Marston Technical Catalogue

Pressure & Flame Protection
Bursting Discs &
Explosion Vent Panels
Bursting Discs &
E x p l o s i o n Ve n t P a n e l s
Bursting Discs - A bursting disc is a non-reclosing
device that is designed to burst or rupture at a
predetermined pressure, thus relieving a dangerous build
up of pressure or vacuum, protecting plant, pipework or
vessels from unacceptable levels of pressure or vacuum.
Conventional Discs
Often referred to as forward acting discs, ideal as a multipurpose and low cost solution.
Reverse Buckling Discs
These discs offer extended service life, particularly within
pressure cycling duties. Ideal for relief valve protection.
Graphite Discs
Provide ideal low pressure protection for highly corrosive
process media applications.
Explosion Vent Panels - Designed to provide low
pressure protection against the effects of dust or gas
explosions. In the event of an explosion a correctly sized
panel will open almost instantaneously to minimise the
effects of the blast.
1
The logical choice
With over 50 years experience, Marston is a leading
manufacturer of pressure relief and explosion
protection devices known as bursting discs (or
rupture discs) and explosion vent panels, providing
safe and instantaneous relief in an ever increasing
range of application requirements.
The applications for these devices are as diverse as
the industries that use them. Chemical, oil, gas and
food as well as cryogenic and transportation are
typical examples. The selection of the most suitable
device can be critical, however our extensive range
provides the optimum solution.
To maintain our position at the forefront of disc and
panel technology, we can call upon the wide range of
technical resources available within Marston.
These state-of-the-art facilities include:
• High temperature testing
• Helium leak testing
• CAD/CAM
• Pressure cycling
• Radiographic inspection
• Laser cutting technology
• Flow test laboratory
2
T E S T I N G A N D C E R T I F I C AT I O N
Marston bursting discs and explosion vent panels are
batch tested in accordance with relevant British or
other National and International standards and a test
certificate is supplied for each batch of discs.
If required by the customer, arrangements can be
made for the batch test procedures to be witnessed
by accredited external inspection authorities.
All Marston explosion vent panels have been type
tested under full explosion trials to prove their
strength and reliability.
Marston’s products carry a wide range of approvals
and comply with the highest International standards
and customer specifications, including:
Certificate Number Baseefa03ATEX0251 was also
issued and all Marston Panels can now be CE-marked
together with the protection coding reference
xll 1 G D identifying their suitability for use in the
most hazardous areas, Zone 0 and Zone 20.
3
BS EN ISO 4126
BS 2915
A. D. 2000 Merkblatt A
ASME Section VIII
Stoomwezen
Chinese Safety Quality Licence
Other Accreditations include:
PED 97/23/EC
ATEX 94/9/EC
BS EN ISO 9001
Q UA L I T Y
Marston is fully committed to a programme of total
Quality Management which is focused on providing
customer satisfaction and confidence. The concern
with quality is evident at all levels within the
organisation and has become an integral part of all
processes.
Marston maintains stringent control of design,
development, testing and production to ensure that
the highest quality standards are achieved in
accordance with BS EN ISO 9001.
A policy of continuous improvement and product
development ensures that Marston is able to meet the
demand for ever-increased safety protection.
3
Note:
The performance of a bursting disc is dependant on its
mounting arrangements. The use of discs in holders or
mounting arrangements not approved by Marston will
invalidate certification.
CONTENTS
Page
Bursting Discs
Page
E x p l o s i o n Ve n t P a n e l s
5
6
7-8
9
Introduction
Product Identification
Product Range
The Protection of Safety Valves
27-28
29
30
Introduction
CSP and TSP
Applications
10
10
11
12
Pressure and Temperature
Pressure
Temperature Ranges
Vacuum/Reverse Pressure Supports
31
31
Pressure and Temperature
Minimum Opening Pressure
32
32
Frames
Frames and Fitting
13
13
14
33
33-34
Accessories
Accessory Range
15
16
17
18
19
Holders
Holder Types
Screwed, Welded and Adapter Type
Assemblies
Optional Features
Location of Holder
Flange Sealing
Foolproofing Features
Fugitive Emissions
35
35
36
37-38
Sizing and Selection
Vent Sizing
Enquiry Form
Guide to Selection
20
20
21
22
Accessories
Excess Flow Valve
Bursting Disc Indicators
Break Wire Indicators
23
23
24
25-26
Sizing and Selection
Material Selection
Enquiry Form
Guide to Selection
4
Bursting Discs
INTRODUCTION
All pressurised systems, conforming to the appropriate National and International standards, are limited to a
maximum overpressure during pressure relief. In accordance with the EU Pressure Equipment Directive (P. E. D.),
all pressure equipment defined therein must have a pressure relief or control system that limits the maximum
overpressure to 1.1 x the maximum allowable design pressure of the equipment. A bursting disc safety device is
a recommended means for pressure relief, and in some cases the preferred device. It is also used as the ultimate
safety device should other pressure limiting equipment fail to function correctly. Marston bursting discs fulfil
these requirements to protect the pressurised equipment.
A bursting disc, often referred to as a rupture disc or a safety disc, is a non-reclosing pressure relief device.
The resultant release of the contents from the protected system must be controlled in accordance with local,
National and applicable EU/International rules and may necessitate the need for a fully contained relief system.
The use of a correctly designed bursting disc device, its assembly and fitting is essential. Bursting disc devices
are often fragile and need to be handled with care. They normally require a dedicated holder assembly.
Bursting disc devices function due to the
differential pressure applied across the disc.
All pressures acting on the disc, including those
induced by vent-side pressure, vacuum, system
draining or cleaning, must be considered during
specification.
Choosing the most appropriate bursting disc
device for a particular application depends on a
number of key factors. This guide has been
designed to assist the disc selection process.
5
P R O D U C T I D E N T I F I C AT I O N
Identification and traceability of the thousands of
bursting discs and holders in use across the world
today is critical.
Each bursting disc device supplied by Marston is
allocated a unique equipment number that provides
exact identification.
At Marston, every item carries a marking that can be
traced back to its original manufacture.
All details of manufacture (including material identity
for each item supplied) are recorded and archived.
Details can be tracked back over 40 years.
Holder Label
The equipment number is shown on the holder label,
disc assembly tag and also on the test certificate that is
supplied with each batch of discs.
Following the original supply, subsequent batches of
bursting discs add a suffix letter to the equipment
number to provide batch identification.
Example:
Original supply :
Holder
‘E’ No. NT 1234
Bursting disc
‘E’ No. NT 1234
(including reverse pressure support if required)
First re-order
of bursting discs
‘E’ No. NT 1234 / A
Second re-order
of bursting discs
‘E’ No. NT 1234 / B
Note:
The equipment number, together with an adequate
description including bursting pressure and
temperature, should be quoted for all replacement
orders.
Disc Tag
6
P R O D U C T R A N G E - F O RWA R D A C T I N G B U R S T I N G D I S C S
NT / NR Conventional Simple Domed
Assemblies.
The simplest of all discs, usually a single domed
metallic foil which will probably fragment upon disc
rupture.
NTG / NRG Conventional Grooved Disc
Assemblies.
A single metallic foil which has grooved lines of
weakness and is designed to be non-fragmenting.
It will normally withstand vacuum conditions without
the aid of a vacuum support.
CS Composite Slotted Disc Assemblies
A forward acting disc which has two membranes.
A load-bearing slotted metallic outer membrane and a
weaker, usually fluoropolymer, seal membrane giving a
non-fragmenting design. This disc is widely used for
lower bursting pressures.
GR Graphite Discs
A flat graphite disc, impregnated with a high quality
resin, giving good corrosion resistance and low
bursting pressures. The unique GR arrangement is
designed to protect the disc from the effects of flange
bolt loading. This disc fragments on rupture.
Monobloc Graphite Discs
A flat graphite disc, impregnated with a high quality
resin, giving good corrosion resistance and low
bursting pressures. This disc does not require a
dedicated holder, and fragments on rupture.
7
PRODUCT RANGE - REVERSE BUCKLING BURSTING DISCS
MN / MO Maxivent Assemblies
Usually a single foil disc which has the pressure applied
to its convex side. The dome inverts and is completely
expelled from its holder and stopped by an arrestor.
RBH / RBF Assemblies
Usually a single foil disc which has the pressure applied
to its convex side. The dome inverts and opens along
a peripheral groove. It is designed to be retained by its
hinge portion.
LRB / LRF Assemblies
Usually a single foil disc which is designed specifically
for liquid duties. The pressure is applied to its convex
side. The dome inverts and opens along a peripheral
groove. It is designed to be retained by its hinge
portion.
