Causes, Corrections and Preventions
The most fortunate drycleaning plants are those that have never experienced an objectionable odor in their solvent. Let’s face it, if the customer is the one to point out an unpleasant odor in the garment, he or she can always take their business elsewhere.
In many cases, elimination of solvent odor can be costly to the affected plant. Depending on the course of action to be taken, the delay in production can be lengthy. In some isolated cases, drastic steps, such as discarding the solvent, are the only remedial solution.
The good news is, in the past few years, IFI is receiving fewer inquiries concerning solvent odor problems. Apparently increased distillation of solvent as conducted in the new machinery is resulting in this welcoming trend. On the otherhand, the odor problems with solvents are not completely eliminated today and should not be ignored. In this bulletin, we will discuss the most prevalent unpleasant odor problems, methods of prevention, and possible corrective measures.
SOLVENT ODORS HAVE MANY ORIGINS
Solvent odor may develop gradually or come about suddenly. The gradual development of odor in solvent is the most troubling for the drycleaning plant operation. If the drycleaning operator does not notice the change of solvent odor, then the customer may be the first to point out an unpleasant odor in the garment. Whereas, the sudden change to an objectionable odor will almost certainly alert the operator.
All solvent odors can occur in either perc or petroleum solvents, except the varnish odor that occurs only in petroleum solvent. Therefore, the course of corrective action is similar for either perc and petroleum solvent
Water Separator Odor
Infrequent water separator maintenance is a common cause of gradual odor development in the solvent. Periodic checks of the water separator for lint, and any foreign odor in the water layer, should be made at least weekly. It is especially important in cases of petroleum machines’ water separators. The concern is that the water will develop a bacterial contamination that in turn can contaminate the solvent.
- Remedial Action – Load the machine by at least 50 percent with all cotton rags or towels. Prior to loading the machine, remove all moisture from the cotton load by drying them in the laundry dryer. Run a regular, full drycleaning cycle and dry at a temperature 20~30 percent higher than normal operating temperature in the drycleaning machine. Afterwards, rags and towels should be washed in the laundry washer with the recommended addition (depending on the size of the load) of Clorox (sodium hypochlorite) bleach. After drying in the laundry dryer, proceed with drycleaning again. Repeat this procedure as many times as needed to remove the odor.
Excess Moisture in Solvent
Excess moisture in solvent can be caused by improper use of spotting and prespotting agents and improper additions of water to the system. Excessive moisture in petroleum solvent machines can accumulate on the bottom of the wash tank.
- Remedial Action – To remove excessive moisture, proceed to dryclean pre-dried all cotton rags or towels as needed in a complete drycleaning cycle as described previously.
High Nonvolatile Residue
High nonvolatile residue develops undesirable solvent odor gradually.
- Prevention – DLI recommends that 8 ~ 10 gallons of solvent should be distilled per 100 pounds of load cleaned.
Contaminated Solvent Base Tank
Contaminated solvent’s base tank clean-up can take up prolonged stoppage of production. Lint and insoluble soil (due to insufficient or malfunctioning filtration) can accumulate in the tank.
- Remedial Action – Your owner’s manual for your drycleaning machine should list the necessary steps on how to clean the base tank. If not, the IFI technical department can provide a guideline on how to proceed with the clean-up, which may remedy the situation. Base tank clean-up can take a long time.
High Distillation Steam Pressure
Excessively high steam pressure during distillation is another possible cause for odor in solvent. It can cause the higher boiling compounds present in the solvent mixture to distill over to the distilled solvent.
- Prevention – Always use the recommended steam pressure to avoid this problem.
- Remedial Action – Most boil-overs will happen when solvent contains high moisture or if there is an accumulation of chemicals that cause foaming of solvent in the still (such as various finishing agents and water repellents). The distillation then must be conducted at the steam pressure that allows only the very slow distillation.
Spotting Chemicals
A build-up of spotting chemicals frequently results in solvent odor problems. Amyl acetate is particularly a problem.
- Prevention – All spotting chemicals must be flushed from the fabrics with either volatile dry solvent or steam, and then dried before drycleaning.
- Remedial Action – Even slower distillation at low steam pressure will not help to eliminate this odor. All cotton rags or towels should be processed in this solvent per the procedure described previously.
Improper Detergents
It is not often the case, but improper use of detergents can also cause solvent odor. Some detergents have certain amounts of solvent in them, i.e., some petroleum solvent detergents are formulated with petroleum solvent. If they are used in a perchloroethylene system, an odor problem is likely to occur. Also, with the new, dry-to-dry petroleum solvent machines, use only the recommended detergent for the system. Any experimentation with other brands of detergents may result in problems.
