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Publication numberUS3766844 A
Publication typeGrant
Publication dateOct 23, 1973
Filing dateDec 21, 1971
Priority dateDec 21, 1971
Publication numberUS 3766844 A, US 3766844A, US-A-3766844, US3766844 A, US3766844A
InventorsT Donnelly, J Haueter, C Lind, W Krisko, D Schoen
Original AssigneeUs Army
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Protective system for contaminated atmosphere
US 3766844 A
Abstract
A system and method to provide protective shelter in contaminated atmosphere areas utilizing a protective shelter, a portable protective entrance, gas-particulate filter unit and associated components, pressure sensing network and associated components and controls, sliding-plate airflow valves, and a power distribution unit.
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Description  (OCR text may contain errors)

United States Patent 1 Donnelly et al. 7 l

[ 1 PROTECTIVE SYSTEM Eon CONTAMINATED ATMOSPHERE [75] Inventors: Thomas GQDonnelly, Minneapolis;

James A. Haueter, Burnsville; William J. Krisko, Eden Prairie; Donald W. Schoen, Saint Paul; Chester S. Lind, Bloomington, all of Minn.

The United States of America as represented by the Secretary of the Army, Washington, DC.

[73] Assignee:

[22] Filed: Dec. 21, 1971 [21] Appl. No.: 210,344

[52] US. Cl 98/33 R, 98/1.5, 49/68,

52/66,135/1 [51] Int. Cl... F24f 13/00 [58] Field of Search 98/1.5, 33 R, 39, 98/40, 41, DIG. 7; 128/204; 135/1, 4; 52/66, 71; 49/68 1 Oct. 23, 1973 [56] References Cited UNITED STATES PATENTS 3,157,185 11/1964 Schoenike 135/4 R 3,501,213 3/1970 Trexler 49/68 3,629,875 12/1971 Dow 135/1 R 3,316,828 5/1967 Boehmer... 98/1.5

3,478,472 11/1969 Kwake 98/1.5

3,587,574 6/1971 Mercer..... 128/204 3,601,031 8/1971 Abel 98/33 Primary Examiner-Meyer Perlin Attorney-Harry M. Saragovitz et al.

[57] ABSTRACT A system and method to provide protective shelter in contaminated atmosphere areas utilizing a protective shelter, a portable protective entrance, gas-particulate filter unit and associated components, pressure sensing network and associated components andcontrols, sliding-plate airflow valves, and a power distribution unit.

13 Claims, 62 Drawing Figures PATENTEU HGT 2 3 \873 'SIEEI mar 13 l/Vl/E/VTORS Thomas G. flannel/y James A. Hauefer William J. Kriska Donald W. Schoen Chester 5'. L/nd Ma Fig. 2

ATT RNEYJ' PAIENIEDHBI 2a 1915 SHEET 0211f 13 "final,"

I/Vl/E/VTORS Thomas G. Donnel/y James A. hauefer William J. Kris/r0 Donald W. .Sclroen Chester 5'. Lind PAIENTEB 0U 23 I915 SHEET 03 0F 13 INVENTORS' 7' homes 6. Donne/I James A. Hauefer William J. lfrl'sko Donald W. Schoen Chester ATTO EYS PMENTEB 0B! 23 1975 SHEET 0'4 0F 13 IHI INVENTORS M m n e d OMMMM HKS W A w S de mnmwwW m mm M 1. TJWDC r ATTO EY5 PATENTEDBCI 23 4973 3 768,844

sum as or 13 Fig.30

//WE NT 0R5 Thomas 6. DonneI/y James A. Hauefer Wi/liam J. Krisko Donald W. .Schaen Chester 5. Lind PAIENIEUmtrza ms SHEEI DBUF I3 INVENTORS Thomas 6'. Donnel/y James AJHaue/er William J. Kris/r0 Dona/d W. Sc/men Chester .5. Lina PAIENIEUumza ms 3155 sum over 13 IWVE/VTORS Thomas 6. flannel/y James A. Haue/er William J. k'rl'sko Dana/a W. Sc/men Chester .5. Lina '72-, 2/2, I

mEmiuocraa ma 3,766,844

sum 08 or 13 Fig.54 4

IMPUT FROM TEST Powrc PRESSURE TRANSDUCER T0 AIRFLOW VALVE MOTOR *W r o R2 7 1 TEST PmfiTD TESTY TO AIRFLW POINT A VALVE W MOTOR l/VVE/VTURS' 7 Thomas 6. flannel/y TEST POINT B James A. Hauefer William J. Kr/sko Donald W. Sahoen ATTOR/V S PATIENIEBMII 23 III:

