BRITISH STANDARD
Oil burning
equipment —
Part 5: Specification for oil storage
tanks
UDC 662.94:683.8/.9:697:621.642
BS 799-5:1987
BS 799-5:1987
Committees responsible for this
British Standard
The preparation of this British Standard was entrusted by the Refrigeration
Heating and Air Conditioning Standards Committee (RHE/-) to Technical
Committee RHE/13, upon which the following bodies were represented:
Associated Offices Technical Committee
Association of Shell Boilermakers
British Combustion Equipment Manufacturers’ Association
British Tar Industry Association
Chartered Institution of Building Services Engineers
Chief and Assistant Chief Fire Officers’ Association
Department of the Environment (Building Research Establishment)
Department of the Environment (Property Services Agency)
Electricity Supply Industry in England and Wales
Engineering Equipment and Materials Users’ Association
Engineering Industries Association
Fire Offices Committee
Health and Safety Executive
Institute of Domestic Heating and Environmental Engineers
Institute of Energy
Institution of Fire Engineers
Water-tube Boilermakers’ Association
The following body was also represented in the drafting of the standard:
Institution of Mechanical Engineers
This British Standard, having
been prepared under the
direction of the Refrigeration
Heating and Air Conditioning
Standards Committee, was
published under the authority
of the Board of BSI and comes
into effect on
31 December 1987.
© BSI 12-1998
First published October 1975
First revision December 1987
The following BSI references
relate to the work on this
standard:
Committee reference RHE/13
Draft for comment 83/77821 DC
ISBN 0 580 16274 5
Amendments issued since publication
Amd. No.
Date of issue
Comments
BS 799-5:1987
Contents
Committees responsible
Foreword
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Page
Inside front cover
iii
Scope
Definitions
Integral tanks
Service tanks
Oil storage tanks
Manholes and inspection openings
Heaters for oil storage tanks
Oil level indicators
Drain valves
Filling pipes and connections
Vent pipes
Outlet valves and pipes
Oil return pipes
Fire valves
Installation of tanks
Appendix A — Pressure test
Appendix B — Overfilling of oil storage tanks
Appendix C — Information to be supplied by the purchaser
Figure 1 — Relationship between design head, pitch of stays
or stiffening and plate thickness for rectangular service tanks of
type S4 and rectangular storage tanks of types III, J and K
Figure 2 — Relationship between design head, span between
supports and plate thickness for rectangular storage
tanks of types III, J and K
Figure 3 — Shallow dished and flanged end
Figure 4 — Dished and flanged end
Figure 5 — Positions of steel cradles for storage tanks of type I
Figure 6 — Positions of steel cradles for storage tanks of type II
Figure 7 — Positions of cradles for storage tanks of types A, B and C
Figure 8 — Typical arrangement of tank heaters with long heaters
to spread heat in tank and short heater fitted on manhole
Figure 9 — Details of filling point with witness hole and protective cap
Figure 10 — Details of filling point with groove and protective cap
Figure 11 — Typical storage tank arrangements
Figure 12 — Graph showing pressure developed when tank is
overfilled with oils classes C and D at a filling rate of 500 L/min
and at a viscosity of 16 mm2/s
Figure 13 — Graph showing pressure developed when tank
is overfilled with oils classes C and D at a filling rate
of 1 000 L/min and at a viscosity of 16 mm2/s
Figure 14 — Graph showing pressure developed when
tank is overfilled with oils classes E, F and G at a filling
rate of 1 000 L/min and at a viscosity of 370 mm2/s
Figure 15 — Graph showing pressure developed when tank
is overfilled with oils classes E, F and G at a filling rate
of 1 000 L/min and at a viscosity of 860 mm2/s
© BSI 12-1998
1
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i
BS 799-5:1987
Page
Table 1 — Minimum plate thicknesses for service tanks of
types S3 and S5
Table 2 — Minimum plate thicknesses for storage tanks of
types I and II
Table 3 — Minimum plate thicknesses for storage tanks of type A
Table 4 — Minimum plate thicknesses for storage tanks
of types B and C
Table 5 — Minimum plate thicknesses for storage tanks of type D
Table 6 — Minimum plate thicknesses for storage tanks
of types E and F
Table 7 — Minimum plate thicknesses for storage tanks of type G
Table 8 — Dimensions of steel cradles for storage tanks of type I
Table 9 — Dimensions of steel cradles for storage tanks of type II
Table 10 — Dimensions for cradles for storage tanks of
types A, B and C
Table 11 — Manholes and inspection openings: minimum
thicknesses of covers and maximum pitch of fixing bolts
Table 12 — Oil and water drain valves: minimum clearway
openings for varying tank capacities
Table 13 — Filling pipes and connection sizes for oils
classes C, D, E, F, G and H
Table 14 — Minimum storage and outflow temperatures for
oils classes C, D, E, F, G and H
Table 15 — Equivalent height of vent: allowances for
horizontal pipe runs, easy and sharp bends at a filling rate
of 500 L/min and at a viscosity of 16 mm2/s
Table 16 — Equivalent height of vent: allowances for
horizontal pipe runs, easy and sharp bends at a filling rate
of 1 000 L/min and at a viscosity of 16 mm2/s
Table 17 — Equivalent height of vent: allowances for
horizontal pipe runs, easy and sharp bends at a filling rate
of 1 000 L/min and at a viscosity of 370 mm2/s
Table 18 — Equivalent height of vent: allowances for
horizontal pipe runs, easy and sharp bends at a filling rate
of 1 000 L/min and at a viscosity of 860 mm2/s
Publications referred to
ii
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5
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8
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Inside back cover
© BSI 12-1998
BS 799-5:1987
Foreword
This Part of BS 799 has been prepared under the direction of the Refrigeration,
Heating and Air Conditioning Industry Standards Committee. It supersedes
BS 799-5:1975 which is withdrawn. It deals with tanks used for the storage of
liquid fuel used in conjunction with oil burning equipment.
Some changes from the previous edition have been made. In particular, upper
limits on tank volumes have been included, certain design heads and plate
thicknesses have been altered for tank types A to L and the tanks to the previous
type H are now included with type E.
Reference to coal tar liquid fuels complying with BS 1469 have been omitted as
BS 1469 has now been withdrawn. The tanks may still be considered suitable for
the storage of coal tar liquid fuels provided that the characteristics of the
particular fuel to be stored can be obtained.
The text dealing with storage capacity in the appendix of the previous edition has
been omitted in this edition because this subject is now referred to in BS 5410 to
which reference should be made for general recommendations in respect of the
installation of storage tanks.
The tank plate thicknesses are in accordance with Table 2 of BS 6722:1986.
General requirements for the design and staying or stiffening of tanks are given.
An appendix C has been included which lists the information to be supplied by
the purchaser.
A British Standard does not purport to include all the necessary provisions of a
contract. Users of British Standards are responsible for their correct application.
Compliance with a British Standard does not of itself confer immunity
from legal obligations.
Summary of pages
This document comprises a front cover, an inside front cover, pages i to iv
pages 1 to 24, an inside back cover and a back cover.
This standard has been updated (see copyright date) and may have had
amendments incorporated. This will be indicated in the amendment table on
the inside front cover.
© BSI 12-1998
iii
iv
blank
BS 799-5:1987
1 Scope
This Part of BS 799 specifies requirements for tanks
for the storage of liquid fuel, used in conjunction
with oil burning equipment, and includes:
a) integral tanks which form a part of a complete
oil fired unit;
b) service tanks;
c) storage tanks with a maximum height of 10 m.
The maximum capacities of the various types of
tank are specified.
This standard is applicable to tanks constructed of
plain carbon steel.
NOTE 1 The requirements of this standard should not be
applied to tanks constructed of plastics or materials other than
plain carbon steel.
NOTE 2 The titles of the publications referred to in this
standard are listed on the inside back cover.
2 Definitions
For the purposes of this Part of BS 799, the
following definitions apply.
2.1
oil
petroleum oil fuels of classes C, D, E, F, G and H as
specified in BS 2869
2.2
integral tank
2.6
design pressure or head at the top of the tank
a vent height of 0.5 m. If the height of the vent pipe
exceeds 0.5 m or where it is not possible to provide a
pressure relief device, the full equivalent height of
the vent pipe including frictional loss is taken into
account when calculating the design pressure
NOTE
See appendix B.
