Had a new chiller installed on the roof of an 80,000 sq ft building. Formally the chiller was in the basement. Subsequently new chilled water piping was installed to the new chiller and welded into place.
The time came for the start up. The mechanic could not get any chilled water flow. The pressures looked ok on either side of the chilled water pump, which was new as well.
Mechanic had came a second time but could not get the chiller started.
Finally a meeting of the engineer, mechanical contractor, and a pump tech to check out the pump. They were thinking that there may be a problem with the impeller. Un-bolted the pump housing and the pump tech checked out the impeller and guess what he found.
A leather glove stuck in the impeller the welders accidentally left in the piping. The glove allowed enough flow through the pump to indicate a higher pressure on the high side of the pump. Just not enough volume. Removed the glove and presto we had the required flow.
Needles to say the mechanical contractor had a little egg on his face.
Just because things are new does not mean that they were installed properly.