ČSN EN ISO 8659 - Termoplastové armatury - Mez únavy - Zkušební metody

3.6 nominal outside diameter

dn

specified outside diameter, assigned to a nominal size DN

Note 1 to entry: The nominal outside diameter dn of pipes is given in ISO 161-1 and of flange adapters and loose backing flanges in ISO 9624[3].

Apparatus

Test apparatus, capable of testing the whole valve assembly with its obturator mechanism. Furthermore, it shall include appropriate devices to perform each step separately, or continuously and automatically.

The apparatus, when clamping the valve assembly, shall not apply to the valve ends any axial force, nor radial force to the valve stem.

The test apparatus shall include appropriate means to discontinue the test cycle during the pressure period and to maintain the pressure in the closed position.

Pressure gauges shall be accurate to within ±1 % of the full-scale reading.

Temperature sensors shall be accurate to within ±2 °C.

Attention is drawn to the need for adequate safety precautions when using compressed air or gas for this test.

Procedure

Test requirements to be taken from product standards

The following specifications shall be taken from the particular product standard.

a) any tests which shall be performed before the endurance test, and those which shall be repeated after completion of the endurance test;

b) whether tightening of the gland packing (if used) during the endurance test is allowed;

c) acceptance criteria for tests;

d) the number of specimens to be tested;

e) the number of test cycles to be performed;

f) the fluid used for the test, and its temperature, pressure and velocity;

g) the ambient temperature.

Endurance test

The endurance test, using water, air or gas as the fluid medium, at the temperature, pressure and velocity specified in the particular product standard, shall be carried out, at the ambient temperature specified in the product standard, as follows:

a) Open the valve

— for multiple-turn valves to the fully open position at a hand-wheel speed of 40 r/min ± 10 r/min for valves of nominal size up to DN 50 and 20 r/min ± 10 r/min for valves of nominal size greater than DN 50.

— for quarter-turn valves, the opening time shall be not less than 2 s for valves of nominal size up to DN 50 and not less than 4 s for valves of nominal size greater than DN 50.

The valve shall be left in the open position for at least 5 s, but not longer than 20 s.

During opening and closing, there shall be no visible leakage at any seal.

b) Close the valve

— for multiple-turn valves at a hand-wheel speed of 40 r/min ± 10 r/min.

— for quarter-turn valves, the closing time shall be not less than 1 s.

Closing shall be performed using the torque specified in the particular product standard.

During opening and closing, there shall be no visible leakage at any seal.

c) After the valve has been closed, an internal pressure shall be applied as specified in the particular product standard. The valve shall be left in the closed position for at least 5 s, but no longer than 20 s.

d) The valve shall be opened as described in 5.2 a).

e) The test procedure described in 5.2 a) to d) shall be repeated for as many cycles as required by the particular product standard.

Test report

The test report shall include at least the following information:

a) a reference to this document, i.e. ISO 8659, and to the product standard;

b) a complete identification of the valve, giving the following information:

1) the type of valve (ball, butterfly, diaphragm, gate and globe) according to ISO 16135, ISO 16136, ISO 16138, ISO 16139, ISO 21787,

2) the material of the valve body,

3) the nominal size (DN) and the socket diameter or spigot diameter,

4) the nominal pressure (PN) of the valve,

5) the manufacturer's name or trade mark,

6) the type of pipe used,

7) if necessary, the flow direction,

8) the closing torque,

9) the opening torque;

NOTE The opening torque is generally higher in ball, butterfly and gate valves as it is influenced by the wear between obturator and seats and by the maximum pressure difference between upstream and downstream side of the valve; the opening torque is lower in diaphragm and globe valves as the upstream pressure, acting on obturator, reduces the effort exerted to operate the valve.

c) a description of the test conditions;

d) the number of specimens tested;

e) whether the valve complied with the test requirements [if the valve failed (leakage or fracture) indicate under what conditions it failed];

f) any operation not laid down in this document, or other occurrences which may have affected the test results;

g) the date of the test.

Bibliography

[1] ISO/TR 10358, Plastics pipes and fittings — Combined chemical-resistance classification table

[2] ISO 6708:1995, Pipework components — Definition and selection of DN (nominal size)

[3] ISO 9624, Thermoplastics piping systems for fluids under pressure — Flange adapters and loose backing flanges — Mating dimensions