SRBH Assemblies
This disc has two membranes. A load-bearing slotted
metallic membrane and a weaker, usually
fluoropolymer, seal membrane giving a nonfragmenting design suitable for low bursting pressures.
RBX Assemblies
A single metallic foil which has pressure applied to the
convex side. The dome inverts and the disc opens
along radial grooved lines. It is designed to retain all
parts and withstand full vacuum without the aid of a
vacuum support.
GRB Graphite Disc Assemblies
A unique disc manufactured from pure graphite
powder. It is suitable for high temperatures and
extremely low bursting pressures. This disc will
fragment on rupture.
8
T H E P R O T E C T I O N O F S A F E T Y VA LV E S *
Safety valve service life can be prolonged
by using a bursting disc in series with the
valve. The disc can be designed to be
fitted at the inlet or at the outlet of the
safety valve.
Bursting discs are:
1) Virtually leak free.
2) Capable of preventing the process
media attacking the internal parts of
the safety valve, either by providing
corrosion resistance or a physical
barrier.
3) Suitable for protecting the vent side
of the safety valve from the ingress of
moisture and associated debris from
the vent system.
Bursting discs are selected with a bore
size suitable for the appropriate inlet or
vent flange of the safety valve.
The free vent area of the bursting disc
used on the inlet side of the safety valve
is always substantially greater than that
of the valve.
A number of international standards are
available to allow the calculation of
suitable bursting disc sizes.
In all cases an excess flow valve is
advised to prevent any pressure build up
between the bursting disc and the safety
valve.
* Safety valves may also be referred to
as relief valves or safety relief
valves. Such valves are characterised by
their ability to relieve excessive
pressures at a pre-determined level and
to re-seal once that pressure has been
reduced to an acceptable, safe level. Such
devices provide re-closing pressure relief
and limit the quantity of product actually
released.
9
Pressure and Temperature
G U I D E TO B U R S T I N G P R E S S U R E S
Bursting pressure capabilities for each type of bursting
disc vary depending on the design, size, material and
temperature.
Please consult one of our Sales Engineers for bursting
pressures outside the ranges quoted in the table.
MINIMUM / MAXIMUM BURSTING PRESSURES : Barg @ 20°C
DISC TYPES
BORE
SIZE
mm
NT
NR
*
CS
MAXI
VENT
RBH
RBF
LRB
LRF
SRBH
RBX
GR/G2
MONO
BLOC
GRB
*
NTG
NRG
*
25
0.8
125
1.5
125
4.0
125
12.4
450
1.8
380
3.0
100
1.2
100
18.9
380
1.0
28.0
1.0
56
0.4
15
40
0.6
83
1.0
83
2.6
83
7.0
315
1.2
380
2.5
75
0.9
65
13.1
380
0.52
21.0
0.5
42
—
—
50
0.4
72
0.75
72
2.0
72
5.5
255
0.9
380
2.0
50
0.6
50
10.3
380
0.275
17.2
0.4
28
0.14
10
65
0.35
50
0.65
50
3.4
50
4.8
210
0.8
175
1.75
40
0.5
40
9.6
175
0.24
16.5
0.4
24
—
—
80
0.3
41
0.5
41
2.5
41
3.4
170
0.7
120
1.5
40
0.4
40
6.9
120
0.21
15.5
0.3
20
0.1
4.5
100
0.2
36
0.35
36
1.9
36
3.0
100
0.6
90
1.4
30
0.3
30
5.5
90
0.14
10.3
0.2
14
0.04
2.5
150
0.14
20
0.3
20
1.4
20
2.0
100
0.5
60
1.25
20
0.25
20
3.8
60
0.07
5.5
0.2
10.5
0.04
1.5
200
0.1
18
0.25
18
1.4
18
1.7
30
0.5
50
1.25
17.5
0.2
12.5
2.8
50
0.07
3.45
0.1
5.5
250
0.1
12.5
0.2
12.5
1.4
12.5
1.7
25
0.5
40
1.25
12
0.2
10
2.25
40
0.07
2.15
0.1
4.5
300
0.07
10
0.2
10
1.4
10
1.7
18
0.5
35
1.25
10
0.2
10
0.02
2.0
350
0.07
9.5
0.15
9.5
1.4
9.5
1.7
18
0.5
27.5
1.25
8.5
0.2
8.5
0.02
2.0
400
0.07
9
0.12
9
1.4
9
1.4
18
0.5
20
1.25
7.5
0.2
7.5
0.02
2.0
450
0.07
7
0.10
7
1.4
7
1.0
16
0.5
17
1.25
7
0.2
7.0
0.02
2.0
500
0.07
6
0.07
6
1.4
6
1.0
14
0.5
14
1.25
6.0
0.2
6.0
550
0.07
5.5
0.07
5.5
-
1.0
12
600
0.07
5
0.10
5
-
0.8
10
750
0.07
4
0.10
4
* Maximum pressures are for standard designs, for higher pressures a welded construction is also available (see page 17).
10
T E M P E R AT U R E R A N G E S
Materials for bursting discs have a limited allowable
working temperature range.
The limitations of joint sealing materials must be
considered as well as possible corrosion from the
process or environmental conditions that prevail.
The table indicates the normal limits for commonly
used bursting disc materials.
MATERIAL
-200°C
-100°C
0°C
100°C
200°C
300°C
400°C
500°C
600°C
ALUMINIUM
NICKEL
MONEL 400
INCONEL 600
HASTELLOY
ST ST 316
TANTALUM
FEP
PTFE
When used as a
corrosion protection
membrane.
PFA
Impreg. GRAPHITE
PURE GRAPHITE
I N F L U E N C E O F T E M P E R AT U R E
11
Bursting disc materials are affected by changes to
temperature. In general, higher temperatures induce a
reduction of strength and consequently bursting
pressure. The following graph shows the typical effect
of temperature on various bursting disc materials for
forward-acting discs:
Reverse buckling discs are generally less affected by
temperature changes than equivalent forward acting
discs. Each batch of reverse buckling discs will be
affected differently, by factors other than just the
material. A ‘typical’ temperature effect graph is
therefore not considered to be helpful.
Where operating conditions dictate its use, a heat
shield can be fitted between the disc material and the
process to provide a thermal barrier. This may be to
preserve the disc integrity or to reduce heat loss.
Teflon FEP and Teflon PFA are trade marks of the Dupont
company.
VA C U U M / R E V E R S E P R E S S U R E S U P P O R T S
Opening Type Vacuum Supports
Many simple conventional discs and most composite
slotted bursting discs are unable to withstand vacuum
conditions without assistance.
To allow them to be used for duties where vacuum is
a possibility, even if only whilst equipment is being
cleaned, a vacuum support can be fitted. Usually this
takes the form of a multi-petal design Opening Type
Support, which when the disc bursts, opens up to
provide a large flow area.
The Vacuum Support is permanently fixed to the
bursting disc to ensure correct fitting. Therefore a
new support does have to be supplied and fitted with
each bursting disc.
When calculating the disc size required, the Free Area
through the support must always be considered.
Auxiliary Support
In some applications, reverse pressures may exist
greater than atmospheric pressure. Often an Opening
Type Support alone will be sufficient. However, sometimes an additional Auxiliary Support is required. This
is designed to aid the opening support, whilst still
maintaining a large free flow area. This type of support
is often used in double disc assemblies, where a secondary disc is used to prevent an often variable
reverse pressure from affecting the performance of
the primary disc. This is common when several bursting discs vent into a common line or flare stack. This
type of support is generally re-useable, with only the
opening support needing to be replaced.
Non-Opening Supports
Some discs, particularly graphite, use a permanent or
Non-Opening Type Vacuum Support. These supports
are not usually attached to the disc but fit immediately
upstream of the bursting disc, sometimes in a recess
provided within the holder.
These supports follow the form of the disc, whether it
be flat or domed, and have holes through which the
product flows when the disc bursts. These supports are
considered to be re-useable and therefore only one is
required for each position.
More consideration must be given to the flow area for
these supports as a typical free area through a
permanent support is around 60%. See the relevant disc
brochure for more details.
Generally, reverse buckling discs do not require any
additional support to withstand vacuum or reverse
pressure.
12
Holders
HOLDER TYPES
The bursting disc holder can have a significant effect
on the performance of a bursting disc. The holder
provides an accurate location, sealing face, vent bore
size and form. Generally, holders will be
manufactured from stainless steel, though other
materials can be supplied when required. Holders
are normally non-torque sensitive.
Insert type
Marston provide holders specifically designed for
each disc type, and to fit the particular application.
