Small leakage, big cost

日期: 2018-12-03
浏览次数: 13

With the development of the economy and the advancement of technology, many machines and equipment in the field of hydraulic and pneumatic transmission have undergone long-term market verification and improvement, and the performance is gradually improving. What is more important than ever is that any slight improvement and improvement of the system at this time may have a certain effect on the performance improvement of the whole machine. For customers using hydraulic and pneumatic transmission equipment, we must ensure that every penny spent on operating and maintaining the system and equipment is spent on the right expenses. In other words, hydraulic and pneumatic systems and equipment that you design, repair, or maintain must not be “leaked”.


Hydraulic systems are generally considered to be long-term consumers of hydraulic fluids, which in turn is an inherent cost of operating hydraulic equipment. If there are some minor leaks in your hydraulic system, such as leaks on pipes, joints, or other seals, the cost of this part will naturally increase. In fact, the actual cost of one or more “small” leaks in a hydraulic drive requires consideration of the following costs: system replenishment, equipment and site cleaning, waste oil treatment, contaminant entry, and equipment safety.


System oil


System refueling costs should be the most obvious cost of hydraulic system leakage. The phrase "should" is because the cumulative effect of one or more slow leaks on costs over time may become very large. Suppose a hydraulic device loses 0.5 cc of oil per minute, which is 30 cc / hour, which is 720 cc / day 24 hours a day, perhaps not a significant loss. But after one month it is equal to 22 liters (260 liters a year). Assuming that the cost per liter of oil is 15 yuan, the annual cost is about 3,900 yuan, which is a small invisible expense for the customer.


Equipment and site cleaning


Wherever there is a hydraulic oil leak, the cost of cleaning should generally be considered. Cleaning costs include labor (return tanks, drip pans, equipment needed to degrease machine surfaces) and consumables (such as detergents and absorbent materials). Assuming that you spend $100 a week on manpower, equipment, and consumables to clean up the equipment mentioned above, the annual cleaning costs will exceed $1,200.


Waste oil treatment


The abolished hydraulic oil cannot be dumped at will because it belongs to the HW08 (waste mineral oil) hazardous waste in the National Hazardous Waste List and needs to be properly disposed of by qualified units. The treatment of environmentally acceptable waste oil and absorbent materials containing waste oil is costly. Assuming that the transportation and disposal costs are 5 yuan per liter, the annual disposal cost caused by the above leakage rate is 1,300 yuan.


Contaminant entry


When there is a leak of hydraulic oil, pollutants such as air, particles and water enter the hydraulic system. The resulting losses and the costs involved include:


Component damage and fluid degradation caused by contaminants entering the system


Downtime caused by equipment reliability issues


Clear ingested contaminants


Equipment safety


Small leakage, big cost


In many cases, oil spills can pose a safety hazard. The cost of mixing with contaminants is the same, because the cost associated with the hazard caused by hydraulic oil leaks is difficult to quantify – except for the actual downtime loss. However, due to the safety risks caused by leakage, more management, such as more frequent cleaning and inspection than other normal equipment, will gradually quantify and clarify this cost.


In general, calculate the cost of oil spills per year for the above-mentioned hydraulic equipment, which exceeds the cost of replenishing, cleaning and disposal by more than 6,400 yuan. And this is just the cost of a piece of equipment. If multiple hydraulic equipment or large-scale units are involved, the cumulative cost over a long period of time will be enormous.


In addition to the leakage of hydraulic fluid, have you considered the leakage of pneumatic products? One of the advantages of pneumatics compared to hydraulics is its cleanliness. But the problem is that air leaks are more overlooked than hydraulic oil leaks because they don't get the attention of the people in the same way, so you don't have to worry about cleaning and disposal costs. Contaminant entry is possible, but it is usually not a major issue. Unless it is a very serious leak; safety is usually not a big problem, so there is hydration (air) left.


Supplemental air


The air is free, but the clean and dry compressed air is not. When considering the additional air cost of a pneumatic system, the following factors need to be considered: depreciation (wear) of the compressor, cost of processing air: filtration, drying and lubrication.


Compressed energy cost


The ideal leak rate is of course zero, but when calculating the free air output (FAD) required for a pneumatic system, we are usually allowed to leak 10% of the total flow based on experience. Suppose a 10 m3/min system leaks 1 m3/min. The power required to compress 1 cubic meter of air per minute to a pressure of 6 bar (90 psi) is about 5.2 kilowatts. Calculated at an electricity cost of 1 yuan per kWh, the energy cost alone exceeds 5.2 yuan per hour. In the same way, according to the calculation method of 24 hours / 7 days / 365 days, this is equivalent to 45,000 yuan per year. In practice, the boot time may be slightly smaller, even if it is 50% of the boot time, it will increase by 22,500 yuan / year. This fee cannot be ignored.


Quantified loss


Although the 10% leak rate may sound a bit high and generally does not continue to occur in the system, up to 25% of the leak rate has occurred, even in well-maintained pneumatic systems. The actual leak rate of the system can be calculated by the following formula:


QL = QC x t / (T + t)


QL = system leak rate (m3 / min)


QC = compressor FAD (m3 / min)


T = compressor off to off time (minutes)


t = compressor off time (minutes)


In a recent case study in the United States, the agency used ultrasonic leak detection equipment to perform leak detection on the pneumatic systems of the two plants. In the first customer, a small factory spent two hours to investigate and found 27 leaks. The calculated energy cost of these leaks is $9,000 per year. In the second customer, it took two days to investigate a relatively large factory and found 260 leaks and phenomena. The calculated energy costs of these leaks exceed $90,000 per year!


Modern transmission control should be fine, efficient, and the leakage of waste in small details may also sneak a 'snap' a large cost, resulting in a large economic loss to the manufacturer, we should try to avoid similar waste After all, the wallet is drumming again, and the loopholes in the bag are also slowly lost. Of course, the high-tech sealing research to prevent leakage has also achieved certain results, such as the seal with the 'self-monitoring' function, as shown in the figure below, when the rod seal moves back and forth, the sealing lip wears. If the conductive substrate reaches the surface, the circuit between the rod and the housing is closed, and the LED can signal that the user is ready to replace the seal.


Small leakage, big cost

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