requires that the valve be disassembled for maintenance Every 2 Years or as Needed
Remove top covers of towers and replace desiccant. Use high temperature silicon tore-seal the covers.
Desiccant Wheel Dryer
– A. Inspect and clean process and regeneration filters
– B. Check system for air leaks and correct as required.
– C. If a belt is used to drive the desiccant wheel check for wear/stretching and replace as necessary Every 6 Months
If a chain is used to drive the desiccant wheel, lubricate the chain Once Each Year
– A. Rotor Seals should initially be inspected after 1 week and 3 months for damage after that, check yearly. They are designed to last for several years
– B. Desiccant rotors should last several years if properly used some are guaranteed for 5-years
Membrane/Compressed Air Dryers
– A. Inspect and clean process air filter
– B. Check system for air leaks and correct as required. Every 6 -12 Months (Depending on model and manufacturer)
– A. Replace 2 coalescing filter elements
NOTE: Some brands of Membrane/Compressed Air dryers use 2-3 times as much energy as other brands. Compare before you buy.
– A. Drain and purge compressed air filter/regulator Every Month
– A. Inspect and clean process air filter
– B. Check system for air leaks and correct as required. Every 6 Months
– A. Inspect canister seals. These are designed to last several years.
Source: Maguire Canada