SIIEEI 09 [IF I3 Fig.56 I

POWER IN 28 V DC Fig. 57

DUST

EXHAUST BLOWER POWER DISTRIBUTION UNIT (DC) DC FAN ASSEMBLY CONTROL/PRESSURE SENSING MODULE DUST EXHAUST BLOWER TRANSFORMER/ RECTIFIER MODULE (GOHZ) POWER IN O-- 208 VAC,

POWER DC FAN DISTRIBUTION UNIT ASSEMBLY 60 HZ. IS-PHASE POWER IN ZOBVAC, 400 HZ,

POWER DISTRIBUTION UNIT (AC) CONTROL /PRESSURE 5 E N S I NG MO DULE FAN ASSEMBLY 5' PHASE Fig. 58

DUST EXHAUST. BLOW R TRANSFORMER] RE CTI FIE R MODULE(400 HZ) CONTROL/PRESSURE Dc SENSING MODULE INVENTORS Thomas 6. Donne/1y James A. Him/afar William J. Kris/r0 Donald W. Schaen Chester 5. .L/Ind Maw 6Mxfm ATTOR/V S PAIENTEDncr 23 ms STATIC PRESSURE (in. wg) AIRFLOW RESISTANCE (in. W9) 0 N a, 5 v6 3 6 6 3,766,844 SHEET 110? 13 Fig. 60

Fan Sfu'ric Pressure Two-Filter GPFU Resistance Three-Filter GPFU Resistance PRIMARY AIRFLOW (cfm) INVENTORS Thomas 6. flannel/y James A. Have/er William J. Krisko Donald W. Schoen Ghesfer .5; ind

A7705 EYS PROTECTIVE SYSTEM FOR CONTAMINATED ATMOSPHERE DEDICATORY CLAUSE The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

Our invention relates to a new method and system having utility for providing protective shelter in a contaminated atmosphere.

A problem has long existed to provide an easily erected means and simple method for providing protective shelter in contaminated atmosphere areas; including means for personnel to perform necessary decontamination procedures before entering a protective shelter while not in a contaminated atmosphere and a means and method to permit personnel to enter and exit the protective shelter without loss of compartment pressurized protection. Our invention was conceived and reduced to practice to solve the aforementioned problem and to satisfy the long felt need for the aforementioned protective shelter and method.

A principal object of our invention is to provide an apparatus and method which is easily erected and simple to use to permit performance of decontamination procedures outside of a contaminatedatmosphere but prior to entering a protective shelter.

Another object of our invention is to provide an apparatus and method to permit personnel to enter and exit a protective shelter witout loss of compartment pressurized protection.

Other objects of our invention will be obvious or will appear from the specification hereinafter set forth.

FIG. 1 is a view showing the utility of our apparatus.

FIG. 2 is a schematic top view of the apparatus shown in FIG. 1.

FIG. 3 is a view of the storage or transit package of our apparatus.

FIG. 4 is a cutaway view of our apparatus and the en-.

trance to a protective shelter.

FIG. 5 is a view through 5-5 of our apparatus shown in FIG. 4.

FIG. 6 is a view of the pin locking means to connect our apparatus to a protective shelter as shown in FIG. 1.

FIG. 7 is an exploded view of the components shown in FIG. 6.

FIG. 8 is a view through 8-8 of our apparatus shown in FIG. 4.

FIG. 9 is a view through 99 of our apparatus shown in FIG. 4.

FIG. 10 is a view of the inlet airflow valve with dust cover for our apparatus.

FIG. 11 is a view of the top of our apparatus which also forms one half of the container means of the package shown in FIG. 3.

FIG. 12 is a view of the door for our apparatus in the assembled mode.

FIG. 13 is a view of the door for our apparatus in the unassembled mode.-

FIG. 14 is a view through 14-14 of FIG. 12.

FIG. 15 is a view through 15-15 of FIG. 12.

FIG. 16 is a partial view of the frame of the door shown in FIG. 12, wall, and a storage pocket of our apparatus.

FIG. 17 is a view of the door shown in FIG. 12 and a cover means for the door window.

FIG. 18 is a view of the pressure sensing module mounted within our apparatus.

FIG. 19 is a view of the asembly means for our apparatus to connect the supports to the top shown in FIG. I 1.

FIG. 20 is a view of the connector means shown in FIG. 19.

FIG. 21 is a view of the supports for our apparatus in the storage mode in the bottom of our apparatus.

FIG. 22 is a view of the sliding-plate airflow valve of our apparatus to control the protective shelter pressur ization.

FIG. 23 is a view of the supports for our apparatus in the folded or storage mode.

