Oxygen regulators are used in aircraft to regulate automatically the flow of oxygen to the pilot from a cylinder at pressures ranging up to 150 atmospheres. The instruments are adjusted to open at an altitude of about 15,000 ft. and thereafter to deliver oxygen at a rate which increases with the altitude. The instruments are tested to determine the rate of flow of oxygen delivered at various altitudes and to detect any mechanical defects which may exist. A method of testing oxygen regulators was desired in which the rate of flow could be determined more accurately than by the test method previously used (reference 1) and by which instruments defective mechanically could be detected. The new method of test fulfills these requirements

Borlik, E L

Sontag, Harcourt

English

NASA Technical Reports Server

TEc~niICAL NOTES 
NATIONAL ADYISORY COMin :::TEE FOR AERONAUTIOS 
--~-.-
~To It 532 
UETSOD OF TESTING OXYGEN REGULATORS 
Ey Earcourt Sontag and E. L. ' Eorlik 
lTc. t ional :Bu.r eau of Stal1darcln 
1VanhiHgton 
Jnne 1935 
https://ntrs.nasa.gov/search.jsp?R=19930081282 2020-03-17T04:09:50+00:00Z
I 
I • 
NATIO!I1'AL ADVISORY COMMITl'EE FOR AERO!rAUTICS 
TECHNICAL NOTE NO . 532 
METHOD OF TESTING OXYGEN REGULATORS 
By Harcourt Sontag and E. L. 30rlik 
SUM ilRY 
A method of calibrating aircraft oxygen regulators 
has been devised in which the instrume~ts in ono chamber 
are maintained at a constant air pressure corresponding 
to any deaired alt itude while tho volume f low o f the de-
livered oxyg en is meas ' red in another chamb er at the same 
pressure. It has the chief adva tage over methods hither-
to used in that a condition of steady f low of the oxygen 
through the app ara t -I.l.S is 0 btD.ined befor e the r at e of f low 
is measured. ~he method is also very useful in disclosing 
an~l leal s which may occur in the rogulators at tho higher 
altitudes only and thus are not detectable at ordinary at -
mospheric p ressures. The apparatus is described and an 
example of the cO i'!lputation of the actual rate of flow is 
given . 
The work was carried out at the National Bureau of 
Standard s , in part with the cooperation and financial as-
sistance of the National Advisory Committee for Aeronautics. 
INTRODUCTION 
Oxyg en re gulators are used in aircraft to regulate 
automa t icall y the flow of oxygen to the pilot from a cylin-
der at pr essures ranging up to 1 50 atmospheres. The instru-
ments are ad juat ed to open at an altitude of about 15,000 
feet and thereafter to deli-..rer oxygen at a rate which in-
creases with the altitude . The instruments are tested to 
determine the rate of flow of oxyg en delivered at various 
altitudes and to detect any mechanical defects wh ich may 
exist . A method of testing oxygen re gu l ators was desired 
in which the rate of f low co u ld be determined more accurate-
ly than by the test method p reviously used (reference 1) 
and by which instruments defective me chanically could be 
detected. The new me thod of test fulfills these require-
ments . 
N. A .C . A. Te chnical Not e No . 532 
DE SCR I P ~ IO N OF THE APPARAT US 
The a ppa r atus include c an airti Ght c hamb e r such as a 
be ll jar an~ ba se B ( f i ~ . 1), a Bas mete r G, a t an~ T 
o f la r g e c apa ci ty , and a v a cuum pump P . I n addi t ion t~ere 
is a U- tu b c water ' manome te r U , a nd a me rcu ri a l ba r ODotc r 
A . S e v e r a l va l ves c on ne c te d as sho wn i n t he fi gu re a r e r e -
qn ire d f o r r e~ulating t he p ressu r e with i n th e a ppa r a t us . 
T~e o xy g e n gas is sues fro m t h e regul a tor un der tost 
aud pas ses t h rou g h rubbe r tub i n g of l a rge interna l diaec t o r 
to the ve rtic a l mani fo ld i n th e bel l j a r . Fr om t h er e it 
f l ow s t h ro u f h t u bin g of one- ha l f inch bore to the inl et 
