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flame safeguard control phần 9 ppsx
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lOll 1000 10.000 100 000 1 000 000
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CAPACITY. IN CFH WITH064 5P GR GAS .. n
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FIG. 8- PRESSURE DROP VS. CAPACI'N FOR A 'NPICAl BUlTERFlY VALVE. MAXIMUM OPENING
ANGLES SHOWN 'ARE USEO AS TRIAL SETTINGS WHEN AOJUSTING VALVES FOR HtGH FIRE.
sure regul!'llor oullel pre,ssure by O~ in. \Of<: to allow for the
additional pressure drcp across the 2 inch SSQVs.
This requires estimating a new pressure dfcp for the
pressure regulator. SSOVs and Firing Rate Control, plus
repealing the sizing procedure.
SIZING CHART FOR FIRING RATE
CONTROL VALVE
Butterfly Valves are otlen used for Firing Rale Control
Valves. SinCe a Butterfly Valve ctleS no! provide light closure, a safely shutoff can!rol valve (SSOV) must be used
l4)slream.
Inaddilion 101M buUerlly control valve size, we neeO 10
know lhe mallimum QQenino angle (in degrees) U'OOd as a
trial selting when adjusting a BUllerfly Valve to hi~ fire.
In our ellample. the eslimaleO pressure drq:J across the
liring rate control is 6.5 inches wC wilh a capaCity of 10,500
294
cfh at standard conditions.
a. If SSOV estimaled <md actual pressure drop are lha
~. Mark the intersection oflhe estimated Butterfly Valve pressure drq:J and capacity, X on Fig. 8.
Use Ihe valve size and opening angle indicaled IYy
lhe nearest slanted line below X. In this case, ar;ply·
ing the estimated pressure drq:J results 'n a 2 inch
valve wHh a mallimum opening angle at 45 degrees.
b. If SSOV aclual pressure droo is less than lbe esli·
malad pressure droo.
Add lhe pressure drq:J difference (0.8 inch we) to the
pressure Orq:J available for the Bullerlly Valve.
0.8 + 6.5 '" 7.3 in. we
Mark the intersection 017.3 in. wc and lhe capacity
y,
Use the valve size and opening angle indicated by lhe
nearest slanteO line below. In lhis case, we have a 2 inch
valve with a 40 degree opening.
V5055 VALVE SIZING NOMOGRAPH
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l4UOO V5055 VALVE
100.000 SIZING CHART
J'!C'~'C
CIlA"'TY COIlAtel'ON
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Yl o.~...,". So>o."f",.~ ... No .,,5055 I INITRuCT<CNI
Non, II ",,",.1 ..' "1'0.,10< ." .." 0."1 ,,~..o. J. Dr I..... G) ''0'" ··C~" .... '0
,k'Q ,,_ on••nd , ......... ' .." .."t. ,~. .1'r " D'QQ·· c...-" _, I,.," ,.<h "" '0
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D.,.,,,,,, 'J) ,.Q... ·" ...<,(OO.~.,,'"'··O'..'"_ , "oeM. 01 101 "d I,,,, @ . ,......1..
So ..,'· __ "",n' "II, bo,_.n ,..., .>0 .. ,i,,,. ,.._.. '~"""'''Q_ aI t,"" (!) ."d 101 '0 ..'
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The correct size V505 5 Industrial Gas Valve can be
quiCkly selected usinog this nomograph. The nomograph is
available in pads at 25 under form number 70-86.27.
Tha 1oll0winog 8)(amples show how to use the VS055
Valve Sizing Char1.
EXAMPLE 1
These are the specifications from our original example:
Type of Gas Milmd
SpeCifiC Gravity 0.72 sp gr
Gas Flow Capacity 7.200,000 Btuh
Heat Content of Gas 800 Btu per Cu. fl.
Estimated Pressure Drcp across V5055
Single Valve 12.2 in. we
2 Valves Piped in Series 5.5 in. we
295
For this chart, we need to know the inlel and outlet pressure for the V5055.
1. Determine inlet pressure for V5055. When 2 valves are
used, lind the inlel pressure of the first valY'6. From Fig.
2 we see thai the V5055 inlel pressure equalS the pressure regulator oullet pressure less lhe piping pressure
loss from the pressure regulator outlet to the V5Q55 il'lIe!. Find the piping lOSS flQJre tram Fig. 3. It we haY'6 5
leet at 2 incll pipe, tM pressure drcp will be 1 inch wc.
Regulator Outlet Pressure - Piping Pressure Drcp
= V5055 Inlet Pressure
27.6 in. we - 1 In. we = 26.6 in. WC
2. Determine tile oullel pressure for V5055. The outlet
pressure equals lhe inlel pressure minus the pressure
drcp across the valve.
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SIZING CHART
EXAMPLE 1 SPH'FIC
G~""'TY
COIIIIECTlO..
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PRESSURE
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Inlel Pressure - Estimated Pressure Drcp
'" Oullet Pressure
26.6 - 12.0 = 14.6 in, we
NOTE: Since we calculated the corrected capacity
under standard conditions, 10,370 cfh. we can skip
lines 1 and 2 In lhe 1,'5055 Valve Sizif'l;l Chart
direcllol"6.
3. Draw line 3 from 14.6 inches we on the Outlet Pressure
scale 10 12.0 Inches we on the Pressure Prep scale.
Since Qutlet Pressure scale is In psi un/Is, multiple 14.6
inches we by (he conversion 1aclor1rom IheAPPENPIX
10 gel the correct psi unl!.
14.6 )( 0.0361 = .527 pst
Draw line 3 from .527 psi on QVllel Pressure scale \0
12.0 Pressure Droo scale.
4. Draw line 4 trom 10,370 cfh on the Burner CFH Gas
Flow caoacity scale through intersection of Ml and line
3, fa the valve site scale 12 inches).
EXAMPLE 2
Determine the 1,'5055 Valve sizQ from lhis job's
5j:lElciflcat ions:
capacity 7,500,000 Bluh
Type of Gas Prcpane
Specific Gravity 1.53 spIJr
Heat Conlent of Gas 2,500 Btu/cu. ft.
Inlel Pressure Available at 1,'5055 13 Inches wC
Eslimated Pressure Drop
across 1,'5055 7 inches wC
OJtlet Pressure al 1,'5055 6 Inches wc