2.7
design pressure or head at the side of the tank
two-thirds the pressure at the bottom of the tank
2.8
tank capacity
the gross internal volume of the tank
2.9
fire valve
an automatically operated quick closing valve held
open by any one of the following methods:
a) by means of the tension of a wire on which are
one or more fusible links;
b) electrically; operated by one or more heat
sensitive devices;
c) pneumatically; the air system is sealed by one
or more fusible plugs;
d) by means of a sealed system incorporating a
sensitive phial placed over the firing point.
a small tank up to 25 L capacity which forms an
integral part of an oil fired unit or appliance and
which requires filling by hand
3 Integral tanks
2.3
service tank
Integral tanks shall have a capacity of not more
than 25 L.
Each integral tank shall carry a prominent notice at
the filling point to indicate that the tank is not to be
filled whilst the burner is alight and specifying the
grade of oil to be used.
Each integral tank shall be so mounted and
positioned that when the ambient temperature
is 25 °C or higher the temperature of the oil in the
tank does not exceed 35 °C with class C oil or 55 °C
with class D oil.
Each integral tank shall be mounted in such a
position that oil accidentally spilled during filling or
escaping is unable to come into contact with any
heated surface.
an auxiliary tank having a capacity of not more
than 1 000 L, which isolates the main storage tank
or tanks from the burner installation
2.4
design pressure or head
that pressure or equivalent head of water acting at
the bottom, sides and top of the tank
2.5
design pressure or head at the bottom of the
tank
the tank depth plus a vent height of 0.5 m. If the
height of the vent pipe exceeds 0.5 m or where it is
not possible to provide a pressure relief device, the
full equivalent height of the vent pipe including
frictional loss is taken into account when calculating
the design pressure
NOTE
See appendix B.
© BSI 12-1998
3.1 General
3.2 Pressure testing
Before being painted, each tank shall be pressure
tested by the manufacturer in accordance with
appendix A. The manufacturer shall provide the
purchaser with a copy of the test certificate for each
tank supplied.
Each tank shall be able to withstand the design
pressure.
1
BS 799-5:1987
NOTE 1 All the pressures to which the tank may be subjected
(see 2.4 to 2.7) should be taken into consideration.
NOTE 2 The purchaser should inform the manufacturer of the
required design pressure [see C.1 a)].
3.3 Construction
All joints below the full fuel level shall be made by
brazing or welding.
NOTE Attention should be paid in the design of integral tanks
to ensure that they can be safely used for the purpose for which
they are intended by providing sufficient strength and rigidity to
resist that distortion which may give rise to hazardous discharge
of oil or vapour. Integral tanks should be resistant to corrosion.
4 Service tanks
4.1 Types
Service tanks shall be designated as follows.
Type S1: cylindrical tanks having a capacity up
to and including 250 L.
Type S2: rectangular tanks having a capacity up
to and including 250 L.
Type S3: horizontal cylindrical tanks having a
capacity over 250 L but not exceeding 1 000 L.
Type S4: rectangular tanks having a capacity
over 250 L but not exceeding 1 000 L.
Type S5: horizontal oval tanks having a capacity
not exceeding 1 000 L.
4.2 General
4.2.1 Service tanks shall have a capacity of not more
than 1 000 L.
4.2.2 The requirements for tank oil heaters, when
installed (see 15.3 and appendix C), shall be as
specified in clause 7.
4.2.3 An oil drain valve and, in addition for coal tar
liquid fuels, a water drain valve shall be provided as
specified in clause 9.
4.2.4 A separate vent pipe or return pipe shall be
provided for each tank, at the higher end.
(See clauses 11 and 13 and BS 5410.)
4.2.5 For oil draw-off lines and where return lines as
specified in 15.1 c) are used, fire valves shall be
provided as specified in clause 16.
4.2.6 Service tanks shall be installed as specified in
clause 15 (see also BS 5410).
4.3 Pressure testing
Before being painted, each tank shall be pressure
tested in accordance with appendix A at the
manufacturer’s works or on site when the tank is
fabricated on site.
Tanks tested on site shall be tested hydraulically.
The manufacturer shall provide the purchaser with
a copy of the test certificate for each tank supplied.
Each tank shall be able to withstand the design
pressure.
NOTE 1 All the pressures to which the tank may be subjected
(see 2.4 to 2.7) should be taken into consideration.
NOTE 2 The purchaser should inform the manufacturer of the
required design pressure [see C.1 a)].
4.4 Marking
The following information shall be permanently and
clearly marked on the tank on the vertical centre
line near the outlet connection:
a) capacity (in L);
b) date of manufacture;
c) manufacturer’s name or trade mark;
d) manufacturer’s reference number;
e) the number and date of this British Standard1)
and type of tank (e.g. BS 799-5:1987 type S1).
4.5 Construction and plate thickness
4.5.1 Service tanks shall be of welded construction
and made of rolled steel sheets which comply with
the requirements for grade CR4 material suitable
for welding as specified in BS 1449-1. Galvanized
steel shall not be used.
4.5.2 The provision of manholes or inspection
openings, if required for access to internal fittings,
shall be as specified in clause 6.
4.5.3 For service tanks having a capacity up to and
including 250 L (types S1 and S2) the minimum
thickness of the steel sheets shall be 1.2 mm.
For cylindrical tanks, the maximum height shall not
exceed 750 mm and the maximum diameter shall
not exceed 600 mm.
NOTE
All welding should be sound and of good penetration.
4.5.4 For service tanks having a capacity over 250 L
but not exceeding 1 000 L (types S3, S4 and S5) all
welding shall comply with the requirements of
BS 5135. Rectangular tanks (type S4) shall be
stayed or stiffened and have a thickness of plate not
less than as shown in Figure 1. For cylindrical tanks
(type S3) the diameter of shell and the thickness of
the shell and ends shall be not less than as given
in Table 1. For oval tanks (type S5) the major axis of
the shell and the thickness of the shell and ends
shall be not less than as given in Table 1.
1) Marking
BS 799-5:1987 on or in relation to a product represents a manufacturer’s declaration of conformity, i.e. a claim by or
on behalf of the manufacturer that the product meets the requirements of the standard. The accuracy of the claim is therefore
solely the responsibility of the person making the claim. Such a declaration is not to be confused with third party certification of
conformity, which may also be desirable.
2
© BSI 12-1998
BS 799-5:1987
Table 1 — Minimum plate thicknesses for service tanks of types S3 and S5
Capacity
L
Up to and including 500
Minimum thickness of plate
Shell
Dished and
flanged ends
Ends dished only
Flat flanged ends
Flat unflanged ends
(stiffened)
Flat unflanged
ends
(not stiffened)
Maximum
diameter or
major axis
mm
mm
mm
mm
m
1.6
1.6
2.0
3.0
0.25
Over 500 and including 1 000 2.0
2.0
2.5
4.0
1.0
5 Oil storage tanks
5.1 Types
NOTE The type of tank to be used will depend on the size of
the plant as well as on the site available (see BS 5410-2
or BS 5410-3).
Oil storage tanks shall be designated as follows.
a) Tanks having a capacity of not more
than 3 500 L and having a venting device or pipe
not exceeding 0.5 m in height or equivalent
friction head:
Type I
Type II
Type III
: horizontal cylindrical tanks;
: horizontal oval tanks (with the
major axis horizontal);
: rectangular tanks.
b) Tanks excluding those covered by a) and not
exceeding 10 m in height:
Type A: horizontal cylindrical tanks having a
capacity of not more than 60 000 L, with
dished or flat ends, for a design head
equivalent to a head of water not
exceeding 0.5 m above the top of the tank;
Type B: horizontal cylindrical tanks having a
capacity of not more than 60 000 L, with
dished ends, for a design head equivalent to a
head of water not exceeding 4.5 m above the
top of the tank;
Type C: horizontal cylindrical tanks having a
capacity of not more than 60 000 L, with
dished ends, for a design head equivalent to a
head of water greater than 4.5 m above the
top of the tank;
Type D: vertical cylindrical tanks having a
capacity of not more than 65 000 L, with
dished ends, for a design head equivalent to a
head of water not exceeding 0.5 m above the
top of the tank;
Type E: vertical cylindrical tanks having a
capacity of not more than 145 000 L, with
dished ends, for a design head equivalent to a
head of water not exceeding 7.5 m above the
top of the tank;
© BSI 12-1998
Type F: vertical cylindrical tanks having a
capacity of not more than 65 000 L, with
dished ends, for a design head equivalent to a
head of water greater than 7.5 m above the
top of the tank;
Type G: vertical cylindrical tanks having a
capacity of not more than 145 000 L, with flat
bottom end plates, for a design head
equivalent to a head of water not
exceeding 0.5 m above the top of the tank;
Type J: rectangular tanks having a capacity of
not more than 150 000 L, for a design head
equivalent to a head of water not
exceeding 0.5 m above the top of the tank;
Type K: rectangular tanks having a capacity
of not more than 150 000 L, for a design head
equivalent to a head of water not
exceeding 7.5 m above the top of the tank;
Type L: rectangular sectional tanks having a
capacity of not more than 150 000 L. These
tanks shall only be used when the use of
factory or site welded tanks is not practicable.
