Methods and apparatus for sanitary steam injection

A steam injection valve for continuously injecting steam into viscous food products such as relishes, sauces, jams and jellies which are continuously pumped through a steam injection zone. The valve has a sanitary irrotational, interlocking valve stem-valve sleeve construction without substantial internal crevices and which has very low maintenance and may be readily assembled and disassembled.

The present invention is directed to methods and apparatus for heating of 
food products by steam injection, and more particularly, is directed to 
such methods and apparatus which are particularly adapted to the 
continuous, direct injection of steam into viscous food products under 
sanitary conditions. 
Viscous food products, such as sauces, relishes, jams, jellies, salad 
dressings and cheese foods are conventionally heated to elevated 
temperatures prior to blending or packaging, by means of direct continuous 
injection of steam at superatmospheric pressure into a pressurized stream 
of the food product. Conventional direct steam injection processing is 
carried out by continuous introduction of sanitary steam through a steam 
check valve into a conduit or injection zone through which a pressurized 
stream of the viscous food product to be treated is also continuously 
forced, concomitantly with the injection of steam through the steam check 
valve. Such direct steam injection processing is typically carried out 
under intense operating conditions, involving high flow rates and intense 
mechanical or sonic vibration. Such processing also may typically produce 
potentially irregular pressure fluctuation or cavitation conditions 
resulting from the intense operating conditions, which conditions are 
exacerbated by the physical difficulties of mixing the steam with the 
viscous fluid product. In addition, in such processing, the steam check 
valve is subjected to impact and thermal stresses upon start up and shut 
down of a processing run. In view of such processing conditions, 
substantial difficulties have been encountered in respect to conventional 
apparatus for continuously introducing pressurized steam into viscous food 
products. In this regard, conventional check valves have presented 
problems, over extended time periods, of undesirable wear and breakage of 
valve components, as well as difficulties in respect to losses of viscous 
food product upon shutdown of the steam injection and back flow of viscous 
food products through the steam check valves. Such wear, breakdowns and 
valve malfunctions have required an undesirably high level of monitoring 
and repair of breakage of steam inlet valves. Conventional steam injection 
valves are also responsible for extensive labor costs in the necessary 
disassembly and cleaning of the processing apparatus to meet high sanitary 
food manufacturing standards, particularly when the valves have permitted 
back flow of the viscous food product through the valve. In this regard, 
the direct steam injection apparatus should function to prevent backflow 
of the viscous food product into the sanitary steam supply system both 
under startup and shutdown procedures, as well as continuous operating 
conditions which may include differential pressure fluctuations across the 
steam injection valve. In addition, the direct steam injection apparatus 
should present no crevices, threads or other irregular or convoluted 
surfaces which are capable of collecting and retaining food solids, yet 
should be capable of being readily disassembled and reassembled for 
cleaning and maintenance. 
Accordingly, it is an object of the present invention to provide improved 
methods and apparatus for introducing sanitary steam into a viscous food 
product. It is a further object to provide sanitary steam check valves 
having excellent wear characteristics in operation which may be readily 
assembled and disassembled for maintenance or cleaning, which present only 
continuous smooth surfaces to the sanitary steam, and which restrain the 
backflow of viscous food products during operation.

Generally the present invention is directed to apparatus for heating of 
food products by direct sanitary steam injection. In accordance with 
apparatus aspects of the present invention, sanitary steam injection 
valves are provided comprising a cylindrical steam inlet conduit provided 
with first connection means for compressively connecting the inlet conduit 
in abutting relationship to a steam supply conduit, and a cylindrical 
valve seat body integrally connected with the cylindrical steam inlet 
conduit distally of the first connection means. The valve seat body 
comprises a cylindrical wall section, a valve seat section distally of the 
inlet conduit, a substantially radially symmetrical frustoconical wall 
section internally of the cylindrical wall section forming with the 
cylindrical wall section and the valve seat section a steam discharge 
chamber within the cylindrical valve body. A valve bearing sleeve is 
positioned along the rectilinear axis of the cylindrical valve seat body. 
