Small design innovation for cement grinding mill to avoid troubles

(Great wall machinery is one of the domestic first-class grinding system integration suppliers. With the advantages of technology, equipment and brand of ball mill, rotary kiln, vertical roller mill for nearly 6 years, Great Wall Machinery devotes itself to carry out business service in many fields and gradually expend the business mode including EPC project, financial leasing and spare parts supply as the increasing maturity of single equipment and turnkey project, successfully realizing the change from manufacture to manufacture + service.)

It’s hard to avoid irregular faults occurred on the cement plant equipment. What troubles has your cement grinding mill occurred? As an operator of the cement plant equipment, you must summarize and accumulate the experience from all aspects all the time and optimize the design for the specific details of production line to avoid equipment occurring the faults. Now let’s see the faults occurred on the cement grinding mill in a domestic cement plant and what methods they adopted to improve and enhance it to ensure the normal operation of the equipment.

Abstract: the type of the main motor of the cement grinding mill in a cement plant is YRKK800-8, power 2500kW with Babbitt metal bearing, material of which is composed of tin, lead, antimony, copper, etc. with the feature of soft texture and low temperature. The highest operation temperature of Babbitt metal bearing of control bearing bush is 100℃. In order to protect bearing bush, the upper limit value of temperature protection is set to 63℃. Once exceeding the setting value, DCS will control the main motor of the mill and stop it. Lubricating oil station of main motor of the mill is equipped with two pressure switches and the pressure are respectively set to 0.12MPa and 0.2MPa. The normal value of oil supply pressure when the oil station operates is about 0.25MPa. If oil supply pressure is lower than 0.2MPa, emergency bearing oil pump will be started to allow the oil pressure to meet the lubrication demands of bearing of main motor; if oil supply pressure is lower than 0.12MPa, there are troubles in lubrication system. Oil pressure signal interlocks main motor of the mill and stops it to avoid the high temperature burning the bearing bush.

1. Fault phenomenon

On January 7, 2015, No. 2 control room of cement grinding mill of a cement plant trips because of the fault of DCS control power supply, which leads to the missing of DO signal of cement grinding mill and causes the tripping of all low-voltage equipment of No. 2 cement grinding mil. Staff finds that main motor of the mill is still operating as routing inspection and presses the emergency stop button on the spot. After inspected by electrical personnel, it finds that rotor journal of main motor wears seriously and front and rear bearing bushes are burned out due to high temperature. After the fault of DOS system leading to the tripping of lubrication oil station, oil pressure lower than 0.12MPa doesn’t stop the main motor and bearing bush with high temperature nor stop it, which is the root cause for serious wear of rotor journal and burn-out bearing bush.

2. Analysis for fault reason

Main motor of cement grinding mill is high-voltage electrical equipment, whose principle of start-stop circuit is shown in figure 1.

Figure 1: diagram of principle of start-stop circuit of main motor of cement grinding mill

As shown in figure 1, motor-driven relay K1 and K2 of DCS system respectively pulse trigger switch closing and switch opening to stop and start the main motor. After power-loosing of DCS system, switch opening commands that K2 cannot stop the main motor; on the other hand, both chain jump stop signal of low oil pressure of oil station and overheat of bearing bush control opening coil through DCS output. DCS fault cannot trigger switch opening of breaker of service truck, which lead to the failure of protection system and trouble parking of equipment.

3. Fault handling

Switch-opening circuit of main motor of the mill is controlled by soft chain of DCS system, while the influence of DCS fault on equipment is not fully considered at design. However, hard chain can solve the problem. For hard wire, low oil pressure signal of lubrication oil station is only need to be led to the switch-opening circuit of high-voltage board of main motor of the mill. While the lubrication oil station is set up on the spot, which is far from the high-voltage board and it is time-consuming and strenuous with high cost if directly install the cable. According to the site situations, electrical maintenance personnel decide to make use of the feature that the lubrication oil station is close to the emergency stop button box of main motor to parallel signals and then send them to high-voltage board. Temperature signal of bearing bush is no modification for gather the analog quantity. Control principle diagram after modification is shown in figure 2.

As shown in figure 2, realize the soft chain and hard chain control for main motor through adding intermediate relay in the control box ALC2 of lubrication oil station. Auxiliary contract of K3 is connected with DI of DCS to realize the soft control for switch-opening coil of equipment and auxiliary contract of K4 is paralleled to button box ALC1 near the main motor to directly act on the tripping circuit of the equipment and realize the hard control for switch-opening coil. After modification, it is successful to separate the switch. After that, the same modification is carried out for lubrication oil stations of grinding head, grinding tail and main reducer and low oil pressure signal of all oil stations is paralleled to switch-opening circuit in figure 2. In this way, fault of any oil station can stop the main motor timely and fault trip reliability of main motor of the mill is increased through soft chain and hard chain.

