Field of thc Invention
'The present invention relates to a compressor unit and i) method to
proccsh 8 working $loid.
Description of the Priirr Art
At1 industrial plant to extract nattlml gas fram a field present under the
seabed is in goncral placed on a platforrli above the sea or on tho
soahed.
In particular, the plant an the seabed con~priscsa submersible
compressor unit and other mad\lles prcusscnlbled on the ground and
thcn placed in seabed itself.
I he submcrsibtc compressor unit conlpriscs generally u centrifugal
colnprcssor puslrirtg the extracted natural gas to the mainland and
anangcd in a housing wiOt an electric motor; this unit c.auld he tluidly
connected with an zxt6rnal scpwator machine placcd between the wcll
anti the inlet nf tkc unit. 'I'kis type of compressor tinit could be a
nlechit~cw ith vcrtical co~lfigurationh aving e vcrtical shaft on which 1s
arranged the rotor of the electric motor and also the centrifugal
impeIlerc, of the compressor. the shaft is supported by a plurality of
~ncchanical bcarings and by a thrust bearing. preferably of a nlagnctic
type. The main benefits of the vertical configuration are that the
druinagc is due to the gravity and the footprint is minimized.
Thcsc two mocttrles (the ciymprcssor unit and the separator machine) are
~tc,uallyp rovtded with rcspecfive inlet and outlet openings that are
closed with valves during the itnrncrsio~tp hase an thc seabed: during
the installation phase, these two openings arc fluidly coupled using a
pipe and then the nvo \ralvcs arc opcncd. Thc hcst practices incfudc that
the valvc on the side of thc separator tlracbine is opened first; then tlic
valve an the side of Ore unit is tinwly opened. In this way, the water
insidu thc pipe could be discharged into thc separator; tho pipu
descends from the unit to thc separator to facilitate the discharging.
-4 dra\vback of this typc of ntschinc lios in the fact that thc valve of the
~ k t ~ciotu ld be opened bcforc the valve of the separator by the operators,
provoking the sea discharge nccidentally inside the cotnpmssor
unit and damaging the xnachanical cctrnponent of the unit itsolf.
The patent application WO-2007:103,238 describes a fluid prctccssing
nlachiile to process n~ultiphsscf- luid streams including gas and tiquid. A
Itousing has an interior chamber, an inlet fluidly connected with the
interior chamber and with u stream source, and first and second outlets.
A scparator clisposcd within the housing chun~bcri s fluidly coupled
with the inlct such that the stream flows thereto and separates the
strcam into gascous and liquid portions. A conlpressor disposed within
ttlc chamber receives and compresses the gaseous portions Cronl the
separator for discharge throllgh the. housing first outlet, the compressor
having an outer surface spaced from tile housing inner sutfacc to define
a flow passage. A pump provided willlitl the chamber has an inlet
fluidly coupled with the separutcjr through the passngo, is spuccd
vertically from the separator so that liquid tlows by gravity from the
separator to the pump, and pressurizes thc liquid for discharge through
the housing secottd outlt'l.
A disadvantage of this type of machine is tllut it requires a separator
inside the compressor unit, increasing the mcc'hsnical complexity and
the cost.
Another disadvantage is that the lower nlcchanical bearing is placed an
aa inf'erior bascpletc of the housing, and so it is nccessary to provide a
se'illng case to avoid the contact with waler or waste. In particular, this
rase has to he a high sealing casc if the hcaring is of tltc magnetic type,
increasing the installation i d design cast and at the same time
dccreiising the reliability, thal 3s parlicular significant arid important for
the applications thal require a non-stop working for m lot of yeus, as
for exa~npleth c submerged one.
Moreotter, the shrift has to bo so long as to place the i~foresaidb earing
on the brtscpliite increasing significantly the design cost.
