By Murphy Mahaffey, Director of International Sales, Polyurethane Machinery Corporation with contributions by Tom Rivera, Director of Technical Services; Mike Burke, Senior Technician
Every profession has its associated tools – the carpenters have their saws, planes, and hammers; the spray foam applicators have their spray system – pumps, hoses, and guns. While the tools are different, the tasks cannot be completed without the proper tools kept in working order – clean, organized, and ready to produce. This article will discuss key care and maintenance points for spray foam systems from the transfer pumps to the spray gun.
Spray foam equipment requires electricity and compressed air, so before starting up the equipment ensure that the air and power supply are able to drive the system. The air supply should generate adequate pressure (expressed in pounds per square inch or psi) but also enough volume (expressed in cubic feet per minute or CFM). The air should be clean and dry. Poor quality air can leave a system underpowered resulting in poor mix; it can also decrease the life of an air motor requiring it to be prematurely serviced. Most of the industry uses air-purge guns for application – an air supply mixed with condensation, oil, or other contaminants will put these materials on the substrate when the gun is triggered, resulting in blisters or off-ratio material.
POWER IT UP
The power supply going to the machine, whether from a generator or jobsite power, should be checked with an amp clamp meter. This should be done daily, and is a simple operation that will preempt problems resulting from inconsistent power.
The voltage going to the machine should be checked and compared with the required voltage noted on the machine’s nameplate. When the voltage is too low, it can cause heat issues and even damage the motor. Jobsite power can vary depending on who is tied in on any given day. When using a generator, be sure that the generator does not “go dry” (run out of fuel) while the machine is in operation. The final moments when the generator is running will send out inconsistent voltage that can damage circuit boards. Manufacturers including PMC have operational lights on their machines to show when power is correct with a quick glance. When the power is off, periodically check the plugs, switches, and coils for loose connections.
A SUCCESSFUL TRANSFER
The transfer system feeds the material from the drums or totes to the main proportioning pumps. Materials should be stored at the proper temperature per the manufacturer’s recommendation on the MSDS or product data sheets. A desiccant dryer should be used on the Iso material drum and may be required on the resin/poly side. As the material level in the drum drops during operation, air displaces or “fills” the drum. The desiccant cartridge filters out moisture in the air as it enters the drum, reducing the chance for Iso to react with the moisture in the air, resulting in crystal formation. If crystals are allowed to form, they will clog the filter screens and begin to build up over time in the transfer hoses and heated hoses. This is one of the leading causes of problems in equipment troubleshooting, yet it has to do with material handling – proper material handling leads to efficient application.
Some systems require mixing prior to and during spray. The drum mixer should be kept clean and free from any buildup that can break free during operation because buildup can cause material feed problems.
The transfer system includes the transfer/drum pumps, the air hoses, material lines, filter assemblies, and inlet monitoring equipment. The transfer pumps should be cleaned of any solid material when drums/totes are exchanged. It is recommended that you add a dab of white lithium grease to the air inlet on a monthly basis to keep the air motor lubricated. Do not use air tool oil on the air motor or spray gun; it is not intended for this equipment. It will break down the O-rings.
The air hoses and material transfer hoses should be inspected for bulges and leaks. It is important to remember that most hose failures take place where the fitting is crimped to the hose. Inspect the entire length of the hose, taking care to look at the entire circumference of the hose crimp. Material transfer hoses that send the material from the transfer pump to the proportioning pump should receive a similar circumferential inspection – if a bulge is noted in the hose it should be immediately removed from the system.
GETTING TO THE HEART OF THINGS
The inlet material screens/Y-strainers between the transfer pumps and the proportioning pumps are there to keep particles that are too big from getting into the proportioning pump. The proportioning pump has two jobs – ratio and pressure. It uses ball checks and seats to achieve this. If a particle that is too big is introduced to the pump, it will prevent the ball from seating properly against the check bevel, which results in pressure and ratio problems. When using a new material the Y-strainers should be inspected daily or when transfer pump pressure begins to fluctuate. If no buildup is noted, the filter inspection schedule can go to bi-weekly or as needed.