An important feature of the steam injection valve is the irrotational 
interaction of the valve bearing sleeve with its associated valve stem, 
which prevents undesirable wear under intense operating conditions. In 
this regard, the valve bearing sleeve has a plurality of at least three 
and preferably four rectilinear guiding surfaces for providing rectilinear 
motion along the axis of the cylindrical conduit. The valve bearing sleeve 
has a length along its axis of at least about 2 times its largest cross 
sectional dimension, and more preferably in the range of from about 2 to 
about 2.5 times its largest cross sectional dimension. 
In addition, the steam injection valve apparatus in accordance with the 
present invention is provided with a valve element comprising a valve head 
and a valve stem integrally formed or joined with the valve head and 
projecting through said valve bearing sleeve. The valve stem extends 
beyond the valve bearing sleeve distally of the valve head a distance of 
at least about 60 and perferably at least about 70 percent of the length 
of the valve bearing sleeve. The valve stem has a plurality of at least 
three and preferably four rectilinear guiding surfaces which interact with 
the rectilinear guiding surfaces of the valve bearing sleeve to prevent 
valve rotation during operation. In the absence of the provision of 
irrotational valve stem-valve bearing sleeve interaction, the valve would 
be free to rotate under the influence of the passage of intense, high 
velocity steam through the valve assembly, thereby producing premature 
wear and possible breakage, damage or disintegration of the device. 
The frustoconical wall projecting inwardly from the cylindrical wall 
section to separate the steam inlet conduit cylinder from the steam 
discharge chamber is provided with a plurality of passageways for 
transmitting steam between the zone internally of said cylindrical steam 
inlet conduit to the steam discharge zone. The passageways should 
desirably be distributed radially symmetrically about the axis of the 
frustoconical wall and should have a cross-sectional area at least about 
50 percent and preferably in the range of from about 60 percent to about 
70 percent of the area of the cross sectional area of the cylindrical wall 
section along its longitudinal axis. 
The check valve assembly is further provided with a valve compression 
spring coil having an outside diameter of less than about 50 percent, and 
preferably less than about 40 percent of the internal diameter of the 
cylindrical wall section, surrounding the outer wall of the valve bearing 
sleeve. An important feature of the present invention is the inherently 
santiary nature of the valve assembly, and relative ease with which it may 
be assembled and disassembled for cleaning and maintenance or inspection. 
In this regard, at the end of the valve stem distally of the valve head 
there is provided a unitary spring compression and retainer element 
positioned circumferentially about the valve stem end, together with an 
interlocking compression fastening mechanism positioned within a smooth 
bore in the valve stem at its end opposite the valve head, for maintaining 
the spring in compressed relationship against the rearward face of the 
frustroconical wall section. In closed position, the spring should provide 
a sufficient compressive force such that at least about 4 psig, and 
preferably in the range of from about 5 to about 30 psig of steam is 
required to open the valve from its valve seat. When assembled, one end of 
the compression spring is retained within a recess in the unitary 
retention element at its side adjacent the spring. A transverse locking 
element is positioned through a bore in the valve stem to prevent axial 
movement of the compression spring cap beyond the bore in a direction 
along the axis of the valve stem toward its distal end. The transverse 
locking element is itself positioned within a recess in the compression 
spring retainer element on its side opposite the compression spring 
recess, which is forced against the transverse locking element by the 
compressed spring element positioned between the retainer element and the 
end of the bearing sleeve, thereby preventing the displacement of the 
transverse locking pin from the valve stem in a direction orthogonal to 
the longitudinal axis of the valve stem. The resulting sanitary assembly 
may be readily disassembled by compressing the unitary compression spring 
retainer element against the spring to disengage the transverse locking 
element from the compression spring retainer element, removing the 
transverse locking element from the valve stem bore, and subsequently 
removing the valve spring retainer element and the valve spring from the 
valve stem. 
Sanitary steam check valves in accordance with the present invention find 
particular utility in methods for heating a viscous food product by direct 
steam injection. In accordance with such methods, a viscous food product 
to be heated is continuously pumped through a steam injection heating zone 
at a pressure in the range of from about 30 to about 45 psia, and sanitary 
steam at a temperature of at least about 310.degree. F. is conducted 
through the steam check valve at a rate of about 0.04 to about 0.08 pounds 
of steam per pound of viscous food product. The valve has excellent wear 
characteristics, and may be readily assembled and disassembled for 
maintenance or cleaning. 
