1. Why can compensators also be related to "energy consumption"? -Start with the heat loss and resistance of the pipeline system
When many people hear "compensator", their first reaction is: Isn't this just an elastic joint on a pipeline? What does it have to do with the electricity bill?
Tsk, it matters a lot. In a pipeline system, the compensator is not just responsible for "telescoping"-it is directly involved in the flow and heat exchange of the medium. Think about it, there are hundreds of degrees of hot flue gas in the smoke duct and thousands of degrees of exhaust gas at the tail of the cement kiln. If the heat insulation of this section of the compensator is not done well, the heat will scatter out. How many turns does the fan have to turn to pull the temperature back? That's the first account: heat loss.
The second account is more hidden-resistance. If the internal structure of the compensator is unreasonably designed or thick-walled metal bellows is used, the medium flow will pass like a "speed bump". As soon as the system resistance is high, the power consumption of the pump or fan goes up directly. For every 1% increase in resistance of fan turbines in power plants and cement plants, the electricity bill is a matter of hundreds of thousands of dollars. Therefore, the energy consumption attribute of the compensator is not blown out, but actually calculated.
2. Where is the "saving" of non-metallic compensator compared with metal? — — Disassembly of three dimensions of thermal conductivity, weight and sealability
Metal compensators (such as stainless steel corrugated expansion joints) are familiar to everyone and have good pressure capacity, but on the low-energy track, they are born to suffer. Let's compare the non-metallic compensator (fabric fiber expansion joint), and the three dimensions can be understood at a glance.
Thermal conductivity:The thermal conductivity of metals is often more than ten or twenty W/ (m·K), while non-metallic fiber fabrics are generally below 0.1, which is hundreds of times worse. In the same working condition, the non-metallic compensator is like wearing a down jacket on the pipe, and the heat loss is extremely low. Especially those high-temperature pipelines used in the cement industry and power station industry. If a non-metallic expansion joint is installed, the surface temperature of the pipeline can drop by dozens of degrees.
Weight:Non-metallic compensators are typically 60% ~80% lighter than metallic compensators of the same caliber. Don't underestimate the weight-light means that the pipe rack is less stressed, the support structure can be simplified, and the installation cost is low. Moreover, the lightweight structure has a small load on the pipeline system itself, which indirectly reduces the vibration and extra friction of the pipeline, which can be invisible energy consumption.
Sealability:Metal bellows are most afraid of fatigue cracks. Once it leaks, the system should supplement fresh air and burn more fuel, and the energy consumption will rise. The non-metallic compensator adopts multi-layer fabric + sealing film structure, such as the rectangular non-metallic expansion joint of this station, which basically does not leak within the design life. It is sealed and the heat and pressure are retained. Can it not save electricity?
3. The key to low-energy design: fabric layer number, thermal insulation filling and structural optimization. Don't underestimate these millimeters
Two days ago, I met a customer, saying that the non-metallic compensator used in their factory was old and leaking heat, and I suspected that the material was not good. I looked at the parameters: What insulation layer has only one layer of glass fiber felt, and the thickness is only 5mm-it is strange that this can be good.
The real low-energy non-metallic compensator pays attention to the "laminated structure" in design. Take the non-metallic expansion joint (fabric fiber expansion joint) of this station as an example. From the inside to the outside, it is: temperature-resistant layer (such as ceramic fiber cloth), heat-insulating filling layer (aluminum silicate cotton, generally 30~50mm thick), airtight layer (fluororubber or polytetrafluoroethylene film) and outer protective layer (stainless steel wire mesh or silicone cloth). The thickness, material and laying angle of each layer are particular. If the heat insulation filling layer is plugged 10mm more, the heat transfer coefficient can be reduced by 20%. Do you think this 10mm is worth it?
There is also structural optimization-non-metallic compensators usually do not have the "peaks and troughs" of metal bellows, the flow channel is smoother, and the local resistance coefficient of medium flow can be controlled below 0.3, while metal bellows often require 0.6~0.8. This gap, multiplied by the flow rate of the fan or pump, saves enough electricity in a year to buy several compensators.