FIG. 24 is a view of the top, bottom and supports of our apparatus in the partially erected mode.

FIG. 25 is a view of the support brace for our apparatus.

FIG. 26 is a view of the support for our apparatus in the partially erected mode.

FIG. 27 is an enlarged view of the pull pin for the support for our apparatus shown in FIG. 26.

FIG. 28 is a side view of the support for our apparatus.

FIG. 29 is a front view of the support for our apparatus. FIG. 30 is a view of the gas-particulate filter unit assembly of our apparatus.

FIG. 31 is a view of the control/pressure sensing module for our apparatus.

FIG. 32 is a view of the stand for the gas-particulate filter unit of our apparatus.

FIG. 33 is a view of the gas filter for our apparatus.

FIG. 34 is a view of the particulate filter for our apparatus.

FIG. 35 is a schematic view showing the air flow through our apparatus.

FIG. 36 is an end view of our apparatus shown in FIG. 30.

FIG. 37 is a view through 37-37 of our apparatu shown in FIG. 36. V

4 FIG. 38 is a top view ofthe outer access cover which retains the gas filter shown in FIG. 33 within the assembly for our apparatus shown in FIG. 30.

FIG. 39 is a view through 39-39 of FIG. 38.

FIG. 40 is a side view of the outer access cover with the bar retaining means in the open position.

FIG. 41 is a view of the inner access cover which retains the particulate filter shown in FIG. 34 within the assembly for our apparatus shown in FIG. 30.

FIG. 42 is a detail view of the latching means for the barretaining means shown in FIGS. 38, 39, and 40.

FIG; 43 is a view of the inner access cover securing means mounted within the bar retaining means shown in FIGS. 38,39, and 40.

FIG. 44 is a view of the hinge means which connects the bar retaining means to the outer access cover shown in FIGS. 38, 39, and 40.

FIG. 45 is a cutaway top view of our apparatus sliding-plate airflow valve showing the internal structure of the valve.

FIG. 46 is a side view of the sliding-plate airflow valve shown in FIG. 45. Y

- FIG. 47 is a partial cutaway top view of the slidingplate airflow valve shown in FIG; 45 to show the sliding-plate structure.

FIG. 48 is an end view of the sliding-plate airflow valve shown in FIG. 45 to show the motor means which activates the sliding plate.

FIG. 49 is an exploded view of the sliding-plate airflow valve shown in FIG. 45 to show components in detail and motor gear track integral with the sliding plate.

FIG. 50 is a top view of the micro switch assembly limit stop means to control the travel of the slidingplate.

FIG. 51 is a side view of the switchmeans shown in FIG. 50.

FIG. 52 is an exploded view of the motor and motor mount means shown in FIG. 48.

FIG. 53 is an exploded view of the micro switch assembly shown in FIGS. 50 and 51.

FIG. 54 is a schematic electrical diagram of the control panel circuitry of our control/pressure sensing module. 7

FIG. 55 is a schematic electrical diagram to show the circuitry of our pressure sensing network to operate our sliding-plate valves.

FIG. 56 is a block diagram of the power distribution through our gas-particulate filter unit components for 28 volt-direct current input.

FIG. 57 is the same as FIG. 56 for a 208 volt alternating current, 60Hz, three phase input.

FIG. 58 is the same as FIG. 56 for a 208 volt alternating current, 4001-12, three phase input.

FIG. 59 is a graphical representation ofa 250 cfm fan airflow resistance through our system.

FIG; 60 is a graphical representation ofa 400 cfm fan airflow resistance through our system.

FIG. 61 is a graphical representation of a 600 cfmfan airflow resistance through our system.

FIG. 62 is a graphical representation of flexible duct airflow resistance in our system.

Our invention and FIGS. 1 to 62 will now be described in detail as follows.

Our protective system can be applied to a wide variety of vans, vehicles or shelters. Several application considerations must be evaluated, however, prior to selecting an appropriate system. The considerations to be evaluated include operational structure, performancecharacteristics, and application of the system. Our invention will be described in the light of the aforementioned considerations to permit those of ordinary skill in the art to determine the applicability of our system to any particular application.