Figure 2: Diagram of control principle of main motor after modification

4. Conclusion

This accident exposes the hidden dangers in the design of equipment. Interlocking relationship among equipment with different voltage grades should be paid special attention in the process of design. Consider the influence of different faults on the equipment and timely find the control dead sector of equipment operation and parking to improve the design and maintain safe operation of equipment and safe production of enterprise.

Introduction to high manganese steel jaw plate of jaw crusher

Moving jaw of jaw crusher is also called jaw head or jaw back. Jaw plate is also called toothed plate, which is the key wear-resistant part of jaw crusher. A set of jaw plate is usually composed of two parts, namely, the moving jaw plate and fixed jaw plate. Jaw plate is the major component of jaw crusher, including moving jaw plate and static jaw plate. There are different sizes according to the different types of jaw crusher, which generally use the material of high manganese steel.

High manganese steel jaw plate

Materials used: Mn13, Mn13Cr2, Mn18Cr2 (namely super high manganese) or special dosing according to working conditions. Jaw plate of jaw crusher manufactured by Great Wall Steel Casting Company is exquisite with rigorous dosing and excellent heat treatment technology. Service life of jaw plate manufactured by our company is higher than 50% of that of the similar products.

Composite jaw plate

Cast by high performance new composite material, the service life of composite jaw plate is more than three times higher than that of ordinary jaw plate, which breaks the record that the service life of new material wear-resisting castings are only 1.5 times higher than that of manganese steel castings. Composite jaw plate, new composite rolling wall and so on transformed by scientific and technological achievement have been recognized by many industries with poor working conditions, such as mining industry and metallurgical industry.

Jaw crusher is used in many fields. Because of its different specification, feed particle size and hardness of materials, the extrusion and impact force to jaw plate is also different. Great Wall Steel Casting Co., Ltd manufactures jaw plates with various specifications and models by high manganese steel and metamorphic high manganese steel respectively to meet the need for jaw crusher in different working conditions.

Structure and features

1. Use manganese steel bonded carbide to make high wear-resisting degree and long service life.

2. Use cold hardening technology to make high hardness.

3. Carry out water toughening to avoid natural phase change in the use and leading to poor performance.

4. Strictly spot checked by laboratory and quality testing department before leaving the factory, so the quality of the product is assured.

Help cast steel gear processing of CHAENG go international

Future development trend of industry is the focus of many enterprises, including casting industry and cast steel gear casting industry. Supply and demand situation is not optimistic in cast steel gear casting industry in recent years. Thus, the development of next few years will be the focus to pay attention.

I think if we want to know the future development trend of cast steel gear casting industry, we need analyze the following aspects:

1. Market research. Only by market research can we grasp the first-hand and real information of market in the first time, which is the base to analyze the future development trend of cast steel gear casting industry.

2. Refer to the basic information reported by related authorities and materials provided by professional research units. Authorities include National Bureau of Statistics, General Administration of Customs, related industry associations and domestic and abroad related newspapers and periodicals. The information reported by them is professional, authoritative and reliable. The information has a significant influence on analyzing current situation of domestic large cast steel gear industry, market supply and demand and industry chain.

3. Refer to the recent development situation of key enterprises in industry, whose development has a certain representativeness. Understanding the development of these enterprises means that master the most of market development situation of industry.

In order to allow large gear processing factories to better strive in cast steel gearmarket in an impregnable position, they must more comprehensively and accurately grasp the development situation and future trend of cast steel large gear industry. Take a panoramic view of the situation and pay attention to details to know development trend of industry.

As a domestic first-class cast steel gear casting factory, CHAENG not only grasps the development trend of cast steel gear industry but also follows the trend of industry development to update technology and improve processing ability.

In addition, CHANG has made a proud achievement in cast steel gear casting. The reason is that there is a large number of talents to be the support. Our company creates a branch of inter-disciplinary talents with the ability of scientific and technological innovation and operating management through implementing the talent strategy to strengthen the construction of talent team. And our company continuously strengthens the function training of whole staff and improves the skills of whole staff.

What is the main produce equipment of Coal grinding station ?

Coal grinding station main production equipment include: coal mill, coal transportation equipment, unloading equipment, dispensing equipment. pulverized coal mill system is the core of the coal grinding station.

However, due to the characteristics of explosive coal dust, and the fineness requirements, a lot of coal grinding plants their technical requirements are higher during the coal preparation.

