Question of the Month: 2011

Question of the Month for December 2011

Write the formula for evaluation of boiler efficiency by direct method.

Answer; Boiler Efficency, % = Q X (H – h) X 100




Q = Steam flow rate in kg/hr h = Enthalpy of fed water kcal/kg
H = Steam enthalpy in kcal/kg q = fuel firing rate kg/hr
GCV = Gross calorific value of fuel, kcal/kg

Question of the Month for November 2011

Where can I find information about Section IV, Tube sheet Ferules “O” rings with regards to making repairs?

Answer: The only place ferules or “O” rings are mentioned for tube to tube sheet attachments is ASME Section IV, New Construction – HG 360.2.

Question of the Month for October 2011

What are the Wisconsin requirements for ammonia refrigeration pressure relief replacement?


Comm 45.35 (3) states “reliefs shall be replaced in accordance with manufacturers’ recommendations but not to exceed 5 years from the date of installation.” See Comm 45 PDF online.

Comm 45.35 (3) AMMONIA DISCHARGE. This is a department rule in addition to the requirements in IMC section 1105.8: Pressure relief valves for ammonia systems shall be replaced in accordance with manufacturer’s recommendations but not to exceed five years from the date of installation. In lieu of the expiration date, a relief valve may be used for a total of 5 five years if a record is maintained of when it was installed and it was not over two years old at the time of installation.

Question of the Month for September 2011

A company has two boilers – a Johnston with two safety relief valves rated at 200 psi, and a Nebraska with one safety valve rated at 160 psi and the other at 165 psi. The boilers are tied to a common header, but only one boiler is in service at a time. Do both boilers have to have safety valves rated at the same psi?


National Board Inspection Code – 2007 Edition, Part2, Section says if boilers are piped together with maximum allowable working pressure differing by more than six percent, additional protective devices may be required on the lower pressure units to protect them from overpressure from the higher pressure unit.