Odors Caused by Fabrics
Textile Finish Odors – Odors that are beyond the drycleaner’s control are the odors caused by various textile finishes applied during the manufacture of textiles. An unpleasant “fishy” odor can be traced to a formaldehyde resin that is used in permapress finishes on textiles.
- Remedial Action – To remove this odor, try to distill at the lower steam pressure (30 ~ 40 percent of recommended pressure). Then run all cotton rags in the wash solvent.
- Smoke or Heavy Soil Fabric Odor – Heavily soiled or smoke-damaged garments cause a solvent odor that is immediately noticed.
- Remedial Action – Distilling the entire wash solvent and a change of cartridge filters should take care of this problem.
- Prevention – As a precaution, suspected problem loads should be pre-washed in a “batch” operation. For a drycleaner, the term “batch,” refers to a fixed quantity of solvent that is pumped into the washer filled with the garments. The drain valve is closed and the solvent is prevented from going through the filters. After the short “batch,” usually five minutes, the entire solvent content from the washer (including the extracted solvent) is pumped into a still. Afterwards, proceed with the regular drycleaning cycle.
Odors Caused by Lint
Odor caused by lint is always the result of insufficient maintenance of the drycleaning machine. Lint on the heating and condensing coils or in the air passageways of a machine can cause a sour or musty odors.
- Prevention – A routine maintenance schedule including the periodic cleaning of the heating and condensing coils should prevent this type of odor problem.
- Remedial Action – The solvent odor in most cases can be removed by running all cotton rags several times in the wash solvent per the procedure described previously.
New Solvent Odors
There is always the possibility that some new solvents have an odor. A drycleaning-grade perchloroethylene with a good stabilizer rarely develops a bad odor unless contaminants are in some way introduced.
Petroleum solvents, unless they are of the “odorless” type, have characteristic odors. Usually, they are a “sweet” type of odor. This odor will vary, depending on the source of the crude oil from which the solvent was manufactured. However, petroleum solvents are more susceptible to develop an odor than perchloroethylene. A “sour” odor can develop in new petroleum solvent when it is stored for a long period of time.
- Remedial Action – Usually this solvent has to be replaced.
Varnish Odor in Petroleum Solvent
Varnish odor is only found with petroleum solvent and is caused by the breakdown of the hydrocarbons that make up the solvent.
- Remedial Action – Unfortunately, there is no known method to correct the varnish odor in the affected solvent. The solvent must be discarded. All solvent must be removed from the system-from the base tanks, filters, pipelines, and storage tanks.
The cleaning of the base tanks, and any part of the machine that the varnish odor solvent came in contact with, should be done with the trisodium phosphate. A complicated process, involving safety precautions and the proper disposal of solvent and cleaning solution, would be too lengthy to include in this bulletin. However, if you need detailed information on how to clean petroleum solvent tanks, contact IFI’s Research Department for a copy of the procedure.
Conclusion
We, as fabricare industry professionals, have to be concerned how the end product of our service is perceived by our customers. Odor in garments returned to a consumer is unacceptable.
The majority of objectionable odors in drycleaning plants can be avoided by conducting periodic maintenance of the equipment. This way, even if we cannot avoid sudden objectionable odor occurrence in the plant, at least we will have control over the gradual build-up of bad odors in solvents.
Identification of objectionable odor and subsequent removal are sometimes difficult tasks. A general step-by-step guideline for what to look for is summarized below for both perc and petroleum solvent.
1. Review your machine’s maintenance schedule.
2. Ascertain that the recommended distillation rate is maintained. Check if over boil of solvent occurred.
3. Distill part of the solvent at the 20 ~ 40 percent of the recommended steam pressure. Collect a small amount of distilled solvent in the clean jar and perform a simple residual odor test. Immerse a clean, odorless cotton towel in the distilled solvent. Use the machine’s manual drying cycle to dry the towel. Once dried, smell the towel for odor, then steam it for no more than five seconds to check if there is any residual odor left. If not, distill the entire content of affected solvent at the same low steam pressure. If you use filter cartridges, replace them. Clean the water separator thoroughly and add new solvent and water.
4. If the slow distillation of affected solvent doesn’t help, run pre-dried cotton rags and/or towels several times in the complete cleaning cycle at the elevated drying temperature. Check for residual odor left after steaming a few rags.
5. As a last resort, empty and thoroughly clean the base wash tank per manufacturer instructions.
This article is from DLI’s TOI-682
