Technical characteristics of cast iron sewer pipes

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In the last cou­ple of decades, var­i­ous types of plas­tic prod­ucts have been active­ly replac­ing met­al prod­ucts from the mar­ket. But due to their dura­bil­i­ty, excel­lent hydraulic prop­er­ties and anti-cor­ro­sion resis­tance, cast-iron lines con­tin­ue to be wide­ly used for lay­ing strate­gic under­ground util­i­ties. They well with­stand the load on the sew­er net­works in places where drain mech­a­nisms are most active­ly used. In addi­tion, cast-iron sew­er pipes have a much longer ser­vice life than plas­tic ones.

Sew­er­age prod­ucts

Cast iron pipes for sewer installation

In the process of con­struc­tion of any struc­ture, it is imper­a­tive to car­ry out a set of works on lay­ing main under­ground com­mu­ni­ca­tions. Among the sys­tems that are part of them is sew­er­age. It is the bet­ter and more durable, the bet­ter the semi-fin­ished prod­ucts used dur­ing instal­la­tion. Access to the under­ground part of com­mu­ni­ca­tion facil­i­ties is often dif­fi­cult. There­fore, they should be made of durable and resis­tant mate­r­i­al.

The most suit­able mate­r­i­al for the instal­la­tion of under­ground sew­er­age is cast iron. It is per­fect for sew­er drains of enter­pris­es whose activ­i­ties are due to large hydraulic loads:

  • meat pro­cess­ing plants, dairies and poul­try farms;
  • cater­ing shops;
  • farms and slaugh­ter­hous­es;
  • health­care insti­tu­tions.

Cast iron, an iron-based alloy with a high (above 2%) car­bon con­tent, is smelt­ed using var­i­ous tech­nolo­gies. Four types of fin­ished met­al are used for draw­ing:

  1. Grey. It con­tains lamel­lar graphite.
  2. White. Car­bon in the crys­tal lat­tice of the cooled met­al is in a bound state.
  3. High strength. Con­tains graphite in the form of micro­scop­ic spher­i­cal mol­e­cules.
  4. Mal­leable. This grade is most often sub­ject­ed to redis­tri­b­u­tion, so graphite has the appear­ance of eas­i­ly destroyed flakes.

The least pop­u­lar are prod­ucts with the Che­ka mark­ing, made of nodu­lar graphite. The tech­nique involves manda­to­ry pas­si­va­tion with cement to form a thin sil­i­cone film. Prod­ucts are used for sew­er­age in places where aggres­sive fecal liq­uids are dis­charged. Their cost is very high, and the lev­el of demand, on the con­trary, is extreme­ly low.

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The qual­i­ty of pipe man­u­fac­tur­ing is ensured sub­ject to the require­ments for the pour­ing process. It is done in three ways:

  1. semi-con­tin­u­ous. It con­sists in the grad­ual pour­ing of molten iron into the mold and its grad­ual solid­i­fi­ca­tion. Next, the not com­plete­ly frozen met­al is drawn into pipes and cut to size.
  2. Cen­trifu­gal. Liq­uid iron is poured into rotat­ing molds. After pour­ing, the cast iron cools down com­plete­ly. To avoid the appear­ance of lay­ers and sur­face defects, the max­i­mum devi­a­tion of the wall thick­ness should not exceed 2 mm. One of the vari­eties of this method is the mod­ern method called De Lavo cast­ing.
  3. Cast­ing in a mold. For smelt­ing pig iron, a spe­cial­ly made form of sand (chill mold) is used. Sand, clay, sodi­um sil­i­cate and oth­er sub­stances are used to bind sand.

To coun­ter­act cor­ro­sion, the pipes are coat­ed with a spe­cial com­pound.

Under­ground pres­sure sew­er com­mu­ni­ca­tions

Cast iron product range

For the man­u­fac­ture of prod­ucts of var­i­ous diam­e­ters used for the instal­la­tion of main sew­ers, gray cast iron is the most suit­able in terms of com­po­si­tion and prop­er­ties. The require­ments of GOST 6942–98 estab­lish three types of nom­i­nal pas­sages. This is how the table looks like, accord­ing to which it is pos­si­ble to deter­mine the diam­e­ters of sew­er pipes of var­i­ous lengths:

Diam­e­ter

(con­di­tion­al pass),

mm

wall thick­ness,

mm

Length,

mm

Weight,

kg

fifty 4.0 750 4.5
1000 5.8
2000 11.0
100 4.5 750 10.5
1000 13.9
1250 16.1
2000 24.9
2100 26.0
2200 27.1
150 5.0 750 15.7
1000 20.7
2000 39.6
2100 41.5
2200 43.4

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GOST tables allow you to deter­mine only the approx­i­mate weight of the pipes. The actu­al dimen­sions of cast-iron main sew­er pipes can vary by up to 5% in one direc­tion or anoth­er.