Regarding operational structure, a flow diagram of the gas-particulate filter unit assembly shown at in FIG. 30 is shown in FIG. 35 to illustrate 'the gas particulate filter unit filtering operation. Air enters the inlet shown at l in- FIG. 35 and is drawn into dust collector 2 where 90 percent of the airborne dust is separated and exhausted back to ambient through dust exhaust 3. The partially cleaned air is then drawn through fan assembly 4 and forced through the particulate filter 5 and gas filter 6 which removes essentially all the particulate and gas contaminants, respectively. The purified air then passes through outlet airflow valve 7 which controls the airflow quantity required for pressurization of protected shelter 8; air being exhausted from compartment 8 to ambient by conventional exhaust means 9. A preferred arrangement of our system is schematically illustrated in FIG. 2 which shows the gas-particulate filter unit, hereinafter referenced as GPFU, remotely placed outside of a protected shelter. The GPFU is shown mounted in a ground stand 11 and provided with an air inlet protective cap 12. Purified air is pushed through the GPFU by the fan assembly and is ducted through the shelter 8 wall by means of duct 13 and entrance 17 by means of duct 76, as shown in FIG. 1. Electrical power is directed to the power distribution unit 14 mounted on the GPFU. From there, power is distributed through interconnecting cables 16, as shown in FIG. 36, to fan assembly 4, dust exhaust blower in the dust collector 2, GPFU outlet airflow valve 7, as shown in FIG. 35, and control/pressure sensing module 15, as shown in FIG. 30. GPFU operation is controlled and monitored by control/pressure sensing module 15 which, installed within the shelter, senses the pressure differential between the shelter and ambient atmosphere and controls the GPFU outlet airflow valve 7 to maintain the predetermined pressure differential by varying the airflow. The GPFU can be mounted outside or inside shelter 8 and can be operated in either a push-through" or a pull-through structure. When the GPFU is mounted outside of shelter 8, as shown in FIGS. 1, 2, and 35, fan assembly 4, as shown'in FIG. 35, is mounted inside the GPFU, and air through the primary filtering elements (gas and particulate filters) is pushed through. When the GPFU is mounted inside shelter 8, not shown in the drawing, fan assembly 4 is mounted downstream from the GPFU and is connected to the GPFU outlet airflow valve by a flexible duct. This is called a pull-through structure, because the fan assembly pulls the air through the primary filtering elements. The GPFU can utilize a single, double, or triple filter to suit a given application and airflow requirement; the airflow range in cubic feet per minute for each filter arrangement being as set forth below.

GPFU Airflow Range (cfm) One-Filter Up to 200 Two-Filter Up to 400 Three-Filter Up to 600 TABLE 1 Primary Alternate GPFU Fan Assembly Fan A embly One-Filter 250 cfm ac None 250 cfm dc Two-Filter 400 cfm an 250 cfm ac 400 cfm do 250 cfm dc Three-Filter 600 cfm ac 400 cfm ac 600. cfm do.

400 cfm dc The alternate fan assemblies provide lower flows and power consumptions for each size GPFU as shownin the Summary of GPFU Weight and Power of Table 2 below. Fan assemblies should not be used with GPFUs smaller than those designated in Table 1 above TABLE 2 28 V D.C. 400 Hz. A.C. 60117.. A.C. power source power source power source Fan Maximum assembly, airflow, Power Weight Power Weight; Power Weight (I PFU c.f.m. c.l'.in. (watts) (1b.) (watts) (1b.) (watts) (lb.)

Ono-filter 250 200 1, 050 158. 7 l, 010 103. 3 1, 100 .238. 7 Two-filter 250 300 1, 210 201. 3 l, 150 205. .l l, 370 281. 3 Two'liltor 400 100 1,020 .200. .2 1,430 214. 2 l, 840 280. 2 'llu'oo-lillcr, 400 180 1,000 256. 8 l, 560 201. 8 l, 800 330. 8 'lliruo-liltoi' 000 000 1, 050 263. ll .2, 030 267. 3, 350 343. l) RCFU 250 200 500 160. 4 470 165. 0 500 240. l

*Rccirculating filter unit.

The power distribution units used on all arrangements of GPFUs must be selected to be compatible with the type of applied electrical power and fan size as indicated in Table 3 below.

TABLE 3 Power Source Fan Assembly 208 V ac 400 Hz 250 cfm 208 V ac 400 Hz 400 cfm 208 V ac 400 Hz 600 cfm 28 V do or 208 V ac 60 Hz 250 cfm 28 V do or 208 V ac 60 Hz 400 cfm 28 V dc or 208 V ac 60 Hz 600 cfm FIGS. 56 to 58 show the power distribution through GPFU components for the different types of powers, and the legends thereon are self-explanatory. Protective Entrance l7 and related hardware and airflow and pressure regulating controls is provided as an entry and exit means to shelter 8; the entrance structure being subsequently described in detail. In addition to allowing entry or exit to shelter 8, the protective entrance provides a place where personnel can don protective clothing before entering the contaminated environment and to perform decontamination procedures before entering the shelter. 'The protective entrance is scavenged with purified air to provide a 1000: l reduction of a completely airborne contaminant concentration within minutes while retaining protective entrance int'ernal pressure between 0.4 0.8 inches wg. The purified air may be supplied either by a one, two or three filter GPFU which simultaneously supplies purified air to pressurize shelter 8 or by a separate recir culating filter unit. FIGS. 1 and 2 illustrate a remotelymounted GPFU in the push through configuration simultaneously supplying purified air to both shelter 8 and protective entrance 17. I