A further disudvatttage is that thc Icngth of the shaft is rclattd to the
vertical length of the chamber, that could vary rmly if the length of the
shaf't varies at the same timc, increasing thc cost and lhc difficulties for
the design,
To date, notwitl~standingth e develapnlents in technology, this poses a
problcm and tl~cn ccd exists to produce sitnplor and cheaper ~rtachincs
to extract natural gas fronl a field prcscnt under the seabed, improving
thc installation phase uncl ut the same time the working phase thereof.
SIJM MARY OF THE INVENTION
According to a first aspect, there is u compressor unit for processing a
working fluid co~nprisinga compressor inside il housing to compress
the working tluid \vlicrein a collection chatuber is fluidly couplcd wit11
s working tluid inlet of said housing.
Acccrrdiny to another aspect. there is a method lo process a working
fluid comprising thc following phases: providing a compression unit
with a housing, con~prisinga compressor and a collection chamber
inside thc housing tluidly couplcd with a working tluid inlet of the
housing itself; associating the conlpression unit to external auxiliaries
each other in the working pluc'c; and operating the compression trnir to
compress the working fluid.
HRlEF DESCRIP'TION OF 'THE XIRAWINGS
This invention will be more itpparent by folloiving the description and
accompanying drawing, which shows a non-lirni ting practical
embodiment of said invention. Mare specifically. in the drawing, where
the sitme nun~bersin dicate the same or corresponding parts:
Figure 1 sl~owsa vertical schenlntic section of a machinc according to
an ernbodi.tncnt of the invention;
Figure 2 sl~owsR schemnatic view of the section 11.-Ti of Fig.);
Figure 3 sl~owsa scheinatic view of the section Ill-Ill of Fig.1;
Figure 4 shows it vertical scction of rt detail of the Fig.1; and
Figure 5 shows it compression system conlprising thc machine of Fig.1
accordills a particular cmboditnent of the invctltion.
DETAILED DESCRlPTTON OF THE INVENTION
In the drawings, in which the salnc nurnbers correspond to the same
parts in all the various Figures. a machine according la the invention is
indicated generically with the number 1. This machinc 1 comprises a
compressor 3 and a motor 5, see Figure 1, located in a pressurized
sealcd carntnon housing 7.
.4ccording to this exemplary embadimcnt, the conrprcssar 3 is a
multistage centrifugal compressor comprising a plurality of
comprcssittn stages 9. 11. 13, each of them having a centrifugal
i1ape1lc.r 9A, 11A and rcspectivcly 13A rotating inside a stator
diaphragm OD, 1 I B and respectively 13B and coupled on a shaft 15
along an axis X 1 ; betwc.cn each stator diaphragms 9D, 1 1 B, 13B there
are stator channels 14A. 14B - sce Fig.4 - for the fluid to be
compressed (each stator channels Formed by u diffuser and a return
channel, not indicated in the drawings for sintplicity and well know at
the skilled in thc art).
Although a lntlltistagc centrif~~gcaol nlprcssor 3 ss described itbo~cis
presenffy preferred. the cutnpressor 3 rnay alternatively be constructed
as a single stage centriftlgal compressor or any other type of
comprcssor capable of coniprersing a gas, such as for cxamplc a radial
comprcssor, a rccil~rocatingc ompressor, i i rotary scrcw cornpressor or
others.
In tl~cp referred embodiment showed in Fig. 1, the unit 1 has u vertical
cont'iguration. so as the shaft 15 (and the axis XI) is placed
substantially in vertical position (during the working of the unit 1)
comprising B superior end and an it~fcriorc nd 15s and respectively 151;
however, it is not to exclude that the unit could have a different
configuration according to specific embodiment or needs of use, as for
cxamplc silbstantially nn horizontal configuration with the shaft (and
the axis) placed sutrstantially in horizontal position.
Advnntagcousiy. thc motor 5 is placed inside tile Rousing 7 and it is
t~~echaniccaol upled to the compressor 3 by the shaft IS, in order to
obtnin a mucl~ine particularly compnct and without outward dynamic
seals. However, it is not to excludc that the motor nlay bc placed
outsidc the housing in accordatice with porticttlar enlbudirncnts of the
invention.