Depend­ing on the instal­la­tion method (chan­nel and non-chan­nel lay­ing by flange or sock­et method), prod­ucts can be man­u­fac­tured and sup­plied to cus­tomers with or with­out sock­ets, as well as longer lengths than estab­lished by the require­ments of GOST.

Cast iron sew­er pipes with a diam­e­ter of 100 mm and 150 mm

Pres­sure sew­er lines are made of cast iron cast­ings with an inter­nal diam­e­ter of 65 to 1000 mm, with a wall thick­ness of 6.7 to 22.5 mm. They are much stronger than those used in the upper com­mu­ni­ca­tion block and can with­stand inter­nal pres­sure up to 1.0 kgf / cm2. When oper­at­ing such prod­ucts, there is one pre­req­ui­site: cast iron prod­ucts can­not be sub­ject­ed to shock loads due to the brit­tle­ness of the met­al asso­ci­at­ed with a high car­bon con­tent in the chem­i­cal com­po­si­tion. Anoth­er dis­ad­van­tage of cast iron prod­ucts is their large mass. This can cause some dif­fi­cul­ties in the process of installing trunk com­mu­ni­ca­tions.

The most pop­u­lar are main pipes 3 m long and sock­et pipes — for sew­er out­let branch­es and sup­ply lines to build­ings and struc­tures:

Mark­ing Type of Length,

mm

Price

for a unit,

rub.

SML 50 sock­et­less 3000 2469
SML 100 sock­et­less 3000 3 840
SML 150 sock­et­less 3000 6 867
50 GOST 6942–98 bell-shaped 2000 1499
100 GOST 6942–98 bell-shaped 2000–2100 2387
100 GOST 6942–98 bell-shaped 2000 4 369

Accord­ing to the type of sock­et con­nec­tions, prod­ucts are divid­ed into three class­es — A, B, and LA.

The inter­nal arrange­ment of the sew­er pipe

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Mark­ing on sew­er pipes made of cast iron ChK or VChShG is applied to their fit­tings. Indeli­ble paint is used for appli­ca­tion. The place of mark­ing is the end or reverse side of the sock­et. After read­ing the imprint, the buy­er can find out the fol­low­ing infor­ma­tion about the prod­uct:

  • man­u­fac­tur­er’s trade­mark;
  • des­ig­na­tion char­ac­ter­iz­ing the prod­uct;
  • man­u­fac­tur­ing stan­dard.

Pack­ing of pipes from which the main sewage sys­tem is mount­ed is car­ried out in three ways:

  • batch;
  • cas­sette;
  • lig­a­men­tous.

Cast iron prod­ucts, with all the mass of advan­tages, have one sig­nif­i­cant draw­back. The met­al is not bend­able, so the instal­la­tion of tran­si­tions and turns of high­ways requires the use of var­i­ous addi­tion­al ele­ments. They are called fit­tings. Fin­ished prod­ucts man­u­fac­tured using mod­ern tech­nolo­gies have improved mechan­i­cal prop­er­ties. In par­tic­u­lar, to increase the abil­i­ty to bend, mod­i­fi­er sub­stances are intro­duced into the com­po­si­tion of cast iron dur­ing crys­tal­liza­tion.

Shaped parts of cast iron sew­er pipes

Sep­a­rate­ly, on pal­lets with box­es or in con­tain­ers, fit­tings for sew­er instal­la­tion are laid:

  • fit­ting;
  • tran­si­tions;
  • cross­es;
  • noz­zles;
  • indents;
  • bends;
  • tees.

Anoth­er ele­ment, called revi­sion, is used to clean clogged parts of high­ways.

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Operational properties

Plas­tic, with all its undoubt­ed advan­tages and low price, is not able to with­stand such gigan­tic loads. There­fore, it is not used for the instal­la­tion of pres­sure sew­ers. Due to the thick walls, cast iron prod­ucts have min­i­mal noise char­ac­ter­is­tics. The aver­age ser­vice life of cast iron main sew­er pipes is more than half a cen­tu­ry. If the oper­at­ing con­di­tions are observed and time­ly pre­ven­tive main­te­nance is car­ried out, it is pos­si­ble to increase the max­i­mum ser­vice life of main com­mu­ni­ca­tions up to 80–100 years.

This is facil­i­tat­ed by the high per­for­mance of cast iron prod­ucts:

  • resis­tance to the for­ma­tion of a cor­ro­sion film on the sur­face;
  • high rate of resis­tance to lin­ear stretch­ing;
  • excel­lent sound-absorb­ing prop­er­ties;
  • immu­ni­ty to sharp fluc­tu­a­tions in ambi­ent tem­per­a­ture;
  • small coef­fi­cient of ther­mal expan­sion.

In addi­tion to the above prop­er­ties, fin­ished cast iron cast­ings are free of seams, cracks and crevices. This caus­es an extreme­ly high resis­tance of prod­ucts for the instal­la­tion of sew­ers to phys­i­cal wear. There­fore, in the near future, a mas­sive tran­si­tion is hard­ly expect­ed dur­ing the instal­la­tion of sewage from a cast-iron pipe to a plas­tic one.

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