The device and rules for installing a shut-off valve

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Lines with liq­uid and gaseous media are equipped with fit­tings in the form of shut-off equip­ment. The main task that the shut-off valve per­forms is to exclude the devel­op­ment of con­se­quences in the event of a mal­func­tion in the pipeline. In par­tic­u­lar, defor­ma­tion of high­ways, leak­age, over­flow of tanks. Devices are dis­tin­guished by response speed, dura­bil­i­ty, pur­pose, design and instal­la­tion.

Shut-Off Valve Overview

A shut-off valve is installed for mechan­i­cal inter­ven­tion in the free move­ment of liq­uids and gas­es through the pipeline. Stop­ping and free­ing the line from the con­tents may be nec­es­sary due to leaks, depres­sur­iza­tion, crit­i­cal tem­per­a­ture or pres­sure drops. That is, the con­tent is either com­plete­ly dri­ven out of the area, or its move­ment is blocked.

Devices are installed on the high­way with gas­es, oil prod­ucts, hot and cold water. These can be both house­hold util­i­ties, gas sta­tions, and more indus­tri­al-scale struc­tures or, for exam­ple, a city heat­ing net­work.

Stop valve

There are dis­pos­able devices that are equipped with replace­able valves or must be com­plete­ly replaced after oper­a­tion. They are usu­al­ly made from plas­tic. Reusable met­al equip­ment is in great demand, as it is char­ac­ter­ized by a long ser­vice life.

Design features

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The device is based on a cast body, seat and cov­er. They are made of cast iron, gal­va­nized steel, brass or poly­mer mate­ri­als with high strength. The sec­ond ele­ment is designed to install the valve in the pipeline.

The shut­ter mech­a­nism is pre­sent­ed as fol­lows:

  • a spring that dri­ves the device (shut­ter and return);
  • the stem respon­si­ble for the dynam­ics of the valve;
  • absorbent pad to pre­vent con­den­sa­tion and leaks.

Elec­tric or pneu­mat­ic actu­a­tors are respon­si­ble for the oper­a­tion of the device. The valve is con­trolled in two ways: man­u­al­ly by a ser­vice oper­a­tor or auto­mat­i­cal­ly. With­out human inter­ven­tion, oper­a­tion occurs, as a rule, due to built-in sen­sors.

Device with sen­sor

Principle of operation

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The func­tion­al­i­ty of the cut-off device is to ensure that the con­tents of the pipeline stop their move­ment in a par­tic­u­lar sec­tion or along the high­way as a whole. The shut-off valve must shut off the flow prompt­ly to min­i­mize the risk of acci­dents. Here are a few rea­sons why they hap­pen:

  • vio­la­tions of the tech­nol­o­gy of instal­la­tion of pipelines, fil­ters;
  • non-com­pli­ance with safe­ty require­ments;
  • end of ser­vice life of con­stituent com­po­nents;
  • var­i­ous kinds of mal­func­tions;
  • unex­pect­ed change in pres­sure or tem­per­a­ture with­in struc­tures.

More prac­ti­cal are devices equipped with spe­cial sen­sors. This is due to auto­mat­ic oper­a­tion with­in a short peri­od of time (from frac­tions of a sec­ond to min­utes). The speed depends on the char­ac­ter­is­tics of the sen­sors and the qual­i­ty of the equip­ment set­tings. The lat­ter is the respon­si­bil­i­ty of trained ser­vice per­son­nel.

Benefits of using a shut-off valve

Com­pared to valves, which ini­tial­ly per­formed the task of shut­ting off the move­ment of liq­uids and gas­es, valves are equipped with var­i­ous kinds of auto­mat­ic response mech­a­nisms. It con­sists either in giv­ing sig­nals to oper­a­tors, or direct­ly block­ing the free pas­sage through the pipeline.

Shut-off valve

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Today, instru­ments elim­i­nate some of the short­com­ings of pro­to­type equip­ment. For exam­ple:

  • due to mud flows and impu­ri­ties, false alarms are exclud­ed;
  • tighter hous­ings are bet­ter able to han­dle small pres­sure drops;
  • response speed is min­i­mized to a few sec­onds.

In addi­tion, mod­ern shut-off valves block move­ment in both direc­tions. And in the designs there are addi­tion­al ele­ments. For exam­ple, sil­i­cone spring gas­kets or shims.

Main types of devices

Pipe fit­tings dif­fer in design and pur­pose. So, nor­mal­ly open devices are dis­tin­guished. They are respon­si­ble for deal­ing with flow in rela­tion to move­ment. Nor­mal­ly closed shut-off devices are usu­al­ly man­u­al­ly oper­at­ed and open in an emer­gency to release the con­tents of a tank or line.

Sep­a­rate­ly, devices for water, oil prod­ucts and gas are con­sid­ered. The actu­a­tion can be real­ized by means of a mechan­i­cal load, a spring mech­a­nism, a pneu­mat­ic or mag­net­ic actu­a­tor. The devices are also dif­fer­ent in terms of char­ac­ter­is­tics, con­nec­tion meth­ods, work in one or two direc­tions. And depend­ing on the mate­ri­als used, man­u­fac­tur­ers offer dis­pos­able and reusable shut-off valves.