4. Typical case: It is used in smoke duct and cement kiln tail of power plant, and the measured system resistance is reduced by 15%
Come on, tell me a real case. The original metal rectangular expansion joint in the flue duct system of a 300MW coal-fired power plant has many cracks after three years of operation, the air leakage rate exceeds 8%, and the induced draft fan current remains high. Later, all of them were replaced with non-metallic compensators (the model is the rectangular non-metallic expansion joint of this station). After the transformation, the wind pressure was measured on site: the system resistance dropped from the original 2800Pa to 2380Pa, a decrease of exactly 15%.
The power of induced draft fan is calculated according to 800kW, and a 15% reduction in resistance means that the power consumption is reduced by about 8% ~10% (the power of fan is approximately 1.3rd power of pressure head). It runs for 7,000 hours a year, saving 448,000 kWh of electricity, which is 224,000 yuan according to 0.5 yuan/kWh. However, the purchase price of a non-metallic compensator is only tens of thousands of yuan, and it is still profitable to pay back the capital in one year.
Cement kiln tail is more typical-high temperature, dusty, negative pressure, and the metal compensator can't last for a few months before wearing out or fatigue fracture. The non-metallic expansion joint, especially the ceramic fiber fabric layer, can last for two or three years, and the sealing performance is good, the air leakage at the kiln tail is less, and the heat consumption is directly reduced.
5. Guide for selection and installation of pit avoidance: air leakage, cracking, inadequate heat insulation, and all energy consumption are in vain
No matter how good the non-metallic compensator is, if you choose and install the wrong one, it will still be useless. Let's list the common pits:
- Air leakage:The main reason is that the flange connection surface is not handled properly. The flange must be flat during installation, and the sealing gasket should be temperature-resistant and corrosion-resistant (such as the flange gasket matched by the rubber compensator of this station). If on-site welding deformation, it must be trimmed and reinstalled.
- Crack:Although the fabric layer of the non-metallic compensator is flexible, the displacement amount cannot exceed the limit. During design, accurate calculation should be made according to the thermal expansion of the pipeline, such as axial displacement and transverse displacement, and then non-metallic expansion joints with corresponding specifications should be selected, and sufficient pre-stretching amount should be left during installation.
- Inadequate insulation:After installing compensators at many sites, it was found that the temperature of the pipe wall was still high-after checking, the original insulation filling layer was flattened, or the filling thickness was not enough. Remember: The key to low-energy design is the insulation layer, which cannot be less thick than the design value, and should be checked regularly for collapse.
And guess what? There is a pipeline in a chemical plant. Because two fewer bolts were screwed when installing a non-metallic compensator, the sealing surface was misaligned, and the air leakage was as high as 5%. It took the fan to open for two months before it was discovered that the electricity bill cost hundreds of thousands more. These details are really no small matter.
6. Cost recovery in three years? Calculate an account: the number of maintenance times is reduced, pump power is saved, and downtime losses are reduced
Finally, let's get the accounts straight. The purchase cost of a low-energy non-metallic compensator is about 1.2~1.5 times that of a metal compensator with the same caliber. But you look at the full lifecycle cost:
- Number of maintenance:On average, it takes 1~2 years for metal compensators to check welds and replace seals, while 3~5 years for non-metal compensators (if the structure is reasonable) to change the outer fabric. Maintenance labor + accessories, saving 5,000~20,000 yuan per year.
- Pump power savings:The previously calculated resistance is reduced by 15%, which corresponds to the saving of electricity bills. Small systems are several thousand dollars a year, and large systems are hundreds of thousands.
- Downtime Loss:Once the metal compensator leaks or breaks, it is often shut down for emergency repair. If the cement kiln stops once, the loss is calculated by the hour, which is hundreds of thousands per hour. Minor repairs of non-metallic compensators can be handled online (such as repair welding of metal frames), and the probability of downtime is greatly reduced.
Taken together, paying back the investment within three years is a conservative estimate. If the system is large and the working conditions are poor, it is not unusual to pay back money in one year. So don't just look at the buying price, but calculate the general ledger-choose the right low-energy non-metallic compensator, and every kilowatt hour of electricity saved is a profit.