·The development prospect of LNG mixer truck is still worrying

In recent years, the use of LNG has become more and more extensive, and it has greatly replaced diesel in various fields. Only with the recent drop in crude oil prices, the price advantage of LNG has weakened a lot. From a macro perspective, the weakening of the price advantage only caused the trade-off between LNG engines and diesel engines to a certain extent. In the field of construction machinery, with the overall downturn of the construction industry in the first half of 2015, the severe shrinkage of equipment demand is the root cause of the serious impact on the development and popularization of LNG engines. From a technical point of view, some of the advantages of LNG are unmatched by diesel. However, is the use of LNG engines really suitable for the working conditions of construction machinery? Is it convenient, fast and safe?
Is the LNG engine "strong"?
LNG engine power performance is relatively "gentle", which is the general consensus in the industry. Of course, experts who admire LNG engines can use a lot of evidence, such as octane number and torque curve, to prove that the LNG engine has been tuned to fully meet or exceed the power performance of the diesel engine. I have no right to deny this. But what about the adjustment of the LNG engine for the working conditions of the concrete mixer? How much impact on fuel economy?
The volume of LNG after gasification is much larger than that of atomized oil, resulting in low air intake efficiency, resulting in a decrease in power. But for construction machinery, the more important than the power is the maximum torque, and the speed range of the maximum torque.
Personally, the low-speed torque of the LNG engine is weak, which is the innate characteristic of the ignition engine. High torque output is not possible unless low gear speed is used. The increase in speed means a drop in fuel economy. If it is in such a long-term condition, the saving effect of LNG will be greatly reduced. Therefore, LNG engines equipped with concrete mixers must be trade-offs in terms of power and economy to achieve similar results to diesel engines.
The working environment of a concrete mixer truck can be described as "half is sea water and half is flame." On the way of concrete transportation, its driving environment is almost the same as other vehicles. Once inside the construction site, it fell from hell to hell. Don't think that I am alarmist. Even in the first-tier cities, there are several construction sites that reserve sufficient circulation space for the construction vehicles, and how many construction sites have completed the hardened roads in the early stage of the project. For many years, I have seen basically narrow, steep slopes and muddy sites. It is not uncommon for concrete mixers to fly at low speeds, resisting slopes, and falling into mud. Therefore, the high torque output of the engine becomes an important requirement for the mixer truck.
The ground mud on the construction site needs a lot of torque. In fact, other construction machinery has the same problem. For example, heavy load lifting shovel and forward sloping conditions often occur in loaders, and the requirements for low speed torque are higher than that of concrete mixer trucks. Therefore, in order to widely assemble engineering machinery for LNG engines, it is the most important issue to ensure sufficient torque to replace diesel engines.
Is it a reliable way to build a LNG refueling station?
It is said that all LNG users who have reached more than 20 vehicles will build a gas station. This is a good thing, but the follow-up questions will inevitably follow:
First of all, where is the gas station built? Usually the size of 20 large vehicles can be reached, and the venue should not be a big problem. However, unless the user replaces all diesel-using equipment with LNG, the diesel and gas stations can only coexist. Among them, whether there is a safety hazard in the location of the diesel engine and the gas station is worthy of careful consideration. The user has a good venue. If there is no venue, where is it built? Many concrete logistics companies dispatch concrete mixer trucks to customer units, and the management agencies and equipment are in a state of dispersion and flow. If there is no LNG filling station in or near the customer unit, it will be very inconvenient to refuel the equipment.
Second, who is the customer of the gas station? If it is open to the public, social vehicles frequently enter the user's factory, who is responsible for the security issue? If you only serve the vehicles inside the user, isn't it the price and economic benefits of the filling station on the customer's tree? If this customer is not well managed, the refueling equipment can only be idle, which is not conducive to promoting the use of LNG.
Again, who is going to manage the gas station? Regardless of who builds the gas station and who owns the property rights, daily management and use operations must be performed by professionals, which is a must. If managed by LNG, it is professional and safe. However, the work schedule, shift change system and performance appraisal of the gas station workers are closely related to the nature and intensity of the users' business. Does their salary need to be formulated by each household and executed by LNG companies? How does LNG balance the difference in wage standards at each gas station? If the user unit is sent to manage, the lack of professionalism is a serious waste factor and security risk.
What if the concrete mixer truck runs out of LNG on the construction site?
Concrete mixers are different from long-haul trucks on highways, and you can plan ahead to refuel in the next service area. In reality, the unloading process of concrete mixer trucks is often uncontrollable, so it is highly likely that LNG will be exhausted at the construction site.
Generally speaking, concrete with ordinary Portland cement as the main cementing material has an initial setting time of about 1.5 hours and a final setting time of about 4 hours. Therefore, concrete companies usually stipulate that the discharge must be completed within the initial setting time. So since the time has been fixed, how can the unloading process be uncontrollable?