5.2 General
5.2.1 The requirements for tank oil heaters, when
installed (see 15.3 and appendix C), shall be as
specified in clause 7.
5.2.2 Tanks shall be provided with an oil level
indicator as specified in clause 8.
5.2.3 An oil drain valve and, in addition for coal tar
liquid fuels, a water drain valve, shall be provided
as specified in clause 9.
5.2.4 Filling pipes and connections shall be as
specified in clause 10.
5.2.5 A separate vent pipe shall be provided for each
tank at the higher end as specified in clause 11.
5.2.6 Outlet valves and pipes shall be provided as
specified in clause 12.
5.2.7 Oil return pipes shall be connected as specified
in clause 13.
5.2.8 For oil draw-off lines and where return lines as
specified in 13.1 c) are used, fire valves shall be
provided as specified in clause 14.
3
BS 799-5:1987
5.2.9 Oil storage tanks shall be installed as specified
in clause 15 (see also BS 5410).
5.3 Pressure testing
5.3.1 Types I to III. Before being painted (see 5.4)
each tank shall be pressure tested in accordance
with appendix A at the manufacturer’s works or on
site when the tank is fabricated on site.
Tanks tested on site shall be tested hydraulically.
The manufacturer shall provide the purchaser with
a copy of the test certificate for each tank supplied.
Each tank shall be able to withstand the design
pressure. Tanks shall not be used on any site that
requires a vent pipe exceeding 0.5 m in height
(or equivalent friction head) unless a pressure relief
device is fitted (see 2.4 to 2.7).
NOTE The purchaser should inform the manufacturer of the
required design pressure [see C.1 a)].
5.3.2 Types A to L
5.3.2.1 Types A to K. Before being painted (see 5.4)
each tank shall be pressure tested in accordance
with appendix A at the manufacturer’s works or on
site when the tank is fabricated on site.
Tanks tested on site shall be tested hydraulically.
The manufacturer shall provide the purchaser with
a copy of the test certificate for each tank supplied.
5.3.2.2 Type L. Where a sectional tank cannot be
subjected to a pressure equivalent to the head of oil
in the tank and vent pipe (such as by overfilling) it
shall be tested by being filled with water to its
capacity. The test shall be maintained for a period
of 24 h.
The manufacturer shall provide the purchaser with
a copy of the test certificate for each tank supplied.
5.3.2.3 Conditions for types A to L. Each tank shall
be able to withstand the design pressure.
NOTE 1 The grade of oil and the pressure to which the tank
may be subject in the event of overfilling (see appendix B) or the
pressure at which the pressure relief device operates if one is
fitted (see clause 11) should be taken into consideration.
NOTE 2 The purchaser should inform the manufacturer of the
required design pressure [see C.1 (a)].
5.4 Painting and cleaning
5.4.1 Types I to III. Each tank fabricated at the
manufacturer’s work shall, before despatch, be
cleaned externally and either:
a) be protected externally with a rust-inhibiting
priming paint; or
b) be left unprotected.
NOTE The tank will be protected externally with a
rust-inhibiting priming paint unless it is specifically requested
by the purchaser that the tank be left unprotected.
The inside of the tank shall be cleaned and all
openings closed to prevent ingress of foreign matter.
Tanks built on site shall be cleaned externally and
internally after testing and painted externally.
5.4.2 Types A to L. Tanks of types A to K fabricated
at the manufacturer’s works shall, before despatch,
be cleaned externally and painted with
anti-corrosive paint; the inside of the tank shall be
cleaned and all openings closed to prevent ingress of
foreign matter. Tanks built on site (including
type L) shall be cleaned externally and internally
after testing and painted externally.
5.5 Marking
The following information shall be permanently and
clearly marked on the tank on the vertical centre
line near the outlet connection:
a) capacity (in L);
b) date of manufacture;
c) manufacturer’s name or trade mark;
d) manufacturer’s reference number;
e) the number and date of this British Standard2)
and type of tank (e.g. BS 799-5:1987 type I).
5.6 Construction and plate thicknesses
5.6.1 General
5.6.1.1 Types I to III. Storage tanks of types I to III
shall be of welded construction and made of rolled
steel sheets or plates which comply with the
requirements for grade CR4 material suitable for
welding as specified in BS 1449-1. Galvanized steel
shall not be used. All welding shall be as specified in
BS 5135.
5.6.1.2 Types A to K. Storage tanks of types A to K
shall be of welded construction and made of rolled
steel plates which comply with the requirements for
grade 43A material as specified in BS 4360.
Galvanized steel shall not be used. All welding shall
be as specified in BS 5135.
5.6.1.3 Access (types I to III and A to L). The
provision of manholes or inspection openings, if
required for access to internal fittings, shall be as
specified in clause 6.
2) Marking
BS 799-5:1987 on or in relation to a product represents a manufacturer’s declaration of conformity, i.e. a claim by or
on behalf of the manufacturer that the product meets the requirements of the standard. The accuracy of the claim is therefore
solely the responsibility of the person making the claim. Such a declaration is not to be confused with third party certification of
conformity, which may also be desirable.
4
© BSI 12-1998
BS 799-5:1987
Table 2 — Minimum plate thicknesses for storage tanks of types I and II
Capacity
L
Minimum thickness of plate
Shell
Dished and
flanged ends
Ends dished only
Flat flanged ends
Flat unflanged
ends (stiffened)
mm
mm
mm
Flat unflanged
Maximum
ends
diameter for
(not stiffened)
tanks of
type I
mm
m
Up to and including 500
1.6
1.6
2.0
4.0
0.75
Over 500 up to and including 1 400
2.0
2.0
2.5
4.0
1.0
Over 1 400 up to and including 2 300 2.5
2.5
4.0
5.0
1.2
Over 2 300 up to and including 3 500 4.0
4.0
5.0
8.0
1.4
5.6.2 Type I. For type I tanks the maximum
diameter of the shell and the minimum thickness of
the shell and ends shall be as given in Table 2.
5.6.3 Type II. For type II tanks the minimum
thickness of the shell and ends shall be as given
in Table 2.
© BSI 12-1998
5.6.4 Type III. For type III tanks the thickness of the
sheet and the pitch of the staying or stiffening shall
be as shown in Figure 1.
The internal stays or stiffening shall be arranged to
allow complete draining. Tanks shall be supported
by two or more transverse supports spaced at
intervals not less than those shown in Figure 2.
5
BS 799-5:1987
Figure 1 — Relationship between design head, pitch of stays or stiffening and plate thickness
for rectangular service tanks of type S4 and rectangular storage tanks of types III, J and K
6
© BSI 12-1998
BS 799-5:1987
Figure 2 — Relationship between design head, span between supports and plate thickness
for rectangular storage tanks of types III, J and K
© BSI 12-1998
7
BS 799-5:1987
Figure 3 — Shallow dished and flanged end
Table 3 — Minimum plate thicknesses for
storage tanks of type A
Internal diameter
m
Thickness
Shell
Dished
ends
Flat ends
mm
mm
mm
Up to and
including 1
4.0
4.0
5.0
Over 1 up to and
including 1.6
5.0
5.0
8.0
Over 1.6 up to and 6.0
including 2.4
6.0
Dished ends
only
Over 2.4 up to and 8.0
including 2.7
6.0
Dished ends
only
5.6.5 Type A. For type A tanks dished and flanged
end plates shall be concave to the oil pressure and
shall have dimensions as shown in Figure 3.
The thicknesses of the shell and end plates shall be
not less than that given in Table 3.
NOTE Type A tanks of 1 m and over constructed in accordance
with BS 2594 will also satisfy the requirements of this standard.
5.6.6 Type B. For type B tanks end plates shall be
dished and flanged, and butt welded or lap welded to
the shell. The ends shall be concave to the oil
pressure and shall have dimensions as shown
in Figure 3.