The inlet monitoring system shows the pressure and temperature of the material going from the transfer pumps to the proportioning pumps positioned after the Y-strainer. This can be accomplished with simple inline gauges that are always visible, or with transducers and thermocouples running signals to a board. The information that these readings provide is at the core of all troubleshooting questions. When the weather changes, causing material ambient temperatures to fall, the same equipment settings suddenly don’t give the expected results. By reviewing the feed temperature and pressure, adjustments can be made to the equipment settings and gun chamber sizes to optimize the Delta T of the machine in use. The inlet monitoring system should be kept clean and checked prior to operation and during startup.
Polyurethane foam formulations require precise temperature and pressure to react, providing maximum yield. The heart of the system does just this – there is a drive system connected to pumps of equivalent volume, which creates pressure and pushes the material through a rapid heating system. The proportioning pump has two jobs – provide the correct ratio of material, and generate the pressure necessary to mix it at the pressure providing the maximum material yield. The vast majority of the material systems are 1:1 ratio by volume.
Drive systems include hydraulic, pneumatic, and electric variations. The undisputed workhorse of the industry is the hydraulic drive system. Hydraulic drive machines have been documented to operate for decades, and there are plenty still in operation from the 1990s – I have recently seen one myself. The key is to inspect the filter, check the hydraulic oil level, and actually change the hydraulic oil when the recommended time comes. Think of it like your work truck – would you let that oil go past 3,000 miles? Then why would you do that to the heart of the machine that is paying for the truck? The hydraulic drive cylinder should be leak-free, and the reversing switch mechanism mounting and position should be inspected monthly.
PROPORTIONERS, SPRAY GUNS, AND HEATED HOSES GALORE
Proportioning pumps should have an Iso pump shaft lubrication system. Typically on horizontal pumping systems there will be a pump lube reservoir. Lubrication material flow should be noted in the lines going to and from the Iso pump housing. The lubrication reservoir should be inspected daily for discoloration, and changed when this is noted. If there is excessive Iso material introduced, the pump must be serviced. Some vertical pumping systems will have a lube cup on the Iso pump – the lubricant should be in a liquid state, and changed when discoloration is noted.
The heating system on polyurethane foam equipment is very rapid, creating a high temperature change or “Delta T”. This is necessary to provide heat to the chemical reaction. Proper maintenance and cleaning of the transfer system will reduce the chance of debris buildup in the heater. Heaters are equipped with over-pressure and over-temperature sensors. They should be checked periodically for loose connections when the power is off.
The spray gun is where the magic happens – two components are mixed with high-pressure impingement at a precise ratio, pressure, and temperature. Most spray guns are air purge, which means that there is a stream of air coming from the gun nozzle when it is not spraying foam. This should be left on during normal operation and checked for condensation or contaminated air. The filter screens in the gun should be inspected and cleaned daily, or when material pressures are out of balance. The gun exterior can be treated with silicon mold-release to avoid material buildup and make cleaning easier, or use a spray cover. Do not allow your gun to get dirty.
The heated hose and temperature sensor unit (TSU) block are designed to withstand the pressure created by the proportioning pump and to maintain the temperature that the primary heaters create. The heated hose system arguably takes the most abuse of the equipment – it is dragged across jobsites, around corners, up walls, and through crawl spaces. Long lengths of hose should be moved by more than one person, and the hose assembly should never be pulled by the whip hose / spray gun section.
The minimum hose rack diameter is four feet to avoid excessive bending of the heating elements or fitting junctions. Take the entire hose off the vertical hanging rack before turning on the heat – if not, undue stress is applied to the portions of the hose that are on the rack supporting the weight of the bundle. It can be stretched out, or put in a S-pattern on the ground during warm-up. The scuff jacket protects the hose insulation and material lines. It should be kept clean of excessive buildup and replaced if damaged.
The operator should be aware of the location of the TSU block to avoid inadvertent damage – this houses the sensor that reads the material temperature and relays a signal to the controller to maintain the correct temperature. Lastly, if there are other trades working in the area, alert them to not run over the hose. It happens.
By following these steps, you can ensure that your investment in equipment will continue to be a good one and that your equipment will continue to perform – correctly and safely for its intended duration. •
Photos courtesy of PMC, Inc.