Usually the holder will be an insert type; one that fits
within the flange bolt circle. This provides an easier
method of fitting replacement bursting discs since
fewer flange bolts need to be removed. Full face
holders with flange bolt holes can be supplied if
required.
Full face type
Holders usually consist of two annular rings that
provide a flat sealing flange for the bursting disc.
Consequently, the performance of the disc should be
unaffected by excessive flange bolt loading. (Certain
graphite assemblies require close control of the
flange bolt torque.) Most holders are supplied with
assembly screws. These can be simply to hold the
assembly together whilst fitting onto the plant, or,
for pre-torque type holders, they are tightened to
pre-set values to ensure an adequate joint is
achieved between the disc and holder before
installing onto the plant. More details of both types
of holders can be found in the individual product
brochures.
For sizes up to 250mm bore, the holder will usually
provide dome protection. Larger sizes are often
supplied without dome protection and where
conditions allow, simple clamp rings may be
acceptable. Where the bursting disc dome is not
protected, extreme care must be taken when fitting
to prevent damage.
For large assemblies, where the holder weight
exceeds 25kg, or where it is considered beneficial
for handling purposes, Marston will make provision
for suitable lifting attachments.
13
Pre-assembled holder
Pre-torqued holder
Protected dome
Unprotected dome
Lifting eyebolt
S C R E W E D, W E L D E D A N D A D A P T O R T Y P E A S S E M B L I E S
Where simple flanged joints are not practical,
alternative designs are available. Marston have the
experience and expertise to supply a wide variety of
screwed assemblies and fully welded units, to satisfy
the most arduous of requirements. These allow for
screwing a disc holder unit into the main body of the
pressurised vessel or for fitting directly into pipelines.
Where it is practical, the discs may be scored so that
they petal open.
Various types are illustrated, with special designs
prepared as required.
TYPE
TYPICAL
CONNECTION
AM
A screwed adaptor as illustrated with male
connection threads. Special designs are often
manufactured to customer’s requirements.
The standard pressure range is up to 700
barg but higher pressures can be made to
special order.
1
AF
A screwed adaptor as illustrated with female
connection threads. Special designs are often
manufactured to customer’s requirements.
The standard pressure range is up to 700
barg but higher pressures can be made to
special order.
WA
A flanged type assembly suitable for
applications up to 100 barg.
WA
A plug type assembly suitable for applications
up to 100 barg.
WA
A stem type welded assembly for
applications such as the protection of rubber
or plastic extrusion presses. The disc is
brazed or welded to the screwed stem
LR
A lens ring style bursting disc. This is
another method of mounting a disc in high
pressure pipework. It provides a leaktight
seal at pressures up to 700 barg.
/4” to 11/4” NPT / BSP
/4” to 11/4” NPT / BSP
1
Up to 6”/150mm NB.
A flanged design for installing
the disc close to the process.
/4” to 1” BSP
/4” to 1“ NPT
1
1
/2” UNF - standard
Other sizes available
1
/8” to 2” NB
8 to 50mm NB
3
14
O P T I O N A L F E AT U R E S
Pressure Tappings
Tappings for monitoring equipment can be
incorporated in the vent-side of the holder, or in the
pressure-side if required. Any thread form and size is
usually possible but this may in some cases require an
increase in holder dimensions.
Corrosion Protection
For corrosive environments, holders manufactured
from resistant materials may prove costly. One
possible alternative offered by Marston is the Glass
Filled-PTFE insert that also provides a non-stick
surface. For extreme conditions a resistant metal
liner such as nickel or tantalum may be suitable.
Steam Heating
Where the duty may be prone to polymerisation the
holder can be heated. This can be achieved by
introducing a chamber around the holder body and
passing either hot water or steam through to prevent
the product from cooling and solidifying.
High Pressure
When the bursting pressures exceed the limits for
standard holder designs to retain the disc satisfactorily, alternative designs are available. Wedge type
holders can be supplied on request but their performance can be affected by possible misalignment or
incorrect torque of the plant flange bolts. For this
reason, Marston would recommend the use of discs
with welded edge rings for high pressures that fit into
a simple recessed holder.
15
L O C AT I O N O F H O L D E R B E T W E E N F L A N G E S
To ensure that the bursting disc holder is installed
concentrically, each Marston bursting disc holder has
an outside diameter manufactured specifically to suit
its corresponding flange.
Holder heights are available on request.
TA B L E O F O U T S I D E D I A M E T E R S
Flange Rating
ANSI
Holder Outside Diameter for Nominal Bores (mm)
PN
25
66
85
104
123
10
73
94
109
129
73
95
111
130
16
73
94
109
129
25
73
94
109
129
73
95
111
130
73
94
109
79
98
143
84
105
79
98
84
85
85
150
300
600
40
900
63/64
1500
100-164
2500
250
Capsule Holders, to fit within the ring of flange bolts as shown above
40
50
65
80
100
150
200
250 300
350 400 450
500 600
136
174
222
279
339 409
450
514
549
606
717
144
164
220
275
330 380
440
491
-
596
698
149
181
251
308
362 422
144
164
220
275
331
144
170
226
286
343
149
194
266
129
144
170
226
165
168
205
115
140
150
176
143
165
174
105
121
146
156
117
146
111
126
16
FLANGE SEALING
Bursting disc holders can usually be provided
to satisfy the requirements of any type of
flange sealing arrangement. The diagrams
below illustrate typical examples. Flange joints
(i.e. those between the holder and the mating
flanges) will normally be provided by the
customer. Marston will supply gaskets for
bursting discs that are designed to be fitted
directly between flanges, such as the
Monobloc graphite disc.
Flat gasket joint
‘O’ ring joint for
minimum leakage
Tongue and groove
Ring type joint for high
pressure/temperature
TA B L E O F F A C E T O F A C E D I M E N S I O N S
Bore Size
TYPE
Std
1/4” NPT
1/2” NPT
Conn Head
Std
NT
1/4” NPT
1/2” NPT
Conn Head
Std
CSB
1/4” NPT
CSB-T 1/2” NPT
Conn Head
Std
RBH
1/4” NPT
RBH-T 1/2” NPT
Conn Head
Std
MV-A 1/4” NPT
1/2” NPT
Conn Head
Std
GR
1/4” NPT
1/2” NPT
Conn Head
Std
GRB
1/4” NPT
1/2” NPT
Conn Head
Monobloc
Std
CST
25
40
50
65
80
100
150
200
250
300
350
400
450
500
600
21
30
38
42
21
30
38
42
38
46
54
58
26
36
48
52
72
72
72
72
17
33
41
45
17
31
39
43
14
21
30
38
42
22
30
38
42
38
46
54
58
27
37
49
53
72
72
72
72
19
35
43
47
17
21
30
38
42
25
30
38
42
38
46
54
58
28
38
50
54
57
57
57
57
21
37
45
49
20
32
40
44
21
25
30
38
42
30
30
38
42
38
46
54
58
30
40
52
56
62
62
62
62
24
39
47
51
22
25
30
38
42
33
33
38
42
38
46
54
58
30
40
52
56
64
64
64
64
28
42
50
54
30
36
44
48
22
30
30
38
42
43
43
43
43
38
46
54
58
32
42
54
58
85
85
85
85
33
45
53
57
35
41
49
53
25
41
41
42
46
59
59
59
59
47
46
54
58
43
51
63
67
116
116
116
116
37
48
56
60
52
52
60
64
29
50
50
50
50
72
72
72
72
56
56
56
58
55
63
75
79
148
148
148
148
41
52
60
64
35
60
60
60
60
68
68
68
68
70
78
90
94
169
169
169
169
47
57
65
69
38
78
78
78
78
85
93
105
109
198
198
198
198
-
84
84
84
84
100
110
118
122
223
223
223
223
-
94
94
94
94
110
120
128
132
255
255
255
255
-
102
102
102
102
125
130
138
142
277
277
277
277
-
108
108
108
108
135
140
148
152
296
296
296
296
-
127
127
127
127
344
344
344
344
-
-
-
-
-
-
-
Other sizes / options may be available. Please consult Marston.
17
F O O L P R O O F I N G F E AT U R E S
A wrongly installed bursting disc can be disastrous.
For this reason, where possible, Marston bursting disc
assemblies are fitted with a foolproofing feature which
is incorporated within the disc tag and holder identity
label.
Marston holders have a permanently attached stainless
steel identity label. This uniquely identifies the holder
type and equipment number. It also indicates the
correct holder orientation relative to flow.
The disc is fitted with a notched stainless steel tag as
shown below. This uniquely identifies the disc type, its
equipment number and batch, the rated bursting
pressure and temperature, the design code and also
indicates the vent side of the disc.
