Assumption of the weld record: SMAW;preheat temperature roomT(≥20℃);interpass temperature≤200℃.
The qualified range of the temperature in accordance with QW-403.1&QW-403.3 : preheat temperature ≥-35℃ (decrease of more than 55℃);interpass temperature≤255℃ (increase of more than 55℃).
Is that OK?

Dear kimishen,
Theoretical you have read the Code in the correct way, but you will never find somebody using this bandwidth.
Regards
Marcel

As a general Engg practice, preheat should not go below 10 deg.C, unless note under Table UCS56 or Appendix R is applicable for Sec VIII div 1 vesels
to maintain min preheat,
QW406.1 limits given because for e.g If your PQr is qualified with 100 deg.C preheat, in WPS you should write min pre heat as 45 deg.c and above.

_________________
Raghuram

The minimun temperature shall be specified in WPS,
When Subcommitee IX developed QW406.1, There was no tolerance in the range of preheat which could be used, based upon value recorded on the PQR. The preheat used on the PQR was the minimum preheat temperature which the PQR was allowed to support.
Code users commented that when they needed a 200°F preheat on their WPS, they established a 200°F preheat on their PQR, but actual PQR result varied above 200°F, pass after pass. Therefore, to allow for a normal tolerance, the variable was changed to state:
"A decrease of more than 100°F in the preheat temperature qualified"
The phrase "In the preheat temperature qualified" means the preheat temperature based on the actual temperature used during of the PQR test cupon. If a PQR test cupon is welded, starting with a 250°F preheat, and during the welding on the test cupon the actual preheat temperature rose steadily within normal tolerance of not more than 100°F, trhe WPS should specify a preheat of 250°F minimum, even though some actual preheat temperature may have reached, for example, 275°F or 325°F.

Regard.
CWI Dayanara

Hi everybody,

please don’t forget ASME IX is a reference code only. That means a WPS has to meet the requirements of ASME IX as well as the requirements of the design code which has referenced ASME IX.
E. g. if the design code is ASME VIII/1 the minimum preheat temperature is 15 °C acc. to UW-30.

_________________
Kind regards,
Juergen Fleischfresser