In the manufacture of such steam injection valves, the cylindrical conduit 
may be welded to the valve seat body and frustoconical wall section 
including the axial valve bearing. The irrotational valve stem may be 
inserted through the matching irrotational valve bearing sleeve, the 
spring is compressively loaded over the valve bearing sleeve with the 
valve stem projecting through the sleeve, and said valve spring is 
maintained in a compressed condition by securing the valve stem cap at the 
distal end of the valve stem by means of the interlocking compression 
fastening mechanism to maintain a compressive force, sufficient to require 
a differential pressure of at least about 4 psig across the valve head to 
open the valve. 
Turning now to the drawings, various aspects of the present invention will 
now be more particularly described with respect to the specific embodiment 
illustrated in FIGS. 1-7. 
Schematically illustrated in FIG. 1 is a direct steam injection packaging 
system 10 which utilizes a direct injection sanitary steam check valve in 
accordance with the present invention. In order to provide and promote 
sanitary conditions, the various components of the system 10 may be 
constructed of a suitably inert and readily cleanable material such as 
stainless steel. 
In the illustrated steam injection system 10, a reservoir 12 of the food 
product to be packaged is pumped by means of a sanitary fluid feed pump 14 
along a direct steam injection conduit assembly 16. The pump 14 is adapted 
to pump the viscous food product at an elevated pressure in the range, of 
for example, about 15 to about 30 psig. Sanitary steam, which has been 
produced and maintained in appropriately purified condition for food 
processing utilization in accordance with conventional practice, is 
provided by sanitary steam supply system 18 at a desired pressure in the 
range of from about 60 to about 100 psig, and at a temperature of at least 
about 310.degree. F. The sanitary steam supply 18 includes appropriate 
controls for providing the steam in the desired temperature range, and for 
initiating and terminating the steam supply to the heating Tee 20. The 
sanitary steam check valve 100, as shown in FIG. 1, is incorporated 
between the heating Tee 20 and the steam supply 18. The temperature of the 
viscous food product into which the steam has been introduced in the 
heating Tee 20 may be monitored downstream of the Tee 20 by means of an 
appropriate temperature measurement device 22 which may be manually read 
by an operator, and/or which may also provide a data channel input which 
signals the product temperature to a process controller 24. Downstream of 
the temperature measurement sensor 22 is a sanitary recirculation valve 26 
by means of which the viscous food product may be redirected back to the 
reservoir 12, or conducted to continuous automatic processing or packaging 
equipment for sterile packaging of the heated product in accordance with 
conventional processing or packaging techniques. 
In operation, it is desired that the viscous food product conducted to the 
continuous automatic processing or packaging equipment should be heated to 
at least a minimum, predetermined temperature such as at least about 
175.degree. F., and it may be desirable that the food product be heated to 
a predetermined, relatively narrow temperature range. In this regard, it 
is desirable to heat viscous food products within the following ranges: 
______________________________________ 
Processing 
Product Temperature 
______________________________________ 
Relishes 175.degree. F. 
BBQ Sauce 190.degree. F. 
Jams & Jellies 175-200.degree. F. 
______________________________________ 
If the temperature of the food product downstream of the steam injection 
Tee 20 has not reached the predetermined, minimum temperature level which 
is determined to be desirable or necessary for processing of the food 
product, the recirculation valve 26 is operated while steam is 
continuously injected into the food stream by means of check valve 100 to 
direct the heated food stream back into the reservoir 12, so that the 
temperature of the viscous food product in the reservoir 12 is gradually 
raised. As the viscous food product stream heated by direct steam 
injection is recirculated to the holding tank, the temperature of the 
viscous food product in the tank is progressively increased, so that the 
temperature of the food product downstream of the point of steam injection 
is also progressively increased. When the viscous food product reaches the 
predetermined, minimum processing temperature downstream of the zone of 
steam injection, the valve 26 may be controlled to cease the recirculation 
to the tank and to direct the heated food product to the automatic 
processing or packaging equipment. In this manner, no food product which 
has not reached the desired, predetermined temperature is permitted to be 
packaged. While these control aspects may be carried out manually, a 
suitable process controller 24 may similarly monitor the temperature of 
the food product in the steam injection conduit assembly 16, and may be 
adapted to control the operation of the pump 14 and/or the steam supply 
18, as schematically illustrated in FIG. 1. 
