Hg76 3 Inch High Frequency Welded BV Pipe Production Line

it is designed to produce welded steel pipes ,include round pipe , squre pipe and deformed pipe.

Adopting roll pass design, the production line can manufacture welded steel pipes with good quality machining and high precision assembling.

Round pipe:φ38-76mm

Square pipe :

30x30,40x40,50x50, 60x60mm

Rec Pipe:

40x20,50x30,60x40,75x45mm

Thickness:0.9-4.5mm

Round pipe:φ38-76mm

Square pipe :30x30,40x40,50x50, 60x60mm

Rec Pipe:40x20,50x30,60x40,75x45mm

Thickness:0.9-4.5mm

0.9-2.0 Max 120m/min

1.5-3.0 Max 100m/min

3.0-4.5 Max 80m/min

Flow:20T/h～30 T/h

Pool Volume:30m3

Compressed Air

(whole system)

Flow:5m3/min

Pressure: 5-7kg/ cm2

1. Double expansion and cantilever mandrels.

2. Contains two main parts: main body and the fixed base.

3. Equipped with pneumatic system to satisfy the needs of expanding, contracting and braking of the mandrels.

4. Mandrel consists of four-bar linkages that could move radially at the same time.

5.The four-bar linkages in two groups are fitted on two shafts respectively. Powered by air cylinder, they expand and contract radially.

It is used to cut the irregular ends of the strips and then connect the strips by welding. So it can let the line runing without stop when the before coil finish

• This unit is main include in press& carry material device, accumulator assemble, carry off material unit, electric control unit.
• It is main include frame, electric motor, brake unit, circling direction transfer power axle of the reduce velocity, press & carry roll, pressure air system of guide roll, inspected velocity unit; it can supply the strip steel to accumulator and the mean times it will transfer the carry velocity information to electric control system, when we demand stop carry the material to this unit, it will stop roll to the electric motor and press& carry material roll by the break, and also could adjust the velocity to carry electric motor and the unit carry material velocity.
• Accumulator frame assemble: include the electric motor, frame , inner circle roll, out circle roll and pressure roll. It can be used to storage the strip steel material from press& carry unit and it could be draw from the center send-off material roll.
• Send-off material device: include frame, guide direction rolls, guide out roll of high or lower place. It can carry the strip steel to shape system and send the carry out material velocity information to electric control device

It is used to precisely cut the pipe to length automatically under the condition that the pipe continuously delivered from the mill at high speed.

1.The finished pipes run along the Roll Table and to be automatically moved onto the Bench. Then simple Packing Machine packs the pipes in hexagon shape.

2.The simple packing machine contains container and pneumatically driven alignment equipment.

3.Motor of Roll Bench: 3KW

Ⅰ. Technical Description

1. Features of new generation H.F. solid state welder

• The solid state H.F. welder adopts Germany IXYS company IXFN38N100Q2 38A/1000V high-power MOSFET and DSEI 2×61-12B 60A/1200V rapid recovery diode to compose series type invertible circuit.
• The solid state H.F. welder adopts modularization design with more compact structure which makes maintenance and high-power realization much easier.
• It has particular technology of bridge-divided over-current protection that guarantees equipment safety.
• It combines international advanced control method of same products, adopts advanced technologies like fixed angle phase-locking control, upper frequency limit/lower frequency limit lock-lost protection and etc. With these technologies, the equipments run more stably, more efficiently, more accurate and effective protections to the inductor short-circuit and open-circuit malfunction during pipe welding production.
• Line-in end of solid state H.F. welder does not need step-up /step-down rectifier transformer, compared with vacuum tube welder and parallel type welder; it has significant energy-saving effects (Under same welding condition, energy-saving ≥30% compared with vacuum tube welder).

2. Model instructions for solid state H.F. welder

3. Working principle of solid state H.F. welder

3.1 Main circuit structure of solid state H.F. welder

Solid state H.F. welder main circuit structure is as follows fig.1; it is a typical AC-DC-AC variable frequency structure. Rectifier adopts 3-phase bridge style thyristor phase-control rectifier circuit, DC side adopts inductor, capacitor to compose LC filter which meet the working requirements of voltage type inverter. The voltage type inverter adopts modularization parallel structure to extend power supply power, each inverter module is single phase MOSFET bridge style circuit connected with series resonance tank circuit by H.F. matching transformer. On one hand, the matching transformer realizes power combination and impedance matching; on the other hand it realizes electric isolation of load and power supply. To put effective and swift protection on over-current malfunction of voltage type inverter, our company introduces special and stable over-current protection circuit which guarantees safe and stable running of inverter.

Fig 1 Circuit structure of solid state H.F. welder

3.2 Working principle of solid state H.F. welder

Voltage type resonance inverter also called series connection type resonance inverter is the most critical part of the whole solid state H.F. power supply; fig 2 shows the structure, output voltage and current wave of inverter module. By controlling connection and disconnection alternatively of MOS 1&3, MOS 2&4, the series connection type inverter output voltage u_H is close to square-wave, due to the inverter output voltage frequency is near by resonance frequency of resonance tank circuit, and now the inverter output voltage fundamental wave from resonance tank circuit to inverter has the minimum impedance value, the maximum impedance value to other high harmonics, therefore load current i_H is close to sine waveform.

Fig 2 Voltage type resonance inverter circuit structure and output waveform

Series connection resonance inverter typical working state can be divided into three types: sensibility, resistive leakage, capacitive. Fig 3 shows separately the three working status’ inverter output voltage, current and experiment waveforms.

