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Structural Tie Rod Install and Anti-Corrosion Treatment

April 16, 2021August 21, 2020 by bluejade

Structural tie rod anti-corrosion treatment is very important for the life span of the building if it is done improperly, structural tie rod might be corrosion influenced, which will lead to more maintenance work. And this can be avoided by good anti-corrosion treatment work. The application of high-strength structural tie rod in this project meets the needs of large-span concrete beam structure, which reduces the steel quantity of the building structure, the building becomes more portable and beautiful. At the same time, steel structural tie rod lever itself has advantages of certain stiffness, convenient for construction and installation, short construction period, saving time and cost.

Installation of Structural Steel Tie Rod

For single structural steel tie rod is more than 11 meters in length, and through the reserved hole, the reserved hole mouth up and down all need double nut and shim (bent truss beam under the mouth does not need), so the single structural steel rod is divided into 2 segments connection is made, namely the ramp between three and bent truss beam by adjusting sleeve 6 80 steel bar connection into three steel bar, in order to meet the design requirements
The double nuts and iron cushion shall be placed in the corresponding embedded casing position in advance, and U-shaped joint shall be welded to steel pull rod end temporarily, so that the rod body does not damage galvanized layer on the surface of the steel pull rod during hoisting.
Installation principle: the installation sequence of structural steel tie rods under the steel beam of the same axis shall be from high to low, from both ends to the middle direction.
Wire rope through the U-shaped joint hole, hoisting should be in place slowly, in advance to choose the structural steel tie rod emplacement path, and prevent scaffolding steel pipe, steel box girder to steel rod impact measures, especially on the connection of the adverse effect of thread.
Steel rod in the process of hoisting, perforation in place, using hand chain hoist and lifting belt auxiliary positioning rod bottom end (perforation), artificial set of structural steel tie rod mat iron, double nut, adopt the method of vertical suspension to control the verticality of pull rod, and the error control within the permit, stay rod elevation, verticality are all meet the design requirements. The upper and lower orifice pads and double nuts of the 3 embedded sleeves in the ramp shall be installed and tightened successively.
Special use special torque wrench turn adjusting sleeve and special fixture (to avoid damage of galvanized steel tie rod surface layer) are installed by the ramp between one and three ramp rod body, avoid with sleeve rotation, the regulating sleeve for the positive and negative screw thread, adjusting sleeve should be installed according to the positive and negative screw thread depth appropriate rotation on both ends of the sleeve, ensure the upper and lower end clearance rod body in the sleeve for about 28 mm, as steel bar stress adjustment allowance.
The same method is used to lift the steel pull rod between the ramp no.3 and the main beam of upper chord successively. After steel pull rod is in place, a special clamp is used to jam the adjusting sleeve, steel pull rod at the upper end of the sleeve is rotated with a special torque wrench, and the depth control of steel pull rod is rotated at the same time, to ensure the end clearance of the two rod bodies within the sleeve is 28mm.
The end contact surface of the structural steel tie rod of the main beam should be polished and level off before installing the contact surface of the iron cushion and the nut to ensure that there is no Angle between the iron cushion and the main beam.

Structural Tie Rods with Upset and Rolled Threads acc. to DIN EN 1993-5

Nominal Diameter	ØD1	Metric	M39	M42	M45	M48	M52	M56	M60
Stressed Area, Thread	As	[mm²]	976	1,121	1,306	1,473	1,758	2,030	2,362
Shaft Diameter	d	[mm]	36	39	42	45	38-39	41-42	44-46

Corrosion Resistance of Structural Steel Tie Rod End Thread Sealing

The structural steel tie rod used in this project adopts the same coating process for surface anti-corrosion, except the end connection thread, so the sealing anti-corrosion at the thread is the key part of the structural steel tie rod anti-corrosion.

This project adopts the neutral room temperature vulcanized high-grade sealant for anti-corrosion. This kind of sealant has good adhesion to a steel beam and zinc-rich primer, good weather resistance, water-resistance, and high and low-temperature property. Its anti-corrosion life can reach to over 30 years, and the service temperature is 65℃ to 300℃.

Steel tie rod installation (threaded connection is not adjusted), after the sleeve, nut, mat iron screw tooth surface and combining with the end to clean up, thoroughly remove grease, rust, and debris on the surface of the sealant with glue gun play at the end of thread surface, as well as the combination of components and shim and oblique beam concrete interface, evenly with flat to be closed.

