The main types of valves for pipelines, their device and installation

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Any engi­neer­ing sys­tem must be equipped with a device that will stop its oper­a­tion if nec­es­sary. So, the shut-off valves include cast-iron and steel valves for pipelines. They are installed in order to par­tial­ly or com­plete­ly block the path for the flow of liq­uid or gas. Met­al prod­ucts are char­ac­ter­ized by ease of man­age­ment and main­te­nance. The scope of such devices depends on the design, assem­bly, con­trol meth­ods and instal­la­tion.

What are pipeline valves

A vari­ety of valves is designed for instal­la­tion on water sup­ply net­works and gas. They serve to com­plete­ly or par­tial­ly block the move­ment, dis­trib­ute the con­tents through the noz­zles, and adjust the pres­sure. Also, by means of valves, it is pos­si­ble to con­trol the flow of liq­uids and gas­es by chang­ing the diam­e­ter of the path.

Valve mark­ings include let­ters and num­bers. They include the type of fit­tings and hous­ing, the mate­r­i­al of the seals and the method of con­trol. For exam­ple, the decod­ing of some prod­ucts is as fol­lows:

Gate valve 30h39r

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  1. 30s41nzh — steel gate valve with a mechan­i­cal dri­ve, cylin­dri­cal gear, stain­less steel seal­ing rings.
  2. 30ch39r — cast iron gate valve with mechan­i­cal dri­ve, elec­tric trans­mis­sion, brass rings.
  3. 30ch6br — cast iron gate valve with pneu­mat­ic actu­a­tor, bronze and brass seal.

The con­struc­tion length of the valve must com­ply with GOST 3706–93. The only excep­tions are devices for spe­cial pur­pos­es (iso­mor­phic). In oth­er cas­es, devi­a­tions from ±2 to ±14 mm are allowed.

Design features

The valve device is char­ac­ter­ized by sim­plic­i­ty. Depen­dence lies in the loca­tion of the lock­ing mech­a­nism. It is built into a cylin­dri­cal met­al body along its cen­tral axis. The equip­ment is mount­ed inside the cais­son cham­ber or man­hole.

Con­trol can be man­u­al or auto­mat­ic. The sec­ond option allows you to adjust the posi­tion of the shut­ter remote­ly. To do this, the oper­a­tor uses a push-but­ton device.

The valve draw­ing is rep­re­sent­ed by a seal­ing ring and a met­al valve. Its shape is con­vex, and on both sides. Lock­ing mech­a­nisms with mechan­i­cal con­trol have a stem and a lever attached to it. Turn­ing it (90॰) dri­ves the valve.

Gate valve dia­gram

Fix­a­tion of the device is car­ried out due to two con­clu­sions on both sides of the disk. They can be rep­re­sent­ed by flanges, thread­ed ele­ments or cham­fers for con­nec­tion to noz­zles by means of a weld­ing machine.

Principle of operation and technical characteristics

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The prin­ci­ple of oper­a­tion of the valve is based on chang­ing the posi­tion of the valve per­pen­dic­u­lar to the flow of liq­uid in the line (smoke in the chim­ney). Tight­ness is ensured by a tight fit of the valve to the seat of the device.

The clas­si­fi­ca­tion of pipeline valves is car­ried out in accor­dance with the fea­tures of the struc­tures, their assem­bly, instal­la­tion, indi­ca­tors of tech­ni­cal char­ac­ter­is­tics, con­trol. They look like this:

  • instal­la­tion is car­ried out above or below ground, with and with­out wells, indoors or out­doors;
  • resis­tance to seis­mic events, cli­mat­ic fea­tures of a par­tic­u­lar area;
  • fix­a­tion flange, weld­ed or com­bined;
  • cast, sheet, cast-weld­ed or stamp-weld­ed assem­bly;
  • man­u­al and elec­tric dri­ve.

The release of valves cor­re­sponds to the per­mis­si­ble val­ues ​​of the diam­e­ter of the branch pipes. The indi­ca­tors are from 5 cm to 2 m. The opti­mal pres­sure is con­sid­ered to be 25 MPa, and the ther­mome­ter read­ings for the work­ing envi­ron­ment are in the range of + 450- + 560 ℃.