Regarding performance characteristics, FIGS. 59 through 61 illustrate the fan head and the airflow resistance of the GPFUs for push-through operation of a 250 cfm fan, 400 cfm fan, and 600 cfm fan respectively. The difference between the fan head curve and the curve for. GPFU airflow resistance is the amount of reserve head available for particulate filter dust loading, duct losses and enclosure pressurization. As an example, in FIG. 59, at 200 cfm, the pan provides approx- Airflow requirements for the user should be deterimately 17.6 in. wg fan head, and the airflow resistance mined initially for the ventilation requirement for personnel in the shelter per Human Factors guidelines, the equipment cooling requirements if ventilated with purified air, heater combustion air requirements, the flow necessary to pressurize the shelter to 1.2 in. wg minimum, and necessary scavenging for any internally generated noxious gases. The GPFU size required is based on the maximum of the flow requirements and whether a protective entrance is employed. Application considerations of mounting location, personnel ventilation, equipment ventilation, leakage of the protected compartment, heaters, air conditioners, and protective entrances are disucssed below; and an example of a typical shelter analysis is included last.

Gas-particulate filter unit (GPFU) assembly 10 can be mounted in the interior of shelter 8, on the exterior wall of shelter 8, or ground-mounted externally of shelter 8. The selection of location depends on several factors, such as weight distribution, space limitations, structural strength, shelter mobility, etc. Where m'obility and protection of the system are prime requirements and space is available, internal mounting is the most advantageous. Specific location of the unit within the enclosure will be dictated by possible restrictions of center of gravity, wall/ceiling structural strength, internal system equipment configuration, location of heaters, air conditions, etc. When internal space is not available, but mobility is critical, an external mounting to the shelter may provide the best solution. Here, again, weight, center of gravity and structural strength are of prime consideration, especially in regard to shelters mounted on trailers or' trucks. In addition, locating the GPFU on the outside of a trailer-mounted shelter may interfere with the vehicle which pulls the trailer. Here the various departure angles between the trailer and the vehicle must be considered. When mobility and quick reaction are secondary considerations or when no shelter mounting locations are available, ground mounting of the GPFU in a stand may be the best solution, as shown in FIGS. 1 and 2. When ground mounting a GPFU, the usual problems of weight and volume are not so severe. The location of the GPFU assembly 10 with reference to shelter 8 must also be considered as excessive duct lengths or bends will reduce the GPFU airflow capactiy due to increased airflow resistance. FIG. 62 demonstrates the airflow resistance of a 6 in. diameter flexible duct 20 ft. long or a 6 in. diameter flexible duct 10 ft. long and curved in an 8 ft. radius.

When using protective entrance 17, several GPFU application choices are available. If it is envisioned that shelter 8 may require protection at times when the protective entrance is not utilized, a standard GPFU shelter application could be used in any of the above GPFU locations, and a protective entrance and recirculating filter unit (for pressurization and scavenging of the protective entrance) could then be provided and used only when necessary. If the protective entrance is required under all operating conditions, one GPFU providing protection for both the protective entrance and shelter is the best selection; as shown in FIGS. 1 and 2. Appli-.

cation of our system to two shelters, one for personnel and one for equipment, is also possible. A single GPFU of the appropriate size can be used for both shelters with the personnel shelter containing the controls and having priority on the airflow from the GPFU. A modification to the GPFU application configurations is possbile, to extend filter life when a protective entrance is used, by using a recirculating duct from the protective entrance outlet to an adapter on the GPFU inlet. All applications of our system to shelters require air duct and electrical feedthrough in the shelter walls, as well as internal space for mounting of the control module(s). When an air conditioner is used, filtered air may be directed to an air makeup intake port through an adapter.