In thc cot~figurationd escribed here, the nlotor 5 is arranged vertically
above the compressor 3, to minimize the chance of liquid intn~sionin to
the ntotar 5. Mai\!evt.r, the niotor 5 nlay otherwise be n~ounted, such as
for cxarnpie to the inferior end 151 of the liousing 7 or providing a fitst
coinpressor abavc the motor and snothw compressctr under the motor;
but, in these cases. it was rcquircd further components (as for example
a lncchanical seal to scal rhc ~rlotor 5 froni tho rest of the machine) and
so the nlechanical cstnplexity and the cost of the machine will increase.
Also, the ntator 5 is preferably an electric motor configured to rotate
thc shaft 15 abotrt its axis XI: it may alternatively be a hydraulic motor,
a steam or gas turbine or any other appropriate motor or engine in
general.
Further. the shaft 115 is preferably directly driven by the motor 5, as
described abctve, but may altmnuively be driven through a belt drive,
pear train or other appropriate transmissiotl means (not shown for
siatplicity).
The housing 7 comprises also a fluid inlet 7I fluidly canr~cctedw ith a
fluid inlet 31 of thc compressor 3 end a fluid outlet 7U fluidly
connected with a fluid outlct 3U of the comgrcssor 3. It has to be notcd
that, according to the vertical configuratiot~t,h e tluicl inlet 71 and the
fluid outlet 7U of the housing 7 art. placcd one above (fie other.
A collectictn charnber 19 is advatttageausly provided inside the housir~g
7 under the! colnpreosor 3 and is fluidly cannocted with the fluid inlot 71
of the housing 7 itself, It has to be notcd that, if the machine! 1 is in
I~orizantalc onfiguration. the collection cl~amberI 9 may be placed in
another position so that the fluid can flow into it.
According to a first advantageous embodiment, the collection chamber
19 is configured to collect completely the liquid possibly entered insidc
said unit I during a submerged installation phase thereof, in order to
avoid substantially thc passage ctf said liquid insidc the camprcssor 3.
Therefore, it is possible to improve the installation {and uninstall)
phase, in particular it is possible to avoid substantially that the liquid
cntcrs inside the compressor of the unit due to wrong operations. In
particular, the seawater (when the comprcsstJr unit is placed under the
sea) results par(icufarly dangerous for the mecliirnical components of
the unit itself.
Accordir~g to a second advantageaus enibadimcnt, the collection
chanlher 19 is tluiilly coupled with a balance systenl 23. see also
description below referred to Fig.4, oftlie cornpressor unit 1 so that this
chan~bor 19 may be filled with part of the working fluid to balance at
least in purl the axial thrust (luring tile working phase; tllc other part of
the working flitid enter inside the conlprcssor 3 to be compressed.
'Thercforc, i t is l>ossible to realize a balancing system inside rho unit
avoiding t~icchanicai flttnges and external pipclinc, reducing the risk for
leakages, vcry important in case of subsea applications.
It has to be noted that the preferred en~bodirr~ccnot mprises the
aforesaid two embodiments irnpiemcnted together on the same
compression unit; ho\vever, it is not to bc cxcludcd that these two
embadinle~~ctosu ld bc i ~nplernentcds eparately according to particular
neuds of construction or use.
Accarditig to a advantageous embodiment, this chanlber 19 has a
vohinre at least equal to the upstream volun~cth at cmld be filled by tho
liquid during the instailation phitsc, sec description b c l o ~ ~ .
However, it is the possibility to size the volunle of the co1lectic)n
chntnber according to specific requirements, without any rncchanicuI
constraint. in particular no need to vary the rotor length.
A normally-closed liquid outlet 20 is advantageously and prefcrahly
provided on tl~eb ottom of tho chamber 19; this liquid outlet 20 may be
opened to discharge said liquid portion during the installation phase,
see description belc)xv.
