FR2490343A1 - METHOD AND APPARATUS FOR MONITORING THE EFFICIENCY OF A SEAL, ESPECIALLY FOR HYDROCARBON RESERVOIRS - Google Patents

Abstract

THE INVENTION CONCERNS A METHOD AND AN APPARATUS FOR MONITORING THE ANTI-LEAKAGE EFFICIENCY OF A SEAL WITH AN EXISTING INTERVAL BETWEEN TWO SURFACES. THE PROCESS IS CHARACTERIZED IN THAT AN ENCLOSURE 30 IS POSITIONED AND FIXED SO THAT IT COVERS THE SEAL 20 AND THE INTERVAL 19 AND EXTENDS UP TO THE TWO SURFACES 12, 15 WITH A VIEW TO FORMING THUS A CAVITY OR CLOSED SPACE 35 AND DEFINED BY THE TWO SURFACES, THE INTERMEDIATE SEAL AND THE ENCLOSURE, IN THAT A GAS CURRENT IS INTRODUCED IN THE CAVITY, IN THAT THIS GAS CURRENT IS DRAINED FROM THE CAVITY AND IN THAT 'THE OUTLET GAS CURRENT IS ANALYZED TO DETECT A POWERFUL CONTAMINANT THAT IS LEAKING THROUGH THE SEAL. APPLICATION TO TANKS OF PETROLEUM PRODUCTS.

Description

The present invention relates to a method and a

  apparatus for determining the effectiveness of seals

  by steam or gas, for example gasket

  the dullness of liquid vault storage tanks or floating roofs. In the field of industrial appliances, it

  There are many cases where it is necessary to leave

  Serve an interval or game between two surfaces or objects,

  although it is desirable, if it is possible

  to avoid the gap by a direct connection of the two surfaces with each other. The elimination of an interval is particularly desirable when dealing with a low or very volatile liquid that can release vapors or gases that can escape through the gap in the atmosphere or in the atmosphere.

  another environment. Since an interval is often

  unavoidable wind, different types of joints were used

  sealing to prevent passage of steam or gas.

  A type of industrial structure that is used

  to store liquid products of a volatile nature, and which has a certain number of intervals or spaces

  play between adjacent surfaces or objects, is

  killed by a vaulted cell or floating roof that can be opened at the top or covered by an external roof. Spaces or play spaces are formed when apparatus enters the floating roof, for example, ventilation ducts, automatic venting devices, dip wells or

  with floats, zones of penetration of

  ladder penetration zones, column penetration zones, double-walled water

  and penetration areas of pipe carrying elements.

  In such areas of penetration, different

  rential seals to limit the passage of

  gaseous fumes emitted by a volatile liquid in the vessel through said intervals. The main source of emissions is, however, located in the edge zone of a tank

floating roof.

  In a conventional floating roof tank, there is a clearance gap between the side wall of the tank and the edge or vertical edge of the roof. he

  it is necessary to provide an interval of play for

  put an unhindered vertical displacement of the roof to

  the inside of the tank. The play interval has a

  lo geur sufficient for localized dimensional variations occurring on the periphery of the side wall or ferrule of the tank, commonly called

  rotundity defects which may result from an adaptation

  unequal foundations, inaccuracies in the production of

  installation, or unusual loads such as high winds and similar causes, do not prevent a vertical displacement of the roof of the tank.

  A classic system for centering a floating roof

  in a tank, and to simultaneously

  the gap between the edge of the roof

  and the inner side wall of the tank, makes

  nir as a means of sealing an elastic ring which is

  suspended from the roof and extending from a zone of

  tact with the roof edge to a contact area with the tank wall. The ring can be formed of a

  sheet of flexible material and it can contain a flui-

  of, namely a liquid or a gas, such as water or

  nitrogen, or an elastic material such as a foam

  of polymer material. In U.S. patents

  Nos. 3,136,444, 3,120,320, 3,075,668, 3,055,533, 2,973,113 and 2,968,420 are disclosed

  sealing of these different types.

  Other devices used to maintain the roof

  centered in the tank and to create an evi-

  both an evaporation loss use several vertical shoes which are arranged to come into sliding contact with the entire circular vertical inner side wall of the tank and means supported by the roof, for example pantograph supports, to apply the hooves against the inner side wall and to support them. A vapor leak between the roof and the hooves is emitted by a non-permeable and flexible fabric barrier, which extends from the top of the hooves to the top edge of the floating roof. A device of this kind has been claimed

  in many U.S. patents, including

  number 2,587,508, 2,630,937, 2,649,985 and 2,696,930.

  Although such types of seals -

  Sealing work quite well in industrial plants, it can still escape steam through the joint. This possibility is significantly increased during windy days as air flowing on the floating roof creates a pressure differential over part of the circumference of the seal. Most

  great pressure exerted by the wind is usually

  in the semicircular part of the edge play interval which is located downstream from the center of the roof, considering the direction of wind flow, then

  that the lowest pressure is located upstream, always

  days considering the direction of wind flow.

