BN-SP-K03 Design Specification for the Limitation of Control Valve Noise

Table of Contents

1. General Design Basis
2. Allowable Noise Levels
3. Noise Level Prediction
4. Valve Noise Summary List
5. Remedial Actions
6. Devision of Work

1. General Design Basis

This specification covers the general engineering and design requirements for the limitation of control valve noise.

2. Allowable Noise Levels

In order not to exceed the total allowable noise emission of the entire plant, in general the sound pressure level measured 1 meter from the piping system and 1 meter downstream of the valve shall not exceed 85 dB(A), however, the job requirements will be governing.

3. Noise Level Prediction

To predict the expected sound pressure levels in dB(A) at 1 m downstream of the valve and 1 m away from the bare pipe, the calculated noise value as per the computerized control valve calculation will be applied.

The accuracy of the calculation results is approximately ± 5 dB(A). Therefore, all noise data quoted in this specification shall be considered as to include the plus tolerance of 5 dB(A).

All noise calculations will be made for design through puts only unless the Client specifies otherwise. However, conditions during regeneration have to be taken into account.

The noise figures shall be obtained from the Badger control valve computer print-out. However, the control valve manufacturers also to quote their estimated and guaranteed noise levels in the bidding stage.

For more complicated cases the ISA handbook of control valves chapter 7, “control valve noise” will be applied.

4. Valve Noise Summary List

All valves with a predicted noise level exceeding the allowable noise level, shall be listed on a valve noise summary list.

For certain projects where stringent community noise limits apply, the noise engineer shall indicate from which noise level valves shall be listed.

Following information will appear on this list:

- Tag number

- Fluid

- Type of operation continuous, part-time continuous or discontinuous

- Predicted noise levels in dB(A)

- Type of valve

- Remedial of valve

- Estimated noise level in dB(A) after remedial actions.

5. Remedial Actions

Selection of special low noise valves and/or silencers shall be done in close cooperation with the client to ensure a mutual acceptable solution.

5.1 Gas and Vapor Service

Depending on the highest predicted sound pressure level in dB(A) the following noise reduction measures will be applied, thereby selecting the most economical solution for the individual item.

5.1.1 Predicted Noise Level dB(A)

Apply one layer of normal thermal insulation.

5.1.2 Predicted Noise Level 79-100 dB(A)

- Apply acoustic insulation in accordance with OCMA specification NH6-5, acoustic insulation class A. (Piping only).

- Provide sufficient space against downstream of the valve for the possible later installation of lo-dB plate, if required.

5.1.3 Predicted Noise Level 100-110 dB(A)

- Apply acoustic insulation in accordance with OCMA specification NH6-5, acoustic insulation classes B or C, on the piping system and the valve body.

- Provide sufficient space downstream of the valve for the possible later installation of lo-dB plate, if required.

5.1.4 Predicted Noise Level 110 dB (A)

- Apply a low noise control valve combined with above mentioned acoustic insulation classes B or C on the valve body and piping system, if required.

5.2 Liquid Service

Actual field noise measurements on control valves in liquid service that exceed plant noise limitations, normally show sound pressure levels in the range of 90 to 100 dB(A). Noise levels above 100 dB(A) are rarely encountered.

Since silencers for liquid service are difficult to obtain (few manufacturers) and their actual dampening effects have not been fully proved, these will not be considered as a remedial measure.

Use solid V-port valve trims for liquid service, also when flashing is expected. Do not apply skirt-guided trims.

Avoid butterfly valves on differential pressures in excess of 3.5 bar(g).

Limit the velocity in the outlet flange to 3 m/sec.

5.2.1 Predicted Noise Level 90 dB(A), 100 dB(A):

Apply one layer of normal thermal insulation.

5.2.2 Predicted Noise Level 100 dB(A), 110 dB(a):

Apply accoustic insulation on the piping system, including equipment if any and the valve body.

5.2.3 Predicted Noise Level 110 dB(A)

Apply a low noise control valve

5.3 Flashing Service

Noise of flashing liquids cannot be predicted as no calculation method is available yet.

The Instrument Engineer to judge each individual case and take special measures as deemed necessary.

6. Devision of Work

The Instrument Engineer to prepare the valve noise summary list, and to update this as required.

Company noise specialist to review the list and to complete as required.

Piping Designed to check for which valves special requirements are involved with respect to piping design.