Where the end plates are made in more than one
plate, the butt joints shall be welded from both sides
of the plate.
The thicknesses of the shell and end plates shall be
not less than those given in Table 4.
8
5.6.7 Type C. For type C tanks end plates shall be
dished and flanged and butt welded or lap welded to
the shell. The ends shall be concave to the oil
pressure and shall have dimensions as shown
in Figure 4.
Where the end plates are made in more than one
plate the butt joint shall be welded from both sides
of the plate.
The plate thicknesses and construction shall be as
specified in BS 5500, but the thicknesses shall not
in any case be less than those given in Table 4 for a
tank of similar size.
5.6.8 Type D. For type D tanks end plates shall be
dished and flanged, and butt welded or lap welded to
the shell.
The dished ends shall be concave to the oil pressure.
The top ends shall have dimensions as shown
in Figure 3. The bottom ends shall have dimensions
as shown in Figure 4.
Where the end plates are made in more than one
plate, the butt joints shall be welded from both sides
of the plate.
The thicknesses of the shell and end plates shall be
not less than those given in Table 5.
Table 4 — Minimum plate thicknesses for
storage tanks of types B and C
Internal diameter
m
Thickness
Shell
Dished
ends
mm
mm
Up to and including 1
4.0
4.0
Over 1 up to and including 1.6
5.0
5.0
Over 1.6 up to and including 2.4
6.0
10.0
Over 2.4 up to and including 2.7
8.0
10.0
© BSI 12-1998
BS 799-5:1987
The thicknesses of the shell and end plates shall be
not less than those given in Table 6.
Tanks shall be supported by a cylindrical skirt, or by
supporting brackets, so that the centre of the end
plate is at least 300 mm clear of the ground.
Inspection openings complying with clause 6 shall
be provided in the skirt.
NOTE Above ground tanks, which may become unstable due to
wind pressure when empty, should be provided with foundation
bolts to prevent overturning.
Figure 4 — Dished and flanged end
Table 5 — Minimum plate thicknesses for
storage tanks of type D
Tank size
Thickness
Diameter
Depth
m
m
Up to and
including
1.0 or
2.0
Over
1.0 or
2.0
Up to and
including
1.6 or
6.5
Over
1.6 or
6.5
Up to and
including
2.7 or
10.0
Shell
Bottom
and top dished
dished
end
end
mm
mm
4.0
4.0
5.0
5.0
6.0
6.0
Tanks shall be supported by a cylindrical skirt or by
supporting brackets, so that the centre of the end
plate is at least 300 mm clear of the ground.
Inspection openings complying with clause 6 shall
be provided in the skirt.
NOTE Above ground tanks, which may become unstable due to
wind pressure when empty, should be provided with foundation
bolts to prevent overturning.
5.6.9 Type E. For type E tanks end plates shall be
dished and flanged, and butt welded or lap welded to
the shell.
The dished ends shall be concave to the oil pressure.
The top ends shall have dimensions as shown
in Figure 3 up to 2 700 mm diameter and as shown
in Figure 4 for larger diameters (see also Table 6).
The bottom ends shall have dimensions as shown
in Figure 4 (see also Table 6).
Where the end plates are made in more than one
plate, the butt joints shall be welded from both sides
of the plate.
© BSI 12-1998
5.6.10 Type F. For type F tanks end plates shall be
dished and flanged and butt welded or lap welded to
the shell.
Where the end plates are made in more than one
plate the butt joints shall be welded from both sides
of the plate.
The dished ends shall be concave to the oil pressure
and shall have dimensions as shown in Figure 4.
The plate thicknesses and construction shall be as
specified in BS 5500, but the thicknesses shall not
in any case be less than those given in Table 6 for a
tank of similar size.
Tanks shall be supported by a cylindrical skirt, or by
supporting brackets so that the centre of the end
plate is at least 300 mm clear of the ground.
Inspection openings complying with clause 6 shall
be provided in the skirt.
NOTE Above ground tanks, which may become unstable due to
wind pressure when empty, should be provided with foundation
bolts to prevent overturning.
5.6.11 Type G. For type G tanks the bottom end
plates shall be welded to the shell from both sides.
The top end plates shall be dished and flanged and
butt welded or lap welded to the shell. The top
dished ends shall be concave to the oil pressure and
shall have dimensions as shown in Figure 3 up
to 2 700 mm diameter and as shown in Figure 4 for
larger diameters.
The thicknesses of the shell and end plates shall be
not less than those given in Table 7.
Tanks shall be so erected that the flat bottom is
uniformly supported.
NOTE Above ground tanks, which may become unstable due to
wind pressure when empty, should be provided with foundation
bolts to prevent overturning.
5.6.12 Types J and K. For tanks of types J and K the
seams shall either:
a) be welded inside and outside; or
b) where access for inside welding is
impracticable, the top seams shall be welded on
the outside only.
The flat plates shall be stayed or stiffened by one of
the following means:
a) stayed with the thickness of the plates and the
pitch of the stays as shown in Figure 1;
9
BS 799-5:1987
b) stiffened by carbon steel sections fitted inside
and/or outside the tank;
c) both stayed and stiffened by carbon steel
sections fitted inside and/or outside the tank.
Table 6 — Minimum plate thicknesses for storage tanks of types E and F
Tank size
Thickness
Diameter
Depth
Shell
Top dished end
Bottom dished end
(see Figure 4)
m
m
mm
mm
mm
Up to and including
1.0
or
2.0
Over
1.0
or
2.0
Up to and including
1.5
or
6.0
Over
1.5
or
6.0
Up to and including
1.8
or
6.5
Over
1.8
or
6.5
Up to and including
2.7
or
10.0
Over
2.7
or
10.0
Up to and including
4.0
or
10.0
4.0
4.0 (see Figure 3)
4.0
5.0
5.0 (see Figure 3)
5.0
5.0
6.0 (see Figure 3)
6.0
6.0
8.0 (see Figure 3)
10.0
6.0
10.0 (see Figure 4)
10.0
Table 7 — Minimum plate thicknesses for storage tanks of type G
Tank size
Thickness
Diameter
Depth
Shell and top dished end
Bottom flat end
m
m
mm
mm
Up to and including
1.0
or
2.0
Over
1.0
or
2.0
Up to and including
2.0
or
7.5
Over
2.0
or
7.5
Up to and including
4.0
or
10.0
4.0 (see Figure 3)
5.0
5.0 (see Figure 3)
6.0
6.0 (see Figure 4)
8.0
Figure 5 — Positions of steel cradles for storage tanks of type I
10
© BSI 12-1998
BS 799-5:1987
Table 8 — Dimensions of steel cradles for
storage tanks of type I (see Figure 5)
Tank diameter D
Minimum width
of cradle B
Minimum length
of cradle C
m
mm
m
0.75
65
0.66
1.0
75
0.90
1.2
100
1.05
1.4
100
1.25
The stays and/or stiffeners shall be so arranged that
they do not:
a) restrict drainage or access to any part of the
internal surfaces; or
b) restrict access to and operation of oil level
indicators, oil heaters, thermostats, etc.
Tanks shall be supported by two or more transverse
supports spaced at intervals not less than as shown
in Figure 2.
5.6.13 Type L. Rectangular sectional tanks shall be
externally flanged with closed top and be as
specified in BS 1564. Access to the bolted joints
shall be provided.
Galvanized materials shall not be used.
NOTE For cast iron sectional tanks (including covers),
see type A(2) of BS 1563.
The jointing material used shall be such that it will
ensure oiltight joints in service. Manholes and
inspection openings shall be as specified in clause 6.
Tanks shall be supported on the flanged joints.
5.7 Cradles (for tanks of types I, II, A, B and C)
5.7.1 General. Tanks of types I, II, A, B and C shall
be supported above ground level by two cradles
arranged so that the storage tank slopes downwards
at the rate of 1 in 50 towards the drain valve.
NOTE Cradles should not be placed directly under joints or
seams of tank plates. A layer of bitumen or bituminized felt
should be interposed between the cradle to its full width and
length and the surface of the tank.
It is important that the construction of the cradle footings and
foundations is such as to be capable of supporting the weight of a
full tank, when full of water, taking account of the height of the
cradle and the nature of the soil or base on which the tank is to
stand.
5.7.2 Types I and II. Brick cradles shall be not less
than one brick thickness (215 mm nominal).
