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water

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it's a familiar sound nearly everyone

has heard

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in their own home when someone slams of

awesome clubs

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you probably also heard it coming from

radiators during the winter heating

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season

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in industrial situations

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a water hammers more than just a noisy

anoint

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water hammer that results from localized

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abrupt pressure drops may never be heard

yet water hammer can acquire

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great force damaging equipment room

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product and potentially putting

personnel everest

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water hammer begins when

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some force accelerates a column of water

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along an enclosed packs the

incompressible nature

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water gives it the powerful steel slab

as it slams into elbows

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to use and valves the resulting

vibrations are transmitted

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along the water column and pipe damaging

fittings and equipment

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far removed from the problem solvers

water hammer can occur in

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any water supply pot or call and its

effects

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can be even more pronounced in by phase

systems

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by phase systems contain both come and

say

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and live or flash steam in the same

space

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heat exchangers tracer lines steam

maynes

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condensate return lines and in some

cases pump discharge lines

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may contain up by phase mix three

distinct conditions have been identified

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which provide the force that initiates

water him these conditions

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hydraulic shock thermal shock and

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differential shop are common too many

industrial fluid applications

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however following a few simple

guidelines will help you minimize the

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occurrence that these shocks

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and diminish the chances damaging water

him

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hydraulic shock

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occurs when a valve is closed to

abruptly

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when water valve is open a solid column

water moves from its source

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at the main to the Val public this could

be a hundred pounds of water flowing at

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ten feet per second

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or about seven miles per hour closing

the valve

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suddenly is like trying to instantly

stop a 100 pound hammer

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a shock wave about 600 PSI

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slams into the valve and rebounds in all

directions

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expanding the piping and reflecting back

and forth

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along the length of the system until its

momentum is dissipated by closing the

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valve

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slowly the velocity of the water is

reduced before the column is stopped

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since the momentum of the water is

decreased gradually

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damaging water hammer will not be

produced sometimes

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check valves can produce hydraulic shock

swing check valves

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are often used to prevent liquid being

drawn into spaces that are subject to

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intermittent vacuums

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they're also applied to prevent back

flow from

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elevated systems when adequate pressure

to raise the liquid cannot be guaranteed

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in either case the acceleration up the

reversing column of liquid

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may be quite high if the swing line for

the check valve is sufficient

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the column will build enough inertia to

cause hydraulic shock

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in the time it takes the valve to slam

shot substitute silent

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or non slam check valves per swing

checks

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00:03:37,031 --> 00:03:42,075

to prevent water hammer in these

situations silent check valves are

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Center guided

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to provide a much shorter stroke then

swing checks

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these valves also use a spring to help

in closing

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the result is that silent check valves

are closed by the law substring pressure

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rather than the reversal of law

preventing hydraulic shock

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water hammer arrestors have correctly

sized

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placed and maintained will reduce water

hammer

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when the forward motion of the water

column is stopped by the valve

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part of the reversing column is forced

into the water hammer arrestor

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the water chamber up the arrester expand

to rate controlled by the pressure

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chamber

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gradually slowing the column and

preventing hydraulic shock

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to prevent water hammer due to hydraulic

shock avoid

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suddenly stopping water columns ensure

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small closure %uh valves and install

spring-loaded

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Center guided non slam or silent check

valves

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that close before floor reversal when

appropriate

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use water hammer arrestors if necessary

but be sure they are sized and placed

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correctly

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and are well maintained

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water hammer may also be initiated by

thermal shock

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in by phase systems steam bubbles may

become trapped in pools of condensate

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since the condensate temperature is

usually below saturation

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the steam will immediately collapse

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00:05:12,034 --> 00:05:16,081

steam occupies hundreds of times the

volume more than equal amount of water

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00:05:16,081 --> 00:05:20,085

when this team collapses water is

accelerated into the resulting vacuum

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from all directions when the void is

filled

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00:05:24,005 --> 00:05:29,091

the water impacts at the center sending

shock waves in all directions

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00:05:30,036 --> 00:05:35,098

one likely place for thermal shock to

occur is in steam utility corridors

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in these areas the drip traps from high

pressure steam engines

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00:05:39,036 --> 00:05:44,054

often discharge directly into the pumped

condensate return lines

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00:05:44,054 --> 00:05:47,133

the temperature of the condensate in

these lines usually ranges from

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00:05:48,033 --> 00:05:52,062

