Budget Step 1: Find out the parameters of working conditions, and don't let the quotation become "artistic creation"
Flue non-metallic compensator, also called non-metallic expansion joint, fabric fiber expansion joint. The core of the budget of this thing is four words: working condition parameters. Temperature, pressure, diameter, displacement-these four numbers are not determined, and the quotation given to you by the supplier is probably "slapping your head". For example, in the desulfurization flue of power station, the flue gas temperature is generally 80~120℃, but the acid is extremely corrosive; The temperature of the cement kiln tail flue directly soared above 400℃. Different temperatures, the materials used for loops are completely different-silicone cloth, fluorine tape or ceramic fiber cloth, and the price difference starts from three times. Pin these figures to the paper first, and all the quotes later will be accurate.
Don't ignore the pressure. The flue system is mostly slightly negative pressure or low pressure, but in case of positive pressure fluctuation, the number of belt layers and flange strength must be adjusted accordingly. Not to mention the diameter size, the processing hours of the DN200 and DN2000 vary by several orders of magnitude. What about the amount of displacement? Mark the axial, horizontal and angular directions respectively. Don't write "compensation amount 50mm" in general-that's digging a hole for yourself.
The material cost is the big head: ring belt, insulation layer and metal frame, how do you estimate them?
The cost of a non-metallic compensator is divided into three large pieces. The first piece is a non-metallic loop band, which is a multi-layer composite fabric. The more belt layers and the higher the temperature resistance grade, the more expensive the unit price. The national standard JB/T 12235-2015 has requirements for the minimum number of layers of the ring belt, but some manufacturers secretly reduce two layers, which is 30% cheaper and has a life span of less than one year. The second piece is internal insulation cotton, which is commonly used as aluminum silicate fiber blanket. The thickness is calculated according to the surface temperature requirements-generally, the outer wall temperature is required to not exceed 50℃, and the thickness of insulation layer starts from 50~100mm. The third piece is the metal flanges or connectors on both sides. There is an easy pit here: the stress at the four corners of the rectangular non-metallic expansion joint is concentrated, which requires additional reinforcement of the structure, and the processing difficulty is much greater than that of the round one. Q235 or 304 stainless steel for metal frames? For desulfurization systems with strong flue gas corrosion, 316L or even higher nickel alloys have to be considered. The selection of materials directly determines the cost of a single unit, so there is no way to be lazy.
For example, in the product information on our siteNon-metallic expansion joint (fabric fiber expansion joint)Commonly used fluorine tape + alkali-free glass fiber cloth + polytetrafluoroethylene film composite, temperature resistance 260℃; WhileRectangular non-metallic expansion jointBecause of the special structure, angle steel reinforcements will be installed around the flange. For the same caliber, rectangle is 15~25% more expensive than round.
Don't ignore the "hidden costs": deflectors, insulation, anti-corrosion coatings
Two days ago, a customer purchased a non-metallic compensator for flue, and cut off the guide tube because the price was high. As a result, the ring belt was worn out by high-speed flue after three months of installation. Re-assembly plus shipping, double the money saved in the first place. What is the role of a deflector? See what we wrote in our FAQ-the protective ring belt is protected from direct erosion by high-temperature smoke, especially when the wind speed exceeds 15m/s. What about insulation? If the thickness of aluminum silicate wool is not enough and the surface temperature exceeds the standard, it may not only burn people but also burn the ring belt. Do you want to make anti-corrosion coating on the flange surface? The sulfur dioxide concentration in the desulfurization system is high, and the ordinary carbon steel flange will rust through in half a year, so it must be coated with epoxy resin or lined with PTFE. The sealing air interface for the linkage of the smoke baffle door also has to be reserved-this detail has no place in many budget tables at all.
Install bolts, gaskets, sealant. The unit price of these bits and pieces is not high, but the quantity is also money, and the price difference between different materials is great. For example, heat-resistant alloy steel bolts should be used in high-temperature working conditions, and a set is four or five times more expensive than ordinary 8.8 grade.