Cor­re­spon­dence of the diam­e­ter of the branch pipe and the out­let of the valve

Main types of pipe valves

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Depend­ing on the char­ac­ter­is­tics, design, dri­ve and mount­ing meth­ods, sev­er­al types of gate valves can be dis­tin­guished. So, there are full bore valves, the seat of which cor­re­sponds to the diam­e­ter of the noz­zle. And the nar­rowed ones have low­er indi­ca­tors of a sim­i­lar sad­dle para­me­ter.

Accord­ing to the type of struc­ture, prod­ucts with a retractable and non-retractable spin­dle are dis­tin­guished. They are char­ac­ter­ized respec­tive­ly as fol­lows:

  1. A part of the stem extends out­ward rel­a­tive to the body dur­ing the rota­tion of the fly­wheel (leak­age is pre­vent­ed by the stuff­ing box locat­ed in the disk). At the same time, the dura­bil­i­ty of the run­ning unit is ensured by the absence of direct con­tact of the mech­a­nism with the con­tents of the line.
  2. Small­er dimen­sions, the mech­a­nism is locat­ed inside the case. The stem does not change its posi­tion, only the spin­dle and the shut­ter move. This option is less resis­tant to aggres­sive envi­ron­ments, so there are instal­la­tion restric­tions.

Accord­ing to the geom­e­try of the sad­dle, there are 2 options:

  • Wedge. The lock­ing mech­a­nism is rep­re­sent­ed by two discs. They are at an angle with respect to the hor­i­zon­tal axis. As the spin­dle rotates, the rings are low­ered. Between them are spac­er wedges, which in the process move towards the sad­dle.
V‑seat
  • Par­al­lel. In this device, the discs can have two posi­tions. At the bot­tom, the flow is cut off, and at the top, the path for the con­tents of the pipeline is opened.

Wedges are avail­able in three ver­sions:

  1. Rigid strict­ly adjust­ed to the shape of the sad­dle. It is rep­re­sent­ed by a met­al plate. Due to the weak­ness to changes in tem­per­a­ture, pres­sure, the field of appli­ca­tion is char­ac­ter­ized by rel­a­tive con­stan­cy and low per­for­mance.
  2. Dou­ble-disk pro­vides max­i­mum tight­ness and is allowed for use in pipelines with max­i­mum sen­sor val­ues ​​(up to 25 MPa, +560 ℃).
  3. Elas­tic is rep­re­sent­ed by disks con­nect­ed by a dynam­ic ele­ment. Com­pared with pre­vi­ous ver­sions, such a device is eas­i­er to man­u­fac­ture. It is suit­able for medi­um oper­at­ing con­di­tions.

Most often, cast iron is used for the man­u­fac­ture of the body and valves, and less often alloyed or stain­less steel. Oth­er mate­ri­als are prac­ti­cal­ly not used. They cope less with pres­sure, tem­per­a­ture and water ham­mer in the pipeline.

Cast iron appli­ance

The weight of the cast-iron valve is notice­ably greater than that of the first. They are installed in pipelines with pres­sure up to 1 atm., where only 2 valve posi­tions are need­ed: open and closed. Devices are con­trolled man­u­al­ly. Steel pipes are allowed for instal­la­tion on a pipeline with high tem­per­a­tures and pres­sures, as well as with aggres­sive media.

Installation of gate valves for pipelines

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The con­nec­tion of branch pipes, valves using weld­ing equip­ment is con­sid­ered the most durable and tight. There­fore, this option is used for high­ways in which high pres­sure is sup­plied. In oth­er cas­es, oth­er meth­ods are also rel­e­vant: a flange or a com­bi­na­tion of meth­ods.

The pro­ce­dure for installing a valve for a pipeline con­sists of four steps:

  1. Rise, instal­la­tion of the device in the set place.
  2. Align­ment of the cen­tral axes of the noz­zles and the body of the device.
  3. Instal­la­tion of a sealant, fas­ten­ers.

Final­ly, the bolts are tight­ened with a wrench or adjustable wrench. Weld­ing work takes place almost accord­ing to the same algo­rithm. Only the device must first be fixed in the desired posi­tion with tacks and check the align­ment of the axes. And after that, weld the ele­ments.

