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


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


  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


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


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.
  • 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


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.


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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