140 to 180 degrees Fahrenheit

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the condensate being discharged from the

steam trap

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is it nearly steam temperature when it

passes through the trap orifice

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when the trap discharge enters the low

pressure come in saline

94

00:06:04,065 --> 00:06:07,152

a great deal of it flashes back into

steam

95

00:06:08,052 --> 00:06:11,147

the flash team immediately collapses

again when it encounters the relatively

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00:06:12,047 --> 00:06:14,112

cool pump discharge water

97

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this thermal shock often causes damaging

water hammer

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the localized sudden reduction in

pressure or near the wall

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chips away piping and tube interiors

100

00:06:27,003 --> 00:06:30,039

oxide layers that otherwise would resist

further corrosion

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00:06:30,066 --> 00:06:35,149

are removed resulting in accelerated

deterioration of piping and equipment

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to minimize such a disturbance the drip

trap should discharge

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00:06:40,041 --> 00:06:44,098

in the direction of condensate flow by

means of a special fitting

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00:06:44,098 --> 00:06:47,132

this method of controlling thermal shock

called sparging

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00:06:48,032 --> 00:06:51,057

reduces the concentration of collapsing

steam bubbles

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and keeps the action from occurring by

the pipe wall

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thermal shock can also occur easily in

steam coils if they are constructed

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as shown here since the steam is

directed toward the center to

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first it can reach the return header

before the top and bottom tubes are

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filled

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consequently steam feeds the more remote

tubes

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from both ends with steam flowing into

both ends for two

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waves have comments AP flow toward each

other

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these waves have the potential %uh

trapping pocket some steam between them

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if this happens thermal shock will

result when the pocket of steam

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collapses

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and water hammer will probably occur

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prevent the thermal shock that is

generated by such a design

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by substituting a constant purge device

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such as a differential cumin seed

controller for the steam trap

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condensate controllers maintain a

positive differential pressure

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00:07:50,086 --> 00:07:55,183

across the coil at all times all the

tubes will be fed from the supply and

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only preventing me entrapment up steam

and the resulting formal shock

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malfunctioning steam traps

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may also contribute to thermal shock

followed by water hammer

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a steam trap that has failed to open

injects

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live steam directly into the condensate

return line

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if this team is mixed with return line

condensate

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up sufficiently low-temperature it will

immediately collapse

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and thermal shock will follow

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to prevent the occurrence water hammer

due to thermal shock

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you must reduce the concentration of

collapsing steam bubbles

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in the condensate if flashing condensate

must be discharged into a cool

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condensate lime

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it should be discharged in the direction

of condensate flow

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and away from the pipe wall

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precautions must be taken that heat

exchanger tubes are always filled from

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the supply and only

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00:08:55,097 --> 00:09:00,123

differential shock like thermal shock

occurs in by phase systems

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differential shock can occur whenever

steam and condensate flow in the same

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line

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but a different velocities such as in

high-pressure condensate return lines

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in by phase systems the velocity the

steam

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is often ten times the velocity of the

liquid

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if this gas flow causes condensate waves

to rise

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and fill the pipe a seal is formed with

the pressure of the steam behind

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since the steam cannot flow through the

condensate CEO

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00:09:31,209 --> 00:09:34,234

pressure drops on the downstream side

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the condensate see all now becomes a

piston that has accelerated downstream

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by virtue of this pressure differential

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00:09:41,829 --> 00:09:44,911

as it is driven downstream the piston

picks up more liquid

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that is added to the existing has to be

a slog

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and velocity increases this is

differential shock

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00:09:54,519 --> 00:09:59,555

if the slug games high enough momentum

and is then required to change direction

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at a tea or elbow or stopped by a valve

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great damage can be done in the demo lab

but Armstrong International we have

157

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assembled a fixture

158

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to illustrate the problem we use this