Personnel ventilation requirements for a given shelter are set by human engineering requirements, and the requirements are dependent on the number of people operating within the shelter and the types of activities that the personnel might be performing during their The ventilation requirement defines the minimum re-' quirement for leakage from the shelter. For example, assume a situation where the shelter houses only personnel, with no heat generating equipment, and only wind and diffusion conditions are considered. The optimum condition would be an airflow into the shelter of a value just sufficient to meet the personnel ventilation requirements while maintaining shelter pressurization. The situation may arise where the shelter leakage is below the ventilation requirements of the personnel. In such a situation, leakage must be created in the shelter if it does not exceed make-up air requirements for an air conditioner. In order not to waste purified air, the purified air should be ducted through the personnel door of the shelter and into the protective entrance, if used, to assist in the scavenging of the protective entrance. Such a built-in leakage device should be designed so as to allow passage of the desired flow rate of air and also serve as a check valve to prevent flow of air from the protective entrance back into the shelter,

Equipment associated with the function of our system may be cooled by means of an air conditioner or with ambient air. When cooled by an air conditioner, the equipment can be located within the same enclosure as the personnel. The cooled air from the air conditioner is directed to the personnel area from which it is drawn through equipment cabinets and to the return up air is provided to satisfy personnel ventilation requirements. When protection equipment is used, the filtered air is introduced into the air conditioner outside air intake port. The air conditioner should have sufficient capacity to cool the additional air required to pressurize the enclosure. When ambient air is used for cooling, the equipment can be located as an integral part of the personnel compartment or may be in a separate adjacent compartment with interconnecting cabinet doors. When protection equipment is used in a personnel compartment with integral equipment, the use of an air conditioner as compared with the large volume of filtered air required to cool the equipment should be considered. When protection equipment is used in a personnel compartment with integral equipment, the use of an air conditioner as compared with the large volume of filtered air required to cool the equipment should be considered. If the equipment is in of the air conditioner to be recirculated. Outside make a separate compartment and requires access through interconnecting cabinet doors during operation, the equipment should be cooled and pressurized with filtered air. The filtered air requirement may be high if an air conditioner is not added. If access to the adjacent compartment is not required during operation and the adjacent compartment is protected from direct contamination, filtered air is not essential. However, the cooling fan should be located so that the adjacent compartment is under negative static pressure. It should be noted in these considerations that air passing through the GPFU increases in temperature 10 to 15 F., depending upon the size unit and airflow rate.

In order to prevent the migration of contaminants into the shelter, the protection equipment must be caatmospheric pressure, is maintained in the shelter. The

range of internal pressures is dictated by the requirement that shelters must be protected under operational conditions of a 50 mph wind. Such air velocity value causes a stagnation pressure on the upstream face of the shelter of approximately 1.2 in. wg. Asecond consideration is the transfer of contaminants from the outside tothe inside of the shelter through gas diffusional forces. In this case, one must consider the velocity of the air through a given opening and ensure that the air velocity developed from the pressure gradient is greater than the diffusion velocity of the contaminants from the concentration gradients. The internal pressures necessary to overcome these gas diffusion forces are generally lower than the internal pressures required to exceed wind stagnation pressure. The two foregoing phenomena require that the pressure within a protected shelter be maintained in the range given. Further, the pressure must be maintained above the pressures of any contaminated area in or around the shelter. Another consideration is the possibility of high pressure areas within environmental control equipment when this equipment is operating in contaminated air. The latter situation arises in the combustor/heat exchanger section of heaters or in the condenser section of air conditioning units. Leakage reduction measures may have to be performed on a particular shelter to keep the filter unit to a minimum capacity for air conditioner or heater make-up air and to keep the volume, weight and power requirements of the GPFU to a minimum. However, for non-environmental controlled shelters, the cost of reduction may surpass the additional cost of a larger filter unit that would accommodate the higher leakage. This condition must be considered when leakage reduction measures are evaluated. In order to reduce leakages and locate the major sources thereof, one must first be able to detremine the magnitude of the leakage. The method used to determine magnitude is to pressurize the compartment to a constant pressure and monitor the air flow required to maintain pressure in the compartment when various areas in the shelter are covered with impermeable material. By recording the reduction in leakage after each major step in sealing leakage paths, all of the significant shelter leakages can be accounted for and the magnitude of leakage determined. Leakage areas can also be located visually in some cases, such as by introducing highly visible, persistent smoke into the pressurized compartment. Another method is to use an ultrasonic leak detector in conjunction with an ultrasonic sound generator. The generator is placed on one side of the shelter, such as inside, and the detector is used on the opposite side of the shelter, such as outside the shelter, to locate the transmission of sound through leak passages. Some common leakage shelter components are ceiling panels and filters, conventionally-hinged doors, bi-fold doors, door knobs, locks, handles, windows, hinges, heating ducts, heating plant, water pipes, wires, cables, light switches, fixtures, electrical receptacles, air exhausts, vents in eaves and roof, root hatches, air conditioners, etc. Sealing materials that minimize air leakage and provide protection against contamination must be impermeable to air, resistant to the contaminant and easily installed. Furthermore, sealing materials must be durable enough to meet environmental extremes and field operation conditions, and they must have shelf lives compatible with normal procurement and usage practice. Use of toxic, flammable, or explosive compounds should be avoided. Many materials can be used for sealing leakage areas in shelters, eitherpermanently or temporarily, such as caulking compounds, non-hardening extruded tapes. non-hardening mastics, spray coatings, pressure sensitive tapes, gaskets, adhesives, plugs, fabrics, and films.