Chaeng (Great Wall Machinery Co., Ltd)as a domestic first-class grinding system integration provider committed to the research and production of coal preparation systems over the years, Chaeng coal preparation systems project engineer for us a detailed introduction.

1.coal fineness of coal grinding plants must be guaranteed

For power plants in terms of pulverized coal boiler, coal fineness not only affect the operation of the larger economy, but also have an important impact on the safe operation of boilers, especially those burning lean coal and anthracite boiler even more so. If coarse pulverized coal, it can easily lead to fire boilers, coking, high-temperature corrosion, Reheater Tube Explosion, combustion efficiency and low wear and tail heating surface a series of questions.

Only the finer coal,which can catch fire and burn rapidly, the smaller the loss of incomplete combustion boiler, a corresponding order to improve the efficiency of the boiler (if the boiler is maintained at the fineness of pulverized coal economy running, each 600MW boiler can save Billions of tonnes per year coal).

2. coal grinding plants must use a variety of measures to prevent explosions in coal preparation process

In the grinding system, pulverized coal is transported by a gas, gas powder mixture is likely to encounter a spark caused an explosion pulverized coal. In a closed system, the pressure generated when coal dust explosion up to 0.35MPa, so in the event of an explosion, the consequences are very serious.

So, how to prevent it?

(1). the higher the temperature of the gas mixture powder, the more explosive. So pulverizing system operation should strictly control the mill outlet gas temperature of the powder mixture. The water is often reflected in the coal mill outlet air temperature, in actual operation, the coal mill outlet air temperature should be selected according to the different powder mixture of coal.

(2). the pulverized coal pulverizing system should be installed in a conduit , which have a certain inclination angle, trying not horizontal pipe, no dead ends, the flow rate of gas powder mixture should not be too low, in pulverized coal pipeline, reduce throttle deposited to prevent the accumulation of pulverized coal spontaneous combustion caused the explosion.

Production limitation and halts is implemented in cement industry for the G20 summit

The G20 summit will be held soon, to help the activity of “blue west lake”, a number of cement enterprises in Hangzhou has carried out production limitation and production halts. Recently, many cement enterprises in other place also start to implement production limitation to prepare for the holding of the G20 summit. Enterprises of cement industry repair cement equipment and replace parts during this period, which will ensure the safety production and high operation rate during the production period.

CHAENG (Great Wall Machinery) has casting bases and parts assembly bases which are few in number in domestic industry with large machining capacity and large steel casting manufacturing capacity. Thus our company can provide the complete spare parts of cement vertical roller mill at any time, such as roller, millstone, hub, rocker arm and so on; spare parts of cement rotary kiln, such as tyre, big ring gear, riding wheel, hydro-damper and so on; spare parts of cement grinding mill, such as big gear wheel, end cap, hollow shaft, bearing housing and processing and casting of other large steel castings.

Figure: Machine shop

Figure:Steel Casting

CHAENG has an after-sales service team with excellent technology and rich experience, who provides quick response during 24 hours and arrives the site within 48 hours, providing superior parts and services for customers at all times and places.

Spare parts inventory service

CHAENG has nearly 60 years of large rotary kiln, vertical roller mill and ball mill manufacturing experience. Our company is familiar with mill technology on the market, so we can process the spare parts according to the type of mill and drawing of customers.

In order to ensure customers get needed spare parts in a shorter time, CHAENG has launched “deposit storage” mechanism, for which customers need only pay a small fee to store the needed parts, and CHAENG will provide parts spot supplies for customers. Our company will store the spare parts to allow every customer to get the needed spare parts in time and reduce the warehouse cost, maintenance cost, logistical cost and time cost of customers.

CHAENG has focused the production and manufacture of cement equipment for nearly 60 years. Our company can provide host device maintenance, spare part process and project construction for customers. Welcome new and old customers call for details.

The 5th China-Eurasia Expo---CHAENG(Xinxiang Great Wall Machinery) is Ready

The 5th China-Eurasia Expo will be held at Xinjiang International Convention & Exhibition Center, Urumqi, on Sep. 20 to 25, 2016. This expo is held with the Chinese Government Support, and undertaken by the Xinjiang Uygur Autonomous Region and relevant National Ministries and Commissions. It is an international expo with inviting domestic and overseas guests and merchants.

To be Chinese first-class grinding system service provider, CHAENG will attend this exhibition and will blockbuster launch the latest upgrade Industrial Waste Residue 2.0 Grinding System sample case, Large-Scale Cement Complete Equipment, etc. The booth No. is Machinery & Equipment B District-U5. Hope to communicate and cooperate with you.