  In the low wind pressure setting area, the higher vapor pressure tends to produce from the underside of the seal, and between this seal and the inner vessel wall, a vapor flow that escapes into the atmosphere. Similarly, in the area of higher pressure-wind, air enters the interior of the

  container, which establishes in the interior volume of the

  container a steam flow circuit between the high wind pressure side and the low pressure side of

  steam, escaping then outside and increasing

  air pollution.

  In order to determine the effectiveness of floating container edge joints of containers with respect to the limitation of vapor emissions, various methods and apparatuses have been developed in the past. One method is to measure the decrease in the volume of the stored material while another method is to measure

  variations in the properties of the stored material. How-

  both processes require a period of several months to several years to

  significant results because of very small changes in

  occur over time with respect to

  the volume and the initial properties of the sto-

  such as vapor pressure and liquid density.

  of. There is therefore a need for a method and apparatus for measuring and evaluating the effectiveness of floating roof edge joints and seals used in other locations in tanks. floating roof and other structures that

  have gaskets to limit the

  flow of vapors or gases in intervals or

play areas.

  In accordance with one aspect of the present invention,

  a method for controlling the effectiveness of a seal placed in a gap between two surfaces, this method of positioning

  and attach an envelope to cover the seal and the

  extend and extend between the two surfaces so as to thereby form a cavity or closed space which is defined by the two surfaces, the intermediate seal and

  envelope, to introduce a gaseous stream into the cavity.

  and evacuate this gaseous stream from said cavity and then analyze the gaseous curvature evacuated to determine the existence of a potential contaminant that leaked by

the seal placed in the gap.

  The envelope may be formed of a rigid material but it is advantageously made of a flexible membrane and impervious to gases. When the gap has a great length, and both when straight and curvilinear, the membrane may be formed by an elongated strip which is connected by its longitudinal edges to

  two surfaces so as to define an elongate cavity.

  To establish a suitable flow of gas into the cavity, and to measure the effectiveness of an appropriate length of the seal, it is desirable to penetrate the gas stream through one end of the seal.

  cavity and evacuate this gas stream through the other end

  tee of the cavity. The cavity may for example be essentially the entire circumferential gap located above the seal of a floating roof. We

  can cause gas to flow in both directions.

  rections from an entrance area into the cavity up to

  an outlet placed in a position approximately

  opposed to the entrance or it may be

  controlling the flow of gas so that it enters an inlet into the cavity and is directed to a nearby outlet, but separate from said inlet, for example a

  output placed at approximately 3600 of said input.

  The process described above is particularly applicable

  cable to control the effectiveness of a seal

  provided in the interval between the edge of a roof flot-

  both of a tank containing said roof, for example a roof

  floating on a liquid product containing a vo-

  latil which constitutes the potential contaminant. In such a test, the casing may be positioned and fixed so as to extend from the floating roof edge to the vessel wall over at least a portion of the casing.

  length of the play interval, thereby forming a cavity

  tee or closed space which is defined by the tank wall,

  the gasket, there roof edge and the envelope.

  To more closely simulate the distribution of

  air and circumferential pressure above the floating roof gasket under the influence of

  the natural flow of the wind on the tank, it is possible to

  radially in the cavity of the vertical

from each other.

  According to a second aspect of the invention there is provided an apparatus for evaluating the effectiveness of a vapor seal, said apparatus comprising a first object having a first surface, a second object provided with a second surface, an existing gap

  between the first and the second surface, a seal of

  placed in the meantime and intended to limit the

  Steam from one side of the gap to

  on the other side, an envelope covering the joint and the inter-

  valle and connected to said first and second surfaces so as to form a cavity or closed space which is defined

  by said first and second surfaces, the seal of

  watertightness and the envelope, a first conduit serving

  introduce a gaseous stream into the cavity through

  envelope and a second conduit to

  to create a gaseous flow of the cavity, via

  envelope, and to channel at least part of the

  evacuated to an analyzer designed to detect a potential atmospheric contamination vapor that has leaked

  through the seal.

  The first conduit of said apparatus may communicate

  quer with one end of the cavity while the second

  conduit can communicate with its other end. EGA-

  the interval can be very long and

  In this case, the envelope can also have a long

  as rigid and flexible.

  The envelope may be constituted by an elongated, flexible and gas-impermeable membrane, which is

  form of a strip connected by its longitudinal edges to

  said first and second surfaces so as to define an elongate cavity.