In operation, the steam injection heating system 10 will be thoroughly 
cleaned to high sanitary food specifications and the viscous food product 
to be heated and packaged will be introduced into the reservoir 12. The 
pump will be turned on with the recirculation valve in recirculation 
position and with the steam check valve 100 in closed position without 
introduction of steam. Typically the pressure of the food product at the 
steam injection Tee 20, without steam injection, may be in the range of 
from about 15 to about 20 psig. The high pressure steam may subsequently 
be introduced at a pressure of 30 to 55 psig through the sanitary check 
valve 100. Upon introduction of the high pressure steam into the food 
product at the steam injection Tee 20, the back pressure exerted on the 
pump 14 may typically rise by an amount in the range of from about 5 to 
about 15 psi, to a pressure typically in the range of from about 20 to 
about 30 psig. 
The embodiment of the sanitary steam check valve 100 utilized in the steam 
injection system 10 is illustrated in FIGS. 2-7. As shown in FIG. 2, which 
is a transparent side view with selected internal features shown by dashed 
line, the illustrated steam check assembly comprises a valve assembly 500, 
a valve seat body 300, and an outer tube or cylinder 400 which is 
integrally joined with the valve seat body 300. The end joining faces 402, 
404 of the valve 10 have tapered, frustoconical end pieces 406, 408 which 
are adapted to be utilized with a suitable compression clamp (not shown) 
to connect the respective valve faces 402, 404 with like faces in the 
steam piping system and viscous food processing apparatus in a fluid-tight 
manner. In this regard, O-ring recesses 410, 412 are provided in the faces 
402, 404 to provide for a compression O-ring seal upon clamping of the 
faces 402, 404 to like faces with an elastomeric O-ring therebetween. 
As shown in FIG. 3, the valve seat body 300 comprises a valve bearing 
sleeve 302 which in the illustrated embodiment has a square cross section 
having a nominal internal width along each of the square sides of 0.375 
inches, and a nominal length of 1.156 inches. The valve seat body further 
includes a radially symmetric steam transmission chamber 304 formed by 
integral radially outwardly extending wall 306, frustroconical wall 
section 308 and cylindrical valve seat and interconnection wall section 
310. The frustroconical wall section 308 is provided with a plurality of 
four steam transmission holes 312, 314, 316 and 318 having a nominal 
diameter of 0.5 inches, which are radially equally spaced about the 
central axis of symmetry of the valve seat body 300. The axes of the 
cylindrical steam transmission holes are respectively each substantially 
orthagonal to the surface of the frustroconical wall section 308. 
In the illustrated embodiment, the effective area of the orifices which 
communicate into the steam injection recess is in the range of from about 
60 to about 65 percent of the cross sectional internal free area of the 
valve body. This provides an interior zone of pressure reduction which 
together with the significant compression force exerted by the valve 
spring, acts to prevent entry of the viscous food product into the steam 
supply system upon steam supply system shutdown or fluctuation of the 
pressure of the viscous food product at the point of steam injection, and 
further may tend to reduce cavitation and vibration within the valve body. 
As shown in FIG. 4, the bearing sleeve 302 has an irrotational cross 
section, which in the illustrated embodiment is a square internal bore 
320. The irrotational cross section of the bearing sleeve 302 prevents 
rotation of the valve, as will be described in more detail hereinafter. 
The bearing has a length of at least about 3 times its minimum cross 
sectional dimension. In the illustrated embodiment, the bearing is 
nominally 1.156 inches long. 
The steam injection apparatus 100 further includes a valve element 500 
(FIG. 5) comprising a valve stem shaft 502, a valve head 504 and a valve 
retainer and spring compression assembly 508 (FIGS. 1, 7). As discussed, 
the valve 500 has an integral square valve shaft section, which is adapted 
to guide and restrain the valve 500 in axial motion along the longitudinal 
axis defined by the valve bearing sleeve 302, while preventing rotation of 
the valve stem 502 within the sleeve 302. The illustrated valve stem 502 
has an outside dimension of 0.370 inches, which is adapted to provide 
close tolerance with the shaft sleeve 302 of the valve seat body upon 
assembly of the injection valve 100, as will be described in more detail 
hereinafter. The length of the square irrotational shaft 502 is 
substantially longer than the bearing 302 to permit axial movement thereof 
within restrained, predetermined values. 
