Welding Inspection & Metallurgy API ICP Self Study Notes

If the normal flow of liquids exceeds these values or if the flow cools the metal
to below dew point, it is advisable to compensate by preheating the weld area
to at least 70°F (20°C) and maintaining that temperature until the weld has
been completed. High liquid flow may cause rapid cooling of the weld area
during the welding, creating hard zones susceptible to cracking. Under these
circumstances, the minimum interpass temperatures may not be attainable,
resulting in undesirable material properties.