  According to a characteristic of the invention,

  effectiveness of the floating roof edge seal, a storage tank provided with

  of a circular cylindrical vertical wall and in the-

  what fleet the circular roof so as to leave

  an interval between the roof edge and the tank wall, comprises in combination an envelope fixed on the

  floating roof edge, extending over at least one

  of the length of said gap and fixed on the vessel wall so as to form a cavity or curvilinear space

  which is defined by the tank wall, the seal of

  the edge of the roof and the envelope, a first con-

  to introduce a gaseous flow through the en-

  veloppe in said cavity and a second conduit for

  the gaseous flow of said cavity through the

  and to channel at least a portion of the evacuated stream to an analyzer for detecting a potential contamination vapor of the atmosphere that has leaked through the seal. The envelope can extend completely around the roof edge, above

  the entire play interval, up to the tank wall of

  to define a circular cavity. The first conduit and the second conduit may be placed in

  diametrically opposed positions so that

  - troduced into the cavity is divided into two currents which

  followed, with essentially equal volumes, a

  semicircular jet to reach the output defined by

  the second leads. Alternatively, a barrier can be placed

  in the cavity so as to virtually prevent a hearing

  gas or vapor from one side of the barrier to its other side, and the first conduit may be positioned to communicate with the cavity at a point near one side of the barrier and the second conduit so that it communicates with the cavity

  at a point close to the other side of the bar-

Rière.

  Other advantages and characteristics of the

  will be highlighted, in the following description

  given as a non-restrictive example, in

  in the accompanying drawings in which - Figure 1 is a plan view of a floating roof tank which is equipped with an evaluation system

  efficiency of a terminal gap seal

  tough; - Figure 2 is a sectional view taken along the line 2-2 of Figure 1; - Figure 3 is a sectional view taken along the line 3-3 of Figure 1; FIG. 4 is a vertical sectional view of the edge of a floating roof comprising a seal

  border interval which is formed of a foam of

  elastic polymerized material; - Figure 5 is a vertical sectional view of the edge of a floating roof with a fabric seal that extends from the roof to hooves, supported by the roof edge and in contact with the wall of tank; - Figure 6 is a vertical sectional view of the edge of a floating roof having a foam edge gap seal of elastic polymeric material and a casing attached to the upper edge of the vessel; FIG. 7 is a vertical sectional view of

  edge of a floating roof tank with an external roof

  tapered; FIG. 8 is a plan view of a roof tank

  which is equipped with a system for evaluating the effectiveness of

  a boundary gap seal by dividing the incoming gas stream into a cavity containing screens spaced apart from each other; and FIG. 9 is a sectional view made in accordance with FIG.

line 9-9 of Figure 8.

  As much as possible, identical or similar parts that appear in the different figures

  have been designated by the same numerical references.

  Looking at Figures 1 to 3, we see that the

  floating roof tank comprises a tank 10 and a floating roof

  15. This tank 10 is provided with a metal bottom

  horizontal circular plane it and a circular wall cy-

  vertical lindrique 12. The floating roof 15 has a circular central metal part 16 essentially

  flat and provided with an annular pontoon or float 17

  around the periphery of the central part 16. The

  17 has an outer vertical wall 18 which is internally spaced from the inner surface of the vessel wall 12, so as to define between them a gap clearance or border spacing 19. On the wall 18 of the floating roof is attached a seal 20. This seal 20 is formed of a vertical metal sheet 21 on which is fixed by gluing, along the outer lateral portion, a horizontal ring 22 made of foam.

  elastic polymeric material. A fabric impregnated with rubber

  rubber 24 is then wrapped around the foam ring 22 and is moved upwards towards the edges

  upper front and rear of the metal sheet 21.

  Bolts or other fasteners then ensure the joining of the upper edges of the metal sheet 21 and the fabric 22 with the flange 25 provided at the upper part of the roof edge. Such a seal is

of a classic construction.

  The floating roof 15 is moved to near the upper part of the tank by pumping a product

  storage, such as a petroleum product or a

  liquid containing a volatile component that is likely to con-

  strongly tamper with the atmosphere. The envelope 30 is then

  positioned to cover the border gap 19.

  This envelope 30 is constituted, in the embodiment

  1 to 3, by an elongate flexible membrane. It can also be constituted by a strip of fabric impregnated with rubber, polyethylene or an equivalent material which is impervious to vapors

  or gases. It could also be formed of material

  rigid or semi-rigid material such as steel or aluminum sheet

  minium. However, the envelope 30 is preferably formed of a non-metallic flexible material such as a sheet of

  transparent plastic material reinforced with nylon.

  A longitudinal edge of the envelope 30 is connected

  at the upper edge of the vessel wall 12 while the

  The longitudinal edge of the envelope 30 is connected to the upper edge of the floating roof 15. Any suitable fastening means may be used such as staples, fasteners, bolts, a pressure-sensitive adhesive tape, and the like.

  pressure, magnets and similar

  to establish a temporary seal essentially gas-tight. The envelope 30 defines in cooperation with the

  adjacent portion of the vessel wall 12 the seal of

  and the top edge of the floating roof, a cavity

  closed tee 35 which can extend around the border gap to the desired distance. The embodiment

  of the invention shown in FIGS. 1 to 3 is intended

  born to evaluate the effectiveness of the seal 20 on

  its entire length in one operation instead of operating

  split. The cavity 35 therefore extends almost over the entire edge interval but

  it is complete, without forming quite a com-

  plet, by a barrier 36 which fills vertically, or

  occupies a vertical zone of the cavity so as to

  to reiterate the circular flow of a gas or vapor in this cavity. This barrier 36 may be formed for example by a vertical sheet, a block of elastic polymeric foam.

  that either a bladder swollen under a low pressure.