side of the meter . Fro m t he out l et of th e meter it fl ows 
il1.to +.: :" 3 t a l.k througl1. the lin e \7hich i nc l udes va l v e v';" 
(S 08 f i S t 1.) 
A be~l ows - type ga s met e r ( fi~ . 2 ) mou~t e d in an iron 
c a s e wh ich i s c a pable o f operat i n~ und er l in e pres su r es 
r ang ine from atmo s p he r ic ~rossuro to about 25 i nch e s of 
me rcu ry b e l ow at mosphe ric 9 r e ssu r e i s used . It s i nd i ca t -
i nc Mc chanisD is eq uipp ed with a tangen t arm maki~s nin e 
re volnt i on s ne r cel.b i c foot of ga s f l ow i ng t hro u gh t he me-
te r . A p r e s;ur e ac r os S th e me t er amountin g t o about one 
ha lf in ch o f wat e r i s re qui r ed fo r ope r a t i on . 
In or der that th e meter be abs olute l y ~irticht al l 
opening s ar e sealed and a heavy Gl a s s windo w i s in stalled 
di rec t l y ove r the t a ng ent a rm so t hat its mo veme n t c an ~e 
o b served . An inde x mar~ed on the windo w i s a n aid in 
c ou n t in g the whol e a n d fr a c ti ona l par t of the r evo l ut i ollS 
th r o u~h wh i ch t h e ta~g en t arm t urns during a test . 
The. mercur i a l b aromet er mea S lr e s the absolu t e p r es -
sn re , o r equ iva l en t al t itude , i n th e bel l j a r . 
The tempera t u re o f the o xy gen is mea su red by a me r-
cu ry-i n- g las s the r momete r 'p l a c ed i n t h e entranc e c hamber 
of the met e r . 
Ru bb e r t ub ing i s us e d for t !J. e oypass acros s th e t wo 
e n d s of t he water mon ometer . Va l v e ~ is a qu ick-r e -
1·ea s i!15 clamp which p inc he s the walls o f t he tu b ing to-
getl1. er . Va l v e V4 i s a l s o a cl ampin g va l ve , not qu i c1:.:-
r eleasin g a s i t is u sed to r egu l a t e t h e o xyg en f low . 
--------- ----------------~ 
N.A.e.A. Technical Note ~o. 532 
Valves V5 and V6 are metallic needle valves with the 
seat part of the valve connecte d to the bell jar. With 
this arrangement the stuffing boxes may leak and not af-
fect the p ressu re in the bell jar. 
3 
Valvea V2 are small, high-pressure, needle valves 
connected to a ~anifold so that the stuffinG boxes are 
subjected to the high-pressure oxygen only when the valves 
are open. Each of these valves con tro ls the flow of oxy-
gen to one regulator when p rovisio n is made for mounting 
more than one regulator on the base of the bell jar. An 
extra valve is used to exhaust the gas from the manifold 
when desired. A fi lter is plac~d in the line between the 
manifold and the oxygen cylinder to clean the o xygen. 
Each re6ulator is individually vibrated during tests 
by means of an electric buzzer. 
OPERATION OF THE APPARATUS 
Initially valves VI, V2 , V4 , and V5 are closed 
and valves 3 and V 6 are open. The pre.ssure of the 
whole system including the bell jar, meter , and tank is 
reduced to that corresponding to the altitude at which 
the test is t o be made . Valve V6 is then closed and 
the p res suro in the tank is reduced to at leas t 30 mm of 
mercur y less than the p res s u re in the bell jar and meter . 
While oxyg en is f lowing during a test, the tank is being 
evacu ated continuous l y b y Deans of tho vacuum p ump . 
With a pp roximately the correct pressure in the bell 
jar, valvG V3 is closed and t:o desired pressur e , or 
equivalent altitude, in the bell jar is obtained by ad-
justment of valves Vs and Vs' 
Valve V4 is opened sli ghtly until the manometer 
shows that the meter is at a pressure sli g ltly less than 
that in the bell jar . ThiR is done so that the rapid in-
crease in pressure obtained when the oxyg eJ is turned on 
wil l n ot b lo w the water out of t h e manom eter before pres -
s u re adjustments ca~ b e made . 
Valve v is op ened an~ the electric vibrator mount-
e d on the insirun ellt to be tested is star ted. 
I 
4 N.A. C. A. Techn ical Note No . 532 
