Rapidly Estimate Steam Losses Through Traps

A simple predictive tool shows good agreement with reported data.

By Alireza Bahadori and Hari B. Vuthaluru, Curtin University

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AN EXAMPLE
Contact pyrometer measurements taken immediately upstream and downstream of a steam trap on a 1,136-kPa (abs) steam line indicate it's blowing live steam. The catalog rating of the trap at that pressure is 2,270 kg/h at saturation temperature (255.4 K sub-cooled). So:

a = 8.0217665022 (from Eq. 2);
b = -1.453738401 × 103 (from Eq. 3);
c = 4.301678566 × 105 (from Eq. 4); and
d = -4.40231517 × 107 (from Eq. 5).

Therefore, condensate flow rate = 1,147.4389 × 103 kg/h (from Eq. 1).

The flow factor is:

FC= 2,270/1,147.44 = 1.9783 (from Eq. 6).

Equation 7 then gives 190 kg/h steam flow. For the trap in question, assuming a rather modest steam cost of $3 per thousand kg, the loss of steam is estimated to cost:

190/1,000($3) = $0.57/h or $113/wk.

The results show good agreement with the $117/week from Branan.

SIMPLE AND USEFUL
We have introduced a method that's superior in accuracy and ease of use. Relevant coefficients can be re-tuned quickly for various cases and if new data become available. This predictive tool enables process engineers to easily monitor steam loss for a wide variety of operating conditions. It also should immensely help combustion engineers estimate the total amount of heat recoverable from boilers using blowdown systems. The method should speed analysis of design and operational modifications.


ALIREZA BAHADORI is a postgraduate student in the School of Chemical and Petroleum Engineering, Curtin University, Perth, Australia. HARI B. VUTHALURU is an associate professor in the School of Chemical and Petroleum Engineering, Curtin University, Perth, Australia. E-mail them at alirez.bahadori@postgrad.curtin.edu.au and H.Vuthaluru@curtin.edu.au.

NOMENCLATURE
A -- Tuned coefficient
a -- Coefficient
B -- Tuned coefficient
b -- Coefficient
C -- Tuned coefficient
c -- Coefficient
CV -- Flow capability
D -- Tuned coefficient
d -- Coefficient
F -- Corrected flow factor
P -- Trap inlet pressure or steam line pressure, kPa (abs)
Q -- Condensate flow rate, kg/h
QC -- Catalog flow rating of trap, kg/h
SA -- Actual steam loss, kg/h
T -- Temperature, K
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