Metallurgical Principles and Practice of Engineering (PE) Study Guide: Question #49

It Is the Policy of The Minerals, Metals & Materials Society (TMS) to Encourage the Professional Registration of Metallurgical Engineers.
A carbon steel tank was "hydrotested" (pressure tested using water as the pressurizing medium) to 50 psig (345 kPa gage pressure). The tank had work performed on some of the inside baffles prior to testing, and the hydrotest was conducted immediately after the work was finished to make up for some previous lost time on the project schedule. The test lasted for about 4 hours and was conducted at ambient temperature of 70ºF (21C). The tank passed the pressure test. When the test water was drained out of the tank, it was tinted light reddish-brown and contained spots of rusty material along with dark flakes. The water was taken from the municipal water supply, which is chlorinated. High-pressure flexible hoses rated at 180ºF (82ºC) similar to those used in washing machines and dishwashers, only larger, were used to connect the tank to the water supply. Select the most likely cause of the discoloration and foreign material.

(A)	The inside walls of the tank corroded during the hydrotest.
(B)	The cause of the corrosion was microbial induced corrosion from bacteria in the hydrotesting water.
(C)	The connecting hoses deteriorated during the tank fill and released material to the testing water.
(D)	The tank was not properly cleaned before hydrotesting, and the observed material was slag, scale, and rust from welding and grinding inside the tank.

The information on this page is maintained by the Nellie Luther (natale@tms.org).

Search PE Study Guide TMS Education Page About TMS TMS OnLine