Tag Archives: Gas Control Valves

The valve is an important chemical pipeline control media flow accessories, this handout is more important than the practical application of the valve principle and structure in detail with reference to the relevant information books cutaway view, the valve consists of body, opening and closing body, valve cover three major composition This focuses on the structural characteristics of the commonly used valve and its correct use of precautions. First, the role of the valve

1, open and close – cut off the communication flow of fluid in the tube;

Regulation – to adjust the pipe flow, flow rate;

3, the throttle effect – the fluid to generate a lot of pressure drop through the valve;

Other role – a. Automatically open and close (b) to maintain a certain pressure c resistance of air drainage.

Second, the type of valves

1, according to use: the cut valve, regulating valve, shunt valve, check valve class, the safety valve class; * z1i9N: r \\\\ \\ W%} j ~ 2, the force points: he moves with valves, the role of the valve automatically. Third, the valve main parameters

PN nominal pressure (to allow the fluid through the maximum pressure);

DN nominal diameter;

TN temperature range (to allow the fluid temperature range). 4, the valve using the pre-check

The inspection items include:

A body inside and outside for any signs of trachoma, cracks and other defects;

2, valve seat and valve body joint is solid, the spool and the valve seat is consistent, whether the sealing surface defects;

3, the stem and is connected to the spool is flexible and reliable, whether the curved stem, thread damage, corrosion;

4, packing, gaskets aging damage;

5, the valve opens and is flexible. 5, the valve process often occur

1, pipe joints, flanges, thread leaks;

Fill Han leakage, lumbar leakage and the valve stem to open does not move;

3, the formation of the loose relationship between the spool and the valve seat leakage. , Chemicals commonly used valve characteristics and Cautions

(A) plug valves (Hancock)

Characteristics: TN less than 150 degrees PN less than 1.6Mpa its structure is simple, open and close quickly, easy to operate, small fluid resistance, etc.

Caution:

Off, a vertical stem the outer end of the square, the diagonal line marked with the valve direction consistent with the body the direction of the open state;

2, the normal switch valve with the Hancock special wrench to avoid stem skidding caused by security incidents; resulting in slip as far as possible without adjustable wrench;

3, opened the valves slowly open the valve after the previous inspection items to check, check, try not to stand in the direction of the sealing surface in the open, when confronted with acid-base fluid are required to wear the mask of anti-acid;

Ball valves and plug valves is the same type of valve, only opening and closing parts of a sphere with a through-hole, the sphere Rao stem centerline of rotation to hoist the purpose.

Jacketed insulation ball valve

Stainless steel ball valve

Stainless steel ball valve fast open ball valve

Features: valve structure, reliable operation, the pipeline for two-way flow of medium, small fluid resistance, good sealing; Disadvantages: medium easy to leak from the stem parts.

Caution:

With plug valves are the same;

Handle the valve with the handle perpendicular to the direction of media flow is turned off, in the same direction as the open state;

Such as the face of the ball valve with jacket insulation should note the following:

Jacket insulation steam should be easy to crystallize in the media in the valve open to melt the rear can open and close the valve, not to the media is not completely melted forced open and close the valve;

When encountered the valve can not open, can not take advantage of the extended arm, forced open the valve, as this will cause the stem by the resistance of the larger and the spool off, resulting in valve damage or damage to the wrench, thus resulting in insecurity. (C) Butterfly

The butterfly valve is the use of a Rao axis of rotation of the disc to control the opening and closing of the pipeline, the corner reflect the size of the valve opening degree of.

Points manual, pneumatic and electric three different butterfly valve according to the transmission mode, commonly used for manually rotating the handle through a gear transmission drive the stem thus from the closed valve.

Features: butterfly valve has a simple structure, a more rapid opening and closing the fluid resistance is small, easy maintenance, but can not be used for high temperature and high pressure situations, PN less than 1.6Mpa, t less than 120 degrees of large diameter water, steam,

Air, oil pipeline.

Caution:

1, the spool can only rotate 90 degrees, CLOSE and OPEN the direction of the arrow will indicate the general body, the hand wheel clockwise rotation is off, otherwise it is open;

If open and close with some resistance, you can use the dedicated F wrench to open the valve, but can not be forced open and close, otherwise the stem gear stir bad;

To prohibit the hand wheel to remove the adjustable wrench pulled the stem; (The same is true for the following valve)

4, opening and closing the gradual opening and closing to observe any abnormal situation and to prevent leakage. (D) cut-off valve

The cut-off valve is the most widely used in chemical production of a truncated class valves, valves with these three truncated compared to not closed the rotation to open and close the valve, but the stem down to drive connected circular disc (valve head), changing the distance between the valve disc and valve seat to control the valve shuts. ] / U!

Flow line type globe valve in American standard cut-off valve

Features: handwheel, stem cut-off valve upper part of the central thread and filler Han sealing section, the small valve stem threads on the valve body, its compact structure, but the stem and the media contact parts, especially the threaded portion of corrosive the cover exposing the valve from the valve stem can determine the cut-off valve structure is more complex, but the operation is simple, less laborious, easy to adjust the flow and the truncated channel, from the closed slow water hammer phenomenon, so the more widely used.