The combination of the notched tag and the offset
identity label, prevents the incorrect assembly of the
disc to the holder.
The holder can also be provided with installation
inhibitors such as ‘J’ bolts. These prevent the holder
from being installed incorrectly between the plant
flanges. (See accessories on page 22 for details.) Other
methods can be considered such as dowels, or tongue
and groove flanges, to ensure correct installation.
When these features are combined with Marston
comprehensive installation instructions, quick and
simple installation is ensured.
The photographs show the offset label on the holder
and the notch on one side of the neck of the disc
identification tag.
These foolproofing features aid correct assembly and
prevent incorrect assembly (as demonstrated in the
two lower photographs).
Offset label on Holder
Notched Disc Tag
Correct Assembly
Incorrect Assembly
18
FUGITIVE EMISSIONS: LEAK TIGHTNESS ACROSS DISC SEALING FLANGE
19
FEATURES
LEAK TIGHTNESS
mbar.l/s
Metal to metal joint
1 x 10-4
Gasket fitted to process side :
G-9900 (Graphite-based )
AFM 34 (Asbestos free )
AFM 30 ( Asbestos free )
PTFE
GYLON BLUE (PTFE)
1
1
1
1
1
‘O’ rings incorporated :
PTFE
VITON
Silver-coated metal
1 x 10-6
1 x 10-6
1 x 10-8
x
x
x
x
x
10-4
10-4
10-4
10-4
10-5
Disc welded to holder
ZERO
Type MN : flat gasket :
G-9900 ( Graphite based )
AFM 34 (Asbestos free )
PTFE / GYLON
1 x 10-3
1 x 10-3
1 x 10-4
Type MO : ‘O’ rings :
PTFE
VITON
Silver coated metal
1 x 10-4
1 x 10-6
1 x 10-8
Accessories
E X C E S S F L O W VA LV E S
Excess flow valves (EFV) may be fitted to prevent back
pressure developing between a bursting disc and, for
example, a safety relief valve during normal plant
operation. The excess flow valves should be fitted in
a horizontal mode. In the event of the disc rupturing,
the excess flow valve will seal the vent system under
the influence of the pressure pulse.
EFV
Standard Dimensions (BSP or NPT)
M
1/4”
1/2”
F
1/8”
1/4”
Pressure Gauges
Pressure gauges are normally supplied by the
user, although Marston is able to supply them
on request.
Jack Screws
To help users to separate the bursting disc
holder from the system flanges during overhaul,
or following an incident, jack-screws may be
required. These are normally incorporated into
pipe-flange drillings, although Marston can supply
suitable screws if requested.
‘J’ Bolt
It is important that bursting disc assemblies are
mounted in the correct orientation relative to the
flow direction. Although the holder is stamped with a
flow arrow, and the vent-side is also shown on the
holder and disc labels, it is often a requirement that
the installation is ‘foolproofed’. One such example is
a ‘J’ bolt (as shown) which is welded to the holder and
locates in a corresponding hole in one of the flanges.
Other methods are also available.
20
B U R S T D I S C I N D I C AT O R S
Once a bursting disc has ruptured, it is often beneficial
to shut down relevant plant equipment as quickly as
possible. One common method of achieving this is to
fit a Burst Disc Indicator. A Burst Disc Indicator is a
simple circuit, usually fitted downstream of the
bursting disc. The signal is usually received in the
plant control room. This then instigates the shutdown
of the relevant equipment.
Recognising industries need to minimise maintenance
time, Marston now introduce the latest design in Burst
Disc Indication.
M A S ( M AG N E T I C A L A R M S YS T E M )
The Marston ‘MAS’ eliminates the need to disconnect
the electrical supply to the rupture disc assembly,
reducing changeover time.
A ‘sensor’ is located in the vent side of the assembly,
retained by a screwed compression fitting. The hole
into which the sensor fits does not pass through to
the holder bore, therefore the sensor does not come
into contact with the product contained in the vent
line. Attached to the vent side of the disc is a small
but powerful magnet. The magnetic field that it
generates is detected by the sensor. When the disc
ruptures, the magnetic field moves away and activates
the sensor. This simple switching effect can be used to
initiate an alarm or a programmed shutdown
procedure.
Magnet
Sensor
Retaining Screw
The Marston ‘MAS’ provides an integral, leak tight
detector. The sensor, once fitted, does not need to be
renewed when replacing the rupture disc. It can be
unscrewed from the holder and replaced when the
new disc is fitted. When the disc is replaced, the new
disc includes a magnet already fitted which ensures
that it will be installed in the correct position.
MAS WITH CONNECTION HEAD
Where an exposed cable is unfavourable, the ‘MAS’
sensor is available with an integral connection head
where the wires terminate inside the head which is
rated IP68. The wires are never subjected to the often
Magnet
harsh environment of an industrial plant; instead, they
pass through a connecting tube between the holder
and the connection head via an ‘O’-Ring seal.
Sensor
Connection Pipe
21
‘O’-Ring
Connection Head
B R E A K W I R E I N D I C AT O R S
Marston also manufactures break wire type Burst
Indicators. Depending on their design they can either
be fitted directly to the bursting disc or fitted
‘remotely’ between the holder and the downstream
pipe flange. This type can be fitted to existing disc
assemblies or to safety relief valves.
Both operate in the same fundamental manner; a small
current passes around a normally closed circuit. When
the disc activates the flow breaks the membrane
carrying the circuit which causes the current to be
interrupted, indicating disc failure.
D I R E C T M O U N T E D I N D I C AT O R S
The direct mounted type has the circuit, or ‘Indicator
Loop’, fixed to the disc. The attached wires then pass
through the vent side holder, along a connection pipe
and connect to pins on a pressure tight, feed through
seal. Short wires on the other side of the seal then
terminate in the connection head.
Burst Disc Indicator fitted
directly to vent side of the disc.
R E M O T E I N D I C AT O R S
The ‘remote’ burst disc indicator has the circuit fixed
to a membrane and is used on the downstream side of
the holder, replacing the usual gasket. The remote
design is not only available for new installations but
can also be fitted to existing equipment and can even
be used downstream of safety relief valves. Note that
remote burst indicators are not suitable for use with
Ring Type Joints or Tongue and Groove flange faces.
There are two types of remote burst indicator, the
traditional plastic membrane or a more robust metal
design. The metal design allows the use of corrosion
resistant metals which permit their use at higher
temperatures.
Both of the ‘remote’ designs are available with a
connector mounted directly onto the unit with its
mating part fitted to a flying lead for permanent
installation into the plant. The wiring does not
therefore need to be disconnected from the plant*
when changing the burst indicator, simply unplug the
connector, fit a new burst indicator, and reconnect
the plug.
*Subject to plant and other local regulations and isolating
the feed if required.
Burst Disc Indicator
for remote fitting
between holder and
vent side flange.
All Marston Burst Disc Indicators have been approved
to II 1 GD 85°C EEx ia IIC T6 (-35°C ≤ Ta ≤ +75°C);
i.e. they do not induce or release sufficient electrical
energy when they function to cause an explosion even
in the most hazardous environment, Zone 0.
The system requires a 100mA maximum supply feed
from an appropriate isolator barrier.
Note:
When a Zener barrier is used, the holder must be earthed
to inhibit high circulating currents.
Burst Disc Indicators are components which have been
considered NOT to require EMC testing on their own. It is
the users responsibility to ensure compliance with the EMC
Directive in relation to their particular system.
22
Sizing and Selection
M AT E R I A L S E L E C T I O N
Materials will normally conform to those listed below.
Other materials are also available.
D I S C / VA C U U M S U P P O R T M AT E R I A L
Material
Name
Number
ASME / ASTM
UNS No
*St.St.316
X5CrNiMo 17 12 2
1.4401
SA / A240 - 316
S31600
*St.St.316L
X3CrNiMo 17 13 3
1.4436
SA / A240 - 316L
S31603
X6CrNiTi 18 10
1.4541
SA / A240 - 321
S32100
*Nickel 200
NA 11
2.4060
SB / B162 - N02200
N02200
*Monel 400
NA 13
2.4360
SB / B127 - N04400
N04400
2.4816
SB / B168 - N06600
N06600
St.St.321
*Inconel 600
Inconel 625
2.4856
SB / B443 - N06625
N06625
*Hastelloy C276
2.4602
SB / B575 - N10276
N10276
B708 - R05200
R05200
SB / B265 - R50250
R50250
*Tantalum
Titanium Gr1
3.7025
EN ISO 4126-2, Annex A, provides a list of all the recommended metallic foils for bursting discs.