Altcrnetivcly. it has to be noted that thc oallection chamber 19 may be
rcalizcd out of the housing 7. but in this case the tr~cchat~ical
complexity end the cost of the machine will increase.
In thc configuration described hcre, the housing 7 includes an inner
surfuce 7P - see Figg. 1. 2, 3 - and the compressor 3 has an outer surface
ZP spaced S from the housing inncr surface 7P; the conrprcssor 3 may
be supported inside the llousing 7 by il radial support 21 extending
circumferential about the axis X1 from the inner surface 7P, this radial
suppon 21 having a plurality crf hales 2 1 F. Thesc holes 21F can have
any shape or form. cspeciatly circular holes. In this way, thc aforesaid
flow passages from the inlet 71 to the chamber 19 is crcated.
However, this flow passage: may bc created in atrother way according to
specitic nne~ds or rcquirements, its for cxarnpie by means of cl~nnnels
extending cxtomully in respect of the housing 7.
Fig.4 shows an advantageously configuration of the present inventicm in
wfiich the balmce system 23 of the cornprcssor 3 is fluidly coupled
with the chalnber 19 so that, wlle11 the chamber 19 is filled with part of
thc working fluid entering in the inlel71 during the working phase, it is
possible to balance at least in part the axial thrust of tho compressor 3
by this part of the working fluid; the other part of the fluid may enter
inside tl~eC OT~~MSSQ~.
This balance systenl 23 lnny comprise substantially u balancing piston
23A coupled with the shaft 5 .in proximity of the last inlpelier 13A of
the compressor 3 so NS it i>rcsents thc maximum pressure of the working
fluid st onc side and the inlct pressure of the working fluid nt the
opposite side.
The Fig.4 shows also thc balancing piston 23A placed between said last
intpeller l3A aad a bearing system 27; the bcaring systttn 27 is
disposed at the inferior end 151 of the shaft 15 in n position able to
avoid the contact with the liquid, when present. In othw wards, the
bearing systetn 27 is preferably placed above the maximurn level of tho
liquid inside thc colfcction ohurnbcrr 19.
The bearing system 27 ccjuld comprisc tt journal bcaring andior a thrust
hearing: preferably. this bearing system is rcalizcd by a magnetic
bearing with a landing bearing associated thereof.
More. it is no1 to be excluded tilet thc piston 23.4 may bu placed it1 a
different position on the shaft 15 or may consist indifferent mcehanicnl
component. according to particular configurations or rcguired needs.
in this configuration, the radial support 21 may co~nprisea t least in part
an inner tlow path or channel 33 tcr lluidly connect the cftanlber 19 to
the halaflce systeni 23; furthermore, Ilru radial support 21 nlay cotnprise
at lcitst in part an outlet volute 31 of the compressor 3 fluidly connect
to the o~~fl7eUt .
Advantageously, the support 21 could be made in a single ,piece with
the housing 7 (as schematically showed in Fig.4) or nlade apart and
.then associated inside with the housing itself.
The Fig.5 shows schematically itn tidvantageaus en~hodin~conft the
invention in which an external separator 37 is tluidly cunnec.tcd with
the aforesaid unit 1 by nleans of a pipe 41.; this separator 37 is able to
separsle nl least in pwt Lhc liquid portion ham lhu gaseous portion of
the working fluid coming from il gas well 39, or other fluid sourccs.
In particular, zhc pipe 41 is connoctcd on the ctne side to thu outlet 371:
of the sepa.rator 3? and on the 0 t hs~id~e t o the inlet 71 of the unit 1.
A first valve 42A is associated with the inlet 71, a second valve 42H is
associntcd with the outlet 37U.