Air conditioning units must be carefully evaluated when installing protection equipment as their design and performance have considerable influence on the ize the shelter for protection, the air conditioner may not be able to sufficiently cool the shelter equipment under high ambient temperatures. If shelter leakage cannot be reduced, a larger air conditioner may be required. Our system fan assembly is cooled by the filtered air and adds about l0 F to 15 F temperature to this air, depending on fan size and flow. This effectively increases the temperature of the make-up air to the air conditioner when the GPFU is operating and must be considered when sizing the air conditioner. An effective interface must be assured for compatible operation of the air conditioner and our system. Two approaches are available, namely; duct the filtered air directly into the shelter and operate the air conditioner in the recirculation mode, or duct the filtered air into the air conditioner external make-up air port and operate the air conditioner with make-up air. In the first case, the two units are operated in parallel, and, in the second, they are in series. With the FPFU mounted within the shelter, the first method would be required; with the FPFU external, either method could be used. The second method is preferred because it allows the air to be conditioned prior to entry into the personnel compartment. Provisions should always be made to ensure that air conditioner ambient make-up ports are sealed during system operation in either installation.

When using our protective entrance 17 with shelter 8, one must consider airflow capacity required for scavenging the protective entrance within the specified essential time limit of 5 minutes, space available around the personnel entry door for an interface, and provision for supporting the floor of the protective entrance when used on a shelter that has the entry door higher than 8.5 in. off of the ground. The minimum airflow required to scavenge the protective entrance within the specified 5 minutes is 150 cfm at 0.4 in. wg. and a maximum of 200 cfm at 0.9 in. wg. Consequently, when determining the GPFU size for'protecting both a compartment and the protective entrance at least 150 cfm must be allowed for the protective compartment. The alternative is to' use a recirculating filter unit for the protective entrance. Space must be allowed around the shelter door for a protective entrance interface. in some cases this cannot be done if there is equipment mounted close to the door hinges or in an area needed to mount the interface channel. It may be necessary to make provisions for supporting the floor of the protective entrance on some shelters. For example, the personnel door of the shelter that is trailer-mounted could be as much as 40 in. off of the ground. Our present interface design can accomodate a door which is 37 in. wide, 66- 7% in. high and whose lower edge is less than 8-; in. off of the ground. Should this door be off of the ground more than 8-% in., the interface will no longer align, unless the top of the door is an equal amount-shorter. A platform also precludes the need to level the ground under the protective entrance. However, there can be instances'where the protective entrance must be used directly on the ground. When the entrance is used directly on the ground, large projections under the floor, such as rocks, must be removed.

The following example demonstrates the preliminary analysis which one might make in selecting the proper protective system for a specific application. Assume that one knows the compartment type, such as a S-280 shelter; the environmental control unit (heater/air conditioner): 18,000 Btu compact horizontal; personnel ventilation: 3 men (1000 cu. ft./person/hr., per HEL- STD-S-3-65 protective entrance required; and shelter leakage with equipment installed: 130 cfm. The airflows as follows can be determined from the foregoing known information.

Required ltem Flow at 1.5 in. wg. Heater 0 (electric) Air Conditioner cfm (maximum) Personnel 50 cfm Protective Entrance 150 cfm Shelter Leakage f The minimum required shelter flow is defined by the personnel ventilation requirement of 50 cfm. If the shelter leakage can be reduced by sealing to less than 90 cfm, the present air conditioner can be retained. A one-filter GPFU then can be used for the combined shelter and protective entrance protection. If shelter leakage cannot be reduced, a large air conditioner and larger or more GPFUs are necessary. This could be accomplished by providing the protective entrance with a recirculating filter unit or by using a two-filter GPFU. Should equipment cooling requirements exist, a larger GPFU and air conditioner are necessary.

