BS ISO 21905:2020 Gas turbine exhaust systems with or without waste heat recovery.
8.8 Noise emission and silencing
a) Where specified by the purchaser, supplier shall include the required silencing measures that are needed as part of the exhaust system in order to meet the overall noise emission requirements sped lied by the purchaser.
It is recommended that the silencer is supplied as part of the exhaust system scope in order to ensure the overall system is optimised, with respect to silencer location, pressure drop and mechanical design.
The purchaser is responsible for specifying noise emission data at the turbine exhaust.
b) Where specified by the purchaser silencer elements shall be replaceable without hot work. This should involve oversized access doors and/or silencer panels in bolt-together sections. Access doors shall be installed upstream and downstream of each silencer, to permit the removal/replacement of the silencing panels and/or any other component that needs maintenance.
c) Site measurement verification shall be in accordance with ISO 3744 or where needed ISO 9614 for duct wall emissions and ISO 10494 for exhaust stack sound power level.
d) If other noise control measures such as acoustic enclosures are required, they should not in any case obstruct operational or routine maintenance activities.
e) If acoustic enclosures are proposed, prior approval of the purchaser shall be obtained for their construction, materials and access requirements.
1) Acoustic insulation of pipes, valves and flanges as necessary to meet the noise level requirements should be agreed with the purchaser.
g) For cold casing systems, no acoustic insulation shall be fitted on the casing outside to meet the noise requirements.
a) Self-supported stacks greater than 4 outside diameters long shall be designed according to a recognised stack design standard (such as CICIND, ASME STS-01 or other stack design code). The supplier and purchaser should agree which code is to be applied.
b) The purchase is responsible for specifying any minimum stack length or discharge height above an agreed datum.
c) The exhaust gas can reach nearby equipment, working areas or interfere with helicopter traffic. The purchaser is responsible for evaluating the impact of such effects of the exhaust gas plume in determining the required stack height.
NOTE A plume cooling device which induces air to mix with the turbine exhaust gas prior to leaving the stack can be considered to mitigate exhaust gas impingement on adjacent equipment, personnel or helicopter traffic.BS ISO 21905 pdf download.