  This barrier 36 thus creates a cavity 35 closed to both

  ends. It is obvious that if we only have to check

  proud part of the seal 20, two barriers are used spaced from each other so as to isolate

  for inspection a corresponding part of the seal of

  chéité. A fan or a pump 40 (FIGS. 1 to 3),

  preferably installed on the floor, communicates with a

  air filtration 41 from which air is

  troduced in a conduit 42 which terminates at one end of the cavity 35, on one side of the barrier 36. A valve 46 is connected in the conduit 42 so as to adjust the air flow. An air flow indicator 43, a fan air outlet temperature indicator 44 and a fan air outlet pressure indicator 45 are connected to the duct 42. An exhaust air withdrawal pipe 45 50 fan, comprising

  a valve 51 connects the conduit 42 to a pipe 52 which communicates

  with the sample pump 53. This pump is

  sample taking 53 ensures the transfer of

  the sample of air or other gas to an analyzer 54.

  A conduit 60 communicates at one end with the end

  outlet tee, or downstream end, of the cavity 35, and is connected at its other end to an air flow mixing part 61 from which the air is discharged into the atmosphere through the intermediate pipe 62. A sample pipe 63 communicates with

  the pipe 62 at one end and with the pipe 52 by -

  the other extremity. A valve 64 is plugged into the pipe

  63 to control the flow of gas-or air.

  The device thus described is used to control

  the effectiveness of the seal 20 or to prevent

  The flow of air delivered by the fan 40 reaches, via the line 41, hydrocarbon ions from a petroleum product in the tank by first engaging the fan 40. in the duct 42 which channels it to the inlet end of the cavity 35. The air follows a curvilinear path along the cavity and it follows that hydrocarbon emissions which have leaked through the seal are then mixed with the air. The stream of air is discharged from the cavity 35, at the same time as the emissions

  driven through line 60.

  Air samples are taken from the neck.

  the air contains emissions before introducing it into the cavity, so that the initial quantities can be subtracted from the total emissions which is measured in the sample taken at sampling point Y of the outgoing current. Valve

  64 is closed, and the valve 51 open, when the sample

  sampled at sampling point X is analyzed

  say that the valve 51 is closed, and the valve 64 open, when the sample taken at the sampling point Y is analyzed. The output signal of the analyzer 54 can

  be registered in order to obtain a registration

  tinti is the concentration level of the emissions

  in the cavity of the concentration of emissions

leaving the cavity.

  When carrying out emission control operations by this process, it is important to use a controlled airflow so that, as the air moves into the seal control cavity,

  it not only ensures the collection of emissions through

  the joint for the purpose of sampling and

  analysis but also simulates the same local distribution

  the air velocity and circumferential pressure that

  that the wind would produce above the seal

  you. To obtain the correct pressure distribution around the seal control cavity, a differential pressure indicator 47 is provided which measures the difference in air pressure at each end.

  of the seal control cavity, this indicator allows

  both to select and adjust the correct airflow.

  In addition to the air flow stop barrier 36 which is located within the seal control cavity, it may be necessary to place a temporary gas stop dam below seal and in the same place as the barrier barrier

  airflow to eliminate air leakage from

* Control downstream of the seal and below the air flow stop barrier to the outlet of the control cavity. Such an arrangement has been represented on

Figure 4.

  The seal 20 shown in FIG.

  re 4 is similar to that shown in Figures 1 to 3, except that in Figure 4 the seal 20 is not placed

  quite as low on the side of the roof. To prevent

  For a vapor or emission flow over a horizontal circular path, a dam 70 is provided below the seal 20. This dam 70 is formed by a panel 71 of elastic polymeric foam which is covered with a sheet A similar panel 75, consisting of an elastic polymeric dobby and covered with a sheet of vapor-tight material 76, is used as a barrier 77 over the joint.

  20 to seal substantially the upper portion

  border interval and thus create a cavity

closed at the ends.

  Figure 5 shows how the invention can be used for the control of a roof gasket

  float using hooves and pantograph racks.

  phe for hooves. The pantograph stands 80

  hold the shoes 81 so that they are in sliding contact with the inner surface of the tank wall 12. The space between the shoes 81 and the side 18 of the floating roof 15 is covered with a flexible fabric 82 impermeable to steam and connected to the roof and hooves on their side edges. A barrier 85 is arranged

  in the space below the fabric 82. This bar

  may be made of a fabric sheet, a polymer foam or a low pressure bladder. A barrier 36 is disposed above the barrier 85 so as to prevent the flow of vapor or gas following

  a circle surrounding the tank border.

  In the embodiment shown on the

  5, the outer edge of the envelope 30 is timed

  It is connected to the vessel wall surface by a series of magnets 87. This fastening means avoids holes in the

  tank wall, or to use an adhesive to establish the desired connection, or to raise the floating roof close to the upper edge of the tank to connect it to the envelope, as indicated on

Figures 1 to 4.