Valve Va l eadinG to t he r egulator to be tested is 
then ' o pened in order to sta~t the flo~ of oxygen . At the 
same tim~ valve V4 is opened and adjusted so that the 
absolute p ressure in th~ meter is the sace as that in the 
bel l jar , a sin d i cat e d by 'i; 11 e wa t e r laa n 0 me t e r • V 801 v e V 4 
must be continuously adjusted dur i ng the test to keep this 
pre ssu re equal . After the gas is f'lo',7ing steadily the time 
for a e iven number of re vo lu t ions of the tan~ ent arm of the 
met er i s obtaine d with a stop watch. 
When tes ting more than one instrument it is necessary 
to close valve Va leading to the first instrument tested 
and afte r the flow of oxygen has stopped to Qpen the v a lve 
leading to the second instrument . 
The change to any other .deoired pressure in the bell 
jar and system is ma de by adjusting v a lves Vs and Vs 
with valves V 1 and Va cl osed and with valve V3 open. 
The accurate determination of the rate of flow de pends 
pr i mari ly on : 
1 . Accurate con trol of the pr essure of the oxygen in 
the mete r so that it is equal to the air pres-
sure in the bell jar . 
2 . Accurate timing of the revolutions of the tangen t 
arm of the meter . 
3 . Low pressure drop in the line botween the oxy g en 
regUlator and the meter. 
4 . Constant pressure in the bell jar during the test. 
TESTS AT LO W TEMPERATURE 
In testing oxygen regulators at 10 1,7 temperature it is 
necessary that th e meter be maintained at room temperature. 
Only the bell jar , therefore , is insta.l led in ' the tempera-
ture chamber and the lines connecting with the r es t · of the 
a pparatus are brought out throug h a hole in the wall of the 
chambe r. A ten-foot len gth of copper tubing of large in-
ternal diameter (o ne half inch) is used to connect the man~­
fold in the bell jar with the meter. Most of this length 
io outcide of the t emperature c hamber . The line is bro k eu 
N.~.C.A. Technical Note . No. 532 5 
about its midpoint and then joined b y a short piece of rub-
ber tubing thus reducing the loss of heat from the meter 
by conduction along the co pp er tube . It was found with 
this arran gem e n t of tUbin g that t ~ e tenperature of the ox-
ygen leavin g the regulator at -35 0 C. is increased to ap-
proximately that of the room when it enters the meter. In 
all other respects the testing procedure is the Same as 
that for tests made at room temp erature. 
MEASUREMENT OF RATE OF FLO W 
~he rate of flow of oxyg en F in terms of liters per 
~inute at a p res sure of 760 mm of mercury and temperature 
of +200 C. is given b y the relatio n : 
P To Y F ::: 
~)o T t 
where P i s a ir p res sure in bell jar in mm of mercu ry 
POI standard p res s ure of 7 60 mm of mercury 
To , standard absolu t e temp era tur e of 29 3 0 C1l. 
T , temp erature o f oxygen in g a s meter i n °C A. 
V, observed f low in liters 
t , o b serve d time in minutes f or flow V 
-I,T _- 2 8 • 3" rJ - ' ,T· t 1 ' ~ 1 t' :J w1 ere J.~ 1 S 18 numoor OI revo u Ions 
9 
of the tan g en t arm o f t h e g as met e r de s cribed above wh en 
t is observed in seconds, 
t/ 60 i s ti me in minu t es . 
With these additional re l ations an d p uttin g into equa-
tion (1) th e v a lues or the constants, there results: 
2 93 x 28 . 3q X GO E- n F ::: -
7 6 0 X 9 T t 
72 . 9 P N ::: 
T t 
6 ~ . A . O.A. Te c h nical Note No . 532 
The f ollowing exampl.;3 illustrates the method of deter-
nininG the r ate of flou . 
A~ o xycen regulator was installed in the bell jar at 
an air p ressure correnponding to an altitude of 35 ,000 feet 
~78 ,, 7 mm of mercury ). The oxygen supply was turned on and 
th~ time interval for five revolu tions of the tangent arm 
of the mete r was,found to be 1 6 . 0 seconds. The temperature 
of the oxygen as measured in the entrance chamber of the 