Structural Tie rod Surface Anti-corrosion Post Treatment

For structural tie rod parts that have been used as antirust primers but have been damaged, re-embroidered, peeled, etc., and parts that have not been used as antirust primers, they should be first polished and cleaned manually. Then, water-based inorganic zinc-rich primers should be used as antirust primers with a dry film thickness of 100um, and then primers, intermediate paints, and topcoats should be sprayed as required to meet the design requirements.

If you happen to be inneed of structural steel tie rod or threaded stud of high tensile strength, send email now for more details now!

Overview of Useful Instructions on Rock Bolt Install

April 16, 2021July 10, 2020 by bluejade

What is Anchor Rock Bolt

Anchor rock bolt are solid or hollow steel rock bolts that are drilled into rock mass during excavation of the surrounding rock to avoid loose collapse of rock mass, which serves to reinforce and connect the soil body as a whole. The mortar or other materials are used to consolidate between rocks and set with steel backing plates

Rock Bolt Install Tips

Rock bolt construction should be carried out after initial shotcrete, anchor rock bolt is driven into the hole with special machinery, and a special impactor should be equipped when using a general air-powered rock drill. The drill hole should be round and straight, and in line with the surrounding rock wall or rock layer where it is located. The main structural plane is in vertical direction.
Lay the position according to design requirements, the allowable deviation of hole position is not more than 10cm, and the insertion length of rock bolt body should not be shorter than 95% of design length.
When rock bolt body – high strength rebar is inserted into anchor hole, the position should be kept in the middle and insertion depth should meet design requirements.
The mortar filled in the mortar anchor hole should be full and dense, and appropriate amount of micro-expansive agent and quick-setting agent can be added to the mortar or cement slurry.
After anchor rod is installed and mortar filled is finally set, pallet should be installed immediately and nut should be tightened.

Common problems on Rock Bolt Worksite

The number and length of anchor rock bolts are lower than the design value, and the distance between anchor bolts is large. The U-shaped welding is not adopted between the lock bolt and the steel frame. The on-site inspection shall separate the advanced small catheter, advanced anchor rod, hollow anchor rod, and lock foot anchor pipe (rod) in detail.
The raw material of anchor rock bolt does not meet the standard. Wall thickness and weighing inspection of anchor rod should be checked on site.
The phenomenon that hollow grouting bolt designed is not grouted or replaced with mortar bolts.
The angle of rock bolt penetration does not meet design requirements.

Rock Bolt Rebar Material of European Standards 42CrMo4

November 29, 2022June 22, 2020 by bluejade

Rock Anchor and Rock Bolt

The material of rock bolt body mainly includes high-strength steel wire, steel strand, hot rolled rebar and other high-strength steel. It can stretch freely under tensile load. When this part of elongation is permanently fixed or “frozen”, a certain pre-compression stress is generated on rock mass or various structures.

Therefore, rock bolt body is the main part to realize medium anchoring by tension. At present, main materials used in prestressed rock bolts in mining are fine-rolled threaded steel bars.

Friction Between Rock Bolt Rebar

The connection of high-strength precision-rolled threaded steel rebar is to prevent mutual sliding of connecting parts by friction between contact surfaces. To make contact surface with sufficient friction, it is necessary to increase clamping force and increase the friction of contact surface. Clamping force between components is achieved by applying a pre-tension to rock bolts, so the connectors (finished rolled rebar, bolts, etc.) must be made of high-strength steel.

Precision-rolled threaded steel bar is a rigid prestressed anchor. It is a steel bar made of 40Si2MnV or 45SiMnV, which belongs to high-strength steel, and has a complete external thread on. At any cross-section, it can be connected or anchored with a connector or anchor with an internal precision rolled screw anchor. The use of this type of rock bolt body is convenient for construction and safe and reliable for anchoring.

European Standard of High Strength Steel Rock Bolt

Steel grade	Yield strength [MPa]2)	European standards
S 355 J2+AR	315 – 335	EN 10025	EN 10060	EN 10204
42 CrMo4	650	EN 10083	EN 10060	EN 10204
34 CrNiMo6	800	EN 10083	EN 10060	EN 10204

As it is designed, rock bolts must be installed one meter into bedrock and one meter along sheet pile. Usually the length of rock bolts is therefore at least 3 meters or longer.

