Mechanical Control Systems for Process Pipeline ... · PDF fileSystems for Process Pipeline &...
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.....using SFC coded-card key interlock systems.TESTED, TRIED & TRUSTED
Mechanical Control
Systems for Process
Pipeline & Maintenance
Operations
ContentsProfile
Safety and Clients
Principles
Products
Applications
From an initial site visit
for risk assessment, to
system design and finally
installation.
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Smith Flow Control (SFC) was established in 1985 to provide engineered
safety solutions for hazardous operations in the oil & gas and chemical processing
industries.
SFC introduced the coded-card linear-key concept in a range of modular key-operated
interlocks to regulate operator execution of work procedures on any form of host process
equipment. Typical applications include every form of valve (including motorised and
instrument valves), switches, vessel closures, access guards, pressure and temperature
sensing systems and rail/road/sea tanker loading systems.
SFC’s solutions in hazardous processes reduce the
scope for operator error and ensure safe continuous
plant operation.
Most offshore installations in the North Sea have been
equipped with SFC systems as well as the majority of
related onshore processing facilities throughout Europe. By 1990, SFC became the
generic term for key interlock safety systems in the international oil & gas industry and our
client base now includes most of the major operating companies in all five continents.
In 1990 SFC became part of Halma plc (quoted on the London Stock Exchange) and in
1993 acquired ISO 9001 accreditation certified by Lloyds Register.
Today SFC continues to be managed by its founders who remain committed to providing
quality assured products delivered on time at a competitive price. SFC employs 50
people including 3 design engineers dedicated
full time to product development, using 3D
modelling, a full-time quality manager and 2
full-time works quality inspectors. Our
manufacturing design office is staffed by
8 design engineers who are all highly
trained in the capabilities of AutoCAD
2000 which is our chosen state-of-the-art
manufacturing design tool.
SFC maintains a crew of 4 full time fully
certified site technicians which enable us
to ofter total turn-key services to our clients.
Company profile and objectives
Mike (M.J.) Smith - Vice-Chairman who
co-founded the company in 1985 has
been involved in the international oil &
gas industry for 25 years.
‘....for over 15 years SFC have never failedto provide a viable technical solution to aclient’s safety operating problem....’
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As a general principle it may be said that operations which are safe when
performed correctly can have catastrophic consequences when performed incorrectly.
The Oil & Gas and ChemicaI processing industries generally have a disciplined
approach to design and operating practice - usually governed by well recognised
international standards and enforced by regulatory authorities and certification bodies.
While good practice begins with good design - both are ultimately hostage to the
'Human Factor'.
Modern process plants are highly automated and
regulated by distributed software management
systems which are simply monitored by 'Production'
personnel - often remote from the physical location
of the plant itself. Indeed, some irregular operations
such as pig launching or receiving procedures can
be effected in semi-automatic mode using push-
button controls (again often from a remote station).
Maintenance procedures however invariably
involve human intervention and interrupt automated
processes creating 'abnormaI' conditions for the
duration of the work. Loading or unloading of pig
traps, changeover of pressure relief valves, turbine
servicing (requiring suspension of C02 Fire Deluge),
coupling or uncoupling of hoses for loading
or discharge of tanker cargoes all involve
human intervention and are hostage to the
possibility of operator
error.
Distributed control
systems (DCS)
cannot effectively
regulate such
(maintenance)
procedures - the SFC
‘Coded Card Key
Interlock System' can!
To say working practices have
changed in recent years is an
understatement. Safety was
something that was addressed
only when somebody was
killed or injured, whereas
today prevention has assured
that fatalities and serious
injury figures have dropped
dramatically
Eliminating chance in industrial environments
Potentially LPG storage tanks are one of
the most dangerous areas of the petro/gas
industry, but with the correct safety system
the hazard is kept to the minimum.
Jonathon Hildrey -Financial Director whojoined SFC in 1993 isa qualified CharteredAccountant and aComputer Sciencesgraduate fromCambridge University.
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SFC hold many client commendations for outstanding performance and are always
pleased to make these available to interested prospective clients.
A significant proportion of our business is repeat work with long-standing clients with
whom we enjoy ‘preferred vendor’ status.
SFC are the only valve interlock manufacturer who can demonstrate total product
reliability, field proven over 15 years.
The reliability of our products is second to none. The satisfaction of our clients is proven.
SFC serve industry by eliminating human error and reducing the opportunities for
procedure violations.
SFC are registered with the ‘Achilles’ and ‘1st Point’ vendor databases and are
accredited to ISO 9001 by Lloyds and are certified also by TÜV.