Non-metalic foils include Graphite, Teflon-PFA and PTFE.
Note: Teflon FEP and Teflon PFA are trade marks of the Dupont Company
H O L D E R M AT E R I A L
Material
Name
Number
ASME / ASTM
UNS No
BS 3146-1
1.0037
SA / A105
K03504
SS 304
X5CrNi 18 10
1.4301
SA / A479 - 304
SA / A182 - 304
S30400
SS 316
X5CrNiMo 17 12 2
1.4401
SA / A479 - 316
SA / A182 - 316
S31600
*SS 316L
X3CrNiMo 17 13 3
1.4436
SA / A479 - 316L
SA / A182 - 316L
S31603
X6CrNiTi 18 10
1.4541
SA / A479 - 321
SA / A182 - 321
S32100
254SMo
1.4547
SA / A479 - S31254
SA / A182 - S31254
S31254
22Cr5NiMo
1.4462
SA / A479 - S31803
SA / A182 - S31803
S31803
Nickel 200
NA 11
2.4060
SB / B160 - N02200
N02200
Monel 400
NA 13
2.4360
SB / B164 - N04400
N04400
Inconel 600
2.4816
SB / B166 - N06600
N06600
Inconel 625
2.4856
SB / B446 - N06625
N06625
Hastelloy C276
2.4602
SB / B574 - N10276
N10276
B708 - R05200
R05200
SB / B348 - R50250
R50250
Carbon Steel
SS 321
Super Austenitic
Duplex
Tantalum
Titanium Gr1
3.7025
EN ISO 4126-2, Annex B, provides a list of all the recommended metallic materials for bursting disc holders.
ASME Section 2 details holder material requirements for ASME UD certified bursting discs
*Denotes standard materials.
G A S K E T M AT E R I A L
The table lists the common jointing materials
(as shown on page 19), detailing the maximum
pressures and temperatures at which they can be used.
23
TYPE
Material
Maximum
Pressure (@20°C)
FLAT GASKET AFM 34
100 Bar
AFM 30
100 Bar
G-9900
138 Bar
Gylon Blue
55 Bar
PTFE
55 Bar
‘O’ RING
Viton
250 Bar
PTFE
350 Bar
Silver Plated St.St.
1000 Bar
Maximum
Temperature
250°C
200°C
550°C
250°C
250°C
150°C
250°C
600°C
Wobaston Road, Fordhouses,
Wolverhampton WW10 6QJ, England
Telephone +44 (0)1902 623550
Facsimile +44 (0)1902 623555
Email [email protected]
Web www.safetysystemsuk.com
To enable Marston to supply the optimum Bursting
Disc Device, certain basic information is essential.
Photocopy this page, completing as much information
as possible and forward to the contact details above.
A size and select CD programme is also available on
request. This allows the user to perform sizing and
capacity calculations in accordance with selected
international standards.
Company Name:
Reference:
Contact Name:
Telephone:
Fax:
Tag Number
Service conditions Upstream of Disc
Medium in contact with disc
Gas / Liquid / Vapour
MW / SG
cp/cv / Visc
Risk of polymerisation?
Normal maximum operating pressure & temperature
Vacuum conditions
Pressure pulsations / Cycling: Give details
Service conditions Downstream of Disc
Medium in contact with disc
Gas / Liquid / Vapour
Normal operating pressure & temperature
Maximum operating pressure & temperature
Vacuum conditions
Installation
Nominal size (or mass flow rate)
Flange standard / facing
Bursting pressure
Temperature at bursting pressure
Sole relieving device / u/s of safety relief valve
Is tapping required? If yes give size
Acceptable disc materials
Acceptable holder materials - upstream
Acceptable holder materials - downstream
Vessel / pipe material
Flange gaskets - type & material
Is fragmentation allowed?
Design pressure
Design code
Accessories
Burst disc indicator Y/N
Excess flow gauge Y/N
Pressure gauge Y/N
Flange bolts Y/N
Jack screws Y/N
Any other relevant information / sketch
Use additional sheet if necessary
Quantities
Discs
Holders
24
G U I D E TO B U R S T I N G D I S C S E L E C T I O N
ASME
VIII
The following information is presented as an aid to bursting disc selection. It will guide the
user through certain criteria to give a general assessment of the choice of bursting disc for
a particular application. It will help to
eliminate those which are unsuitable for
specific reasons
NT/NR
APPLICATIONS
2
Simple application
where a disc is the
primary safety device.
Negative pressure
may require a reverse
pressure support.
3
Two discs mounted
in parallel with
interlocked valves
enabling rapid
changeover from a
ruptured disc to a
second disc.
4
Two discs mounted
in series. Used where
process media is
likely to attack a disc
material.
6
A disc used to
protect a safety valve.
Essential in some
corrosive or viscous
applications.
7
Where corrosion
could attack the
ventside of a safety
valve, discs may be
employed as a
protection.
8
Two discs mounted
in series. Used where
multiple relief
streams vent into a
common manifold.
25
2
4
NTG/NRG
CS
1
3
–
5
7
1
0.4 / 1.2
8
2
4
6
GR/G2
3
5
7
1
0.6
8
2
4
6
LPCS
3
5
7
1
–
8
2
6
Kr
3
5
4
8
2
4
3
5
–
7
MONO
BLOC
1
MN/MO
1
2
4
2
4
RBH/
RBF
1
LRB/
LRF
1
SRBH
1
6
3
8
2
3
1.0
5
7
8
2
4
3
5
7
1
0.5 / 1.0
5
4
6
–
8
7
3
1.0
5
7
8
2
4
–
8
2
4
1
(i) Under certain conditions a Vacuum or
Reverse Pressure Support may be required.
This depends on the disc size, material and
rating. Refer to the individual Product
Brochure for more detailed information.
3
2
4
6
GRB
–
5
7
6
RBX
3
5
7
6
REVERSE BUCKLING BURSTING DISCS
5
A disc used as a
secondary safety
device. In the event
of safety valve failure
to vent, the disc
provides the ultimate
protection.
1
7
FORWARD ACTING BURSTING DISCS
1
Simple application
where a disc is the
primary safety device
on a pressurised
system
Applications
3
5
–
7
(ii)The Operating or Working Ratio is the ratio of the
Working Pressure to the minimum tolerance Burst
Pressure. Reverse Buckling discs can offer a higher
capability than Conventional Tensile-loaded discs.This ratio
can be affected by disc material and operating temperature.
Bar g
Size
Range
NB
mm
0.3
to
1030
3
to
1200
0.3
to
1030
25
to
800
0.07
to
125
25
to
1100
0.08
to
10
25
to
300
0.07
to
28.0
25
to
450
0.1
to
56
25
to
350
0.1
to
450
25
to
1200
0.5
to
100
25
to
500
3.0
to
100
25
to
500
0.2
to
100
25
to
500
Generally
Required
1 x 10 -3
0.90
2.25
to
380
25
to
250
Generally
NOT
Required
1 x 10 -4
0.95
0.04
to
15
25
to
150
Required
where
Pb<1.2barg
1 x 10 -3
0.90
Pressure
Range
Relief
Phase
SRV
Isolation
Support
Required for
Vacuum
Duty (i)
Leak
Tightness
mbar. l/s
@ 20°C
Generally
Required
1 x 10 -6
0.75
NOT
Required
1 x 10 -6
0.80
Required
1 x 10 -3
0.80
Required
1 x 10 -3
0.50
Required
where
Pb<1.7barg
1 x 10 -2
0.80
Required
where
Pb<1.7barg
1 x 10 -2
0.80
1 x 10 -4
0.95
(v)
Generally
NOT
Required
1 x 10 -4
0.95
(v)
Generally
NOT
Required
Generally
NOT
Required
1 x 10 -4
0.95
Gas/Liquid
✗
✗
✗
(v)
(iii) Fragmentation of the Disc during
bursting may be unacceptable. Certain discs
are designed to eliminate the likelihood of
fragmentation.
✗
(iv) The effects of pulsating or cyclic pressures on
discs need to be considered. Reverse buckling discs
generally offer greater resistance to cyclic conditions
than conventional discs.
Operating
Pressure
Fragmentation
Ratio @ 20°C
(ii)
(iii)
Pulsating
Pressure
Capability
(iv)
(v) A gas/vapour space, or energising volume,
is required if these discs are to be used on
liquid applications.
26
Explosion Vent Panels
INTRODUCTION
The occurrence normally called
an explosion is more accurately Pmax –
referred to as a deflagration.