met er was +2 50 C. (2 98 0 CA ). Substituting tho known value~ L1 
equation (1) above 
Flow = l~~~Q 72.9 298 X 16 
= 13 . 7 liters per minute 
If it is desired t o measure the rate of fl ow at a few 
definite altitudes th e c omputations can be simplified by 
combining the press'cu e P with the constant of equation 
( 3). Further, if the time is measured for the same number 
of revolutions of the tangent arm o f the meter the term N 
l:lay also be included with the co nstant . Formula ( 3) then 
bc coDes 
F == Y1 
Tt 
(4 ) 
A table ruay be prepared g iving the values of Kl/T for the 
desired alt i tudes and for differ ent temperatures. Th o com-
~utation required for determi n inG the rate of flow then be-
comes ono of the simple division of the number properly se-
lected from the table , by the elapsed time in seconds. 
EFFECT OF LEAKS 
, The testing apparatus slould be leak-tight for the 
bent resultc . A small leak wh ich does not increase the 
pressure in the b e ll jar at a rate exceeding about 0.2 D1n 
of mercu r y per minute has been foun d by experience with the 
use of the apparatus not to affect a pp reciably the accuracy 
of the cethod of measurement . I t is desirable to compen-
sate for the effect of a leak, however, by opening valVO 
V6 a ~d adjusting it GO that the pressure within the bell 
jar r ema ins constant . A small leak in that part of the 
N.A.C. A. Technical Note No. 532 7 
system lying betwoen the meter and the vacuum pump and in-
cluding tank T does not a ff ect t h o results of the tests 
but does impose a greater load on the pump . 
Diaphragm-actuated valves arB used in the construction 
of oxygen regulators t o reduce the pressure o f oxygen as it 
issues from the cYlinder to a predetermined value which ex-
ceeds the atmospheric pressure . Up on failure of a dia-
phragm , which may occasionally occ u r, the oxyg e n is wast ed 
before it is delivered to the p ilot. It is imp ortant, 
t herefore, that any leaks, which may be present in the reg-
ulators, be de t ected bef or e the instrumen ts are us ed. An 
increase in the p ressure indicated b y barometer A is the 
direct ev iden ce of a leak in the regulator to which oxygen 
is b eing delivered from the supp ly c y lind er. 
CONCLUSIONS 
The results of tests made on a large number of oxygen 
re gulators have shown the val ue of this method of test for 
accurately determining the rate of f lo w a nd for detec ting 
leak s in the instruments . In add i t io n a condition of 
steady flo w of the o xyg en through the apparatus Can b e 
maintained f or any des ired length o f time . No observ ations 
covering a peri od of less than 1 5 seconds are made due to 
the increased inacc~racy of determining the time interval 
over a shorter pe rio d. . The method is an imp rov ement over 
that p revio us l y employed in that a precise contro l o f the 
air pressure to whic~ the regulators are subjected is ob-
tained, and in the facility with which leaks are det ected, 
REFERENCE 
1. Hunt, F. L.: Oxygen Instruments. 
1925. 
T.R. No. 130, N.A.C.A., 
.-t 
· till 
-,-I 
I%t 
C\l 
f? 
rr~ 
II J3 
' Ii :Bell jar ~ I r 11~-~J1~11 ~! I~~~ i I II I I II II l J A 
'\ I I I I I I I I 
• 11 21~ I-~ I~ H;b I-~ rM ~ , II 
o ..r---"; L-J 
G 
Gas me t er 
M 
1 II r---water manometer 
U Vacuum gage - - -?t jf 
V4 
T 
50 gallon 
tank 
; !~ ~ ~ V5 ~V6 ~LI\ l ~ ,I I .. 
~ I <-, II _~ ! \ " Pressure gage ~ 
.BY / 'P 0 1 -
(!) Filter I /-- ~ ! ~ V ~/ . 0. xygen cYlinde ... r .. .. <Xl 1 " 
· 
-- - - - -- - -----o 
· <Xl 
· lz; 
Figllre 1.- Diagram of 
appara tus 
for testi~g oxygen 
regulators. 
Vacuum 
pu.mp 
',," 
B.A. C • .A. Teclm1cal Note No. 532 Fig. 2 
• 
l1cUre 2.- Photograph of modifled gaa meter. 


Method of Testing Oxygen Regulators

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