  Figure 6 shows the use of fasteners 90 to temporarily secure the upper edge of the envelope to the upper edge of the vessel. It also shows how the conduit 60 (or 42) can be conveniently connected to the enclosure in a leak tight manner. Sheet

  91 is attached to the end of the conduit 60 and a breast plate

  blable 92 is placed inside the envelope. Each sheet 91, 92 has a central hole which is aligned with a corresponding hole in the envelope. Similar bolts or fasteners may then pass through the two sheets, between which the material of the casing is arranged so as to connect the end of the duct t490343

corresponding to the envelope.

  Figure 7 shows the application of the invention

  floating roof with conical roof

  95. The floating roof 15 is raised, by floating

  on the liquid product on the tank 10,

  close to the outer roof 95. Then

  installs the envelope 30 so that it extends from the edge of the floating roof to a flange 96, provided inside the outer roof 95 and on which it is temporarily fixed. A barrier 36 is placed in the space above the seal 20

  extending to the outer roof 95, up to the envelope

  pe 30 and up to the wall 12 to prevent emissions

  to follow a circular flow path, as explained

  previously. A ventilation pipe 98 is closed, or if necessary one of the conduits 42 or 60 may be

  connected to this pipe if properly positioned.

  When performing emission control operations using the method according to the invention,

  it is important to have a clean air flow

  carefully controlled so that when the air moves

  this through the sealing cavity control cavity

  it not only ensures the collection of

  through the joint for their sampling and

  their analysis but also simulates the same distribution

  tion of air velocity and circumferential pressure

  than that which the wind would otherwise establish

  above the seal. For these two conditions to be met, an appropriate number of vertical sieves, placed radially in spaced-apart positions within the seal control casing, can be provided. The characteristic pressure drop occurring only in space

  airflow which is located inside the

  Seal control veloppe generally does not allow for very narrow simulation of effects

  wind on the emissions passing through the seal.

  However, using an appropriate number of sieves of one

  appropriate type which are distributed within the enclosure.

  loppe seal control, it is possible to simulate

  very closely the effects of the wind.

  It is known that the average air velocity above the seal of a commercial floating roof tank is approximately equal to 25% of the wind speed flowing on the floating roof tank. By measuring

  the wind speed on the tank, and by measuring

  air pressure at different spaced points on the seal, the pressure distribution around the

  specific wind speed. The resulting data allows

  establish a model that can be reproduced by the control system according to the invention to thereby simulate operating conditions. It is obvious that other models can be determined from the same

  way for different wind speeds.

  Once the wind speed conditions to be simulated have been defined, the air velocity

  cavity and one can control the desired pressure drop.

  in this cavity by placing sieves in this cavity

  spaced from each other, arranged vertically and posi-

  radially. The size and number of sieves to be used can be defined using

  known characteristic curves giving the fall of pres-

  depending on the flow through the sieves.

  For the control of seals in a floating roof tank in accordance with the present invention, an appropriate pressure drop or pressure drop can be established using a standard insect screen and

  conveniently available, such as that used for

  houses and doors of dwellings. A suitable screen consists of a mesh of 16 x 18 mesh (ie 16 threads per 2.54 cm of sieve length and 18 threads per 2.54 cm of sieve width), the thread having a diameter

0.28 mm.

  Figures 8 and 9 show the use of the apparatus according to the invention with a seal of the liquid filling type. The device uses sieves in the cavity to create a drop in

  predetermined pressure when the gas flow of

  control passes into the cavity. The apparatus shown in FIG. 8 uses pumps, valves, and manometers as described above with reference to FIGS. 1 and 2, so that these elements, visible in FIG.

will not be described again.

  As shown in FIGS. 8 and 9, the wall

  18 of the floating roof supports a sealing gasket

  100 in the border gap between the roof and the tank wall. This seal 100 comprises a flexible bag 102 of tissue, which contains a liquid 101 and which extends completely around the border of

  roof being supported by a flange 103.

  Ten triangular shaped frames 105 are posi-

  vertically spaced at equal intervals to contact the vessel wall and the floating roof edge, and extend downwardly into the edge gap between the gasket 100 and the tank wall. Each frame

  has a vertical wooden bar 106 and a bar

  A suitable wire screen 110 is attached to each side of each frame 105, but by giving the screen a suitable structure, it is possible to

  use one for each frame. In the mode of

  In all, twenty sieves are used in ten frames. To prevent virtually any gas leakage under and around the screen 110, there are

  lengths of pressure sensitive adhesive tape 111

  be the lower sieve edges and the roof surfaces

  floating 15 and the seal 100 on the other hand.

  An envelope 115 formed of a transparent plastic film is fastened by staples to the

  top of each slanting wooden bar 107 of each

  105. The envelope extends completely around the border gap and its inner edge 116 is

  attached to the upper part by means of the adhesive strip 117

  top of the floating roof. The outer edge 118 of the enve-

  loppe 115 is fixed on the tank wall with a banana

  In this way, a cavity 125 essentially

  leak-free is formed below the

veloppe 115.