In order to be well know and good communication with Central Asia clients, CHAENG is much considerate to specially make Russian Display Board, and arrange the Russian translators to provide the clients the one-to-one service.

Since the company establishment in 1958, CHAENG closely developed and cooperated with the clients from Central Asia and other regions. Based on the principle of different countries/regions customers to the most fitting cement equipment,CHAENG hold the management spirit of “building CHAENG by grinding and service ” to build base of “Industry-University-Research Cooperation” with Henan University of Science and Technology and other domestic excellent scientific research institutions. We developed the Cement Powder Grinding outfits with the high efficiency and energy-saving. The multinomial technologies are awarded with National Patent.

Specially, Chaeng Machinery 4.2 X 13 m double tracks cement grinding mill is the first domestic product to fundamentally solve the congeneric products problem of “On account of excess temperature of bearing bush in discharge end, the machine cannot continuous work”. It is awarded with Patent for Utility Models. Patent Number is ZL201020285841.9.

So far, CHAENG have totally produced all kinds of Cement Ball Mill, Rotary Kiln more than 3000 sets, all kinds of Cement/Slag Vertical Grinding Mill more than 200 sets. These products are popular in all over the country, and exported to overseas market including India, Pakistan, Bangladesh, Indonesia, Vietnam, Kazakhstan, Uzbekistan, etc.

On Sep. 20 to 25, 2016, CHAENG will take the latest R&D achievement to appear in The 5th China-Eurasia Expo. Welcome to discuss and cooperation.

Raw Mill / Slag vertical roller mill technology innovation

Powder concentrator is one of the most important part of slag vertical roller mill (hereinafter referred to as “slag vertical mill”), the function of which is to make qualified finished product after grinding enter into the precipitator through outlet piping of body by steering flow while semi-finished particle (over the specified size) will be threw out and sink under gravity. After leaving the scope of centrifugal force, they will be collected by a collector to return to the mill for grinding once again. Steering flow is formed through wind board, which make the mixture of powder and air from vertical rise to tangential flow and the fineness of the finished product depends on the clearance between wind boards, the angle of the wind board and the speed of the rotor.

1. Facing problems

Traditional wind board is fixed and nonadjustable. The controlled access of the fineness of the finished product produced by the slag vertical mill equipped with such wind board is single and the variety of the grinding materials is limited. The article will introduce a new type adjustable wind board, which make the controlled access of the fineness of the finished product diversified and easy to operate. And can also grind different kinds of materials to make the mill production diversification and bring the users more economic benefits.

Tangential to adjust the wind board or enhancing the rotor speed will produce more fine finished product after separation while reducing the rotor speed or radial direction to adjust the wind board will produce more coarse product; similarly, there is different situation when grind different materials and the fineness of the finished product needed is also different, all which can be settled by technical proposal mentioned above.

2. Improvement plan

Structure diagram of traditional fixed wind board is showed in figure1.

Figure 1: Structure of traditional fixed wind board

Clearance b between wind boards and self-angle α of the wind board in figure 1 are fixed value. Thus, only by adjusting rotor speed or roller pressure can achieve the different fineness of the finished product, which cannot produce the high fine finished product with high energy consumption and serious wear at the same time.

Structure diagram of new type adjustable wind board is showed in figure 2.

Figure 2: Structure of new type adjustable wind board

In figure 2, the new type adjustable wind board is weld on the core shaft of the wind board, and the adjustment to all wind board device can be achieved through the adjustment to core shaft of wind board by adjusting handle and then change the clearance value between wind boards. When the fineness of the finished products meet the requirements, fix the position of the wind board and record the figure on the dial to realize the serialization of fineness value of different kinds materials corresponding to the value of the wind board position.

Specific fixed approach diagram of new type adjustable wind board is showed in figure 3, which is that weld the fixed support to the core shaft of the wind board and after adjusting the wind board, make fixed bolt through the hole on the fixed support and screw it in one of the screwed hole adjusting the position on fixed block (weld on the body on the spot). The advantage of the fixed way is that lock nuts above the wind board will not be loose by the vibration of slag vertical roller mill and cause the position shift of one of the wind board. In addition, screwed hole adjusting the position on fixed block realize the adjusting function of the wind board and make the clearance value between wind boards adjustable.Figure 3: Fixed approach diagram

Figure 3: Fixed approach diagram

3. Reforestation effect

Currently, the equipment has been used on a 5.6m slag vertical roller mill of a building material company in Tangshan at the end of 2013. By adjusting the new type wind board reasonably, vertical mill can achieve or even surpass the design production when grind different kinds of materials. The using effect is good.