The mixing truck is deeply trapped to cause the chassis. In fact, there are many reasons why the unloading process is uncontrollable. For example, the concrete mixer truck itself or the concrete pumping equipment suddenly fails, causing the mixer truck to fail to discharge. What's more, construction management chaos is also a common cause of multi-vehicle concrete backlog on site. To put it bluntly, the concrete quality specification has not been sufficiently respected in reality, and the completion of unloading within 1.5 hours has not become a rigid regulation. There are many reasons for this, but it is attributed to the fact that the buyer's market problem in the concrete industry has caused great obstacles and injuries to the implementation of concrete quality specifications.
Since the unloading process is uncontrollable, the waiting time for unloading may exceed expectations. However, the concrete is not a steel bar or a wooden floor. The particularity of concrete is that it is in a semi-finished state when delivered to the customer. After loading the car, the concrete begins to unidirectional solidification reaction in the mixer truck, so the concrete tank needs to be rotated continuously to maintain the workability and fluidity of the concrete. Therefore, as long as the concrete mixer is waiting for discharge, it is necessary to keep the engine running.
This of course will consume valuable fuel. But the more terrible situation is that it was originally expected that the LNG balance of the concrete mixer truck was sufficient to complete the transportation, but waiting for the unloading time to be too long caused the LNG to be exhausted at the scene.
People who don't understand concrete construction may ask: "Why do you not return immediately or raise the spot when LNG is about to run out?"
First answer the question of “return immediately” If the LNG margin is expected to be insufficient, we will list two options for the concrete company to choose: wait for it to successfully discharge, but not enough to return; no discharge can guarantee return, concrete after return Need to scrap or downgrade adjustments.
I believe that concrete companies will choose the first way. This is because, for concrete companies, concrete is the main commodity, and the use of lower grades leads to chaotic production and concrete quality hazards. Concrete scrapping means direct loss. After the mixer is unloaded, it is possible to wait for the LNG to be filled in a safe place. The loss is only a small part of the capacity and time.
Furthermore, not all site conditions allow the concrete mixer to return. I have seen a scene where a heavy truck enters a pouring position under a steep slope. The empty car climbs back to the original road and returns. The heavy car returns cannot climb. Of course, this is a case.
To answer the question of "on-site replenishment", I heard that there is an LNG mobile refueling car, which is specially used to solve the problem of on-site refueling. However, due to the on-site environment of concrete construction, it is very likely that the flow-filling car will not reach the front. If it is used to rescue a mixer truck or other construction machinery at the construction site, it is recommended that the LNG flow filling vehicle have at least two conditions. First, if the mobile filling vehicle is also using LNG as its own fuel, then there must be enough power and torque to ensure that it successfully comes to the rescue vehicle and successfully evacuate. Second, the pipeline for filling LNG must be long enough. Strong enough, not less than 10 meters in length, the strength must be able to withstand the shackles of sand and steel.
Difficulties in narrowing the site. In addition, the process of heavy-duty concrete mixer trucks waiting for LNG flow filling vehicles will be a tormenting process. Since the can body cannot rotate, the concrete is accelerating in the agitating tank to cause a solidification reaction. In this case, time is not just money, it is quality. Long waits or cause concrete to solidify in the tank or cause instability in the quality of the concrete.
Someone will say, "Isn't diesel exhausted the same?" That's right! The consequences and hazards of diesel and LNG depletion are the same, but the difference is that diesel fueling requires only one oil drum, and it can also be rescued by a mixer truck, and LNG is at least not available at present.
In fact, there are still some problems that affect the use of LNG on concrete mixer trucks, such as the problem of fuel tank depression caused by the rugged scene. Although LNG gas storage tanks can guarantee strength and safety, whether the slight enthalpy that occurs at any time will gradually affect the heat preservation performance of the gas storage tank, which is also a major event related to fuel costs. Whether the mixer manufacturer using the LNG engine can change the position of the gas tank, or at least increase the ground clearance. At present, the state's measures to control the rated agitation volume of concrete mixer trucks actually provide excellent conditions for the use of LNG. In the past, in order to enlarge the tank, there was almost no space left on the mixer. Now the 8 x 4 chassis is fitted with an 8 cubic meter tank, and the remaining space is very large. If you place the gas tank in a position higher than the fender, you can definitely avoid the problem. It's just a little more difficult to refill, but isn't the LNG loader's gas tank higher?
Moreover, the irregular running time of the concrete mixer truck is also an important factor affecting the LNG saving effect. If the heat preservation effect of the gas storage tank and the pipeline valve can be improved, the loss caused by leakage under the stop state will be effectively reduced.
For those of us who are used to diesel, low-temperature and high-pressure LNG storage tanks and liquid LNG gasification mixed combustion gas supply systems are relatively unfamiliar. A large number of special precision valves and control components, professional maintenance and maintenance costs. The most important factor in concrete construction is efficiency. It is hoped that the convenience and timeliness of specialized maintenance and service will be improved while the LNG supply is being carried out.
I talked a lot about the use of LNG, not to deny the advancement and feasibility of LNG. In an era when energy can change the world's pattern, I believe that LNG is currently the development trend. However, in the process of development, there are always shortcomings and deficiencies that need to be perfected. At least at this stage, LNG is widely used in the field of construction machinery, and there are some “homework” to do. Although the loyalty is against the ears, it is definitely the heart of the hope for the healthy development of LNG.

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