Size and displacement: Why can the quotation be half the difference for the same caliber?
It is also a rectangular flue with a length of one meter. If it only absorbs 20mm axial displacement, a single wave structure is enough; If you need to compensate the displacement in three directions (axial + transverse + angular) at the same time, you must design a composite structure or increase the wavenumber. With more wave numbers, the number of circle layers may also be added, and the flange width will change accordingly. There is also the installation length-when the site space is limited, the compensator is short and the compensation amount is not enough; If the long flange bolt holes don't match, it will cost money to weld and repair the holes on the spot. These parameters must be clearly marked on the drawing: wave number, compensation per wave, total length, flange screw hole distribution. Only when the supplier gets these parameters can he quote a reliable price, otherwise he can only quote a "benchmark price", and a bunch of additions are waiting for you.
And guess what? Some customers only give a diameter size and let them quote. As a result, after getting the price comparison sheet, they found that A quoted 5000, B quoted 8500, and C quoted 12,000-how to choose? In fact, B and C may have given enough safety margin according to the standard design, and A cut corners. Therefore, when budgeting, we must write the displacement and installation size to death, and then let the supplier calculate according to the national standard. Inside our stationCorrugated expansion joint for power station industryAndHigh temperature axial expansion jointThere are clear displacement compensation curves, so you can refer to the design logic.
Inquiry Comparison: Several quotations are put in front of you, and these three points are focused on
First, is it implemented according to the national standard JB/T 12235-2015? This standard specifies hard indexes such as the number of bands, tensile strength and airtightness test of non-metallic expansion joints. If there is no standard implementation, the default is according to the industry minimum standard-be careful. Second, what does the offer contain? Some only report bare parts, and the freight, on-site welding and installation, bolts and gaskets are all calculated separately; Some quote all-inclusive price, but the warranty period is only half a year. Third, the warranty period and after-sales service-once the flue compensator fails, the exhaust gas leakage directly affects the environmental protection emissions, and the loss of hundreds of thousands a day after production is stopped. So don't just stare at the cheapest one, list these three items clearly, and then let the three companies compare prices. How to do it? Build a comparison table.
Here, the practical template: seven columns are built in Excel-working condition parameters, material selection scheme, structural size, quantity, accessory list, freight installation and warranty terms. Take this form and ask the supplier. If the other party can't report or is vague, just pass. For example, you say you want to add a deflector and he asks "What is a deflector?"-then don't talk about it.
Budget Template: From Zero to Issue Order, One Table Does It
If you estimate it yourself, there is a simple formula: the unit price of rectangular non-metallic compensator ≈ (belt area × belt unit price + flange weight × steel unit price) ×1.2 (machining factor). How to calculate the area of the circle belt? Perimeter × width (the effective width of the band). Look up the table for flange weight according to section steel specification. Ask several suppliers for specific figures, and take the median as the bottom line of the budget. Similarly for circular non-metallic compensators, the area is calculated according to the circumference, and the machining coefficient can be lowered to 1.1.
A 1000×800mm rectangular flue with a band width of 300mm and a temperature resistance of 300℃ is made of fluorine tape composite structure. The unit price of the band is about 800 yuan/m², the band area (1.0+0.8) ×2×0.3=1.08m², and the band cost is 864 yuan. The flange is made of Q235 angle steel, the weight is about 150kg, the unit price is 6 yuan/kg, and the cost is 900 yuan. Total 1764 yuan ×1.2=2117 yuan. This is just a bare estimate, plus the guide tube (about 500 yuan), the insulation layer (about 300 yuan) and the freight (depending on the distance), and the total budget is about 3,000 yuan. The actual quotation may fluctuate by 20%, but if you have a bottom in your heart, you won't be pitted.
Don't use low-grade materials in key parts to save money. Once the flue non-metallic compensator fails, the maintenance window is short, and the loss of shutdown is far greater than the price difference of equipment. Bookmark this article, and go through the list next time you make a budget, at least no items will be missed.