GOST 3845-75

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  ГОСТ 3845-75

GOST 3845−75 Pipe metal. Test method hydraulic pressure (with Amendments No. 1, 2)

GOST 3845−75

Group В69

INTERSTATE STANDARD

PIPE METAL

Test method hydraulic pressure

Metallic tubes. Hydraulic pressure testing method

ISS 23.040.10
AXTU 1909

Date of introduction 1977−01−01

The decision of the State standards Committee of the Council of Ministers of the USSR from 30.12.75 N 4102 date of introduction is established 01.01.77

Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)

REPLACE GOST 3845−65

EDITION (September, 2010) with Changes No. 1, 2 approved in April 1980 and October 1986 (ICS 5−80, 1−87)


This standard applies to pipes of steel, cast iron, non-ferrous metals and sets the method of testing their internal hydraulic pressure to test the strength and density of the base metal of pipes and welded seams.

The standard fully complies ST SEV 480−77 in part of the hydraulic pressure test.

(Changed edition, Rev. N 1).

1. EQUIPMENT AND APPARATUS

Hydraulic press of any design, providing testing in accordance with the requirements of this standard.

The gauges of the 1st class of accuracy- to control the test pressure when testing extremely thin-walled tubes (0.01 when 102 mm); the pressure is not below the accuracy class of 2.5 — when testing other pipes.

2. PREPARATION AND TESTING

2.1. The greatest value of the test pressure is calculated according to the formulas given below.

2.1.1. The highest test pressure for round monometallic seamless pipes with diameter up to 550 mm and welded pipes with a diameter up to 480 mm inclusive (), MPa (kgf/cm), and (), MPa (kgf/cm), calculated by the formula:

;

(1)

;

;

(2)

,

where  — the minimum (subject to a minus tolerance) wall thickness of pipe, mm;

 — nominal outside diameter of pipe, mm;

 — allowable stress in pipe wall during the test, MPa (kgs/mm);

 — calculated pipe diameter, mm, which can be used:

outer diameter (casing and tubing),

the average diameter (seamless, including boilers, certapay and welded pipes with attitude ).

Formula (2) are used for seamless, including boilers, certapay and welded pipes with attitude.

2.1.2. The value of the test pressure or design formula (or link to it) and allowable stress point in the normative-technical documentation for specific product.

2.1.3. The greatest pressure () MPa (kgf/cm), for bi-metal circular pipes is calculated by the formula:

;

(3)

,

where  — the allowable stress for the metal inner and outer layers, MPa (kgf/mm), set standards for the respective types of pipes;

 — the thickness of the inner layer of metal, mm. When calculating the test pressure when in the formula (3) is substituted for most (including plus tolerance) of the thickness of the inner layer. Provided that , in formula (3) is inserted to the smallest (including negative tolerance) thickness of the inner layer.

If the allowable stress of each layer separately is unknown, the calculation of the test pressure for bimetallic tubes is carried out according to the formulas (1) substitution and average allowable stress.

2.1.1−2.1.3. (Changed edition, Rev. N 2).

2.1.4. The highest test pressure for welded pipes with diameter of 530 mm or more calculated by formulas (1) substitution .

Calculation of test pressure () MPa (kgf/cm) under the test pipes on presses of various designs with axial support is carried out according to the formula (4), which is equivalent to the test pressure without axial pressurization :

;

(4)

,

where  — coefficient taking into account the bending stresses that occur under the action of the mass of the tube and fill liquid;

,

 — greatest distance between the supports holding the pipe during hydrotesting, or maximum pipe length in the absence of supports, m;

 — coefficient taking into account the axial backwater, dependent on the method of sealing the cavity of the welded pipe at the time the hydraulic pressure test equal to:

for presses with mechanical resistant seal

,

for presses with rotary shaft seal with tracking

,

for presses with mechanical seal spacer

,

where is 0.07 — factor, which guarantees sealing of the internal volume of the pipe;

the inside diameter of the movable part of the sealing head press, mm.

the diameter of the Central cylinder of water flow, mm.

When testing double-layer pipe as a minimum wall thickness in the formula (1), (4) substituted the total thickness of layers given the total negative tolerance.

(Changed edition, Rev. N 1, 2).

2.2. The greatest value of the test pressure for profile, roll-formed and cast-iron pipes set in the standards for the respective types of pipes.

2.3. As filler, transmitting the pressure on the pipe wall, use water, emulsion or other liquid.

2.4. Before the test, the air from the tube should be squeezed out of the filling liquid.

2.5. The pressure increase during the test all pipes and discharge pressure when testing extremely thin-walled tubes (0.01 when 102 mm) produce smoothly (without hydraulic shocks).

2.6. The time of exposure of the pipes under the test pressure set the standards for the respective types of pipes.

2.7. Welded steel pipes with diameter of 530 mm and more, as well as cast iron pipe of all sizes during their exposure at the test pressure should be mechanized to obestochivaete hammers or rollers with a mass of 0.5−0.8 kg. By agreement between the consumer and the manufacturer obstaravanie may be omitted.

3. PROCESSING OF THE RESULTS

3.1. Pipe shall be deemed satisfactory if, when tested, will not be visually detected leak of a working liquid and, after the test, permanent deformation (buckling) of the wall that shows the pipe diameter for maximum deviations.

4. TEST REPORT

In the test report indicate:

— material and size of pipe;

— the results obtained.

(Added, Rev. N 1).