(a)small sensitivity status (b)small capacitive status (c)resistive leakage status

Fig 3 Series connection resonance inverter output waveforms

When series connection resonance inverter works at small sensitivity status (fig 3a), inverter’s working frequency is higher than inherent resonance frequency of resonance tank circuit a little bit, i.e. load current i_H lag to load voltage u_H a electric angle . Now current-exchange of inverter has several features: 1) Part’s startup is zero voltage (ZVS), zero current (ZCS), theoretically the wastage of the part’s startup is zero; 2) Part’s shutdown is zero voltage, non-zero current, but due to small current when part’s shutdown, plus zero voltage current-exchange (ZVS), so part’s shutdown wastage is small too; 3) circuit stray inductance has small effect on inverter current-exchange; 4) current-exchange has no requirement on backward recovery features of inverse parallel diode, the parts suffer very small surge impact when current-exchanging.

When series connection resonance inverter works at capacitive status (fig 3b), inverter’s working frequency is lower than inherent resonance frequency of resonance tank circuit a little bit, i.e. load current i_H advance to load voltage u_H a electric angle . Now current-exchange of inverter has several features: 1) Part’s shutdown is zero voltage (ZVS), zero current (ZCS), theoretically the wastage of the part’s shutdown is zero; 2) Part’s startup is high voltage, large current, so part’s startup wastage is very big; 3) circuit stray inductance has strong effect on inverter current-exchange; 4) backward recovery current of inverse parallel diode of MOS yield strong voltage current oscillation, the parts suffer very strong surge impact when current-exchanging, it threatens power part safety running severely.

When series connection resonance inverter works at resistive leakage status (fig 3c), it’s working frequency equals inherent resonance frequency of resonance tank circuit, i.e. load current i_H has the same phase position with load voltage u_H. Theoretically the resistive leakage status is the best working status, but actually due to the effects of dead zone period and resistance & capacitance absorption circuit, inverter current-exchange part’s working status is not in good condition, also load fluctuation makes inverter deviate to capacitive working status easily, it threatens stable and safe running of inverter.

From the analysis above we know that the best working status of series connection resonance inverter is small sensitivity standard resonance status.

Besides, compared with other company’s parallel connection resonance H.F. power supply, our company’s series connection resonance H.F. power supply parts not only has small switch wastage and high power supply efficiency, but also has much better protection to various malfunctions of resonance tank circuit.

4. Technical parameters of 300kW solid state H.F. welder

① Designed parameters

• Nominal power: 300kW
• Rated DC power: P_d=360kW
• Rated DC voltage: U_dN=380V
• Rated DC current: I_dN=800A
• The whole efficiency: η≥85%
• Output power: P_out＞300kW
• Designed frequency: f=300~350kHz
• MOSFET inverter: 120kW×3
• Tank circuit output mode: no welding transformer output, secondary resonance

② Power distribution requirements

• Nominal power: 300kW
• Rated DC power: P_d=360kW
• Line-in power factor: COSφ≥0.9
• Power distribution capacity: S≥400kVA
• Power supply voltage: 3-phase 380V/60Hz
• Line-in current: I=650A
• Line-in cable: each phase adopts two pieces of 150mm² copper cable connected in parallel, 3-phase 4-line

③ Water-water cooling system

• With the adoption of water-water heat exchanger
• Pressure of inner circulation water: 0.15~0.25MPa

• Flow of inner circulation water: 18m³/h
• Temperature of inner circulation out water: ≤40℃
• Temperature of inner circulation back water: ≤55℃

• Heat exchanger area: ≥15m²
• Flow of external circulation water: 30m³/h(provided by user)

• Temperature of external circulation inlet water: ≤35℃
• Temperature rise of heat exchanger external circulation water: ≤15℃
• Pressure of inlet water: 0.25～0.3MPa (approximately 2.5～3kg/cm²)
• Volume for external circulation water pool: ≥30m³(provided by user)

5. Core technical instructions of control and protection

• Solid state H.F. welder adopts the most advanced fixed-angel phase-locking control technique, inverter working status do not change as load tank circuit change, which keep the work at the best small sensitivity resonance status all the time, welder works stably with high efficiency.
• Solid state H.F. welder has advanced functions like high/low lock-lost protection, frequency upper limit/lower limit protection, invert over-current, tank circuit over-voltage and etc. Also more accurate and efficient on open-circuit, short-circuit, arcing of inductor malfunction, it guarantees welder stable running.
• Besides regular protections, each inverter bridge adopts multiple protections, such as DC side over-current, AC side over-current, AC side over-voltage and etc. It realizes protection redundancy, guarantees inverter safe running.
• Rectifier side control circuit adopts single chip technology which solves automatic phase-recognize successfully, i.e. no requirements on 3-phase power supply input line; thyristor trigger circuit adopts all digital equal interval triggering, it reduces non-characteristics harmonics furthest and power net pollution.
• Rectifier control circuit has soft startup, soft stop function which prevents welder over-current and over-voltage caused by rising too much of current and voltage when startup/stop.
• It adopts matching transformer to realize electric isolation and load matching of solid state H.F. welder with merits of whole set high efficiency, easy matching regulation.
• The welder has large power allowance, when in good load matching conditions it allows running under 110% rated power for a long time at least.
• With the adoption of PLC and touch-screen to compose HMI control system which is high intelligent and easy operation.