Page 16 - Clothesline - November 2020

PAGE 16 / NATIONAL CLOTHESLINE / NOVEMBER, 2020

WRENCH WORKS

BY BRUCE GROSSMAN

Troubleshooting boilers gone bad II

ou may recall that last wanted solids clog pipes,
month our discussion valves and boiler tubes. A 6<037206 2) ,03523(5 %2,/(5 :$7(5 75($70(17
Ywas about pressure pro- properly operating make up
posing (steam pressure regu- water valve (ball float valve),
larly falls between normal soft water and boiler com-
operating pressure and a lower pound are all essential in con-
7<3,&$/ $&,' ,1'8&(' &25526,21 &$86(' %<
pressure like 30-40 PSIG). trolling these twin bogeys. ,03523(5 &21&(175$7,21 2) %2,/(5 &203281'
Space limitations did not allow What follow are the most com- ,1 7+( )((':$7(5
the “cures” for this family of mon causes of return pump
boiler malfunctions. cavitation.
This month we will be look- 1. The most frequent cause
ing at how to determine what’s of vapor lock pump cavitation

causing this problem. First let’s is probably faulty check
take the easier cause to fix valves. Check valves allow flu- /226( &203281' )((' 78%( 63,//,1* &203281'
29(5 7+( 723 2) 5(7851 7$1. &2552',1* 0(7$/
which is vapor lock. To review, ids (water in this case) to flow
vapor lock or “pump cavita- in only one direction only. The
tion” (the more scientific direction in this case would be
name) is when bubbles of from the return pump into the
vapor form between the impel- boiler. Scale and debris in the
lor (rotating part of pump) and piping and return tank often
raceway (stationery part of break off and prevent these
pump) preventing the pump valves from shutting com-
from pushing water under pletely. When this occurs pres- 727$//< %/2&.(' %2,/(5 '$1*(5286 $02817 2) 6&$/,1* '8( 72
/2$' 2) 6&$/( $7
pressure into the boiler. The surized water in the boiler 7+( 23(1 +$1' +2/( 78%( 7+$7 $&78$//< ,168)),&,(17 &203281' &21&(175$7,21
&$86(' %< /($.(< %$// )/2$7 9$/9(
root cause of rapidly develop- (remember this water is above 21 $ 78%(/(66 %2,/(5 583785(' '8( 72
29(5+($7,1*
ing valve and piping failure is the normal boiling point be-
usually leaking make-up water cause it is under pressure) is piping. Piping between the re- using a wire brush and/or allowing a continuous flow of
valves (ball float valves). forced back through the turn tank and boiler will be emery cloth or flush with steam back into the return tank
This type of valve uses a boiler’s water inlet piping into very hot (spit will evaporate in descaling compound (my rec- thereby raising the water tem-
ball-shaped float to control the the pump. a second on these pipes when ommendation is to replace the perature to a point where the
addition of new water into the Outside the boiler the super- the check valves fail and re- vales annually instead of try- pump becomes ineffective; the

return tank maintaining the heated water, under less pres- member the finger tip rule ing to repair them). Be pre- mechanical action of the pump
proper water level in the tank. sure than it was in the boiler from last month). pared to discover a lot of and extra heat supplied by the
When these valves leak, as flashes (boils off) into steam You must shut off the boiler damaged piping when you pump motor are enough to
they often do, untreated oxy- while inside the pump, hence and blow down until there is start repairs in this area so push the water in the pump to

gen-rich water containing high vapor lock. Vapor lock pre- no boiler pressure! Do not do make sure when you tackle the the boiling point. Viola! Vapor
levels of scale forming com- vents the pump from pushing any repairs on a boiler under job any pipe nipples or other lock by another route.
pounds continuously bleed more water into the boiler pressure under any circum- parts are available if you re- If there are several traps
into the return tank. Oxygen in which will eventually shut stance! quire them. blowing through there will be
the newly added water com- down on a low water level When the boiler has no pres- 2. Another cause of vapor a continuous stream of steam
bines with carbon dioxide to error. You can often identify sure left you can disassemble lock pump cavitation is exces- from the return tank vent on

form carbonic acid which cor- this problem by a violent the check valves (you might as sive temperature in the return the roof. An easy way to trou-
rodes metal components and knocking sound coming from well do them all) clean out any tank. This is generally the re- bleshoot this problem is to get
piping. High levels of scale the return tank as well as obvi- debris from the valve and any sult of steam traps sticking a bag of ice and place it on the
forming salts and other un- ous vibration of the tank and scale from the valve parts open (blowing through) and pump (not the pump motor
but the pump where the pip-
ing is). Also, if you have access
to the make-up water valve
you can add cold water to the
tank itself. Within a minute or
WANT TO IMPROVE move water into the boiler. Ob-
two the pump will begin to

viously if this is the problem
YOUR PLANT’S you need to find and repair the
faulty steam traps.
Bruce Grossman is the chief of
R&D for EZtimers Manufactur-
PRODUCTIVITY? ing, the manufacturer of the Tat-
tler steam trap tester; Drop In
The Bucket and Sahara line of
high purity separator water mis-
ter/evaporators and the new EZ
Level line of return tank level
and temperature controllers. The
CONTACT DON DESROSIERS EZ Level replaces the problem-
Over 40 years of experience in dry clean operations, atic ball-float valve in your boil-
work昀ow engineering and management consulting ers’ return tank, helping to
means that you will be in good hands! Solutions for eliminate boiler damage and lost
all types of plant operations; bar codes, automated production caused by boiler
assembly and conventional tag systems. down time. See our ad in this
issue and for further information
617.207.5218 I TAILWINDSYSTEMS.COM on the EZtimers product line or
visit www.eztimers.com. Ad-
dress any questions or com-
ments to [email protected]
or call (702) 376-6693.
To learn more, visit www.natclo.com/ads