It would be difficult to name aparticular industry that would notbenefit from an SFC coded-card keyinterlock system.
Global market interests
Elf
Exxon
Fina Neste
Foster Wheeler
Gas Authority of India
Hitachi Zosen
Hoechst
Hyundai Heavy Inds. Co Ltd
ICI
JGC Corporation
Kvaerner Process
John Brown Eng. & Cons. Ltd
Karachaganak Petro. Op. B.V.
Kvaerner Oil & Gas
Lasmo Nederland B.V.
Linde A.G.
Maersk
Marathon Oil UK
Mitsui
Mobil
Montell Carrington
M W Kellogg
Natco
National Petroleum Con. Co.
NAM
Neles - Jamesbury
Norsk Hydro
Nynas UK
Occidental Petroleum
Petrobras
R M Parsons
Repsol
Apart from the big users of key exchange
interlocks in the power, industrial,
commercial and petrochemical sectors, a
large market for these systems exists in the
small and medium scale industries (SMIs).
Adnoc
AAF
ABB Lummus Global
ADMA-OPCO.
Agip
Air Products
Aker
Amerada Hess
Amec
BP Amoco
AOC International
Arco British
A/S Norske Shell
Azerbaijan Int. Op. Co.
Bayer
Babcock Water
Baker Hughes
Barmac
BASF
Bechtel
BG Exploration
BHP Petroleum
BOC Process
Borealis Polymers
BP Oil
British Nuclear Fuels
British Gas
Britoil
Brown & Root
BHP Petroleum
Butagaz B.V.
Calor Gas
Chevron
Chiyoda
CIBA
Conoco
Costain
Daelim
Daewoo
Doha Petroleum
Dong Ah Consortium
DOW
DSM
Du Pont
Pennzoil
Petroland
Petronas Gas BHD
Phillips Petroleum
Preussag Fire Protection
Q.G.P.C.
Saudi Basic Industries Corp.
Saga Petroleum
Samsung Engineering
Score (Europe)
Scottish Nuclear
Scomark Engineering
Shell (UK) Expn & Prodn
Single Buoy Moorings Inc
SLP Engineering
Smithkline Beecham
Snamprogetti Spa
Sable Energy Corp.
Statoil A/S
Sasol
Stone & Webster Engineers
Technipetrol Spa
Terra Nova Alliance
Texaco
Technip
Total Oil Marine
Umoe Olje OG Gass AS
Union Carbide
Whessoe LGA Gas Tech.
Wintershall
Wood Group Engineering
Woodside Petroleum
Transfield Worley Eng.
Wormald Engineering
Zeneca
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“you only get one chance in this game!”
Controlling the sequence of events in which process activities are conducted
has been achieved historically using a Permit to Work (PtW) accompanied by documented
instructions.
However, this system is hostage to ‘human factors’. Distractions, failure to interpret
correctly, ignorance of the system - all can lead the operator to make errors which can
manifest themselves in industrial accidents of varying magnitudes.
Trapped Key Interlocks are simple mechanical devices which can be customised to
implement a safe sequence of operation in any process activity.
In the following pages we show how our mechanical key interlock system ensures that pig
trap valves are disabled and proven shut and the vessel is isolated, drained and vented
BEFORE opening of the closure for loading or unloading of pigs, or, how the spare pressure
safety relief valve is on stream BEFORE an in-service relief valve can be isolated and
removed, or, how we prevent a tanker from departing a loading/discharge station BEFORE
the cargo hoses are disconnected.
These and any other work tasks executed by human intervention can be completely
regulated by SFC's coded-card key interlocks - simple and total mechanical reliability to
prevent operator error or violation to protect your plant, the surrounding community and the
environment.
In addition to our range of high-integrity coded-card key interlock safety products, SFC
also offer a comprehensive range of valve and process equipment security products for high
and low-criticality applications.
BE SURE - BE SAFE - CHOOSE SFC - YOUR PARTNER
FOR TOTAL PLANT SAFETY & SECURITY.
The principles of interlocking
With the simple act of retrieving a key from
the central key cabinet, a sequence of
events is initiated that eliminates chance or
any one person gambling on an action that
may or may not work.
The hazards of the sea are bad
enough but the hazards of loading
and unloading thousands of tons
of LNG presents another set of
dangerous activities. With SFC
safety systems in place, ships and
their crews enjoy maximum safety.
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In 1988, the Piper Alpha platform sustained a
devastating explosion and loss of life that
could and should have been prevented.
In the ensuing enquiry the Cullen Report*strongly recommended that all PtW systems
should incorporate mechanical locking
arrangements.