159

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24 two-inch diameter glass pipe to act

as a condensate return line

160

00:10:19,017 --> 00:10:22,426

the pipe is pitch one-quarter inch in 10

feet

161

00:10:22,579 --> 00:10:27,615

to provide gravity flow flowing through

the pipe we have cold water

162

00:10:27,939 --> 00:10:30,976

in addition to water we can also have

compressed air

163

00:10:31,309 --> 00:10:35,366

flowing in the system to simulate flash

steam flowing across the top of the

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condensate

165

00:10:36,829 --> 00:10:39,858

by virtue of differential pressure

166

00:10:40,119 --> 00:10:44,140

one flow meter constantly measures the

flow rate of the water

167

00:10:44,329 --> 00:10:49,335

another flow meter continuously monitors

the flow rate up the compressed air

168

00:10:49,929 --> 00:10:54,050

as you can see we now have 1500 pounds

per hour water

169

00:10:54,005 --> 00:10:58,534

flowing in our glass pipe and no

compressed air

170

00:10:58,579 --> 00:11:03,360

under this condition are pipe is

approximately half filled with water

171

00:11:03,036 --> 00:11:07,117

as we increase the flow rate of water in

our pipe to 2,000 pounds per hour the

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depth of the water increases

173

00:11:10,036 --> 00:11:14,575

to 5/8 we now introduced compressed air

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00:11:14,899 --> 00:11:19,921

into the system to simulate flash steam

with the flow rate of about 200 standard

175

00:11:20,119 --> 00:11:21,170

cubic feet per hour

176

00:11:21,629 --> 00:11:25,540

and the depth of the water receipts

177

00:11:25,054 --> 00:11:28,097

we are increasing the speed of the water

flowing through the pipe

178

00:11:28,097 --> 00:11:32,756

by virtue of the velocity of the gas

flowing across its surface

179

00:11:33,629 --> 00:11:37,650

observe now as the compressed air flow

increases

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00:11:37,839 --> 00:11:40,860

the waves formed on the surface of the

condensate

181

00:11:40,086 --> 00:11:44,124

become higher further increasing the air

flow causes the waves

182

00:11:45,024 --> 00:11:48,233

to block of more of the cross section of

the piping

183

00:11:48,449 --> 00:11:53,420

until the seal is formed completely

closing of the pipe

184

00:11:53,042 --> 00:11:57,073

a slug compensators accelerated

downstream by the pressure differential

185

00:11:57,073 --> 00:12:03,122

becoming a piston that gains in mass and

velocity is a travels

186

00:12:03,779 --> 00:12:07,845

the proper sizing and pitching comments

8 lines are the only means of guarding

187

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against this type of problem