Typical rock bolt diameters vary between Ø 50 and Ø 90 mm. Contractors tend to prefer small diameters of rock bolts with high steel grades (42CrMo4 is most common), which reduces the weight, and consequently simplifies its handling which is normally done by hand.

These standards are most commonly used in Norway, however, other steel grades may be utilised. The differences in quality of rock bolts defined in different standards should normly be of little importance for this specific type of application.

Rock Bolt Application in Tunnel Roof Supporting System

April 16, 2021June 15, 2020 by bluejade

Tunnel is an underground passage through a mountain, beneath a city or under a waterway or Tunnels are enclosed roadways, railways, waterways, etc. With vehicle, trains, ships, etc. access that is restricted to portals regardless of type of structure or method of construction.

Rock bolt used as roof bolt is a main method to provid safe working environment for miners, prevent ground falls and save human lives and properties from hazards. Roof bolting structure is scientificaly calculated by engineers according to the rock and earth conditions, it is a great improvement compared with the old standing support. As rock bolt rebar is the main force bearing part, it is of great importance to understand and use it wisely in mining underground support system.

Roof Bolt Development in Mining

Roof bolt specification include the rock bolt type, tensile strength, stress level,length, etc. Although engineers has experiences and knowlege to analyze the underground situation, the understanding is still in-efficient. Various types of rock bolts have been developed for now, and they all work in some specific conditions, it is hard to say which type is better.

Mining underground roof falls accident happens for more than 1000 times every year.
Inorder to fully research roof bolting system, engineers and institutes has been following evaluation of mining roof fall incident allover the country.
Rock bolt specifications and its stress levels can be used to consider the capacity, 3 basic ones are rock bolt length, rebar tension, grout length.

why Rock Bolt Design Matters in Mining

The portion where the work is carried out while its construction is called the face (heading) and all efforts are made in advancing this face as fast as possible till the end of tunnel is reached.

Rock bolts are the first line of defense protecting mineworkers from the hazards of ground falls. Because rock bolts utilize the inherent strength of the rock mass, they have many advantages when compared with earlier standing support systems. Due to their central importance, roof bolts have received more research attention than any other ground control topic, with the possible exception of coal pillars.

Roof bolt design consists in specifying the proper bolt type, capacity, length, and pattern for a particular roof rock, stress level, and application. The interactions between these variables are very complex, and our understanding of their mechanics remains imperfect. Numerous roof bolt design methods have been proposed over the years, but none has gained widespread acceptance by the coal mining industry.

Common Anti-corrosion Methods for Mining Rock Bolt

April 16, 2021April 13, 2020 by bluejade

Various types of anti-corrosion methods for mining rock bolts are being developed. As mining rock bolts are made of steel, if they are stored and pretreated improperly, once rust occurs, it will lead to serious accidents with loss of both human lives and treatures. Usually it is started with corrosion and scrap. Therefore, anti-corrosion treatment measures for mining rock bolt are very necessary.

The problem of corrosion and cracking of rock bolts in coal mines and other underground mines, and high variability of mine water corrosivity in mining industry, it has been noted by late corrosion study. The use of higher-tensile steels for rock bolts and anchor bolts, presents a risk for a greater incidence of corrosion, which is dangerous in underground environments. There are many other corrosion issues that need to be taken care of but are not included here.

Common Anti-corrosion Methods for Mining Rock Bolts

Brush coating method:
Coating is a widely used anti-corrosion method, and it is an indispensable anti-corrosion material and identification mark on mining anchor rock bolt products. Paint is also a non-metallic material. It is usually made of synthetic resin, rubber slurry, vegetable oil, solvent, etc., and covers metal surface to isolate medium from atmosphere to achieve anticorrosion.
Metal Surface Treatment:
Metal surface treatment processes include sleeping coatings, surface penetration, and surface oxidation and passivation. Its purpose is to improve corrosion resistance and mechanical capabilities of metal.
Add corrosion inhibitor:
Adding a small amount of other special substances to corrosive medium and corrosive substances can greatly slow down corrosion rate. This special substance is called corrosion inhibitor. Corrosion inhibitor is always consist of sodium nitrite and sodium chromate, which can form a passivation film on anchor bolt surface. The solvent can slowly dissolve corrosion inhibitor and can also act as a lubricant. Zinc powder is added as a sacrificial metal. In fact, zinc is also a corrosion inhibitor. It can first combine with chloride in asbestos, so as to reduce chance of contact between chloride and rock bolt, thereby achieving purpose of anticorrosion. If corrosion inhibitors such as red lead and calcium lead acid are added to coating, spraying on the surface can prevent atmospheric corrosion.

