Abstract Introduced the lifting weight structure of the hydraulic control check butterfly valve and the mechanical and electromagnetic combined locking mechanism, and explained its composition, working principle, and characteristics.
Keywords Check valve; butterfly valve; heavy hammer; lock; principle
Overview
Many large water pump outlets use hydraulically controlled check butterfly valves to prevent the backflow of the medium from damaging the water pump when the pump is stopped. Hydraulic control check butterfly valves generally adopt a swing arm heavy hammer structure, which relies on the potential energy of the heavy hammer to close the valve, but the swing arm heavy hammer takes up a large space, and the heavy hammer may fall off during the swing process, which poses a serious threat to other equipment and personal safety on site. threat. At the same time, maintaining the potential energy of the heavy hammer needs to ensure a certain oil pressure, and the hydraulic lock and hydraulic reversing valve inevitably have internal leakage, and the oil pump needs frequent oil supplement pressure to maintain the potential energy of the heavy hammer and the valve opening, which increases Operating cost reduces the life of the oil pump. According to needs, a hydraulically controlled check butterfly valve with a lifting weight structure and a mechanical-electromagnetic combined locking mechanism is designed.
Structure
The lifting weight device of the hydraulically controlled check butterfly valve is composed of a frame, a sector plate, a pulley block, a weight, a steel wire rope, and a driving cylinder (Figure 1). It is characterized in that the rotation center of the sector plate and the swing arm of the drive cylinder are connected with the valve stem. A steel wire rope is fixed on the arc edge of the sector plate, and the other end of the wire rope bypasses the pulley block and is connected to the upper end of the weight. Set in the frame, the structure is relatively compact. When the valve is opened, the device transmits the hydraulic pressure of the hydraulic station to the valve stem (to drive the butterfly plate to open) and the heavy hammer (to raise the heavy hammer to generate potential energy). When closing the valve, the potential energy of the heavy hammer is reversely transmitted to the valve stem (to drive the butterfly plate to close).
1. Heavy hammer 2. Wire rope 3. Pulley group 4. Spring 5. Sector plate limit 6. Spring return cylinder 7. Limit block 8. Frame 9. Pin 10. Pull hook 11. Electromagnet 12. Solenoid bracket 13. Swingarm 14. Sector plate 15. Drive cylinder
Figure 1 Lifting heavy hammer hydraulic control check butterfly valve
The mechanical-electromagnetic combined locking mechanism is an additional part of the hydraulically controlled check butterfly valve, which is composed of a spring return cylinder, a wedge, a limit block, an electromagnet, and a hook. When the valve reaches the fully open position, the spring-returning oil cylinder acts to feed oil, and the limit block is extended to block the limit of the fan-shaped plate. The electromagnet is energized to attract the hook, and the wedge on the hook will move the wedge on the limit block. Hook to form an interlock. Its function is to lock the potential energy of the heavy hammer after the increase and prevent the heavy hammer from falling by itself.
working principle
1 . Lifting hammer structure
When the valve is opened, the oil supply and lifting cylinder of the hydraulic station is used to drive the butterfly plate to rotate 90° counterclockwise through the swing arm to drive the valve stem and other parts to achieve the purpose of opening the valve. At the same time, the action of the lifting weight structure, that is, the force of the cylinder also lifts the weight vertically to a high position through the fan-shaped plate, wire rope, and pulley block, and converts the weight of the weight into potential energy to prepare the power for closing the valve. When the valve is closed, the electric control is used to cancel the lock by the mechanical and electromagnetic combined locking mechanism. At this time, the potential energy of the heavy hammer drives the butterfly plate through the wire rope, pulley block, fan plate, swing arm, valve stem, and other parts to drive the butterfly plate to close and move slowly according to the pre-set speed. And the slow closing program is closed.