Steel cradles for tanks of type I shall have the
dimensions given in Table 8 and be positioned as
shown in Figure 5.
Steel cradles for tanks of type II shall have the
dimensions given in Table 9 and be positioned as
shown in Figure 6.
5.7.3 Types A, B and C. Cradles shall have the
dimensions given in Table 10 and be positioned as
shown in Figure 7.
Table 9 — Dimensions of steel cradles for
storage tanks of type II (see Figure 6)
Tank capacity
Minimum
width of
cradle B
L
mm
Up to and including 1 300
50
Over 1 300 up to and including 3 500 65
Figure 6 — Positions of steel cradles for storage tanks of type II
© BSI 12-1998
11
BS 799-5:1987
Table 10 — Dimensions for cradles for storage tanks of types A, B and C (see Figure 7)
Tank diameter
D
Length of shell
A
m
Minimum width of cradles
B
m
Steel
Concrete
Bricka
mm
mm
mm
Minimum length
of cradles
C
m
1.00
2.50
75
150
215
0.90
1.25
2.50
100
150
215
1.10
1.50
2.50
100
150
215
1.30
1.50
3.00
100
200
215
1.30
1.75
3.00
150
200
215
1.60
2.00
3.00
150
200
215
1.80
2.00
3.25
175
200
215
1.80
2.25
3.00
200
200
215
2.00
2.25
4.25
200
300
327.5
2.00
2.25
5.25
200
300
327.5
2.00
2.50
4.75
225
300
327.5
2.20
2.75
4.50
250
350
327.5
2.40
2.75
6.00
250
350
327.5
2.40
2.75
9.00
250
350
327.5
2.40
a
Based on a brick format of 225 mm × 112.5 mm × 75 mm (see Table 1 of BS 3921:1974).
Figure 7 — Positions of cradles for storage tanks of types A, B and C
6 Manholes and inspection openings
All cylindrical tanks over 1 m diameter and all
rectangular tanks over 3 500 L capacity shall be
provided with a manhole.
12
Vertical tanks over 3.5 m in height shall be provided
with an additional manhole near the bottom of the
vertical shell.
NOTE 1 The need for manholes in cylindrical tanks below 1 m
diameter or rectangular tanks below 3 500 L capacity and the
need for inspection covers should be stated by the purchaser
[see C.1 b)].
© BSI 12-1998
BS 799-5:1987
NOTE 2 Section 30 of the Factories Act 1961 applies if there is
a likelihood of dangerous fumes being present within a tank to
such an extent as to involve risk of persons being overcome.
The relevant part of Section 30 of the Factories Act 1961 states:
“The confined space shall, unless there is other adequate
means of egress, be provided with a manhole, which may be
rectangular, oval or circular in shape, and shall be not less
than 18 inches long and 16 inches wide or (if circular) not less
than 18 inches diameter.”
These sizes are equivalent to 457.2 mm × 406.4 mm
and 457.2 mm diameter respectively.
Section 30 also applies to the lack of oxygen within a confined
space. Reference may be made to subsections (9) and (10) of
Section 30 for the full legal requirements.
Manholes shall be not less than 460 mm in diameter
if circular in shape and not less than 460 mm long
and 410 mm wide if oval in shape; the 410 mm
dimension shall be measured along the longitudinal
axis of the tank.
Manholes and other large inspection openings shall
be stiffened by the provision of a flanged neck ring
welded or rivetted round the opening or
alternatively in the case of a rectangular tank by a
flat faced compensating ring welded round the
opening. Holes for studs and set screws shall not
penetrate the tank plate.
Inspection openings shall be not less than 150 mm
diameter.
Where practicable, manholes and inspection
openings shall be located on top of the tank. Each
manhole or inspection opening shall be provided
with a cover securely fixed by bolts, studs or set
screws and shall have a liquid and vapourtight joint
made with a gasket of oil-resistant material. The
maximum pitch of fixing bolts for tanks of types A,
B, D, E, G, J and K shall be as given in Table 11.
The minimum thicknesses for covers for manholes
and inspection openings shall be not less than the
thickness of the body plate for service tanks and
storage tanks of types I to III and shall be as given
in Table 11 for tanks of types A, B, D, E, G, J and K.
The plate thickness and fixing details of manholes
and inspection openings for tanks of types C and F
shall be as specified in BS 5500.
NOTE 3 The thicknesses specified in Table 11 have been
adopted to provide for a minimum number of fixing bolts, studs
or set screws and to enable top and bottom manhole covers on
vertical tanks to be interchangeable.
Table 11 — Manholes and inspection openings:
minimum thicknesses of covers and maximum
pitch of fixing bolts
Type of tank
Cover
thickness
Maximum pitch of
M16 bolts, studs or
set screws
mm
mm
A, J
10
100
B, D,G, K
10
80
E
12
90
© BSI 12-1998
7 Heaters for oil storage tanks
7.1 General
Heaters shall be selected from the following types:
a) the immersion type, inserted through the
outlet end of the tank;
b) the submersion type, inserted through the top
of the tank;
c) the outflow type, where the heating elements
are concentrated around the outlet.
NOTE 1 The means of heating may be electricity, steam or hot
water (see also C.2 a) and BS 5410).
NOTE 2 Details of some typical tank heater arrangements are
shown in Figure 8 and Figure 11 b).
7.2 Electric heaters
The electric loading shall not exceed 1.3 W/cm2 of
element sheath surface. The design surface
temperature shall not exceed 175 °C. Thermostatic
control shall be employed; for outflow heaters a
safety cut-out shall be provided in addition as
specified in BS 799-4. Elements and thermostats
shall be of the dry type so that they can be
withdrawn without emptying the tank.
NOTE The element sheath or pocket should be of sufficient
strength to prevent damage to the element and be supported as
necessary along its length by cradles or other supports.
Heaters fitted to tanks placed in the open air shall
be provided with weatherproof terminal covers.
7.3 Steam and hot water heaters or coils
(including high pressure hot water heaters)
Heaters or coils shall be constructed of seamless
steel tube either:
a) without joints within the tank; or
b) where unavoidable, with joints within the
tank.
NOTE Where such joints are unavoidable they should be
welded.
Heaters shall be designed to allow free expansion
and be supported at intervals along their length by
cradles or other supports.
Steam heaters shall be arranged to drain freely and
not be subject to water hammer.
Water heaters shall be so designed that any
entrapped air is vented automatically.
The maximum temperature of the heating medium
shall not exceed 175 °C.
7.4 Location
All heaters and controlling thermostats shall be so
located in relation to the draw-off level that their
surfaces do not become exposed (see clause 12).
NOTE Provision should be made for visual and audible alarms
to give warning when the oil level falls below a depth of 300 mm
above the heater.
13
BS 799-5:1987
7.5 Pressure testing
All parts of the heater subject to internal pressure
shall be subjected to and be capable of withstanding
a hydraulic test carried out at 1.5 times the
maximum working pressure or 7 bar3), whichever is
the greater.
Electric heaters shall be independently earthed.
The insulation resistance between the elements and
the heater, when measured at room temperature
with a voltage of not less than 500 V d.c., shall be
not less than 1 MW.
7.6 Marking
The following information shall be permanently and
clearly marked on each heater:
a) manufacturer’s name or trade mark and
identification mark or serial number;
b) test pressure and date of test;
c) maximum working pressure;
d) on heaters containing electric elements, also:
1) voltage;
2) wattage.
e) a diagram of electrical connections where there
are more than two terminals exclusive of the
earthing terminal.
8 Oil level indicators
8.1 General
Oil level indicators shall be selected from the
following types:
a) dip stick;
b) float gauge;
c) hydrostatic gauge (operated by the static
pressure of the oil in the tank acting upon a
diaphragm or bellows and transmitting the
deflection to a pressure gauge);
d) electronic gauge (which measures a changing
electrical capacitance as varied by the movement
of the oil level in respect of a static sensor);
e) displacer gauge (consisting of a semi-buoyancy
unit having its out-of-balance weight
mechanically transmitted to a dial, and/or a
device for the remote transmission of the
measurement);
f) sight tube.
NOTE 1 The main purpose of an oil level indicator is to show
the approximate contents of the tank.
NOTE 2 Float, hydrostatic, electronic and displacer types of
gauge allow the operation of an indicator placed at some distance
from the tank if desired.
8.2 Dip stick
A calibrated dip stick shall be used or, in the case of
a large tank, a dip tape in conjunction with a
calibration chart previously prepared for the tank.