Pmax Maximum pressure generated
This is the rapid burning of a
during an unvented explosion
mixture of dust or gas within
Pred Reduced explosion pressure
an oxygen-rich atmosphere
generated as a result of fitting
(typically air) leading to a very
a venting device
rapid pressure rise inside the
Pstat Static opening pressure of the
Pred –
vessel or system. Unless this
venting device
pressure is relieved the vessel
or system can be ruptured,
Pstat –
causing the products of the
rapid combustion to be
Time
released uncontrollably.
This results in the devastating effect referred to as an explosion, causing widespread damage to plant and
personnel.
Operators of plant handling flammable gases are well aware of the dangers of explosions and the need for
continual care and attention to prevent ignition. Perhaps less well known is that there is a similar risk when
handling materials that produce dusty conditions, such as foodstuffs, grain, sugar, coal and some plastics and
metals. Where dusts can be present and suspended in the atmosphere, then an equally disastrous explosion can
occur if the mixture is ignited.
The severity of an explosion can be affected by a number of factors, which are often inter-related.
The damage that an explosion can cause is directly related to the pressure that can be generated. This pressure
is affected by the individual characteristics of the dust or gas, the volume and geometry of the vessel being
operated and the strength or ‘rupture pressure’ of the weakest section of the vessel.
Dusts and gases burning uncontrollably within a vessel can rapidly generate pressures up to
10 Barg (145 Psig) or higher. Unless the vessel is sufficiently strong this high pressure will cause the vessel to
deform or even rupture at its weakest point. Where such vessels are long and relatively narrow the weak point
could be the end-cap. The resultant explosion could induce a fierce jet effect.
A correctly sized and fitted explosion vent panel, or group of panels, will help to reduce the likelihood of major
damage to the vessel and anything nearby.
The vent panel will open at a low pressure and allow the pressure to be released.
The vent area is dependent on the geometry of the equipment being protected. Elongated equipment can
develop very high pressure as a result of ‘pressure piling’, resulting in detonations if the explosion is incorrectly
vented.
Care must be exercised when considering venting, in particular the safe siting of the vent panel. In the event of
an explosion, flame, product (both burnt and unburnt) and pressure waves will result.
The equipment being protected will also need to be capable of withstanding the internal pressure and any
resulting reaction forces due to the venting process.
Often, protected equipment will be located indoors, in areas where it is impractical or unsafe to vent. In these
instances it may be possible to vent the explosion through an outside wall, via a duct. The duct should be as
short and straight as possible to minimise its effects on the venting process. A vent may need to be considerably
larger if a duct is used.
27
Who is at Risk?
Many industries are at risk of an explosion. The more common ones are:
• Paper
• Pharmaceutical
• Food
• Wood
• Aggregates
• Plastics
• Metal fines
In addition, bulk-handling systems in any industry may be at risk. Equipment such as Blenders, Dryers Cyclones
and Mills are the source of many explosions, not forgetting Filters and Silos, which together account for almost
half of reported explosions. Consideration must also be given to connecting equipment. Conveyors, Ducts and
Elevators are common sources of explosions. Interconnected equipment must be given special attention as an
explosion propagating from one piece of equipment to another can cause even more devastation than one in
isolation.
The ignition can originate from many sources, such as sparks, friction, mechanical failures, flames or even static.
It is very often impossible to eliminate every ignition source, or prevent completely the risk of an explosion.
Therefore venting is probably the most economical form of protection for your plant.
The Solution
Explosion vent panels provide an economical method of minimising the effects of an explosion.
When equipment is unvented, high pressure can quickly be generated. In many cases this pressure is sufficient to
cause permanent and sometimes catastrophic damage.
Marston explosion vent panels are a recognised and effective solution. These panels are of a lightweight
construction and are designed to open and vent, providing almost instantaneous relief at low pressures, typically
0.1 Bar (1.5 Psig). Care must be exercised when siting the vent to ensure that the products of any resulting
explosion are directed to a safe location, minimising the risk of damage or injury.
Marston explosion vent panels provide a fully certified,
reliable, maintenance free solution to the problem of
explosion venting. They are designed to be nonfragmenting and are simple to install on both new and
existing equipment.
28
C S P E X P L O S I O N V E N T PA N E L S
The CSP type explosion vent panel is a traditional
composite slotted design.
The opening pressure is controlled by the slotted
metal membrane, whilst the system integrity is
provided by the seal membrane, usually manufactured
from Teflon.
Primarily this type of vent is flat, but it can just as
easily be domed to suit operating conditions.
Under steady conditions, flat panels may operate at up
to 50% of the minimum activation pressure, whilst
domed panels may operate at up to 70%. Neither is
suitable for vacuum conditions, unless a support is
fitted.
This design of panel provides accurate, cost effective
explosion protection on equipment generally
operating at, or near to atmospheric conditions.
T S P E X P L O S I O N V E N T PA N E L S
The TSP type explosion vent panel
moves one step further from the CSP
type with the addition of a second
slotted membrane on the process side.
This gives the panel some resistance to
vacuum without adding a support. It
also protects the delicate Teflon seal
membrane from abrasion.
Like the CSP membrane this too can
be flat or domed and can be provided
with additional support where higher
vacuum conditions prevail.
A flat TSP explosion vent panel will
withstand pressures of up to 25% of its
minimum pressure, in both directions.
Domed panels will withstand 40% of
their activation pressure, but generally
no vacuum. In the event of greater
levels of vacuum a support can
generally be fitted.
29
Vent side frame
Slotted Membrane
Seal Membrane
Process Side Membrane
(TSP only)
Gasket
Process Side Frame
Mesh Support
(Where required)
A P P L I C AT I O N S
Explosion vent panels can be used for almost any
application where explosion relief is required. This
could range from a simple storage silo to a
complicated processing system. Each application
requires individual appraisal and consideration to
ensure that the correct venting device is employed.
Some of the more common equipment where venting
may be required is discussed in the following
paragraphs, along with some of the special
considerations that need to be addressed.
Silos
A silo as an individual piece of equipment poses no
real problems although any ancillary equipment
associated with them may. The only real concern in
many cases is the length to diameter ratio discussed in
the sizing section. Often silos are long and as a result
require large vent areas to protect them.
Filters/Separators
Explosion vents should always be located on the dirty
side of the filter elements, and in a position that is not
obstructed by the filter units. When determining the
volume being protected, consideration should be given
to the effect of any explosion on the filter units.
Will they collapse or burn, resulting in a much larger
volume than first estimated?
Elevators/Conveyors
Long, small section equipment needs to be approached
in a different way to that detailed on pages 5 and 6.
It is common to fit vents of a size equal to the cross
section of the equipment at regular intervals. Contact
Marston for more assistance.
Mills/Grinders
Often mills and grinders are built strong enough so
that they will withstand a deflagration. If venting is
required, special attention needs to be given to
vibration and its effect on a relatively weak venting
device.
Interconnected Equipment
Greater care must be taken when considering
explosion protection in one piece of equipment that is
linked to another. The ensuing explosion, which
occurs as a result of an explosion propagating from
another source, can be far more violent than an
isolated incident. Vent areas may need to be doubled
to provide satisfactory relief. Contact Marston for
further assistance.
Cyclones
Cyclones require smooth internal surfaces to allow
them to work effectively. Often, due to their relatively
weak construction, it is not possible to fit sufficient
vent area onto the flat, top face of the vortex. In this
case, consideration should be given to a curved panel
which can be designed to follow the shape of the
cylinder.
Dryers
Spray dryers in particular tend to have large volumes,
which in turn require large vent areas. The explosion
vent may then become a major source of heat loss,
reducing the dryer’s efficiency. Panel selection should
be made with this in mind, using a heat shield to
reduce the heat loss where necessary.
30
Pressure and Temperature
MINIMUM OPENING PRESSURES
CSP
Nominal Diameter/Minimum Opening Length
Units
Seal Material mm
250
300
350
400
500
600
750
1000 1200
(ins)
(10)
(12)
(14)
(16)
(20)
(24)
(30)
(40)
(48)
Temp
FEP/PFA
Barg
(Psig)
0.16
(2.4)
0.16
(2.4)
0.12
(1.8)
0.12
(1.8)
0.08
(1.2)
0.05 0.05 0.05 0.05
(0.75) (0.75) (0.75) (0.75)
200°C
(390°F)
PTFE
Barg
(Psig)
0.2
(2.9)
0.2
(2.9)
0.15
(2.2)
0.15
(2.2)
0.1
(1.5)
0.07
(1.0)
0.07
(1.0)
0.07
(1.0)
0.07
(1.0)
250°C
(480°F)
Aluminium
Barg
(Psig)
0.3
(4.4)
0.3
(4.4)
0.3
(4.4)
0.3
(4.4)
0.3
(4.4)
0.3
(4.4)
0.3
(4.4)
–
–
–
–
425°C
(800°F)
Max
Note: If a Heat Shield is used it may be possible to use at higher temperatures. See Accessories section.