Self Drilling Mining Anchor-Rock Bolt

November 18, 2022April 9, 2020 by bluejade

Self drilling mining anchor – rock bolt is one of the important support part in coal mines. Its existence solves many problems in construction and can ensure grouting effect under the chaotic geological conditions.

Mine anchor – rock bolt is used as a tensile member deep into the stratum. One end is connected to engineering structure and other end is deep into stratum. The entire anchor section is divided into a free segment and an anchor segment. In free segment, tensile force at anchor head is transmitted, The anchor function area is to apply prestress to anchor rod; anchoring section refers to area where cement slurry binds prestressed tendons to soil layer. Its function is to increase conflict effect between anchor and soil layer. The anchoring effect is added to transmit tensile force of free section to the soil of deep depth.

Advantages of self drilling mining anchors:

Self-contained drill bit, which can be used for self-drilling mining anchors, which have both the functions of drill rod and anchor rod. The process of inserting anchor rod into drill rod is cancelled, which can prevent rework due to hole collapse
Mining bolt body can be extended, with a variety of specifications, easy to use.
Compared with solid rod with the same cross-sectional area, hollow rod has greater resistance, bending resistance and surface adhesion.
Mining anchor is hollow, and can be grouted to ground through mining anchor. General mining anchors are solid steel bars, while self drilling mining anchors are hollow steel pipes. (Mine anchors are grouting pipes. Mortar enters from the end of the mine anchor, passes through the hollow web and hollow drill, and is used from mine. The front end of anchor rod overflows, and grout comes back to the end, which can ensure filling of mine anchor to turn around open ground and consolidate rock mass, fully ensuring grouting and anchoring quality. The stopper plug can ensure dense grouting and can reach a pressure of 1.5 ~ 2.0MPa.)
Mining anchor is equipped with arched backing plates and nuts, which can apply prestress to the ground.
It can be drilled by ordinary drilling machinery, such as hand-held wind drill.

What Types of Anchor Bolts are used as Wind Tower Fastener

November 18, 2022January 14, 2020 by bluejade

The Importance of Wind Tower Anchor Bolt

Chinese wind power industry have developed from the stage of digesting and introducing overseas technologies to the stage of independent technological innovation, which compared with other countries, has advantages in terms of both technology and price. In recent years, China’s wind power industry, especially large-capacity megawatt-scale large-scale wind power generators, has developed rapidly. Wind power fasteners are the main connector of wind power generators. In power generators, high-strength anchor bolts are used in large numbers. It accounts for about 22% of the total number of wind turbine components. Pitch bearing and blade, hub and pitch bearing, hub and main shaft, main frame and yaw bearing, main frame and generator frame, main bearing and main frame, gear box elastic support and main frame, tower and offset high-strength anchor bolts are used to tighten the brake discs, the connection between tower parts, and locking discs used to connect main shaft to gearbox planet carrier. It can be seen that almost all key components are connected by high-strength anchor bolts. The cost of a wind turbine’s fasteners accounts for about 3.5% to 6.0% of the total equipment cost. Although the parts are small, they have a great effect. High-strength anchor bolt for wind power require strong fan stability due to long-term field service, harsh environments, and poor maintenance conditions. Under normal continuous working conditions, wind power fasteners must guarantee a service life of more than 15 years.

Due to randomness of its power source, harshness of operating conditions, particularity of manufacturing and installation, and high cost of maintenance, wind turbines have set extremely high requirements for anchor bolted connections. It is necessary to start from its characteristics in structural design and manufacturing. Necessary measures must also be taken on the process, workshop and on-site production assembly to ensure that anchor bolt connection is foolproof. Most of high-strength anchor bolts for wind power use 10.9 grades, and a few are 8.8 or 12.9 grades. High-strength anchor bolt quality for wind turbines is greatly affected by raw materials. From a series of aspects such as appearance quality, chemical composition, low magnification structure, depth of decarburized layer, non-metallic inclusions, microstructure (grain size) and upset test, all have a significant impact on anchor cage foundation bolt quality . For high strength anchor bolt fastener industry, wind power fasteners will undoubtedly be a huge market. Opportunities and risks coexist in the wind power fastener market.

