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Two stage pneumatic cut-off valve

NegotiableUpdate on 06/12

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Nature of the Manufacturer: Producers

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Overview

Two stage pneumatic cut-off valve

Product Details

Two stage pneumatic cut-off valve

summary:

A two-stage pneumatic cut-off valve is a type of cut-off valve that can achieve two-step opening or two-step closing action. It consists of a three-stage pneumatic actuator and ball valve, namely 0 °, 45 °, 90 ° or 0 °, 90 °, 180 °. Valve opening stage: In the first stage, open 20% and wait for stability before fully opening in the second stage. The same goes for closure. In the first stage, 80% will be closed, and once it stabilizes, all will be closed. By changing the piston stroke of the additional cylinder, the actuator and valve angles are stopped at a pre-set angle (45 ° -90 °), thus adjusting the valve flow rate This device relies on two solenoid valves to control the flow of the valve. Due to the use of rapid exhaust and throttling functions within the actuator, the two-stage ball valve has excellent switching characteristics. Slow down the opening and closing speed of the valve, ensure smooth fluid changes in the pipeline, prevent water hammer caused by impact, and prevent flammable fluids from exploding or damaging flow meters and other instruments in the system due to impact. Optional double acting and single acting (valve automatically closes in case of failure), can be equipped with a handwheel mechanism (can be manually operated in case of power failure), making it suitable for flow control systems in industries such as petroleum, chemical, and light industry, especially for oil storage and transportation systems.

characteristic:

Media used: Compressed air, non corrosive gases, and oil:

Pressure range: Double acting 2-8 bar, single acting 2-8 bar

Working temperature: Standard type: -20 ℃ to+80 ℃; Low temperature type -40 ℃ to+80 ℃; High temperature type -20 ℃ to+160 ℃.

Maximum operating pressure: Input air pressure not exceeding 10 bar (Bar);

The travel adjustment has an adjustable range of ± 4 degrees at the 90 degree position

Torque: 6~3000Nm;

Control mode: switch type, regulating type, bus control (with solenoid valve and locator required);

Action frequency: 2000 times per hour;

Input signal: ONOFF, 4~20mA, 0~10V (requires solenoid valve and locator);

Output signal: 4~20mA, contact signal (requires locator and limit switch);

Environmental temperature: -35 ℃~+85 ℃;

Usage restrictions:

1Temperature and pressure limitations

(1) The nameplate displays the maximum operating pressure allowed by the ball valve at the maximum and minimum operating temperatures;

(2) The valve seat and seal made of cast steel or all stainless steel material should be operated at a temperature of -29 ° C℃Up to 180℃between. Operating temperature of other types of valve seats and seals;

(3) The nominal pressure rating (PN) of a valve: It indicates the maximum working pressure of the valve at normal temperature.

2Prohibit throttling operation

Please do not keep the ball valve in a half open state frequently (flow control), as pressure differences in the pipeline and fluid impact may cause damage to the ball valve or valve seat.

Installation and maintenance

1Installation

(1) Remove the protective covers on both sides of the flange end and perform flushing and cleaning with the valve fully open;

(2) Before preparing to connect with the pipeline, rinse and remove all accumulated impurities in the pipeline;

(3) Before installing the valve, carefully check whether the valve chamber is clean. If there are any debris, make sure to clean it thoroughly. Check if the flange surface is damaged and ensure that it is undamaged. During the installation process, the connecting pipe should not be subjected to force, otherwise it may cause air leakage.

(4) Wiring: Open the explosion-proof junction box, there are a total of 5 terminal posts,①、②、③、④And grounding, among which①、②As a group, connect solenoid valve 1:③、④Connect solenoid valve 2 as a group.

(5) During installation, please do not use the valve stem or handle as a fulcrum for lifting objects to avoid collapse and other accidents;

(6) The pipeline near the installation point should not have low hanging or external force bearing objects, and pipeline brackets or supports can be used to clear the deviation of the pipeline;

(7) After connecting with the pipeline, please use the specified cross locking flange connection bolts;

(8) During the handling and installation process, be sure to handle with care to avoid damage, deformation, and loosening of the gas pipeline and various joints.

2Maintenance

The two-stage pneumatic ball valve has a long service life and maintenance free period, and the actual service life depends on the following factors: normal working conditions, maintaining a harmonious temperature/pressure ratio, and reasonable corrosion data.

Maintenance precautions:

(1) When the ball valve is in the closed state, there is still pressurized liquid inside the valve body;

(2) Before maintenance, release the pipeline pressure and keep the valve in the open position;

(3) If there is slight leakage at the packing point, the valve stem nut must be tightened again, but be careful not to tighten it too tightly. Usually, tighten it half a circle more, and the leakage will stop.

Operation and use

(1) Before operation, it is necessary to confirm that the pipelines and valves have been thoroughly flushed.

(2) The operation of the valve is completed by rotating the valve stem (manual or automatic control mode): when rotated clockwise by 1/4 turn (90 degrees), the valve closes. When rotated counterclockwise by 1/4 (90 degrees), the valve opens.

(3) When the direction of the groove on the top of the handle or valve stem is parallel to the pipeline, the valve is in the open state.

(4) Gas source requirements: The gas source should be clean and free of oil stains, with a pressure of 4-8 bar.

(5) Wiring: Explosion proof conduit should be connected to the inlet end of the explosion-proof junction box for wiring.

Principle steps

1Control principle

Taking loading as an example, the specific process is that solenoid valve 1 is energized, all valves are opened, and loading is carried out. When approaching the set value, solenoid valve 2 is energized, solenoid valve 1 loses power, and the valve enters a low flow state. When the flow reaches the set value, solenoid valve 2 loses power and all valves are closed.