188

00:12:11,449 --> 00:12:15,170

the Armstrong's team conservation

handbook includes a chart

189

00:12:15,017 --> 00:12:18,926

that helps you in deciding the correct

condensate return line size

190

00:12:19,079 --> 00:12:22,155

for your particular application

191

00:12:22,839 --> 00:12:26,864

differential shock can also become a

problem when elevated heat exchange

192

00:12:27,089 --> 00:12:30,150

equipment is trained with a substantial

vertical drop

193

00:12:30,699 --> 00:12:34,786

ahead of the trap under normal

conditions condensate drains down the

194

00:12:35,569 --> 00:12:37,350

walls of the pipe

195

00:12:37,035 --> 00:12:41,084

a sufficient volume up steam constantly

flows down the center of the pipe

196

00:12:41,399 --> 00:12:44,441

to replace the steam that is condensed

by radiation losses

197

00:12:44,819 --> 00:12:48,730

the piping and the trap body itself

198

00:12:48,073 --> 00:12:52,152

the steam flow rate increases if a

thermostatic elements such as the

199

00:12:52,809 --> 00:12:57,230

bellows or way for in an F in T trap

opens

200

00:12:57,023 --> 00:13:01,292

if a slug of condensate seals of the

pipe steam collapses

201

00:13:01,499 --> 00:13:05,568

downstream of the seal again a pressure

differential forms

202

00:13:06,189 --> 00:13:10,214

and this along with gravity accelerates

the slog

203

00:13:10,439 --> 00:13:14,170

when this piston strikes the trap it can

damage afloat

204

00:13:14,017 --> 00:13:18,246

the thermostatic element or other parts

about mechanisms

205

00:13:18,399 --> 00:13:21,466

to avoid differential shock arising from

the situation

206

00:13:22,069 --> 00:13:26,050

use in FNT trap and back fed it to the

top of the vertical line

207

00:13:26,005 --> 00:13:29,084

to maintain near equal pressure

throughout the riser

208

00:13:29,129 --> 00:13:33,100

even if a slug condensate forms

209

00:13:33,001 --> 00:13:37,006

in both the two previous cases the

condensing up steam downstream of the

210

00:13:37,006 --> 00:13:37,665

seal

211

00:13:38,259 --> 00:13:42,298

produced the acceleration it follows

that the likelihood a differential

212

00:13:42,649 --> 00:13:43,661

shocker rising

213

00:13:43,769 --> 00:13:46,867

and causing water hammer is greater in

uninsulated pipes

214

00:13:47,749 --> 00:13:52,761

especially on outdoor systems then

insulated pipes

215

00:13:52,869 --> 00:13:55,912

long runs have any kind between the heat

exchange equipment

216

00:13:56,299 --> 00:14:01,326

and the trap can produce the situation

and should be avoided

217

00:14:01,569 --> 00:14:05,611

damaging water hammer may also occur due

to differential shock whenever there's

218

00:14:05,989 --> 00:14:07,360

an improperly dripped

219

00:14:07,036 --> 00:14:10,225

pocket and head over control Bell

220

00:14:10,549 --> 00:14:14,578

condensate builds up in front of the

valve while disclosed

221

00:14:14,839 --> 00:14:18,856

when the valve is opened the slug

condensate is driven through the valve

222

00:14:19,009 --> 00:14:23,035

and into the piping and equipment by the

live steam

223

00:14:23,269 --> 00:14:27,850

the placement of a riser and a drip trap

immediately upstream of the control

224

00:14:27,085 --> 00:14:27,684

valve

225

00:14:28,449 --> 00:14:31,910

will prevent this rampaging slog

226

00:14:31,091 --> 00:14:36,000

to control differential shock you must

prevent condensate seals from forming in

227

00:14:36,819 --> 00:14:38,820

by phase systems

228

00:14:38,829 --> 00:14:42,923

condensate lines must be sized correctly

and long vertical drops to the traps

229

00:14:43,769 --> 00:14:45,786

must be back to read

230

00:14:45,939 --> 00:14:48,946

the link to the lines to traps should be

minimized

231

00:14:49,009 --> 00:14:53,071

and the lines may have to be insulated

to reduce condenser

232

00:14:53,629 --> 00:14:56,684

the installation a proper drip leg ahead

of control valves

233

00:14:57,179 --> 00:15:00,211

will prevent differential shock from

occurring when the control valve is

234

00:15:00,499 --> 00:15:00,575

opened

235

00:15:01,259 --> 00:15:04,353

after a period of closure careful

attention

236

00:15:05,199 --> 00:15:09,800

to these few guidelines will prevent

most modern

237

00:15:09,008 --> 00:15:11,105

prevent the sudden stopping the water in

pipelines

238

00:15:12,077 --> 00:15:16,143

by closing manual valves slowed and by

installing spring-loaded

239

00:15:17,043 --> 00:15:22,069

Center guided silent check for homes

were appropriate prevent thermal shock

240

00:15:22,069 --> 00:15:23,073

by using the sparging

241

00:15:24,009 --> 00:15:28,091

to wherever flash team is discharged

into condensate at a lower temperature

242

00:15:28,091 --> 00:15:31,104

and by ensuring that heat exchanger

tubes

243

00:15:32,004 --> 00:15:38,029

our field from one and prevent

differential shocking by phase systems

244

00:15:38,029 --> 00:15:41,030

by providing return lines that are

properly pitched

245

00:15:41,003 --> 00:15:46,060

and adequate size avoid training

equipment with long lines to the track

246

00:15:46,087 --> 00:15:52,155

and insulate compensate lines whenever

necessary following these guidelines for

247

00:15:53,055 --> 00:15:57,073

the proper design and operation your

system will minimize the likelihood the

248

00:15:57,073 --> 00:15:57,138

shocks

249

00:15:58,038 --> 00:16:02,135

the cause water this in turn will

greatly reduce the likelihood of damage

250

00:16:03,035 --> 00:16:04,044

to your system

251

00:16:04,044 --> 00:16:11,044

to your product and to your personnel

252

00:16:16,008 --> 00:16:17,030

no