In the case of plas­tic pipes, the process looks a lit­tle dif­fer­ent. The process looks like this:

Gate valve for plas­tic pipes
  • the flange is put on the sleeve;
  • the sleeve is weld­ed to the pipe;
  • a rub­ber seal is laid;
  • using a key (open-end), the flange and the valve are con­nect­ed;
  • bolts are tight­ened cross­wise.

The design with a clamp­ing flange and a rub­ber cuff is installed as fol­lows:

  • the pipe is cut at an angle of 90॰;
  • the cast-iron flange is put on the branch pipe and shift­ed towards the main line;
  • clamp­ing ring is strung;
  • struc­tur­al ele­ments are cen­tered;
  • the flange is pushed onto the cuff until it stops;
  • pre­lim­i­nary fix­a­tion and align­ment check;
  • fas­ten­ers are tight­ened with a wrench.

Chim­ney valves are installed in accor­dance with the instruc­tions, which may vary. Instal­la­tion takes place dur­ing the lay­ing of the hood.

Impor­tant! If con­stant ven­ti­la­tion of the fire­box is nec­es­sary, then addi­tion­al per­fo­ra­tion is orga­nized in the valve. The diam­e­ter of the holes in this case can be from 10 to 15 mm.

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Recommendations and typical mistakes

Experts advise before installing devices to check them for leaks. To do this, the valve is doused with hot water, and after dry­ing, an audit is car­ried out. A faulty con­di­tion will be detect­ed imme­di­ate­ly.

Check for tight­ness in the closed posi­tion of the shut­ter

Before installing a cast-iron valve, the work sur­face must first be pre­pared. Hor­i­zon­tal or ver­ti­cal pipelines must be cleaned of scale, impu­ri­ties, scale and dried. The valve fly­wheel must be direct­ed upwards, and fas­ten­ers must be tight­ened even­ly, with­out dis­tor­tion. In the pass­port, the man­u­fac­tur­er always indi­cates the pro­ce­dure for installing the device. It is unac­cept­able to devi­ate from it.

There is also a set of rules that applies to the instal­la­tion of any type of shut­ter:

  • steel rein­force­ment dur­ing weld­ing must remain open;
  • clos­ing the flow path is accom­pa­nied by a small force so as not to lead to twist­ing and sub­se­quent break­age;
  • heavy devices for instal­la­tion are pro­vid­ed with props;
  • before choos­ing, it is impor­tant to con­sid­er the allow­able pres­sure lim­its;
  • instal­la­tion is pos­si­ble only on a straight sec­tion of the pipeline, where there is no risk of over­pres­sure, which leads to fatal water ham­mer.

When choos­ing a shut­ter instead of a valve, it is worth con­sid­er­ing some of the weak­ness­es of the devices:

Shut-off valves
  • can­not be used if the con­tents of the pipes have sol­id and large com­po­nents;
  • there are restric­tions on the per­mis­si­ble pres­sure in the line;
  • there is a risk of water ham­mer valves due to the rel­a­tive­ly low rate of block­ing the flow path.

In addi­tion, the valves are notice­ably more dif­fi­cult to repair, replace worn seals. And the instal­la­tion is accom­pa­nied by a greater height than is required for the shut-off valve.

Impor­tant! Elec­tric devices do not have strict reg­u­la­tions regard­ing the posi­tion. It is impor­tant that the dri­ve itself is not at the bot­tom. And if the spin­dle is locat­ed hor­i­zon­tal­ly, then an addi­tion­al sup­port must be pro­vid­ed under the mech­a­nism.

But­ter­fly valves, despite the rel­a­tive­ly low pres­sure lim­its, can be installed in almost any pipeline with liq­uids or gas­es. You can do the instal­la­tion your­self, but it is impor­tant to fol­low strict rules in order to avoid alter­ations or com­plete replace­ment of the device. The damper posi­tion can be con­trolled man­u­al­ly or remote­ly using the remote con­trol. And as a mate­r­i­al for man­u­fac­tur­ing, cast iron, alloyed or stain­less steel are used, which are respon­si­ble for the strength and dura­bil­i­ty of the shut­ter.

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