The valve stem shaft 502 flares at one end thereof to form a radially 
symmetrical valve head element having a diameter of 1.5 inches. The valve 
head is provided with a beveled valve seating surface 506 at a 45 degree 
angle to the longitudinal axis of the valve unit 500, which is adapted to 
seat against the corresponding valve seating surface of the valve seat 
body 300. The illustrated valve element 500 is fabricated from stainless 
steel, with the valve seat body being heat treated at a temperature of 
1850.degree. F. for 1.5 hours, air cooled to room temperature and reheated 
to 325.degree. F. for one hour in order to provide a Rockwell "C" hardness 
in the range of 45-48. 
Illustrated in more detail in FIG. 1 and FIG. 7 is the interlocking valve 
spring retainer assembly 508 particularly including the sanitary valve 
assembly/disassembly spring compression retainer element 702 and 
interlocking pin 704. As shown in FIG. 7, the spring compression retainer 
element 702 is a unitary cylindrical fastener having a cylindrical recess 
706 (FIG. 2) with an internal diameter slightly larger than the outside 
diameter of the compression spring 402. The compression retainer element 
702 has an axial bore 708 of square cross section corresponding to that of 
the valve stem shaft, such that upon insertion of the shaft through the 
opening, the retainer cup of the spring is secured in the recess 706 of 
the spring retainer element. The retainer element is also provided with a 
recess 710 on its side opposite recess 706 retaining the interlocking 
split pin element 704. In this regard, the split pin 704 is compressed 
orthagonally of its axis and inserted through the bore 712 at the end of 
the valve stem shaft while the retainer element 702 is compressed against 
the spring to expose the bore 712. Upon releasing the cup, the inserted 
split pin, which has a length permitting it to be retained within the 
recess 710, but larger than the length of the bore 712 and the base 708, 
is locked in position by the retainer cup recess 710 and the action of the 
split pin end projections. The illustrated compression element 702 may be 
subjected to substantial impact stresses and is accordingly fabricated 
from stainless steel and heat treated the same as valve element 500. 
In manufacture of the direct steam injection valve assembly 100, the valve 
stem 502 of the valve element 500 is inserted through the steam input 
cavity and through the square bearing sleeve 302. The spring 402 is then 
inserted over the outer portion of the bearing shaft, as shown in FIG. 2, 
and the retainer element is placed over the end of the valve stem 502, 
forcing the spring inward. The split roll pin 704 is inserted through the 
transverse roll pin assembly bore at the distal end of the valve to lock 
the valve and spring assembly in place within the direct steam injection 
check valve assembly. The illustrated valve 100 should be loaded with 
sufficient spring tension to require at least about 5 psi to initially 
open the valve. The spring is adapted such that at least about 5 psig of 
steam pressure greater than the pressure on the valve face from the 
pressurized viscous food product is required to fully extend the valve. In 
the illustrated embodiment, the travel of the valve from its closed 
position to its fully extended position is approximately 0.4 inches. Upon 
full extension of the valve, the proximate surface of the end cup adjacent 
the valve body shaft surface comes in direct contact with such surface, 
without placing additional wear or compression or impact upon the spring. 
Direct steam injection valves in accordance with the present invention may 
be utilized in operation for extended periods of time with minimal wear 
and maintenance expense. In addition, such direct injection valves may be 
readily disassembled for cleaning, and upon disassembly contain no 
substantial recesses, crevices, threads or similar surfaces which require 
meticulous cleaning to maintain sanitary conditions. Accordingly, it will 
be appreciated that improved direct sanitary steam injection valve systems 
have been provided in accordance with the present invention, as described 
hereinabove. While the present invention has been particularly described 
with respect to the specific embodiment illustrated in FIGS. 1-7, it will 
be appreciated that various modifications and alterations may be made 
based upon the present disclosure and are intended to be within the scope 
of the following claims.