Safety classes

In addition to general-purpose valves, PromArm supplies industrial valves for nuclear industry enterprises.

The basic regulating document that specifies requirements for industrial valve manufacture is ‘Federal rules and regulations in nuclear energy use (НП-068-05) ‘Industrial valves for nuclear power stations. General technical requirements’. In accordance with the document, valves for nuclear power stations (NPS) are divided into four safety classes (refer to Table 1).

Table 1 – Classification of industrial valves by function and operating conditions.

Classified designation Design pressure, MPa Function and operating conditions
Up to 25 Valves included in Group A (according to ‘Rules for arrangement and safe operation’)
2ВIIа Above 5 Valves included in Group B (according to ‘Rules for arrangement and safe operation’), working in contact with coolant whose activity is equal to 3.7x105 Bq/l or higher or where coolant activity is below 3.7x105 Bq/l, but the valve is inaccessible while the reactor is in operation
2ВIIв Up to 5
2ВIIIа Above 5 Valves included in Group B (according to ‘Rules for arrangement and safe operation’), working in contact with coolant whose activity is below 3.7x105 Bq/l, and the valve is accessible while the reactor is in operation.
2ВIIIв Above 1,7 до 5
2ВIIIс Up to 1.7 and below atmospheric pressure (under vacuum)
3СIIIа Above 5   Valves included in Group C (according to ‘Rules for arrangement and safe operation’)
3СIIIв Above 1,7 до 5
3СIIIс Up to 1.7 and below atmospheric pressure (under vacuum)

Safety class 2 comprises the following parts of the NPS:

- parts whose failure results in damage;

- safety system parts whose single failure causes complete failure of the system.

Safety class 3 includes the following parts of the NPS:

- safety-related systems, not included in classes 1 and 2 according to ‘Basic safety rules for nuclear plants (ОПБ-88/97)’;

- parts containing radioactive materials released to the environment upon failure in amounts exceeding those stated in radiation safety standards.

Industrial valves included in classes 2 and 3 are manufactured in accordance with ‘Basic safety rules for nuclear plants (ОПБ-88/97)’ and ‘Federal rules and regulations in nuclear energy use (НП-068-05)’.

Safety class 4 comprises reactor components, necessary for normal operation, which do not affect safety and are not included into classes 1, 2, and 3. Industrial valves that fall into class 4 are manufactured in accordance with safety requirements НП-001-97 and technical requirements НП-068-05.

Manufacturers of industrial valves for nuclear power stations confirm the quality of their production with construction permit and manufacturing license for nuclear facility equipment.

Industrial valves are constructed in accordance with different requirements depending on the safety class.

Gate leak tightness of the valves included in groups A, B, C (according to ‘Rules for arrangement and safe operation’) must conform to classes A, B or C for nominal diameters below 300 mm and to classes B, C, D for nominal diameters above 300 mm and for the valves fitted with solenoid actuators.

Valves included in classes А, 2ВII, 2ВIII are installed under such conditions that unintended movement of their closure member can affect nuclear power station safety. That is why such valves must contain a gate position indicator included in the information and computer system that connects all the valves.

Safety valves related to classes 1А, 2ВIIа, 2ВIIв must not contain gland packing for the stem.

Besides, valves of different safety classes are subjected to different kinds of material tests. For example, valves included in groups 1А, 2ВIIа, 2ВIIв, 2ВIIIа, 2ВIIIв, 2ВIIIс, 3СIIIа are not subjected to hot tensile tests, critical brittle point verification, or ultrasonic inspection. While analysis of nonmetallic content in corrosion-resistant steel is applicable only to valves included in safety classes 1 and 2.

To estimate the cost of industrial valves for NPS you should complete requirements specifications in accordance with the standard НП-068-05.

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