To pay attention to the direction of flow cut-off valve installation, pipeline fluid flow through the port seat, and the so-called \"low prices\" from the bottom up, the aim is to reduce the fluid resistance, open effort and off the lower stem packing Han The part does not contact with the media to ensure that the bypass valve stem and packing will not be damaged and leak. The stop valve is mainly used for the piping of water, steam, compressed air and a variety of materials can be more accurately regulate the flow and closely truncated channel, but can not be used for viscosity, easy to crystallize materials.

Caution:

1, before the opening of check valve with or without defects, especially the filler Han for leaks;

Stem can not hand rotate directly available special F wrench to open and close, still unable to open and close, do not lengthen the wrench arm to force open and close, resulting in valve damage caused by security incidents;

3 for medium pressure steam piping and valves, should open the condensate in the first tube row of the net, then slowly open the valve 0.2 to 0.3Mpa steam pipe preheat, avoid pressure suddenly l cause damage to the sealing surface of the high, when the examination was normal after the pressure to the required state; (e) gate valve

Gate valve, also known as a gate valve or gate valve, which control the opening and closing of the valve through the rise and fall of the gate, the gate perpendicular to the direction of flow, changing the relative position between the gate and valve seat can change the channel size.

The levers valve dark rod gate valve

, Depending on the stem movement when the gate valve, gate valve to clear the rod and two dark rod.

The levers valve stem threads are exposed to the external body, open the valve stem out of the hand wheel, its advantages is the extended length of the stem to determine the valve to open the small size of the stem and the contact with the medium length, thread part of the capital not subject to the corrosive medium affects the disadvantage is that the overhanging space height.

Want to tie in with the dark rod valve stem thread on the threaded stem internal gate, open the valve stem only rotation rather than up and down movements, the gate is increased along the stem threads. Rod gate valve has the advantage of the dark overhang the space is small, the shortcomings can not stem the situation to determine the valve opening, the stem threads are long-term contact with the media vulnerable to corrosion.

Valve has the fluid resistance is small, and medium flows unchanged on the slow water hammer phenomenon, easy to adjust the flow, etc. The disadvantage is that the complex structure, large size, opening and closing a long time, the sealing surface maintenance difficulties. As in the large-diameter pipes

1, when the stem open and close in place, can no longer force it, otherwise it will pull off an internal thread or bolt screw, so that the valve damage;

2, opening and closing valves available in the hand can not directly activate F wrench to open and close;

3 attention to observe the sealing surface of the valve opening and closing the valve packing gland Department to prevent leakage. (6) throttle

Throttle valve, also known as a needle valve, its shape and the cut-off valve, a disc shape, showing the cone or parabolic, commonly used in chemical instrumentation, often threaded connection.

Caution:

A threaded connection, so the opening and closing, first check the thread connection is loose leak;

Opening and closing the valve slowly, because the smaller circulation flow rate of the larger, may cause corrosion of the sealing surface should observe carefully, pay attention to the pressure changes. (7) Check

The check valve is the use of pressure on the media before and after the valve is automatically open and close, controlling the media, one-way flow valve, also known as non-return valve or check valve.

The check valve according to the structure divided into the lift (jump heart-type) and swing (shake pole) two.

Lift Swing

Caution:

Attention to the valve direction arrow and medium flows, such as the media easy to crystallize may cause the valves can not be pressure to not achieve command, only to return to the role. (8) safety valve

The safety valve is automatically open and close the valve of a medium pressure, medium pressure exceeds the set value, it can automatically open the valve emissions Relief, equipment, piping from the danger of destruction, the pressure returned to normal and can automatically closed.

Depending on the pressure within the balance, the safety valve lever hammer and spring-loaded two types.

Caution:

1, the safety valve must be in the validation period of validity;

2, piping, equipment installed on the safety valve control valve cut-off valve must be opened to ensure safety valve to work effectively;

3, regular disc slightly lift the media to blow the impurities in the wash valve.

4, such as the safety valve can not work within the set pressure must be re-tested or replaced (nine) trap

The traps are automatic intermittent condensate, but also to prevent steam from escaping a valve in the steam pipes, heaters and other equipment. The common bell-shaped float-type thermal power and pulse several.

Caution:

1, prior to use with the pipeline bypass valve condensate water, steam, close the bypass, activate the trap right way, otherwise the valve will be closed the water will not achieve hydrophobic interaction;

Careful not to be scalded by the steam from the closed valve. (10) various types of sampling valve

Sampling valve is the name suggests is used to obtain the media samples to chemical analysis of the valve, usually installed in the equipment or pipeline is broadly divided into the following categories:

Double to open the valve, flange clip valves, and sampling valves with insulation jacket;

The use of attention to the method:

A double to open the valves are generally formed by two ball valves play a sample security and in the vacuum through the linkage to achieve the purpose of sampling; near the device when the first sampling, the second channel of the pipe the valve is closed, open the first the valve and let the media flow to the space between the two valves; and then close the first valve to open the second valve, the sampling containers placed sampling port costumes media;

2, the flange clip valve stem at the top of the cone and the valve seat taper seal, sampling by the rotation of the handwheel stem taper from the, so the media can taper the flow of external sampling containers;

3, the sampling valve with jacket insulation should note the following:

I should be open jacket insulation steam valves are vulnerable to the crystallization medium melt the rear can open and close the valve, not to the media is not completely melted forced open and close the valve;