TSP
Nominal Diameter/Minimum Opening Length
Units
Seal Material mm 250
300
350
400
500
600
750
1000 1200
Max
(ins)
(10)
(12)
(14)
(16)
(20)
(24)
(30)
(40)
(48)
Temp
FEP/PFA
Barg
(Psig)
0.25
(3.6)
0.25
(3.6)
0.2
(2.9)
0.2
(2.9)
0.15
(2.2)
0.1
(1.5)
0.1
(1.5)
0.07
(1.0)
0.07
(1.0)
200°C
(390°F)
PTFE
Barg
(Psig)
0.3
(4.4)
0.3
(4.4)
0.25
(3.6)
0.25
(3.6)
0.18
(2.6)
0.1
(1.5)
0.1
(1.5)
0.08
(1.2)
0.08
(1.2)
250°C
(480°F)
Aluminium
Barg
(Psig)
0.4
(5.8)
0.4
(5.8)
0.4
(5.8)
0.4
(5.8)
0.4
(5.8)
0.4
(5.8)
0.4
(5.8)
–
–
–
–
425°C
(800°F)
Note: If a Heat Shield is used it may be possible to use at higher temperatures. See Accessories section.
PTX
Material
Panel Size Reference
Units
645.
710.
645.
710.
920. 1000. 920. 1000. 1000.
365
450
645
710
586
710
Max
920
920
1000
Temp
Stainless Steel
Barg
(Psig)
0.1
(1.5)
0.1
(1.5)
0.05 0.05 0.05 0.05
(0.75) (0.75) (0.75) (0.75)
0.07
(1.0)
0.07
(1.0)
0.07
(1.0)
300°C
(570°F)
Nickel
Barg
(Psig)
0.1
(1.5)
0.1
(1.5)
0.05 0.05 0.05 0.05
(0.75) (0.75) (0.75) (0.75)
–
–
–
–
–
–
400°C
(750°F)
Inconel
Barg
(Psig)
0.1
(1.5)
0.1
(1.5)
0.07
(1.0)
–
–
–
–
–
–
550°C
(1020°F)
Aluminium
Barg
(Psig)
0.07
(1.0)
0.07
(1.0)
0.05 0.05 0.05 0.05 0.05 0.05 0.05
(0.75) (0.75) (0.75) (0.75) (0.75) (0.75) (0.75)
0.07
(1.0)
0.07
(1.0)
0.07
(1.0)
100°C
(212°F)
Note: If a Heat Shield is used it may be possible to use at higher temperatures. See Accessories section.
Marston explosion vent panels can meet or exceed the advisory limits recommended in the
various codes and guides. For details or to discuss pressure requirements below the limits
set out above, the engineer, contractor or user should contact the factory direct.
Tolerances
The table opposite lists tolerances for Marston
explosion vent panels when used in a Marston
approved frame. In some instances it may be
necessary to increase tolerances where the frame
is not in accordance with Marston limits.
31
Activation Pressure
CSP
TSP
PTX
(<1.0 Psig)
±50%
±50%
±40%
0.07 – 0.09 Barg (1.0 – 1.3 Psig)
±30%
±30%
±25%
0.1 – 0.3 Barg (1.4 – 4.3 Psig)
±25%
±25%
±20%
±20%
±20%
±15%
< 0.07 Barg
> 0.3 Barg
(>4.3 Psig)
Frames
FRAMES AND FITTING
Marston explosion vent panels are usually mounted
into a bolted frame to enable them to be fitted onto
the equipment they are protecting. Using a frame
guarantees the opening size and therefore the
accuracy of the opening pressure. They also ease the
installation procedure in many cases. The frame
section employed by Marston is generally flat which
allows the user to bolt directly to the protected
equipment and allows the simple connection of
downstream ducting. The frames can be supplied with
either the Marston recommended hole configuration,
or to suit the clients own or existing arrangement.
cleaning, or it could be a reverse pressure such as
wind loading. Whatever the reason, any restriction
must be taken into account when establishing the
required vent area.
Generally frames are constructed from either Stainless
Steel or Carbon Steel, although it is possible for other
materials to be considered.
Marston are always ready to provide a custom
designed solution to satisfy the individual needs of the
customer. This can involve differing shapes and sizes,
rectangular, circular, semi-circular, trapezoidal,
triangular and even curved panels are just some of the
shapes available.
In some instances, the frames may be fitted with a
support grid or mesh. This can be to prevent
implosion of a membrane or to prevent injury to
personnel falling through. Implosion may be as a result
of a vacuum condition during normal operation or
We also appreciate the need to provide the user with
a readily available, standard solution.
w
W
M A R S T O N R A N G E O F S TA N D A R D F R A M E S I Z E S
l
L
Size Ref
Inside length
l
mm (ins)
Overall
Length L
mm (ins)
Inside Width
w
mm (ins)
Overall
Width W
mm (ins)
Vent Area
A
m3 (ft3)*
645.365
645
(25.39)
705
(27.76)
365
(14.37)
425
(16.73)
0.23
(2.53)
710.450
710
(27.95)
770
(30.31)
450
(17.72)
510
(20.08)
0.3
(3.44)
645.645
645
(25.39)
705
(27.76)
645
(25.39)
705
(27.76)
0.4
(4.48)
710.710
710
(27.95)
770
(30.31)
710
(27.95)
770
(30.31)
0.5
(5.43)
920.586
920
(36.22)
980
(38.58)
586
(23.07)
646
(25.43)
0.5
(5.80)
1000.710
1000
(39.37)
1060
(41.73)
710
(27.95)
770
(30.31)
0.7
(7.64)
920.920
920
(36.22)
980
(38.58)
920
(36.22)
980
(38.58)
0.8
(9.11)
1000.920
1000
(39.37)
1060
(41.73)
920
(36.22)
980
(38.58)
0.9
(9.90)
1000.1000
1000
(39.37)
1060
(41.73)
1000
(39.37)
1060
(41.73)
1.0
(10.7)
1130.1130**
1130
(44.49)
1190
(46.85)
1130
(44.49)
1190
(46.85)
1.25
(13.7)
Note: *Free area may be reduced as a result of fitting supports.
**1130.1130 is not available in PTX series.
32
Accessories
A C C E S S O RY R A N G E
Indicators
In line with all other Marston products, explosion vent
panels can be supplied with Indicators, which, when
connected to the plant operating systems, can shut the
plant down in the event of an explosion. Indicators are
certified in accordance with ATEX Directive 94/9/EC.
The Indicator takes the form of a simple wire loop, which,
upon opening of the vent panel, breaks, interrupting the
circuit. The device is certified to EEx ia IIC T6
(-35ºC ≤ Ta ≤ 75ºC) for use in hazardous areas (Zone 0).
It is also accredited by CSA (Canadian Standards
Authority)
to Ex ia IIC T6:
Class 1, Zone 0, - 35ºC ≤ Ta ≤ 40ºC (for Canada), and
Class 1, Groups A, B, C and D, T6 (for USA and Canada).
Reverse Pressure /Vacuum supports
Reverse Pressure/Vacuum supports can take different
forms. Often a simple grid or mesh fitted to the inlet
frame is sufficient. This support is non-opening and is
generally re-useable. Alternatively, each membrane
may be fitted with an opening style support. This may
be flat (usually in conjunction with mesh and /or grid)
or domed to closely match the profile of a domed
panel.
Sometimes a domed panel, when used with a foam
damper, may have a flat opening support fitted below
the damper.
Earthing Strap
To minimise the risk of a static discharge, panels can be
fitted with a braided Earth Strap. Often this is not
necessary as the panel is usually earthed via the flange
bolts. However in some applications where static
discharge is a high risk, an Earth Strap is a valuable
addition.
33
Heat Shield
A Heat Shield may be required for one of two reasons.
Firstly, it may be required to insulate a panel from a
very high process temperature, secondly, it may be
required to prevent the accumulation of condensation
on the inside face of a panel, which may affect the
efficiency of the process in the equipment being
protected.
Depending on the application, the heat shield may be a
thin layer of ceramic paper or a thicker layer of ceramic
fibres fitted to the process side of the panel. In extreme
cases heat shields can protect panels from
temperatures as high as 1000ºC (1832°F).