  Line 42 channels the control gas, which

  usually air, below the envelope 115 jus-

  cavity 125. The air flow is essentially divided

  in two halves, one of which flows towards the

  right following one half of the cavity while the other

  it flows to the left following the other half of the cavity. The two currents meet after having traveled half of the cavity, to an area where

  duct 60, communicating with the cavity 125, ensures the evaluation

  cuation of the total current. Each half of the initial air stream, which has been divided as described above, passes through ten sieves, so that it occurs

  in each of the two currents a balanced pressure drop

  anced. Since a natural flow of air passing over

  a floating roof tank produces a divi-

  in a similar way in the border range, it is clear that the above-described

  rather closely simulates the conditions existing in

you.

  Although it has been shown in the mode of

  In the case of sieves 8 and 9 of the sieves made from yarns, it is obvious that other sieves consisting of a perforated metal sheet or a plate of perforated resinous material could be used as well. We could also use

  sieves formed by molding and having appropriate holes

requested.

  Although the application of the invention described above

  above relates more specifically to measuring the effi-

  ciency of a floating roof seal to emissions from petroleum products stored in tanks, it is possible, by appropriate modifications to the type of emission control equipment, to measure other types of emissions, the measures being

  done separately or in combination.

  The control cavity, formed in part by the casing, must have a uniform cross-section to

  obtain a uniform flow of air or another gas. Equal-

  the cross-section of the cavity must be maintained

  in practice to an appropriate value to reduce in the middle

  nimum the dimensions of the fan required for simu-

  the effect of wind on the area of the seal.

  However, the cross section must be large enough

  to minimize localized effects of

  at high speed. Furthermore, by minimizing the flow section of the air flow, the total pressure on the seal control casing is also minimized, and therefore the retaining forces on the fasteners of fixation

  of the envelope on the floating roof and the tank wall.

  In addition to the methods already described above for temporarily fixing the envelope on the roof

  and the tank, it is also possible to use

  vacuum-fixing devices, fixing devices

  spring-loaded devices, counterweight devices,

  fasteners by cables or turnbuckles, and all

combinations of said devices.

  It is also important to ensure proper ventilation of the control cavity

  seal to prevent dangerous accumulation

  hydrocarbons or emissions during periods when the effectiveness of the seal is not performed.

  The process and apparatus described above

  are easy to use and put into practice

  can be performed by poorly trained operators.

  The device is portable and can be easily moved from one tank to an adjacent tank or any other location. The control method described above is particularly suitable for defining the equivalence of a seal with respect to another seal, such as a seal.

  seal approved for the environment. By measuring the

  passing through two different seals for the same airflow and air pressure,

  directly compares their effectiveness.

  The response time with this method of control is quite fast and the operation is often completed in a few minutes after the installation of the apparatus. Of

  the speed of the control process, it is possible to

  to measure the effect of different variables on the

  emission rate. These variables may be varia-

  of ambient barometric pressure, changes in ambient temperature, losses due to a tank emptying process, tightening conditions of various seal components, vapor pressure

product and wind speed.

  The control method according to the invention can be used with many types of seal, including metal shoe seals, foam filled seals, liquid filled seals, wiper seals, seals. flaps, etc. he

249034?

  can also be used with many types of multi-joint structures with primary, secondary and tertiary sealing elements. This method of control may be applied to most types of new and existing floating-roof tanks with a riveted or welded structure, including internal floating-roof tanks and tanks with external floating roofs, tanks with metal ferrule and ferrule

  metallic, coated ferrule (or lining) and vi-

  uncoated role, and contact and non-contact type

(of the floating type).

  Instead of placing a waterproof envelope

  around the circumference of a floating roof, it is also

  It is also possible to place it on small segments of the seal to determine the local effectiveness of this seal. This allows, during an audit

  maintenance, to locate areas where the seal of

  has suffered a severe deterioration. To perform tests on segments of the joint, it is necessary

  to set up an appropriate stoppage of temporary stoppage of

  gas at the ends of the gasket segment.

  trôler. The control method can be used with

  many different stored liquid products,

  a wide range of hydrocarbons such as oils

  raw materials (light oils, viscous oils, oils with

  sulfur content, etc.), gasolines (automotive and aviation), distates, naphthas, narrow boiling range fractions, pure compounds, base oils with high and low vapor pressure, etc. . It should be noted that the density variation method for the measurement of hydrocarbon losses from floating roof tanks is not applicable to certain products such as viscous crude oils, narrow boiling range fractions, high pressure base oils

steam and pure compounds.

  This process can be considered as a direct emission measurement process because it allows emissions to be collected and measured directly, unlike other control processes that have an indirect action and measure changes in volume or properties of the raw material considered, or

  who use a gas as a tracer.

  Since the response time obtained with this control method is rapid, the

  time out of the tank for control.

  The accuracy obtained in individual measurements, such as measurements of air flow, air temperature, air pressure and total hydrocarbon concentration in incoming air and outgoing air, can be quite high and as a result one can get

  a very good global accuracy-measurement of emissions.

  The instruments used work well in the limi-

  The design and measurement quantities are not extremely small, as is the case for some other control processes that require very small changes in the properties of the material.

to control.