Angular

Angle valve

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The scope includes lines for liq­uid prod­ucts flow­ing under high pres­sure. The body of the equip­ment is made of high-strength steel. The equip­ment has a pis­ton hydraulic dri­ve. The prin­ci­ple of oper­a­tion is designed for incom­ing and dis­trib­ut­ing move­ment.

checkpoint

It is rel­e­vant to install a direct-act­ing shut-off valve in pipelines where there is a risk of leak­age. The con­tent in this case can be both clean and with impu­ri­ties or impu­ri­ties, bub­ble inclu­sions. At the same time, micropar­ti­cles do not set­tle and do not accu­mu­late in nodal joints. With regard to mate­ri­als, the main cri­te­ria are impact resis­tance, wear resis­tance and pro­tec­tion against cor­ro­sion dam­age.

double saddle

This device has two land­ing sad­dles and a plunger. Instal­la­tion is allowed on pipelines with a large cross-sec­tion and high pres­sure drops. Dou­ble-seat­ed shut-off valves are used in con­di­tions of explo­sion haz­ard and active chem­i­cal reac­tions.

single saddle

Such a lock­ing device is installed on pipelines of rel­a­tive­ly small diam­e­ter. The same applies to the ampli­tude of low pres­sure drops. The device has a sin­gle plunger that blocks the flow in one direc­tion.

sin­gle seat valve

Auto

Shut-off valves of this type usu­al­ly have a steam damper. It works with­in 1.5–10 sec­onds after a mal­func­tion occurs. They are also char­ac­ter­ized by dura­bil­i­ty and min­i­mal sus­cep­ti­bil­i­ty to defor­ma­tion. For greater effi­cien­cy, devices are equipped with spe­cial con­trollers. They respond to changes in pres­sure, tem­per­a­ture, in the com­po­si­tion of the con­tent, which must remain con­stant.

Shut-Off Valve Selection Guidelines

One of the main cri­te­ria is the speed of response of the device. Espe­cial­ly if the flow of liq­uid or gas occurs under high pres­sure. How­ev­er, this is not the only option. The fol­low­ing is also impor­tant:

  1. Appli­ca­tion area. Under this con­cept, flow­ing sub­stances, their com­po­si­tion, and the degree of aggres­sive­ness are hid­den.
  2. Oper­at­ing con­di­tions include pres­sure and tem­per­a­ture.
  3. Through­put means the cross sec­tion of the line.
  4. Tight­ness. The reli­a­bil­i­ty of the equip­ment depends on this indi­ca­tor.
  5. Strength affects the dura­bil­i­ty of devices.
Cast iron valve

When choos­ing a shut-off valve, design fea­tures and action in one or two direc­tions are tak­en into account. Regard­ing mate­ri­als, not only the body is con­sid­ered, but also gas­kets, seals, seals.

Shut-off valve installation rules

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The lock­ing device is installed accord­ing to the man­u­fac­tur­er’s instruc­tions. Self-instal­la­tion is allowed only for water sup­ply in the pri­vate sec­tor. At the same time, war­ran­ty ser­vice and oper­a­tion of the device may not cor­re­spond to the declared one due to the inex­pe­ri­ence of the installer. There­fore, it would be right to entrust the work to spe­cial­ists.

Mount gate valves in acces­si­ble places for main­te­nance or replace­ment of equip­ment. At the same time, areas in which stag­na­tion and hydraulic “bags” can form should be exclud­ed. There are also rules regard­ing the place:

  • on ver­ti­cal tanks, the upper bot­tom (or on the hel­met tube) is con­sid­ered;
  • on hor­i­zon­tal ones — in the vapor phase zone (the upper gen­er­a­trix of the cylin­der).

An impor­tant point is the exclu­sion of freez­ing of the con­tents of the pipeline in the nodal con­nec­tions. And the cross sec­tion of the branch pipe should be 1.25 times greater than the total anal­o­gous indi­ca­tor rel­a­tive to the valves installed on it.

The ratio of the diam­e­ter of the noz­zle and valve

Operations Expert Tips

Use of equip­ment to con­trol the flow of the con­tents of the main is pro­hib­it­ed. There­fore, the valves must be in the ful­ly open or closed posi­tion. Dur­ing instal­la­tion and main­te­nance work, it is impor­tant to exclude any clog­ging of the inter­nal sur­face of the hous­ing and the ingress of for­eign objects. Oper­a­tion is fea­si­ble only in strict obser­vance of the instruc­tions, anoth­er pur­pose is unac­cept­able.

Moments relat­ed to safe­ty are pre­scribed in GOST 12.2063–2015 and 32569–2013, in the norms estab­lished by orga­ni­za­tions such as Ros­tekhnad­zor, the Cus­toms Union, the Eurasian Com­mis­sion. It is also impor­tant to use per­son­al pro­tec­tive equip­ment. And only trained spe­cial­ists with tol­er­ances are allowed to ser­vice devices, replace them.

Shut-off valves are wide­ly used due to their pur­pose. Thanks to these devices on high­ways, there is a chance to local­ize the con­se­quences of mal­func­tions, cor­rect them and put them back into oper­a­tion. This is true both for util­i­ty net­works and for large-scale pipelines.

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