Under normal circumstances, the solenoid valve of the emergency shut-off valve should be powered off and in a normally open state, while the valve body should be in a closed state when there is no air source. When using air source operation, the first thing to confirm is that the adjustment screw and locking nut of the manual mechanism are in a disengaged state. When operating, first turn on the air source. When the pressure of the instrument air source is greater than 0.3Mpa, the piston rod moves forward under force, squeezes the spring, and drives the shaft and valve stem to rotate, causing the valve core to open and the valve to be fully opened.

If the cut-off valve needs to be closed, the upper computer issues a closing command to turn on the solenoid valve and close it, releasing the gas in the cylinder. When the pressure of the instrument gas source drops below 0.1Mpa, the spring force is greater than the gas source pressure, causing the piston rod to move backward and the shaft to start reverse movement. When the pressure drops to zero, the shut-off valve is completely closed.

When using manual mechanism operation, the first step is to cut off the air source, exhaust the air in the cylinder, and make the instrument air source pressure zero.

At this time, the shut-off valve should be in the closed state due to the lack of air pressure. If you want to open the shut-off valve, you should rotate the handle on one side of the spring cylinder counterclockwise. When the adjusting screw is about 8cm out of the spring cylinder, you can clearly feel the resistance. At this point, the screw of the manual mechanism is locked by the locking nut. Continue to rotate the handwheel counterclockwise until the adjusting screw drives the spring to stretch, causing the piston rod to move forward. When the adjusting screw is about 21cm out of the spring cylinder, the shaft completes a 90 'rotation. At this point, the shut-off valve is fully opened.

If you want to close the shut-off valve, you should turn the handwheel clockwise. At this time, the spring slowly returns, causing the piston rod to move backward and the shaft to rotate in the opposite direction. When the adjustment screw disengages the spring cylinder to a length of 8cm, the spring is fully reset. The shut-off valve is closed. Continue to rotate the handwheel clockwise, and when no resistance is felt at all, the screw of the manual mechanism disengages from the locking nut. During manual control, it is strictly prohibited to open the air source for ventilation.

When the cut-off valve is in the normally open state, the adjusting screw of the manual mechanism cannot be locked by the locking nut.

Control schematic diagram

2Control steps:

Taking the example of one stage opening, two stages closing, and small flow control, the specific control steps are as follows:

（1）①，②Live, open all valves, and proceed with loading;

(2) When approaching low flow control,⑧，④Charged;

(3) 3 seconds later①，②Power loss, valve closed to low flow state;

(4) When the loading is completed,⑧，④Power loss, all valves are closed.

(5) If reloading, repeat steps (1) to (3).

3Small flow opening adjustment:

Two stage pneumatic ball valves can pause once during the opening or closing process, allowing for precise flow control according to system requirements. They are particularly suitable for chemical or oil loading systems, such as opening all valves at once to start loading. When the flow rate approaches the set value, the valve closes to a low flow state, and when the set value is reached, all valves are closed. Small traffic can be set on-site between 0% and 45%, such as 5%, 8%, 10%, 15%, etc., ultimately achieving precise control. The small flow rate has already been set at the factory. If on-site adjustment is required, the steps are as follows:

(1) Loosen the protective sleeves at both ends;

(2) Use an Allen wrench to loosen the locating pin on the copper shaft;

(3) Rotate a section of copper shaft by hand to set a smaller flow rate, rotate the copper shaft clockwise to set a larger flow rate, rotate the copper shaft counterclockwise, adjust and fix the positioning pin tightly, conduct a ventilation test, and see if it meets the requirements. If not, adjust it several times until it meets the requirements.

(4) In the fourth control step, in the second step, rotate the other section of the copper shaft by hand to ensure that both ends are in the fourth control step. In the third step, tighten the cylinder end cover tightly and apply force while tightening the positioning pin.

(5) Cover both ends with protective end caps.

Pneumatic flange ball valveMain performance specifications

Nominal diameter DN (mm)		15-250
Nominal pressure PN (MPa)		1.6		2.5		4.0
Nominal pressure PS (MPa)	strength test	2.4		3.75		6.0
	Sealing test	1.76		2.75		4.4
Material code		C		P		R
Main parts	valve body	WCB		ZG1Cr18Ni9Ti		ZG0Cr18Ni12Mo2Ti
	Disc	2Cr13		1Cr18Ni9Ti		1Cr18Ni12Mo2Ti
	valve stem	2Cr13		1Cr18Ni9Ti		1Cr18Ni12Mo2Ti
	sealing ring	Enhanced polytetrafluoroethylene to polystyrene
	filler	Polytetrafluoroethylene flexible graphite
Applicable working conditions	Applicable Medium	Water, steam, oil products	Nitric Acid		Acetic acid
	Temperature	-28℃～300℃
actuator	model	BAWSeries, GT series, SW series
	Mpa	0.4-0.7Mpa

Pneumatic flange ball valveMain dimensions and actuator configuration

Nominal diameter DN (mm)	Size (mm)							Model of actuator
Nominal diameter DN (mm)	L	D	D1	D2	b	f	n-Φd	Model of actuator
15	130	95	65	45	14	2	4-14	AT32
20	140	105	75	55	14		4-14	AT50
25	150	115	85	65	14		4-14	AT50
32	165	135	100	78	16		4-18	AT63
40	180	145	110	85	16	3	4-18	AT75
50	200	160	125	100	16		4-18	AT75
65	225	180	145	120	18		4-18	AT88
80	250	195	160	135	20		8-18	AT100
100	280	215	180	155	20		8-18	AT125
125	320	245	210	185	22		8-18	AT145
150	360	280	240	210	24		8-23	AT160
200	457	335	295	265	26		12-23	AT190
250	533	405	335	320	30		12-25	AT240