Application Scope

This method can be applied to the various reinforcing bars with ribs which fall into the domestic grade HRB335 and HRB400 and have diameter from Φ16 to Φ40, and it can be even applied to the reinforcing bars with poor weldability and to those imported reinforcing bars equivalent to above mentioned domestic ones. Also it is suitable for the connection of the reinforcing bars with same diameter and of the ones with different diameters.

Connection Equipments

The extrusion connection equipments consists of the three major parts which are the superhigh pressure pumping installation, superhigh pressure oil pipe and crushing clamp.

A. Operation Method

Preparation of the reinforcing bars

It needs to remove the unnecessary attachments on the ends of the reinforcing bars before extrusion connection such as rust, greasy dirt and mortar.

The ends of the reinforcing bars should be straight and such things as the burr and flash which affect the installation of the steel coupler should be removed.

The locating mark should be made on the ends of the reinforcing bars by using the paint according to the requirements. The distance from the locating mark to the ends of the reinforcing bars is half of the length of the steel coupler.

B. Extrusion

Before extrusion, it needs to check the extrusion facilities. And the extrusion process requires to adjust the relative working oil pressure. Also it needs to select the matching extrusion die according to the specifications of the reinforcing bars and the type of the steel coupler. The extrusion die should match with the bar diameter and the type of the steel coupler, and the confused matching is not allowed ( refer to the below table). The detailed process of extrusion is as follows:

Insert the reinforcing bars into the steel coupler, and the insertion depth must be determined according to the locating mark.

When extruding, the steel coupler should be kept to the center of the rounded cutting edge of the extrusion die. Also it needs to keep the axis of the crushing clamp normal to the axis of the reinforcing bar.

When extruding, it needs to adjust the crushing clamp to make the die edge aim at the indentation mark on the surface of the steel coupler. And the extrusion must be made in proper sequence from the indentation mark in the middle of the steel coupler to the two ends of the steel coupler. It is not allowed to extrude from the two ends to the middle.

When extruding, it needs to try best to press the extrusion die on the transverse ribs of the reinforcing bars so as to achieve the connection with best performance.

When extruding by operating the reversing valve handle, the control of pressure should be based on compliance with the minimum impression diameter specified in the above table, which means that the pressure obtained at the time when the diameter is measured to be qualified by the vernier caliper is the appropriate extrusion force. When starting the extrusion, it can happen that the operator does not know how much of the pressure should be used to achieve the required impression depth. If in this case, the operator may first use less pressure and then check with vernier caliper, and if the required depth is not achieved, he can increase the pressure in the original place until the realization of the required depth. Then he can continue to extrude by using the appropriate pressure. Regardless of the specifications of the steel coupler, when the last pass is extruded, the impression diameter will be smaller or will go out of the lower limit due to the reduced constraint, which is a normal happening.

After the extrusion is completed, it needs to check every steel coupler by vernier caliper. If the extrusion depth and passes are out of requirements, such coupler should be re-extruded or be cut off.

⑦ The extrusion connection can be divided into the ground prefabrication and the fixture connection. The ground prefabrication can first be completed on ground. The extrusion connection of the ends of the reinforcing bars is completed on the fixture.

Operation cautions and maintenance of the equipments

The operation of extrusion connection equipments can be easily done and easy to be grasped. For it is done on the construction site, it is important to maintain the equipments. The below are several key points about their usage and maintenance:

If no oil is fed into the pumping installation or its oil level is not enough, it is not allowed to turn it on. Before operation every day, it needs to check if the oil level is good, and if not, it needs to feed enough oil. When operation is done frequently, the oil tank should be rinsed every half year, and the new oil should be fed into meanwhile.

Due to the fast extrusion speed, the operator should focus his attention when in operation. And he needs to timely reverse when the required pressure is achieved in order to avoid excessive extrusion.

When the superhigh pressure soft pipe is used, the folding and the dead bending ( bending radius less than 250mm) of the pipe can not happen, and no other objects are allowed to load on it, and it is not allowed to use it to pull other facilities.

The extrusion can be done in all-weather condition. However, the oil working temperature is 20-50℃. If the oil temperature goes too high in operation, the cooling measures should be adopted or the operation may be stopped so that the oil is cooled down. If the oil temperature goes too low, it can be warmed up by external heating. When operating in rain, the appropriate water-proof measures should be adopted.

In operation, when the extrusion die is inserted into the crushing clamp, please make sure that the low die is inserted in place.

When reversing by pulling the reversing valve handle, the force should be applied horizontally , and it should not be pressed down or raised up by hand excessively. The force should be applied smoothly and evenly. If the pressure goes up too slowly when reversing, the position of the handle can be slightly turned. In case of non-extrusion or when stopping the operation of the extrusion die, the handle must be placed in zero position.

At the place in the middle of the steel coupler where no extrusion mark is painted, no extrusion is allowed. The extrusion must be done in appropriate sequence from the middle to the two ends.