The dip opening shall be provided with a
non-ferrous screwed cap or plug.
NOTE 1 It is recommended that, when frequent dipping of the
tank is necessary, a reinforcing pad be welded to the inside of the
bottom of the tank directly under the dipping opening.
NOTE 2 Commercially precalibrated dip rods are not normally
considered to be an accurate means of tank contents
measurement.
8.3 Float gauge
Float gauges shall be of either of the following two
types:
a) a float attached to a cable, chain, rod or metal
tape passing through the tank top within a fitting
that does not allow ingress of water or dust or the
egress of oil, and indicating on a dial or by radial
arm or sliding pointer;
b) a float imparting a movement to a magnetic
coupling, the two parts of which are separated by
a metal body which itself forms part of the tank
wall and withstands the test pressure of the tank.
NOTE The outer part of the magnetic coupling may be used
to drive a pointer, and/or other transmission device, by
mechanical, electrical, hydraulic or pneumatic means.
Figure 8 — Typical arrangement of tank heaters with long heaters to spread heat in tank
and short heater fitted on manhole
3)
1 bar = 105 N/m2 = 100 kPa.
14
© BSI 12-1998
BS 799-5:1987
8.4 Hydrostatic gauge
The transmission systems of hydrostatic gauges
shall be one of the following three types:
a) mechanical, where the indicator takes its
movement directly from the bellows or
diaphragm;
b) sealed types, where the transmission is via
single or double pipes containing liquid, air or
gas, with or without temperature compensating
gear;
c) non-sealed types, where an air pressure is
imparted to the system at the time the reading is
taken.
NOTE The hydrostatic gauge has to be calibrated to the relative
density of the oil in use, and any change in grade or storage
temperature may necessitate recalibration. Dials should be
clearly marked with the relative density of the oil for which they
have been calibrated.
8.5 Electronic gauge
The sensor for electronic gauges shall be fixed
through the top of the tank and be able to withstand
the test pressure of the tank.
Table 12 — Oil and water drain valves:
minimum clearway openings for varying tank
capacities
Capacity of tank
L
Nominal
pipe size
mm
Up to and including 1 500
20
Over 1 500 up to and including 3 500
25
Over 3 500 up to and including 7 000
40
Over 7 000 up to and including 20 000 50
Over 20 000
65
9.2 Water drain valves
For coal tar liquid fuels, in addition to the oil drain
valve, a water drain or skimming valve, preferably
of the full way wedge-gate pattern, shall be placed at
a convenient height above the outlet. Sizes of these
additional valves shall also be as given in Table 12.
10 Filling pipes and connections
8.6 Sight tube
10.1 General
The material of the sight tube shall be unaffected by
the oil used.
For oil of classes F, G and H a means shall be
provided for all filling lines to be drained after each
delivery of oil or, alternatively, pipe heating shall be
provided.
When bottom filling of storage tanks is employed a
non-return valve shall be provided.
When the filling pipe is continued below the surface
of the oil and forms a siphon, an anti-siphoning
device, such as a hole drilled in the pipe, shall be
provided above the maximum oil level within the
tank.
NOTE The material should be pliable and not liable to fracture
under working conditions, and should be adequately supported
and protected throughout its length.
There shall be a valve between the bottom of the
sight tube and the tank. This valve shall be of the
type which remains automatically closed except
when readings are being taken. The valve shall be
so designed that it cannot be wedged in the open
position.
This type of gauge shall not be used for tanks
exceeding 3 500 L and shall only be used for oils of
classes C and D.
9 Drain valves
9.1 Oil drain valves
A screwdown gate valve or glanded cock shall be
fitted at the lowest part of the underside of the tank.
Unlubricated plug valves shall not be used.
Drain valves shall be of gunmetal or steel. Cast iron
valves shall not be used.
Drain valves and cocks shall be capable of being
locked in the closed position.
The clearway opening of the valve shall be at least
equal to the cross-sectional area of the appropriate
pipe size given in Table 12.
Access to the drain valve shall be available with
room to place a suitable receptacle, e.g. a bucket,
beneath the valve.
© BSI 12-1998
NOTE Wherever possible the filling line should fall away from
the filling point towards the tank.
10.2 Road tank wagon deliveries
For tanks to be filled from road tank wagon
deliveries, either:
a) the filling pipe dimensions shall be not less
than those given in Table 13; or
b) for tanks having capacities not
exceeding 1 350 L a filling orifice, of not less
than 150 mm diameter and having a raised rim
that can be closed by means of a weatherproof
hinged lockable lid, shall be permitted instead of
a fixed filling pipe, the orifice being used as a
vent.
NOTE 1 The supplier should be consulted for the current filling
pipe and connection sizes.
NOTE 2 Where the pipe-line is of exceptional height or length
or exposed to extreme cold, a pipe of larger bore should be used.
The connecting thread shall be protected by means
of an easily removable non-ferrous screw-on cap
which shall be secured by a chain.
15
BS 799-5:1987
Where the filling point is below any portion of the
filling line, a screw-down full way type oil valve
shall be provided close to the filling end of the line
and a small witness hole (see Figure 6) or groove
(see Figure 7) shall be provided.
NOTE 3 The witness hole or groove will give an immediate
warning should an attempt be made to remove the cap without
the valve being properly closed.
Where the filling pipe is continued below the surface
of the oil and forms a siphon, an anti-siphoning
device, such as a hole drilled in the pipe, shall be
provided above the maximum oil level within the
tank.
10.3 Rail tank wagon deliveries
For tanks to be filled from rail tank car deliveries,
the platform coupling shall be a 100 mm bore
quick-acting coupling.
11 Vent pipes
The bore of the vent pipe shall, for tanks over 250 L
capacity, be not less than 50 mm nominal diameter
and at least equal to the bore of the filling pipe.
NOTE 1 The vent pipe should be free from sharp bends and
should have a continuous rise. While being as short as
convenient, it should terminate in the open air in a position
where it cannot be tampered with. The end of the pipe should be
kept away from any zone in which the discharge of air and vapour
might be dangerous or offensive.
Figure 9 — Details of filling point with
witness hole and protective cap
16
NOTE 2 If a common vent pipe has to be fitted when more than
one tank is installed, this may be done providing the tops of all
tanks are at the same level and providing there is not more than
one common vent pipe.
The cross-sectional area of the vent pipe connection
and of the vent pipe shall be such that no oil tank
will be subject to pressure in excess of the design
pressure during filling due to the tank being filled to
overfilling.
NOTE 3
See appendix B.
The open end of the vent pipe shall be turned down
and fitted with an open mesh wire cage; gauze shall
not be used.
Where a vent pipe pressure relief device is provided
to limit the head due to overfilling to the value of the
design pressure of the tank the cross-sectional area
of the pressure relief device shall be not smaller
than that of the vent pipe.
The pressure relief device shall be set to open at the
pressure equivalent to a vent height of 0.5 m.
Valve seat material and moving parts shall be of
non-ferrous construction.
Any spillage of oil shall be led to a catchpit or tank
chamber.
Vent pipes from service tanks shall be carried back
to the storage tank(s) or to the open air in
accordance with the recommendations of BS 5410.
Figure 10 — Details of filling point with
groove and protective cap
© BSI 12-1998
BS 799-5:1987
Table 13 — Filling pipes and connection sizes for oils classes C, D, E, F, G and H
Oil
Classes C and D
Total length of filling
pipe
Minimum bore {nominal) of filling pipe
Hose coupling connection,
male pipe thread
complying with BS 21
m
mm
in
up to 12
32 for tanks up to and including
1 500 L capacity
2
50 for tanks over 1 500 L capacity
2
50 for tanks up to and including
1 500 L capacity
2
65 for tanks over 1 500 L capacity
21/2
up to 12
65
3
over 12
80
3
80
3
over 12
Class E
Classes F, G and H
12 Outlet valves and pipes
The outlet pipe from the storage tank for all oils
except classes C and D shall be so arranged as to
leave a minimum of 75 mm of dead space in the
bottom of the tank at the draw-off end except that in
the case of tanks having heaters there shall be a
minimum depth of 150 mm of oil above the heater
surfaces at all times. (See 7.4.)
The outlet pipe shall be located as far from the drain
valve as practicable. A valve shall be provided on the
pipe as close to the tank as possible.
13 Oil return pipes
13.1 Oil return pipes to the tank shall be connected
in one of the following ways.
a) Terminated at the top of the tank, except when
carrying coal tar liquid fuel.