  It goes without saying that modifications can be made to the embodiments which have just been described, in particular by substitution of technical means

  equivalent, without departing from the scope of the present

the invention.

Claims (36)

  1.- Method for controlling the anti-efficiency   leakage of a seal placed in a gap existing between two surfaces, characterized in that a casing (30) is positioned and fixed so that it covers the seal (20) and the gap (19) and extends to both surfaces (12, 15) to thereby form a closed cavity or space (35) and defined   both surfaces, the intermediate seal and the enve-   loppe, in that a gaseous stream is introduced into the cabin   and evacuating this gas stream from the cavity.   and analyzing the outgoing gas stream to detect a powerful contaminant that leaked through seal in the meantime.   2. A process according to claim 1, characterized   in that sieves (110) spaced apart from one another   are arranged laterally in the cavity so as to increase   to reduce the pressure drop or pressure drop in the gaseous stream 3.rise in that flexible and 4.- rised in that which is connected 5. riser faces in that   between one side of the sieve and the other side.   Method according to claim 1, characterized   said envelope (30) comprises a membrane impervious to gases.   Process according to claim 3, characterized   the membrane (30) is an elongated strip   by its longitudinal edges to both sur-   thereby defining an elongated cavity (35).   Process according to claim 4, characterized   1-th gas stream is introduced to an ex-   tremity of the cavity (35) and is evacuated to the other end. of this cavity.   6. A process according to claim 1, characterized   in that the seal is placed in a storage tank   -24 ge of a liquid product containing a volatile component which   constitutes said powerful contaminant.   7.- Method for controlling the effectiveness of anti-leakage   of a seal placed in the boundary   a method exists between a floating roof edge and a vessel containing said roof, characterized in that an envelope (30) is positioned and fixed so that it extends from the edge of the floating roof (15) to the vessel wall (12). on at least a portion of the length of the border gap to thereby form a cavity or closed space which is defined by the vessel wall (12),   the seal (20), the roof edge (15) and the   veloppe (30), in that a gaseous stream is introduced   in the cavity, in that it is evacuated from the cavity and in that the outgoing gas stream is analyzed to detect a strong contaminant released by a stored product   in the tank and that leaked through the seal.   8. Process according to claim 7,   in that sieves (110) are arranged laterally in the cavity (35) so as to increase the drop in   pressure when the gaseous current flows in quick.   9. A process according to claim 7, characterized   in that said envelope (30) is closed to both ends.   10. A process according to claim 7, characterized   in that said envelope (30) comprises a membrane flexible and impervious to gases.   11. A process according to claim 10, characterized   in that the membrane (30) is formed by an elongated strip thereby defining an elongate cavity and in that at one end of the cavity is introduced the current   gas that is evacuated at its other end.   12. A process according to claim 7, characterized   in that the roof (15) floats on a liquid product.   containing a volatile component which constitutes the said contam- powerful miner.   13. The process according to claim 7, characterized   characterized in that the envelope (30) extends completely around the roof edge over the entire edge gap formed with the vessel wall thereby defining a circular cavity (35), in that a barrier (36) is placed   in the cavity so as to virtually prevent a flow of   gas from one side of the barrier to the other side, in that the gas stream is introduced into the cavity at a point near one side of the barrier (36) and in that it is evacuated from the cavity at a point   near the other side of the barrier (36).   14. The process according to claim 7, characterized   in that the seal (20) comprises   bots (81) which are supported by the roof (15) through   pantograph supports (80) and that a flexible and gas-impermeable fabric (82) extends from the edge   roof (15) to the top of shoes (82).   15. A process according to claim 7, characterized   in that the seal (20) comprises an annulus   horizontal bucket of elastic polymeric foam (22) which is   placed between the roof (15) and the tank wall (12).   16. A process according to claim 7, characterized   in that the seal (20) consists of a flexible sheet defining a pocket (102) filled with liquid or gas and placed in a horizontal ring   located between the roof (15) and the tank wall (12).   17. The process according to claim 7, characterized   in that the envelope (30) is attached to the edge   upper wall of the tank (12).   18. A process according to claim 8, characterized   in that the number and dimensions of the sieves (110) are selected and the flow rate of the gas stream is controlled to a preselected value to simulate the same local distribution of air velocity and pressure circumferential than that which would be obtained with a specific wind speed on the floating roof tank (10).   Apparatus, characterized in that it comprises: - a first object (10) having a first surface, - a second object (15) having a second surface, - an interval formed between said first and second surfaces,   - a seal (20) placed in the   tervalle and intended to limit the flow of steam from one side to the other of said interval,   an envelope (30) covering the seal of   sealing and gap and connected to said first and second surfaces so as to form a closed cavity (35) defined by said   first and second surfaces, the gasket   and the envelope, - a first conduit (42) for introducing a   gaseous flow in the cavity (35) through mediate the envelope (30),   a second duct (60) for evacuating the neck   gas introduced into the cavity and for   transfer at least part of the current   as far as an analyzer to detect a   vapor of powerful contamination of the atmosphere   which leaked through the seal chéité.   