Moreover, In this Figure is shown schetnaticslly a pressure piping 43 to
fluidly connecl the outlet 7Li of the unit 1 to a production pipeline (not
shown for simplicity) and a draining piping 15 to fluidly connect said
liqutd outlct 20 to the separator 37 in ordcr to dischsrgc. the liquid
portion of tllc working tluid during the instullatton phase. During tlte
installation phase, the co~nprcssionu nil 1 and the separator 37 rnay be
installed on the seabed and then fluidly connecting them each other by
the pipe 4 1 and with the other n~achinesa nd systems by Il~ep iping. 43.
45.
In particular, the connection phase bctwcen the unit 1 and thc separator
43 may be realized mechanically coupling the pipe 4 1 to the inlet 7I
and to thu oullet 37CJ and then opsr~ingth e valves 42A and 32B. In this
way, the \stater that fills the pipe 41 may flow into the separator 43 {the
pipe 41 could bc inclined to facilitate the flowing of the water into the
separator 43): but it is not to exclude that at least part of that water
could flow inside the unit 1.
In the case of at lcosl part of the water flows inside the unit I , thcn the
water Rows long the flow passages realized, in this particular
embodiment by said space S and holes 21F and thcn the water flaws
inside thc collection chamber 19; the watcr collected inside thc chamber
19 may be discharged by opening the normally-closed liquid outlet 20.
According to an advantageous ambodintant, said working place is: on
the scaheci anti tho phase (h) comprises a suh-phusc in which tho liquid
possibly e~ltercdin to the unit is drained inside the collection chamber
19 during the installation phase of the unit itself in order to avoid
substantially the passage of said liquid inside llie compressor 3.
According ro anather advantageous exnbodiment, during the operating
phase (c) of the unit, it is provided a sub-phase fur filling the collection
chamber 19 with part of the working fluid in order to balance at least in
part thc axial tl~rusot f the conlprcssor 3 by tnealtv of fluid connections
to the balance system 23; the other part of the gaseous portion entered
inside the compressor 3 to be worked.
Lluring the working phase, the working fluid is fed from the scparator
37 to the compressor unit I where nlost of the fluid flows inside the
cornpressor 3 and, at the same time, a small amount of suid fluid may
flow inside suid flow passages S and 11 F to fill the chi~mhut 19.
In the cornpressor 3 the working fluid is cornpressed and flows ikon1 the
irtitlet 71; at thc outlet pressure: in the chanlhcr 19 the working fluid is
collected to feed thc balancing system 23, as described upon.
It's clear that Fig.5 merely represents ti possihle ctnhodiment of the
invention. which may t1i$ry in forrns and arrangelncnts accorditlg to
specific industrial plants or systems. In particular, the compressor unit
1 according to a particular embodiment of thc invention could be used
to work acid gas for terrestrial applications, in which is rcquired sealing
compressors to avoid substlnntially rhal the acid gas could escape front
the unit ilscft:
The disclascd exemplury cmhodiments provide a compression unit and
a method to process a working tluid for easily compress said fluid. 'The
mechanical complexity of these exemplary embodiments is relative low,
so that is particular significant and important t'or the sub~nerged
applications, that requires a ntrn-stop working for u lot of years.
Said embodiments arc also able to bo installed under tlrc sea and to
work for R lot of yoars (in gancral for a lot of years) without stopping
and maintenance.
h.2oreovcr, it is possible to usc tl~esee mbodiments in other industrial
applications maintaining substantially the abuvt: advantages, as ,for
example to compress a scrur and acid gas or other.
It sho111d he tmderstaod that this description is not intcndod to lintit the
invcntton. On the contrary, the exemplary cnlbodiments are intended to
cover altenlativcs, modifications and cquivislents, which are included in
thc spirit and scope oC the invention as defined by the appended claims.
Further. in tile detaiied description of the cxcmpiary embodiments,
nurncrous specific derails arc set forth in ordcr to provide a
cornprehensivc understanding of the clairncd invention, 1-lowever. one
skillad in the art wouid irnderstand that various embodiments may be
practiced without such specific details.