2. Locking mechanism
When the valve is fully opened in place, the spring-returning oil cylinder moves to make the limit block extend to the locked position to pull the fan-shaped plate to limit the position, forming a mechanical locking initial lock. Then the electromagnet is energized so that the electromagnetic force overcomes the spring force to drive the hook action, and the hook hooks the wedge on the limit block to form an electromagnetic lock.
When the valve is closed, the electromagnet is de-energized, the hook is restored under the action of the spring force, and the restraint on the limit block is released, and the electromagnetic lock is canceled. As the restraint of the limit block disappears, the spring return cylinder drives the limit under the action of the spring force. The position blocks recover together, the mechanical lock disappears, the fan-shaped plate drives the valve stem and the butterfly plate to rotate together under the action of the potential energy of the heavy hammer, and the valve closes.
The potential energy of the heavy hammer is absorbed by the mechanical lock of the limit block, the release of the mechanical lock is restricted by the electromagnetic lock, and the release of the electromagnetic lock is controlled by the electromagnetic force of the electromagnet. As long as the electromagnet is energized, its electromagnetic lock and the mechanical lock can be controlled to ensure that the butterfly plate is always in the fully open state (minimum flow resistance state) after it is turned on, and there is no need for any oil or pressure compensation measures.
Design
1 Heavy hammer force
The weight Q required to close the valve is
Q = M/ r
In the formula M ———Total torque, N·mm
M = M T + MC + Mb
M T — the friction torque between the valve stem and the packing,
N·mm
M T =½ Q T dF1
Q T ———Friction force between packing and valve stem, N
Q T = f m d T bT P
d T ———packing depth (designed), mm
b T ———Filling width (given by design), mm
f m ———The friction coefficient between the packing and the valve stem
P ———Valve nominal pressure (design given), MPa
dF1 ———The diameter of the valve stem at the packing (given by design), mm
MC ———the friction torque between the valve stem and the bearing, N·mm
MC = ( ½Qc f c d F2) 2
f c ———The friction coefficient at the bearing
dF2 ———The diameter of the valve stem at the bearing (given by design), mm
QC ———Load acting on the bearing, N
QC =¼πD2 P
D ———Butterfly plate sealing diameter (given by design), mm
Mb ———Valve automatic closing torque, N·mm
Mb = 1.3 ( M T + MC)
r ———The force arm of the heavy hammer, mm
2. Spring return cylinder
The return spring is calculated according to the requirements of the relevant spring in GB/T 1239. The spring wire diameter d is
In the formula Fmax ——— Maximum working load, N
Fmax = F1 + F2
F1 — the friction between the limit block and the limit of the sector plate,
N
F1 = Qf 1
f 1 ———Limit friction coefficient of limit block and sector plate
F2 ——— Friction between cylinder shaft and cylinder head, N
F2 = Qf 2
f 2 ———The friction coefficient between the cylinder shaft and the cylinder head
K ———Turning ratio
C — Curvature coefficient
〔Τp〕———allowable shear stress of spring, MPa
The effective number of springs n is：
In the formula
D1 ——— spring middle diameter, mm
G ———Material Shear Modulus, MPa
The spring stiffness T is:
The total number of spring turns n1 is：
n1 = n + 2
The spring free height H0 is:
H0 = nt + 1.5 d.
t———spring pitch, mm
Concluding
The hydraulically controlled check butterfly valve adopts the lifting weight structure and the mechanical electromagnetic combined locking mechanism to reduce the installation space, the valve structure is compact, and the installation and maintenance are convenient. After the valve is opened, only one electromagnet is powered and the current consumption is very small. Hydraulic components such as oil pumps and solenoid valves do not need to operate frequently, prolonging the service life. The valve not only has the function of a check valve, which can eliminate water hammer to protect the safety of the water pump and pipe network system but also has the function of a butterfly valve (or gate valve), which can completely cut off the pipeline medium, reducing various costs and operating expenses. When the nominal size> DN1400, its good performance, and advantages can be more reflected.
Author: Chuntao Song
