API 673 and Fan

2.4 EXTERNAL FORCES AND MOMENTS
O 2.4.1 Fan housings are generally designed to accept small external forces and moments from the inlet and outlet con- nections. It is the purchaser’s responsibility to specify the external loads to be imposed on the fan housing from the ancillary equipment (ducting, sound trunks, silencers, filters, etc.) if this equipment is not supplied by the fan vendor. The vendor shall design the housing to accept the specified loads such that:
a. Distortion resulting from imposed loads does not affect performance. b. No internal rubs result.

2.4  외력
2.4.1 송풍기의 케이싱은 일반적으로 작은 외력에 대한 입력측과 토출측 연결부를 설계한다. 구매자의 제안에 의해 송풍기의 케이싱에 붙는 송풍기 공급자가 제공하지 않는 부속품( 덕트, 소음통, 소음기, 필터 등)의 외력을 정의해야한다. 공급자는 그 케이싱의 설계를 그 외력 내에서 해야 한다.
  가. 외력에 의해 왜곡된 결과는 성능에 영향이 없어야 한다.
  나. 내부 간섭이 없어야 한다. 

E.2.4 External forces and moments
Fan housings are generally designed for low external forces and moments from the inlet and outlet connections. It shall be the responsibility of the heater vendor to specify on the data sheets the expected external loads to be imposed on the fan housing from the ancillary equipment (that is, ducting, sound trunks, silencers and filters) if this equipment is not supplied by the fan vendor. The fan vendor shall design the housing to accept the specified loads. The following information shall be provided:
a) maximum allowable external forces and moments;
b) expansion joint information and recommendations if joints are required for thermal expansion, vibration isolation or both.