Although the fcaturcs and clements of tl~op resent excnlp'lary
cmhodintents arc described in the e~nbodiznents in particular
conibinations, each feature or cten~enct an bc used alone without the
other features and etenlenls of the arnhodimcnts or in various
combinations wilh or without other features and elemcnts disclosed
herein.
'This written description uses examples to disclose the invention,
inchdin$ the best tnode, itt~d also to enable any person skilled in the art
lo practicc the invention, including making and using any clcvices or
systems and performing any incorpomtod methods. Thc pattntablc
scope of the invention is defined by the claims, and may incltlde other
examples that occur to those skil'tcd in the art. Such othcr exaxnple are
intended to be within tho scope of Ihc clairr~s if they hnvc structural
elenlents that do not differ from tho literal languag~o f the claims, or if
they include cquivalcnt structural clcments within the literal languages
of the clairns.

We Claim:
I . A compressor unit for processing it working flttid contprising a
comprcssor (3) inside a hottsing (7) to comprcss the working fluid,
whcrcin ir collcctiot~ charllhcr (1 9) is fluidly coupled witit n working
fluid inlet (71) of said liousin~(7 ).
2. The comprcssor [lait as recited in claim I , wharei~t said
collection chamhcr (19) is configured to drain a liquid possibly entered
insidc said con~pressor unit during a submerged instailation phase
thereof in order to avoid substantially tho passage of the liquid inside
said cotnpressor (3).
3. 'l'hc conlprcssor unit as recited in claim I or 2, wherein said
collctstion chambcr (19) is tluidly coupled with a balancc system (23) of
said con~pxcssnr (3) and said chaniber (19) is filled with part of the
working fluid to hulance at least in part the axial ~hrust of said
compressor (3) during the working phase; thc otl~crp art of thc \vorking
fluid cntcring inside said compressor (3) to be worked.
4. Thc subsea comprt.ssion unit as rccited in one or ~norc of the
previous cleims. wherein said collection chamber (19) has n volume at
leas1 equal to tl~e upstream volunic that could be lilted by the liquid
during thc installittion phase.
5. 'The subsea compression unit as rccited in one or Inore of the
previous claitns, wherein said collection chamber (19) coniprises a
nomtally-closed discharge opening (20) that colrld he opened to
discharge thc liqttid.
6. The comprcssor unit as ~ c i t c din one or tnore of. the previous
claims, wherein a tnotor (5) is placed inside said !lousing (7) and it is
nlecllanical coupled to said comprcssttr (3).
7. Tfre comprcssar unit as recited in one or nwre of the previous
cluims, wherein said conlprcssor unit is of a vertical (ype comprising
said shaft (7) rotatable about a central axis (XI) extending st~bstantially
in vertically direction; said shaft (7) con~prising an inferior cnd (151)
having u hewing sysle~n (27) placed between said compressor (3) and
said collection chamber (19) in a position able to avoid the contact with
the liquid, when present.
8. A method Lo process a working fluid comprising:
providing a compression unit ( I ) with u housing (7). comprising
a compressor (3) and a collection chamber (19) inside said housing (7)
fluidly couplcd with a working fluid inlet (71) of said housing (7);
associating said cumprcssion unit (1) to extcrnal auxiliaries (37)
on a wrking place; and
operating said compression unit ( I ).
9. The method of claini 8, wherein the working plwe is on the
seabed and thc phase (b) con~prises a sub-phase in which the liquid
possibly entered into said unit (1) is drained inside said callcction
charnber C19) in order to avoid substnntially the passage of the liquid
inside said compressor (3) during the installttlion phase.
10. The rnethod of claim 8 or 0, whercin. during thc operating phase
(c), it is provided a sub-phase for filling said colleotion chamber (19)
with pmt of the working fluid in ortier to balance at least in part the
axial thrust of said compressor (3): the other part of the working fluid
cnfcring inside said comprcssar (3) to bc worked.