To assemble our system, shelter 8 is constructed in the conventional manner, but it is provided with an interface 18 fixedly attached around the perimeter of door 19. The case shown at 20 in FIG. 3 is opened, as in FIG. 24, so that section 21 of case 20 forms the bottom and section 22 of case 20 forms the top of protective entrance l7. Impermeable fabric, such as butyl coated cloth 101, which forms the walls of the protective entrance, as shown in FIGS. l and 4 for example, is not shown in FIG. 24 for clarity purposes, but the impermeable fabric is fixedly sealed to supports 23 and the door frame shown at 28 and stored in a folded posture in bottom 21. Also, door 24, shown in FIGS. 12, 13, and 17, is stored in bottom 21 in the folded position shown in FIG. 13. Supports 23 are opened by hinge means 69 and 70, as shown in FIGS. 23, 26 to 29, and top mounts 25 are inserted within support 23 and secured therein by the thumb nut connection shown at 26, as shown in FIGS. 19 and 20. There are two top mounts 25 fixedly connected to top 22, as shown in FIG. 24, at the side of protective entrance 17 which connects to shelter 8. Supports 23 are opened from the folded position shown in FIG. 26 to the open position shown in FIGS. 28 and 29 and maintained in the open position by knobs 68 in the same manner as discussed below regarding knobs 29. Support braces 44 are opened, as shown in FIGS. 24 and 25, and the braces are held in open position by retaining pin 27. Top 22 is supported on the side opposite to supports 23 by the door frame shown at 28 which is opened, as shown in FIG. 24, and locked in the open position by pushing down on knob 29 which causes a protrusion fixedly connected to knob 29 to be inserted within member 30 to lock member 30 to member 31. Support braces 44 are similarly locked by pin 27. Anchor means shown at 33 in FIG. 21 are utilized to store the supports in bottom 21 in the storage mode, and valve 34 is provided to eliminate any water that may accumulate in protective entrance 17. Supports 23 are locked in the storage position by pull pins 35 held within retainer means 71 under tension by springs 36, as shown in FIGS. 23 and ing pin 41 through the mated holes, as shown in FIGS. 6 and 7. Door 24 is assembled, as shown in FIGS. 12 and 13, by opening from the folded position shown in FIG. 13 to the standard door mode position shown in FIG. 12 by means of hinges 42 mounted in the middle of the door and securing the door in the open position by thumb nut means 43 in the same manner discussed above regarding knob 29 for lokcing the door frame member 30 and 31 together. Door 24, after assembly as described above, is hung in the door frame, shown at 28 in FIG. 24, in the conventional manner by means of hinges 45. Door 24 is provided with conventional window 46, conventional door knob and latching mechanism 47, and a window cover 48 to use as desired;

window cover 48 being removably attached by means of conventional fabric fastener means member 49 sewed to cover 48 and conventional fabric fastener member 50 sewed to the butyl coated cloth fabric of the door, as shown in FIG. 17. Cover 48 is held in the open position by fastening fabric fastener 59 to fabric fastener 60. Pressure sensing module 52 and entrance light 53 are mounted within protective entrance 17, as

shown in FIGS. 4 and 18. Electrical power is supplied to light 53 by electrically connecting, in the conventional manner, the light to module 52 by means of electrical cable 54, and module 52 is in turn electrically connected, in the conventional manner, to power distribution unit 14 by means of electrical cable 56 through conventional electrical feed through 57. Light 53 is provided with a conventional three position switch 61 and a conventional white and red bulb, not shown in drawing, to permit use during blackout conditions; the light having electrical requirements of one ampere at 28 volts direct current. Conventional pneumatic tube 62 is connected to control/pressure sensing module 15, mounted within shelter 8 in any convenient location, through feed through 57, as shown in FIG. 18.

Pressure sensing module 52 contains the pressure sensing electrical network shown in FIG. 55 which senses and controls the pressure differential between 17 and ambient to operate the sliding-plate -airflow valve shown at 64; module 52 pressure sensing network being adjusted to control the pressure within entrance 17 at 0.4 to 0.8 inches wg. and having an electrical power input of 28 volts direct current and a power consumption of less than one ampere. Control/pressure sensing module 15 contains the main GPFU control panel having the electrical circuitry shown in FIG. 54 and the pressure sensing network shown in FIG. 55 which monitors the pressure differential between shelter 8 and ambient; the pressure sensing network of module 15 being present to maintain pressure in shelter 8 between 1.2 inches wg and 1.7 inches wg. The designations on,

electrical component values in FIG. 55 are as set forth below.

ELECTRICAL COMPONENT VALUES (FIGURE 55) BIZ-330K

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Classifications
U.S. Classification454/238, 135/93, 454/255, 135/153, 55/385.2, 95/2, 96/18, 135/148, 135/904, 454/251, 96/113, 96/421, 49/68, 454/334, 135/116, 52/66
International ClassificationF24F3/16
Cooperative ClassificationF24F3/161, F24F3/1603, Y10S135/904, F24F2221/12
European ClassificationF24F3/16B, F24F3/16B5