NOTE This method is unsuitable for coal tar liquid fuels as
accumulated water on the surface of the fuel would be
distributed. (See 13.2.)
b) Extended downwards into the tank. To prevent
the formation of a siphon when pipes terminate
below the highest oil level, the pipes shall be
fitted with an antisiphoning device, e.g. a 5 mm
hole drilled in the pipe within the air space in the
tank.
c) Connected to the tank below the highest oil
level, in which case they shall be treated as outlet
pipes and be connected in accordance with
clauses 12 and 14.
d) In a storage tank for residual grades of fuel
(classes E, F, G and H), the return shall be piped
back to the suction side of outflow heater.
NOTE No hot oil should be returned direct to the tank as this
could have an adverse effect on the stability of the stored oil.
© BSI 12-1998
13.2 For coal tar liquid fuels, the return pipe shall
terminate within 300 mm of the bottom of the tank
to prevent remixing of water that may have
accumulated on the surface of the fuel.
14 Fire valves
NOTE 1 Fire valves should be situated in an easily accessible
position as near to the tank as possible and, where practicable,
within the boundary of the tank chamber or catchpit retaining
wall. Where more than one tank is situated within a tank
chamber or catchpit retaining wall, one fire valve may be fitted
on the common outlet pipe. Where circumstances render the
fitting of a fire valve close to the tank impracticable, it should be
fitted in the boiler room at the point where the oil line enters the
boiler room.
Fire valves shall be so constructed as to ensure that:
a) they cannot be rendered inoperative by the
frictional resistance of a manually adjusted gland
or other manually adjustable sealing device;
b) when operated, complete closure is effected
without delay.
NOTE 2 Some oils contain solid matter which can be deposited
on valve surfaces and under these conditions the valve should
still shut-off without delay.
Materials for the construction of fire valves and
associated parts shall be as specified in BS 799-4.
NOTE 3 Cast-iron valves should not be used in positions where
they may become water-logged and subject to temperatures
below 0 °C, nor where the valve could be subject to mechanical
stress, such as might be caused by tank movement.
NOTE 4 Exposed moving parts situated in the open air should
be resistant to atmospheric corrosion.
Fire valves shall be subjected to and shall withstand
the same pressure or backing test as the pipes into
which they are fitted (see clause 39 of
BS 5410-2:1978).
Fusible links or other heat-sensitive devices used in
conjunction with fire valves shall operate at a
temperature of 68 °C to 74 °C, except that in cases
where the ambient temperature may exceed 49 °C,
a fusible link or other heat-sensitive device which
operates at 93 °C shall be provided.
17
BS 799-5:1987
At least one fusible link or other heat-sensitive
device shall be placed directly above the firing point
such that the height of the fusible link above each
fire box does not exceed 1 m.
Any pulley, guide or similar device which enables
the wire [see 2.9 a)] to change direction shall not
restrict the wire on its release and so prevent
closure of the valve.
Pulley diameters shall be not less than 40 mm.
Valves incorporating a fusible device shall only be
used in addition to a fire valve as otherwise specified
in this clause.
All fire valves shall require manual reset after
operation of the fusible link or other heat-sensitive
device.
Electrically operated fire valves, except in the case
of fully automatic oil burners, shall require manual
reset after a momentary or prolonged failure of the
electricity supply. Any failure in the electrical
circuit of a fire valve shall cause the valve to close.
A sealed system shall be of fail safe design and
automatically close the fire valve in the event of a
fault, e.g. air or fluid leakage from the valve’s sealed
circuit.
Hand release of the link line or operation of electric
or pneumatic system shall be provided in an
accessible position for emergency use and for
routine testing of the fire valve system. These hand
releases shall be clearly indicated.
In the case of industrial furnaces, in those instances
where it is not possible to install a fire valve in the
locations recommended in note 1, an automatic fire
valve shall be provided in the oil supply pipe-line
adjacent to the furnace. A manually operated quick
closing valve shall also be installed in a safe position
away from the furnace.
If a transfer or booster pump is used in the oil fuel
line from the storage to the burner then controls
shall be incorporated for the automatic stopping of
this pump when the fire valve is actuated.
a) Where the occurrence of an oil leak might have
serious consequences, i.e. such as contamination
of a water catchment area.
b) Where the water table is likely to rise above the
bottom of the tank.
c) Where the soil is acid-bearing and corrosive to
ferrous metal.
NOTE Typical storage tank arrangements are shown
in Figure 11.
15.1.2 Service tanks. Service tanks shall be located,
fitted and provided with vent piping in accordance
with the recommendations of BS 5410.
15.2 Tank chambers and catchpits
Tank chambers shall be constructed and have a fire
resistance in accordance with the recommendations
of BS 5410.
Catchpits shall be provided and constructed in
accordance with the recommendations of BS 5410.
15.3 Storage temperatures
The oil in storage and at the outflow shall be
maintained at the minimum temperatures given
in Table 14 (see also BS 5410). Where ambient
conditions are such that these temperatures may
not be maintained unaided facilities shall be
provided to maintain the temperature required.
Table 14 — Minimum storage and outflow
temperatures for oils classes C, D, E, F, G
and H
Oil
Minimum storage
temperatures
C and D
E (see note)
F
G
H
a
°C
Atmospheric
10
25
40
45
Minimum outflow
temperatures
°C
Atmospheric
10
30
50
55
a See
BS 6380 for low temperature properties.
NOTE Thermostatic control of heaters should have a minimum
setting above 10 °C.
15 Installation of tanks
15.4 Tank insulation
NOTE 1 The bye-laws of many local authorities give
requirements for the location of storage and service tanks and for
the provision and design of tank chambers and catchpits.
Materials for tank insulation shall be
non-combustible (see BS 5422).
NOTE 2 See 5.1 of BS 6380:1983 for recommendations for good
design and installation of bulk storage systems under cold
weather conditions.
15.1 Location
15.1.1 Storage tanks. Storage tanks shall be
located in accordance with the recommendations
of BS 5410.
In addition, storage tanks shall not be buried direct
in the ground in such cases where any of the
following conditions apply.
18
NOTE 1 The oil draw-off lines and filters of tanks for the
storage of distillate grades of fuel (classes C and D) should be
lagged except in the case of service tanks where it is preferable to
place the outlet filter inside the building.
NOTE 2 It is recommended that tanks for the storage of
residual grades of fuel (classes E, F, G and H) should have all
tank and fuel line surfaces lagged.
NOTE 3 Insulation should be fitted in such a manner that
replacement of contaminated lagging can be effectively carried
out (see BS 5970).
© BSI 12-1998
BS 799-5:1987
Figure 11 — Typical storage tank arrangements
© BSI 12-1998
19
BS 799-5:1987
Appendix A Pressure test
With the exceptions of vertical storage tanks of
types D to G the test shall be carried out with a total
head of water, or equivalent pressure, measured
from the bottom of the tank, equal to 1.5 times the
sum of:
a) the height of the tank; and
b) the design pressure above the top of the tank
(see 2.6).
Vertical storage tanks of types D to G shall either be
tested vertically at the pressure given above or
alternatively shall be tested horizontally to a
pressure equivalent to a head of water not less
than 0.7 m above the design pressure (see 2.4).
NOTE 1 The testing of vertical storage tanks of types D to G
horizontally should be subject to agreement between the
purchaser and the manufacturer. When testing flat bottom
vertical tanks horizontally the flat bottoms should be suitably
stiffened for the test.
NOTE 2 The test pressure should be increased slowly and
steadily until the specified test pressure is reached and that
pressure should be maintained for a period long enough to permit
a thorough examination to be made to ensure that the tank is
sound and shows no leaks or undue distortion.
NOTE 3 Attention is drawn to the importance of knowing the
hazards involved in pressure tests involving compressible fluid
such as air or gas; essential precautions should be carefully
considered by the manufacturer and/or purchaser. (See 5.8.4
of BS 5500:1988.)
NOTE 4 Due to the presence of one or more undetected defects
in the vessel or for some other unforeseen reason, a major rupture
of the tank may occur at some stage during the first application
of pressure. The test procedure to be followed, therefore, should
be agreed upon after consultation by the manufacturer and/or the
purchaser and should ensure, as far as is practicable, that no
person is exposed to injury should the vessel fail during the
testing operation.