*The Public Enquiry into the Piper Alpha
Disaster by The Right Hon Lord Cullen
presented to Parliament Nov. 1990
Mike D’Anzieri -Managing Director andco-founder of thecompany has over 20years experience inmarketing andmanufacturing ofindustrial safetyproducts.
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Interlocks for Lever and Handwheel Manually Operated Valves
'QL' - Compatible with:1. Ball valve
2. Butterfly valve
3. Plug valve
PRODUCTS
1 2 3
These illustrations show our basic
product range - the 'QL' interlock for 90o
quarter-turn lever-operation ball, butterfly
or plug valves - and the 'GL' interlock for
handwheel-operated gate, globe and gear-
operated valves.
Each of these lock models are available
with purpose-machined mounting
couplers, or with universal mounting kits
(where the valve topworks details may be
difficult to obtain). For each lock model
('QL' or 'GL') the universal mounting
arrangement is denoted with the suffix
'U' - e.g. 'GLU'.
All SFC products are manufactured from
316 stainless steel material and are supplied
with manufacturers' Certificate of Conformity
to BS EN 10204: 1991 Section 2. 1.
Standard modular products are
manufactured as lost wax investment
castings - 'specials' may be machined
from 316 stainless steel bar stock.
Every interlock assembly is protected
with stainless steel self-sealing
weatherstrips fitted to the key entry
apertures to prevent the ingress of dirt into
the internal lock mechanism.
SFC interlocks are operated using the
'Coded Card Key' design developed
originally by SFC in 1985 - today there are
thousands of units installed and working
successfully in most of the major oil/gas
provinces worldwide. Despite attempts by
others at producing cheap imitations - SFC
products are most-preferred by clients -
our name remains a byword for quality and
reliability.
Type 'QL' with purpose-machined mounting coupler for direct mounting
onto spindle of specifically nominated valve.
Type ‘QLU’ with universal mounting kit for adaption to non-specific
lever-operated 90o ball, butterfly or plug valve.
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PRODUCTS
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'GL' - Compatible with:1. Rising Stem Gate Valve
2. Rising Handwheel Globe Valve
3. Gear-Operators
4. Diaphragm Valve
• All 316 stainless steel.
• Fire rated to 700oC.
• Ultra-low temperature tested to -57oC.
• Destructively tested to extreme parameters.
• Sea-salt spray mist tested.
• Grit-blast tested.
• Thousands of units field proven over 15 years.
• Adapt to any valve without any modificationto the host equipment - no welding / no drilling / the certified pressure envelope of the host valve is never compromised.
• Retro-fit to live plant without the need for shutdown.
• High integrity mechanical control system.
• Ergonomic design.
• Coded Card, Linear Key concept.
Type 'GL' with purpose-machined mounting coupler for direct mounting
onto yoke or shaft of specifically nominated valve.
Type ‘GLU’ with universal mounting kit for adaption to non-specific
handwheel-operated gate, globe, diaphragm or gear operated valve
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Having implemented a good key
interlock control system, the next most
important step is to apply a good Key
Management System.
For storage, ease
of access and issue,
SFC key cabinets
provide all that is
required.
A key cabinet
should be located in
a safe place; typically
a control room
whereby initiating
keys are issued by
the Shift Supervisor,
Offshore Installation
Manager (OIM) or
other person in
authority.
Cabinets vary in
size and can
accommodate from 1
- 227 system initiating
(or spare) keys. Keys
can be located via
means of hooks or
holsters. (The holster
locator provides
increased capacity).
Each interlocked
system has a
dedicated engraved
tag location within the key cabinet. During
periods of normal operations, all interlock
system ‘permit’ (initiating) keys are visually
displayed within the cabinet in dedicated
locations.
Each key cabinet tag is engraved with
the relevent piping package data - this
same data is also replicated on each
system key.
Key Cabinets
PRODUCTS
When the key is removed, a ‘Visual Alert’
tag is revealed providing details of the key
which has been issued, its designated
location, and the words ‘WORK IN
PROGRESS’.
Control Room staff have clear and easy
indication of work status at any time.
Key cabinets can also accommodate
mimic diagrams. These are extracts of the
P&ID diagram engraved onto a Traffelite
plaque and show clear details of all valves
which are interlocked.
Design Features and User Benefits
• Carbon or Stainless Steel construction.
• ‘Glazed’ door provides key status
without the need to open.
• Ingress Protection from IP55 to IP66.
• Lockable Doors.
• External wall mounting brackets.
• Total integrity by using dedicated
(coded) key locations.
