Cleaning is a critical task within the entire printing process. Technology has resulted not only in new chemical products but new cleaning processes like solvent impregnated cloth. These changes are directed towards performance and controlling emissions during and after use.
Blankets, rollers and metering rollers must be in a condition to minimize any negative effects to the current and following printing jobs. Press components can be cleaned manually or through use of Automatic washing.
Manual cleaning has the potential to be the largest emitter of Volatile Organic Compounds (VOC). The inherent arbitrary nature of the process itself is a problem. Some press personnel might be frugal in their application of cleaning agent, where others may feel that more is better. An important issue is worker exposure to the cleaning agents. The use of personal protective equipment (PPE) such as gloves, goggles, aprons and respirators, should be an important consideration for the pressroom manager. Each situation must be assessed individually.
Chemical resistant gloves and goggles are universally accepted. Contributing to the possibility of increased emissions is that during manual cleaning, the wash solvent might not be applied solely to the roller or blanket. Splashing during application or handling increases the amount of VOC generated due to non –cleaning activities. Soiled worker clothing or uniforms, used press rags and VOC in the working environment are other reasons why manual methods are problematic. Consideration of disposal procedures for rags or towels is critical because these items could be considered hazardous waste! Finally, solvent residue on the clothing of plant personnel could also be a source of concern.
Two of many approaches to minimizing the VOC generated during manual cleaning are to use a wash concentrate or a LOWVOC wash. A wash concentrate is designed to be diluted with water up to 50% by volume. This water-in-oil emulsion does an efficient job of cleaning of conventional ink along with paper lint and other water soluble contaminants that may build up on the rollers or blankets. Lower emissions result because there is less solvent involved in the cleaning process itself.
Some low-VOC wash products have vapor pressures (VP) often below 1 mmHg@20¬∫C and are simply not volatile. Simply put, low VP products do not evaporate. They are designed either as concentrates that can be cut with water or when used as-is, rinsed with water or cleaned/wiped up with a damp press towel or sponge. Whether diluted or used-as-is, low vapor pressure wash products emit zero to low-VOC!
The towels and sponges used for low vapor pressure wash products could be considered as non-hazardous chemical waste and present the user with a lower disposal cost. These wash products tend to have flashpoints higher than 142¬∫F and do not meet any other RCRA hazard class. Automatic Wash Systems have the potential of limiting VOC and over time providing a good return on investment due to the reduced amount of wash products used.
AUTOMATIC WASH UP SYSTEMS
The significance of using an Automatic wash up system is that it can approach the attributes of being a closed system. A properly adjusted unit can measure the amount of wash used for cleaning, recapture it and recycle most of it for reuse. The water component can be properly treated and discarded.
One critical aspect of an Automatic wash up system is that during the process, water is separated from the solvent, removing most of the water from the product.
This water, as is, is typically unacceptable for discharge into industrial or domestic sewerage systems. It is the responsibility of the user to determine whether their discharge water is acceptable under local sewer regulations. Most municipal utility authorities require that a certified environmental lab check out discharge water on a monthly basis.
Accounting for VOC use should be easier since Automatic wash up systems either have or can be modified to have holding tanks or feed tanks that can be manually or electronically monitored for content or consumed quantity over time.
An Automatic wash up system unit is adjusted to deliver a specific amount of wash for each cleaning cycle. This removes the random element present in manual cleaning operations and will normally contribute to a lower quantity of solvent used. This control directly affects the VOC emitted when using a high vapor pressure material and the quality of water-wash generated in the process. The optimum means to control both wash waste and VOC emission is to use a low-VOC (low volatile) wash in an Automatic wash up system. A wash product with low to no volatility minimizes the VOC emitted during the cleaning process and the collected wash-water mix can be efficiently recovered. The volume of low-VOC washes recovered may be higher due to a lower loss rate during the cleaning process. Printers’ Service markets a recycling unit which can be used with most Automatic Wash Systems to increase the overall return on investment of a drum of wash. Accessories such as separation tanks round out the equipment required to put together a total system.
A uniform Automatic cleaning process that doesn’t rely on manual methods with their potential excess use of product, high-VOC emissions and potential solid waste issues, is clearly beneficial for any plant operation.
WASH PRODUCT SELECTION
The selection of wash products depends on several factors.
‚Ä¢ Does the wash meet applicable VOC regulations?
‚Ä¢ Will it be cost effective to purchase and properly dispose?
‚Ä¢ Is the product approved by the press manufacturer?
‚Ä¢ Is the product compatible with the Automatic wash up system unit itself?
‚Ä¢ Can the product be recovered efficiently with current technology?
‚Ä¢ Does the recovered product require additives?
‚Ä¢ Is the product compatible with rollers and blankets?
There are significant differences between the composition of blankets, rollers and the components in Automatic wash up system so selecting a wash product is not a simple process. Wash selection requires either a knowledgeable supplier or reviewing the literature provided by the press, roller and blanket manufacturer.
Regulatory changes on the West Coast have resulted in wash manufacturers introducing a wide variety of low-VOC wash products. Past regulatory requirements hinged on vapor pressure alone but now in some air quality districts, the VOC content is the deciding factor. Testing methods have also changed and while Method 24 is still used, wash suppliers are using the South Coast Air Quality Management District (SCAQMD) Method 313. The latter method involves the use of Gas Chromatography and Mass Spectroscopy.
The regulatory climate in California has prompted significant research into low and zero-VOC solvents. Printers’ Service, along with many other wash manufacturers, products that have a minimum environmental impact while providing reasonable cleaning performance. Advances in product reclamation technology, provide the opportunity for printers to recapture these materials when used in an Automatic Wash System applications and recover a significant portion of their wash product investment.
The ultimate goal is to operate your printing businesses profitably while meeting Federal, Provincial and Local air, water and disposal regulations. Suppliers of washes and cleaners to the printing industry are now required to consider many more factors in their product R&D. The simple goal of checking if a low priced solvent cleans the ink lies in the past. Now, relationships with the press manufacturer, roller manufacturer and blanket manufacturers have created an environment where the printer will have access to wash products that have been significantly screened for their application. In the end, this leads to products that are ready to use with significantly less potential for something to go amiss. This translates to printing jobs being completed on time and operating profitably without incident in our highly regulated industry.