Foam Infill Damper
In many installations, particularly filters, the system is
subjected to short, sharp pressure pulses. Though
often small, these pressure pulses create a change in
system pressure such that the membrane fluctuates.
Where this fluctuation is frequent, as is the case with
reverse jet filters, it can lead to fatigue of the slotted
membrane ligaments. To overcome this, the vent side
slotted membrane is domed and a foam ‘damper’ is
fitted between the membranes to prevent any
unwanted movement.
Gaskets
Standard Marston panels are supplied fitted with simple
soft sponge rubber gaskets. To accommodate various
operating conditions, alternative gasket materials are
also available. In hygienic applications, particularly those
involving food, a white neoprene gasket may be used.
Where process temperature is too high for simple
sponge rubber gaskets, a synthetic fibre gasket may be a
suitable alternative. Whilst these are the most
common alternative gasket materials, any other material
preferred by the user may be considered.
34
Sizing and Selection
VENT SIZING
The sizing and selection of the most suitable explosion
vent panel can often be critical to the safety of plant
and personnel. Marston’s team of Application
Engineers possess both expertise and experience,
enabling them to assess each customer’s individual
specifications and design a high quality, cost effective
solution. This ensures that every explosion vent panel
offered is the best technical solution for the required
duty.
Marston generally work to one of two recognised
guides:
VDI 3673
Pressure relief of dust explosions
VDI - Verlag Dusseldorf Germany
NFPA - 68
Guide for Venting of Deflagrations
National Fire Protection Association,
USA VDI 3673 addresses only dust explosions
whereas NFPA-68 provides guidance on both dust and
gas explosions.
35
Marston Engineers are always available for advice.
Providing sufficient information is available, vent areas
can be established in accordance with the agreed guide
such that in the event of an explosion, the fully opened
panel will release the products of the combustion and
relieve the pressure.
The calculated vent area is dependent on various
design and operating criteria. The vessel will dictate
the volume, geometry and the maximum allowable
pressure. The operating conditions of the system,
along with the maximum allowable pressure, will help
to determine the opening pressure of the panel.
Generally this is 0.1 Barg (1.5 Psig). The product
(dust or gas) will define specific characteristics related
to explosivity, such as the maximum unvented
pressure capability and the rate of pressure rise that
can be generated.
This data can be used to establish the required vent
area by using either nomographs or, more accurately,
by calculation.
Wobaston Road, Fordhouses,
Wolverhampton WW10 6QJ, England
Telephone +44 (0)1902 623550
Facsimile +44 (0)1902 623555
Email [email protected]
Web www.safetysystemsuk.com
To enable Marston to supply the optimum Explosion
Vent Panel, certain basic information is essential.
Photocopy this page, completing as muich information
as possible and forward to the contact details above.
Company Name:
Contact Name:
Reference:
Telephone:
Fax:
Tag Number
Service conditions
Product
KSt
Pmax
Normal maximum operating pressure & temperature
Vacuum conditions - State if none
Reverse pressures - eg. Wind load - State if none
Pressure pulsation’s/Cycling: Give Details
Installation
Volume of enclosure
Enclosure dimensions (Please provide sketch if possible)
Vent area required
Preferred vent dimensions (if known)
Activation Pressure (Pstat)
Temperature at Activation Pressure
Acceptable membrane materials
Acceptable frame materials - Upstream
Acceptable frame materials - Downstream
Enclosure material
Gaskets - Type & material
Design pressure
Design code
Accessories
Indicator Y/N
Thermal Insulation Y/N
Any other relevant information/sketch - use additional sheet if necessary
Quantities
Vent Panels
Frames
Enclosures
To enable Marston Engineers to provide the best possible solution to your application,
please provide a drawing of the installation wherever possible.
36
E X P L O S I O N V E N T PA N E L S E L E C T I O N G U I D E
Applications
Applications
****
1. Silo/Hopper
CSP-F
Atmospheric pressure
fill/empty effects only.
CSP-FM
2. Filter
Atmospheric pressure
steady flow only.
CSP-D
CSP-DV
4. Cyclone
Low pressures, steady flow
conditions.
5. Drier
Atmospheric pressures
with no flow and elevated
temperatures.
CSP-DIM
TSP-F
TSP-FI
TSP-FM
TSP-D
6. Bucket Elevator
Atmospheric pressures with
vibration and abrasion.
TSP-DIM
PTX-F
1
****
Item Descriptions
C
S
P
F
M
D
V
I
T
PTX
R
37
Composite Panel with Seal
Slotted Membrane
Panel
Flat
Mesh Support in Frame
Forward Domed
Vacuum Support Fitted
Infill Damper
Triple Panel with Seal
Protex
Reverse Domed
PTX-D
PTX-DV
PTX-R
2
5
1
3
6
2
5
1
3
2
1
3
2
1
3
2
1
7
6
3
5
3
6
2
5
4
7
3
6
2
5
7
6
5
4
3
2
1
7
6
5
4
3
2
1
7
6
5
4
3
2
1
7
6
5
4
3
2
1
7
6
5
4
3
2
1
4
7
2
1
4
7
5
1
4
3
2
1
4
7
6
5
4
7
6
5
4
7
6
5
7. Mill
Atmospheric pressures
with vibration and abrasion.
Vacuum
(Minimum Activation Pressure x)
3. Reverse Jet Filter
Low pressure with
pulsations/bag cleaning.
Maximum Operating
Pressure
4
7
3
6
4
7
0.3
0.3
0.7
0.7
0.7
0.25
0.25
0.25
0.35
0.35
0.2
0.75
0.75
0.2
✗
✓
✗
✓
✓
✓
✓
✓
✓
✓
✓
✗
✓
✓
Hygienic
*
✓
✗
✓
✗
✗
✗
✗
✗
✗
✗
✓
✓
✗
✓
Non
Fragmenting
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
**
**
**
Max Temp
Max Pred
ºC (°F) Barg (Psig)
***
Vibration
✗
250 (480) 2.0 (29)
✗
250 (480) 2.0 (29) ✓
✓
250 (480) 2.0 (29) ✓
✓
100 (210) 2.0 (29) ✓
✓✓
250 (480) 2.0 (29)
✗
150 (300) 2.0 (29)
✓
250 (480) 2.0 (29)
✗
250 (480) 2.0 (29) ✓
✓
100 (210) 2.0 (29) ✓
✓✓
500 (930) 2.0 (29) ✓
✓✓✓
500 (930) 2.0 (29) ✓
✓✓✓✓
500 (930) 2.0 (29) ✓
✓✓✓✓
500 (930) 2.0 (29) ✓
✓✓✓✓
250 (480) 2.0 (29)
Flat Composite Slotted vent panel, suitable
for equipment operating at or near
atmospheric pressure without vacuum.
Flat Composite Slotted vent panel, suitable
for equipment operating at or near
atmospheric pressure where vacuum may be
present.
Domed Composite Slotted vent panel,
suitable for equipment operating under
positive pressures.
Domed Composite Slotted vent panel with
vacuum support, suitable for equipment
operating under positive and negative
pressures.
Domed Composite Slotted vent panel with
foam infil, suitable for equipment operating
under fluctuating pressures.
Flat Triple Skin vent panel, suitable for
equipent operating at or near atmospheric
pressure.
Flat Triple Skin vent panel, with foam infil,
suitable for equipment operating under
slightly fluctuating pressures.
Flat Triple Skin vent panel, suitable for
equipment operating at or near atmospheric
pressure, where vacuum may be present.
Domed Triple Skin vent panel, suitable for
equipment operating under positive and
negative pressures.
Domed Triple Skin vent panel with foam infil,
suitable for equipment operating under
fluctuating pressures.
Flat Solid Metal vent panel, suitable for high
levels of cleanliness and slight pulsating
pressures.
Domed Solid Metal vent panel, suitable for
high levels of cleanliness and high positive
pulsating pressures.
Domed Solid Metal vent panel, with vacuum
support, suitable for high positive and
negative or fluctuating pressures.
Reverse Domed Solid Metal vent panel,
suitable for high levels of cleanliness and high
levels of vacuum.
* Hygienic means that the vent panel has no slots or crevices where product can accumulate. Food quality materials
should be used wherever necessary.
** Lightweight infill material will be expelled upon venting.
*** For higher temperatures a heat shield may be used. See Accessories, page 37.
38
Marston,Wobaston Road, Fordhouses
Wolverhampton,WV10 6QJ, UK
Tel +44 (0)1902 623550
Fax +44 (0)1902 623555
Email [email protected]
Web site www.safetysystemsuk.com
MAPR1109
Registered Office:
Victoria Road, Leeds,
LS11 5UG, UK