Classification of Wind Tower Anchor Bolt

At present, there are roughly 3 types of fasteners used in domestic wind turbines and foundations:

Tower bolts. High strength bolts used on the wind turbine tower are mainly GB / T 1228 ～ 1231, DIN6914 ～ 6916 and DAST.
Bolts of wind turbine. Or foundation bolt, onshore anchor cage bolt, high strength anchor bolts used on wind turbines are mainly hexagonal head bolts such as GB / T 5782, GB / T 5783, GB / T 70.1, GB / T 6170, and GB / T 97, hexagon bolts, hexagon nuts and washers.
Blade bolts. That is, anchor bolts connecting wind turbine blades are mainly non-standard double-headed studs and T-round nuts, blade bolts, T-nuts and morse washers, etc.

Steel Material Used for Wind Tower Bolts

High-strength anchor bolt for wind power are widely used in medium-carbon steel and medium-carbon alloy steel with a carbon content of 0.25% to 0.55%. For products ≤ M24, the material is 20MnTiB steel; for M27 and M30 bolts, 35VB steel is used; a small number of products are also allowed to use 30 CrMnSiA steel; ≥ M 3 3 are all 42CrMoA, B7, 40CrNiMoA steel.

Generally, 45 and 35 steels are used for wind power nuts, and some products are specified with 35CrMoA steel; gasket material is 45 steel. The elemental composition of the materials used for bolts, screws, studs, nuts, and washers is directly related to the mechanical properties of the fasteners, so it must not be lower than the requirements of the recommended materials.

Why Choose ASTM A193 B7 Round Billet for Anchor Bolt

November 24, 2022January 11, 2020 by bluejade

Chemical Composition of A193 Grade B7

B7 steel is a high-strength fastener suitable for high-temperature and high-pressure environments in American ASTM A193 / A193M “alloy steel and stainless anchor bolt materials at high temperatures” standard. This special fastener standard specifies chemical composition range of B7 grade，inspection is based on the furnace batch number, so it is suitable for high temperature and low temperature requirements and special structure types. This type of fasteners is mainly used in manufacturing industrial equipment, pipelines and wind turbines.

ASTM A193 Grade B7 Chemical Composition
Carbon	Manganese, max	Phosphorus, max	Sulfur, max	Silicon	Chromium	Molybdenum
0.08-0.15	1.00	0.040	0.030	1.00 max	11.5 – 13.5	0.15-0.25

ASME / ASTM, ISO898.1 and GB / T3098.1 fastener standards generally do not specifically specify chemical composition of each grade, but only give a wide range, allowing manufacturers to ensure that performance meets standard requirements. According to respective process conditions, it is selected from many blanks; delivery inspection of finished product is carried out according to production batch, and larger batch can be composed of different brands and different batches, so quality level is equivalent to (slightly higher) than ordinary standard parts.

Why Choose B7 Grade For Anchor Bolt Production

B7 steel has a wide range of chemical composition, especially carbon content. In the U.S. alloy structural steel system, B7 includes totally 6 grades such as AISI 4140, 4142, 4145, 4140H, 4142H, 4145H steel, compared with the 35CrMoA anchor bolt material grade commonly used in GB / T307721999 “alloy structural steel”, not only significantly increases carbon content, Reached the level of 42CrMoA material; and Mn content is also high.

Therefore, fastener companies must pay attention to this difference when preparing round billets. The billets of 2 types of materials cannot be used interchangeably.

Excellent Mechanical Properties of Grade B7 Steel

B7 is a high hardenability steel for quenching and tempering. Its mechanical properties, composition (especially carbon content of elemental that affects hardenability), heat treatment process and cross-sectional size are closely related. According to hardenability test, critical diameter of B7 oil quenching is 42-45 mm. Therefore, although composition range of B7 is relatively wide, in fact, it is to meet the needs of varies product specifications, and at the same time, it gives the fastener manufacturer a greater choice of round billets and heat treatment process systems.