20. Apparatus according to claim 19,   characterized in that a plurality of sieves (110) spaced apart from each other extend through the cavity (35) between the   first conduit (42) serving to introduce the current   in the cavity and the second conduit (60) serving   evacuate the gas stream into the cavity.   21. Apparatus according to claim 19, ca   characterized in that said gap is elongated and in that the envelope (30) comprises a flexible and gas-impermeable membrane, said membrane being constituted   by an elongated band which is joined by its long edges.   longitudinal with said first and second surfaces,   so as to define an elongate cavity (35).   Apparatus according to claim 21,   characterized in that the first conduit (42) communicates   with one end of the cavity (35) while the   conduit (60) communicates with the other end of the cavity (35).   23.- Installation characterized in that it comprises: - a storage tank (10) having a circular cylindrical vertical wall (12), - a floating circular roof (15) in the tank, - a border gap existing between the roof edge and the vessel wall; - an envelope (30) fixed on the edge of the floating roof (15) and extending over at least one   part of the length of the space gap-   up to the tank wall (12) on which   it is fixed so as to form a cavitation   closed curvilinear tee (35) delimited by the   tank king (12), the seal (20), the roof edge (15) and the casing (30), a first duct (42) serving to introduce a   gaseous stream, through the enve-   loppe (30) in the cavity (35) and a second   conduit (60) for discharging a current   zeux of the cavity (35) via   envelope and to have at least one   This output is fed to an analyzer for detecting a strong atmosphere contaminating vapor that has leaked through the seal.   24.- Installation according to claim 23,   characterized in that a plurality of sieves (110) spaced apart from each other extend through the cavity (35) between the first conduit (42) for introducing the gaseous stream into the cavity (35) and the second conduit (60) for evacuating the   gaseous current of said cavity (35).   25.- Installation according to claim 23, characterized in that an inlet end of the conduit (42) is connected to a pump (40) for passing a   air flow in said cavity (35).   26.- Installation according to claim 23, characterized in that said envelope (30) is closed at both ends.   27.- Installation according to claim 26,   characterized in that the envelope (30) comprises a membrane flexible and impervious to gases.   28.- Installation according to claim 27,   characterized in that the membrane (30> is an allon-   thereby defining an elongated curvilinear cavity (35),   in that the first conduit (42) communicates with an   tremity of said cavity (35) and that the second   duit (60) communicates with the other end of vity (35).   29.- Installation according to claim 23,   characterized in that the roof (15) floats on a liquid product containing a volatile component which constitutes said   powerful atmosphere contamination vapor.   30.- Installation according to claim 23,   characterized in that the envelope (30) extends completely around the roof edge (15) above the entire   the gap formed with the vessel wall (12) in defined   thus forming a circular cavity (35), in that it is pre-   seen in said cavity (35) a barrier (36) for preventing gas or vapor from flowing from one side of the barrier to the other side, in that the first conduit (42) communicates with the cavity near one side of the   barrier (36) and that the second conduit (60) communicates   only with the cavity at a point close to the next to the barrier (36).   31.- Installation according to claim 23,   characterized in that the seal (20) comprises shoes (80) supported by the roof via supports   pantograph (81) and that a flexible and imperforate fabric   gas duct (82) extends from a roof edge (15)   to the top of the hooves (80).   32.- Installation according to claim 23,   characterized in that the seal (20) comprises a horizontal ring (22) of resilient polymeric foam which is disposed between the roof (15) and the vessel wall (12).   33.- Installation according to claim 23,   characterized in that the seal (20) comprises   a sheet of flexible material delimiting a pocket   fold of gas or liquid and placed in a horizontal ring   zontal located between the roof (15) and the tank wall (12).   34.- Installation according to claim 23,   characterized in that the wall of the storage tank is made by riveting.   35.- Installation according to claim 23,   characterized in that the wall of the storage tank is performed by welding.   36.- Installation according to claim 23,   characterized in that the envelope (30) extends   around the roof edge (15) above the entire spacing gap with respect to the vessel wall (12) so as to thereby define a circular cavity (35) and that the second conduit (60) communicates with the cavity in a position substantially diametrically opposed to the communication position of the first conduit (42) with the cavity (35).   37. Installation according to claim 36, characterized in that sieves (110) spaced apart from each other extend through the cavity (35) and are provided in number and with spacings, equal in each   semicircular segment of the cavity defined by the first   first and second conduit communicating with the cavity (35).   38. Installation according to claim 23,   characterized in that the first conduit (42) includes means (46) for adjusting the flow rate of the gas stream to a   preselected value to simulate a local distribution   air velocity and circumferential pressure wedge above the gasket which is identical to that established by a specific wind speed on the tank to floating roof (10).   39.- Installation according to claim 24,   characterized in that the number and size of   sieves (110), as well as the flow rate of the   gas, so as to simulate a local distribution of   of air and circumferential pressure which is identi-   than that which would be produced above the seal of   dyed by a specific wind speed on the tank to floating roof (10).