Appendix B Overfilling of oil storage
tanks
When an oil storage tank is overfilled to the extent
that oil flows from the vent pipe (or unloading
device), the friction of the oil passing through the
pipe causes a pressure to be set up in the tank in
addition to that due to the head of oil in the vent
pipe. If the vent pipe is too small in diameter or too
long, the total pressure due to friction plus the static
head may be sufficient to cause serious damage to
the tank. The pressure developed at the top of the
tank depends upon the height, the bore, the total
length and the number of bends in the vent pipe, the
viscosity of the oil and the filling rate.
As shown in the examples in this appendix, the
pressure at the top of the tank due to overfilling can
be determined from Figure 12, Figure 13, Figure 14
or Figure 15 when used in conjunction with
Table 15, Table 16, Table 17 or Table 18
respectively for different values of viscosity and oil
flow.
20
Having determined the pressure at the top of the
storage tank, it may be necessary to revise the
layout of the oil storage installation. Consideration
should therefore be given to the following items and
their relevant clauses in this standard;
a) type of tank(s) to be used, cylindrical or
rectangular;
b) design pressure of tank(s);
c) vent pipe diameter and length, and unloading
device (if any);
d) location of tank(s).
If a revised layout is decided upon, further reference
to the appropriate figure and table should be made
to check the new conditions.
Pressure developed will vary for different classes of
oil. Where E, F, G or H grades of fuel oil are
contemplated, it is better to design the storage
installation to suit the maximum viscosity fuel oil
available and suitable for the oil-burning
equipment.
Example 1. Calculate the total head developed for
a 50 mm bore vent pipe of 7.5 m vertical
height, 7.5 m horizontal run and four easy bends.
Total equivalent vent height (using Table 15)
Vertical height:
(including entry, exit, return bend)
Horizontal run of 7.5 m
(pro rata from table)
Four easy bends
Total equivalent vent height
=
m
7.5
=
2.6
=
=
1.2
11.5
From Figure 12, a vent of 11.5 m height and 50 mm
bore would result in a head of 17.5 m of water at the
top of the tank.
Table 15 — Equivalent height of vent:
allowances for horizontal pipe runs, easy and
sharp bends at a filling rate of 500 L/min and
at a viscosity of 16 mm2/s
Fitting
Bore of vent
mm
mm
mm
50
65
80
Equivalent height of vent
m
m
m
10 m of horizontal run 3.5
1.5
0.5
Each easy bend
0.3
0.15
0.08
Each sharp bend
0.6
0.3
0.15
Example 2. Calculate the total head developed for
a 65 mm bore vent pipe of 7.5 m vertical
height, 7.5 m horizontal run and four easy bends.
© BSI 12-1998
BS 799-5:1987
Total equivalent vent height (using Table 16)
Vertical height:
(including entry, exit, return bend)
Horizontal run of 7.5 m
(pro rata from table)
Four easy bends
Total equivalent vent height
=
m
7.5
=
2.6
=
=
2.0
12.1
Table 16 — Equivalent height of vent:
allowances for horizontal pipe runs, easy and
sharp bends at a filling rate of 1 000 L/min and
at a viscosity of 16 mm2/s
Fitting
From Figure 13 a vent of 12.1 m height and 65 mm
bore would result in a head of 19.2 m of water at the
top of the tank.
Bore of vent
mm
mm
mm
50
65
80
Equivalent height of vent
m
m
m
10 m of horizontal 6.5
run
3.5
2.0
Each easy bend
0.7
0.5
0.25
Each sharp bend
1.4
0.9
0.5
Figure 12 — Graph showing pressure developed when tank is overfilled with oils classes C
and D at a filling rate of 500 L/min and at a viscosity of 16 mm2/sa
a
1 mm2/s = 1 cSt.
© BSI 12-1998
21
BS 799-5:1987
Figure 13 — Graph showing pressure developed when tank is overfilled with oils classes C
and D at a filling rate of 1 000 L/min and at a viscosity of 16 mm2/s
Example 3. Calculate the total head developed for
an 80 mm bore vent pipe of 7.5 m vertical
height, 7.5 m horizontal run and four easy bends.
Total equivalent vent height (using Table 17)
Vertical height:
(including entry, exit, return bend)
Horizontal run of 7.5 m
(pro rata from table)
Four easy bends
Total equivalent vent height
=
m
7.5
=
3.0
Fitting
Bore of vent
mm
mm
mm
65
80
100
Equivalent height of vent
m
=
=
0.8
11.3
From Figure 14 a vent of 11.3 m height and 80 mm
bore would result in a head of 19.2 m of water at the
top of the tank.
22
Table 17 — Equivalent height of vent:
allowances for horizontal pipe runs, easy and
sharp bends at a filling rate of 1 000 L/min and
at a viscosity of 370 mm2/s
m
m
10 m of horizontal 6.0
run
4.0
2.0
Each easy bend
0.3
0.2
0.1
Each sharp bend
0.6
0.4
0.2
© BSI 12-1998
BS 799-5:1987
Figure 14 — Graph showing pressure developed when tank is overfilled with oils classes E,
F and G at a filling rate of 1 000 L/min and at a viscosity of 370 mm2/s
Example 4. Calculate the total head developed for
an 80 mm bore vent pipe of 7.5 m vertical
height, 7.5 m horizontal run and four easy bends.
Total equivalent vent height (using Table 18)
Table 18 — Equivalent height of vent:
allowances for horizontal pipe runs, easy and
sharp bends at a filling rate of 1 000 L/min and
at a viscosity of 860 mm2/s
Fitting
Bore of vent
Vertical height:
(including entry, exit, return bend)
Horizontal run of 7.5 m
(pro rata from table)
Four easy bends
=
m
7.5
=
4.5
=
0.4
10 m of horizontal 8.0
run
6.0
4.0
Total equivalent vent height
=
12.4
Each easy bend
0.15
0.1
0.07
Each sharp bend
0.3
0.2
0.14
mm
mm
65
80
100
Equivalent height of vent
m
From Figure 15 a vent of 12.4 m height and 80 mm
bore would result in a head of 30 m of water at the
top of the tank.
© BSI 12-1998
mm
m
m
23
BS 799-5:1987
Figure 15 — Graph showing pressure developed when tank is overfilled with oils classes E,
F and G at a filling rate of 1 000 L/min and at a viscosity of 860 mm2/s
Appendix C Information to be
supplied by the purchaser
C.1 The following information is to be supplied by
the purchaser at the time of enquiry or order:
a) the tank design pressure (see 4.3);
b) the number of manholes or inspection covers
(see clause 6).
24
C.2 The purchaser may wish to specify:
a) whether tank oil heating is required and the
heating medium (see 7.1);
b) if external protection of tanks with a rust
inhibiting priming paint is not required prior to
despatch (see 5.4.1).
© BSI 12-1998
BS 799-5:1987
Publications referred to
BS 21, Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the
threads (metric dimensions).
BS 799, Specification for oil burning equipment.
BS 799-4, Atomizing burners over 36 litres per hour and associated equipment for single burner and
multi-burner installations.
BS 1449, Steel plate, sheet and strip.
BS 1449-1, Specification for carbon and carbon-manganese plate, sheet and strip.
BS 1563, Specification. Cast iron sectional tanks (rectangular).
BS 1564, Specification for pressed steel sectional rectangular tanks.
BS 2594, Specification for carbon steel welded horizontal cylindrical storage tanks.
BS 2869, Specification for fuel oils for oil engines and burners for non-marine use.
BS 3921, Specification for clay bricks.
BS 4360, Specification for weldable structural steels.
BS 5135, Specification for process of arc welding of carbon and carbon manganese steels.
BS 5410, Code of practice for oil firing.
BS 5410-1, Installations up to 44 kW output capacity for space heating and hot water supply purposes.
BS 5410-2, Installations of 44 kW or above output capacity for space heating, hot water and steam supply
purposes.
BS 5410-3, Installations for furnaces, kilns, ovens and other industrial purposes.
BS 5422, Specification for the use of thermal insulating materials.
BS 5500, Specification for unfired fusion welded pressure vessels.
BS 5970, Code of practice for thermal insulation of pipework and equipment (in the temperature range
of – 100 °C to + 870 °C).
BS 6380, Guide to low temperature properties and cold weather use of diesel fuels and gas oils (classes A1,
A2 and D of BS 2869).
BS 6722, Recommendations for dimensions of metallic materials.
© BSI 12-1998
BSI
389 Chiswick High Road
London
W4 4AL
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