B7 steel has a wide applicable temperature range, up to 538 ℃. After tempering, it has good low temperature toughness. Generally, brittle transition temperature is below (-50 ℃). The ASME pressure vessel code stipulates minimum temperature for B7 steel to be exempt from impact energy test is-48 ℃.

When working temperature of fastener is lower than -48 ℃, a low temperature impact energy test must be performed on B7 steel. At this time, corresponding AISI 4040H, 4142H, and 4145H steels should be selected to ensure low temperature impact performance. The chemical composition of this type of steel is basically the same of B7 steel. In addition to steel strength, main quality indicators must also include low temperature impact work tests.

Analysation of Self Drilling Rock Bolt Advantage in Application Fields

April 16, 2021January 2, 2020 by bluejade

First you need to confirm drilling depth, and it shall not be less than effective length of rock bolt bar, extra length of rock bolt is usually less than 100mm. Drilling direction should be perpendicular to excavation surface. If excavation surface is not parallel to anchor surface, vertical deviation from excavation surface should not be greater than 20°; self drilling rock bolt arrangement is relatively concentrated, so waterproof work of external under basement floor is more convenient.

The drilling depth of self drilling rock bolt should not be less than the effective length of the anchor rod body, overlength of rod body should not be greater than 100mm. The drilling should be straight, and drilling direction of the system should be perpendicular to the excavation surface.

Advantages and Disadvantages of Self Drilling Rock Bolt

For the case where self-drilling rock bolt have insufficient bearing capacity, due to the fact that with more self-propelled anchors sharing, the stronger resistance forms. Let’s look at the advantages and disadvantages of 3 self-propelled anchor arrangements.

Self drilling rock bolts installed in points around columns; Advantages: the vertical force transmitted from upper structure can be fully used to balance out some of water buoyancy; due to the concentrated arrangement of rock bolts, basement floor waterproof construction is also more easy, there is more resistance due to more anchor rod sharing in case bearing capacity of rock bolt at certain point is not enough.
Self-drilling rock bolts are installed in concentrated line, The vertical force transmitted by the superstructure cannot be fully used to balance out some of the water buoyancy (personally, it is considered unsafe if considered, for floor beams with a span-to-height ratio less than 6, the vertical force transmitted by the superstructure can be properly considered To balance out some of the water buoyancy), it is required to be anchored in hard rock, not suitable for soft rock and soil; the basement floor plate is relatively reinforced.
Self-drilling rock bolts are uniformly arranged in the surface, evenly under the basement floor; advantages: applicable to all soil and rock masses; basement floor beams and slabs have less reinforcement. Disadvantages: The vertical force from upper structure cannot be fully used to balance out some of water buoyancy self-drilling rock bolt.

Anchor Bolt Important Role in Wind Turbine Foundation

April 16, 2021December 6, 2019 by bluejade

Anchor Bolt for wind turbine cage foundation is used to attach wind turbine to steel rebar and concrete structure. Anchor cage bolt requires high strength as well as anti-corrosion characteristic, so anchor bolt manufacturing include 2 processes: anchor bolt production and anti corrosion treatment. Anchor Bolt is mostly made of high strength steel 42Crmo steel rod, it is fastened onto anchor ring plate to form a cage shape and fixed with steel rebar and concrete structure for onshore wind turbine foundation. .

Why Anchor Bolt is So Important

Wind turbine anchor cage foundation failure always related to 2 parts: anchor bolt strength failure and concrete structure crack failure. Anchor bolt is the connection between anchor ring plate and steel concrete structure, if anchor bolt fails, it will lose the integrity and lead to further failures. Anchor cage foundation design, bolt length, configuration, materials are also critical to project safety.

Anchor Cage Bolt Length

Anchor cage bolt for wind turbine is a cast-in-place high strength fastener, wind turbine is a heavy equipment which need to be mounted on poured concrete structure. Why anchor cage bolt is long? Accident record of anchor cage bolt shows that short anchor bolt has higher risk of anchor bolt failures of crack in horizontal direction,as well as adding post-tensioning effect. A qualified designer can give a cost efficiency plan according to reality.

Main product of AGICO is Anchor Cage foundation for wind power tower of onshore projects. In all, AGICO purchase high strength steel rod for anchor bolt assembly production, anchor cage will not be installed before delivery, installation is accomplished on site by professional workers.

Top Chinese supplier of rail bolt and anchor bolt.