• Complete key status awareness.
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PRODUCTS
Manufactured as standard to IP55
specification. Higher IP ratings are
available to special order. Locked
door ensures that the total
operational control of interlock
systems resides with the
Designated Authority.
Constant visual indication of
effective management of Permit to
Work procedures.
‘Work in Progress’ status indicated by
the removal of a procedure initiation permit
key. Additional detailed process
description also revealed to indicate where
work is taking place. Key tags can be
colour co-ordinated with mimic graphics.
Gloria Young -Shipping Clerk whohas been with SFCsince 1993
Jackie West - ProjectsCo-ordinator has beenwith SFC since 1990and is responsible forproject documentationand management ofsite services.
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Where valves are actuated by means of
Pneumatic, Hydraulic, Gas or Electrical
power sources SFC interlocks can be
integrated into the actuator operation to
provide complete manual control of the
valve.
The same basic principles of
interlocking apply; establish and prove the
desired position of the valve and
immobilise the valve in that position. For
actuated valves, there may be two or more
means of operating the valve and all need
to be accommodated within the interlock
scheme.
The high torque applied during valve
actuation means that physical
(mechanical) locking of the valve operating
motion is not practicable.
Instead, mechanical interlocking of the
actuator control mechanism is the
preferred method.
ELECTRICAL ACTUATORS
1. A mechanical interlock placed over the control
push button station (SLU) prevents operation of
the controls without the permit key.
2. An ‘actuator key exchange’ (AKE) unit placed
over the gearbox or valve stem provides
mechanical valve status indication *.
3. A multi-turn interlock fitted to the manual
override handwheel (HWL) prevents the
Interlock scheme being overridden manually.
*It is imperative to ensure the valve has reached
its fully open, or fully closed position before
proceeding to the next stage of the interlock
sequence. The AKE unit provides ABSOLUTE
proof of valve status.
PNEUMATIC ACTUATORS
Pneumatic actuators normally operate on a
'spring return - fail safe' principle. Interlocking
such vaIves simply requires the introduction of a
small diameter 3-way ball valve into the
pneumatic power line. This valve is locked in the
open position - (power 'ON' - valve
'ENERGISED'). Unlocking the interlocked 3-way
valve permits the air supply to be ‘vented' through
the 3rd port - simulating power failure which will
cause the actuator to move the process valve to
its open or closed fail-safe position.
Actuators
PRODUCTS
'AKE' Actuator key
exchange unit.
'SLU' Switch lock unit.
'HWL' Manual override
handwheel unit.
HWL
SLU
AKE
HYDRAULIC ACTUATORS
Hydraulic actuators simply require the
introduction of an interlocked
block valve in the power line
sited between the field control
cabinet and the actuator
itself. This unit is interlocked
with an 'AKE' unit positioned
on the valve gearbox - after
operation, the hydraulic power supply
line valve is unlocked and closed and then
locked closed to release a key which is
exchanged through the 'AKE' unit to confirm
the main valve's new position.
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Access into pressure vessels is a
potentially hazardous exercise. Residual
pressure, volumes of residual liquids or
gases all can be harmful - typical
examples of these potential hazards
include pig traps, slug catchers and filter
housings.
Locking the vessel closure in the closed
position ensures access into the vessel
can be achieved only under controlled
safe conditions. The operating key is held
in a secure place - e.g. Control Room or
Supervisor's office or is retained (trapped)
in some other related interlocked item of
equipment.
As a minimum, vessel closures are
usually interlocked with vessel venting and
draining functions - the interlocking
arrangement can be extended to
incorporate all process items of equipment
relating to the vessel’s function.
The SFC 'DL3' interlock is adaptable to
all types of vessel/access closures and is
very simple to use. In pig trap applications
where the closure incorporates a bleed
device, the 'DL3' interlock will be
designed to interface with the bleed
function to ensure the bleed screw cannot
be removed until the interlock permit key
has been inserted to unlock the 'DL3'
assembly.
When the 'DL3' is incorporated into
vessel access safety procedures, total
equipment and personnel safety is assured.
Any type of closure can be fitted
with the DL3 interlock, regardless
of their method of operation.
Design details can be provided on
request.
Closures
PRODUCTS
Chris Tonks - SalesOffice Manager has
been with the companysince 1992 and is
responsible for projectmanagement of all major
project orders.
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Specials
PRODUCTS
Road Barrier Interlock
Customer Problem:
To prevent product spillage and damage to loading equipment as a
result of vehicle drive-away during loading.
SFC Solution:
Where any liquid gas or powder product is being transferred from store
to tanker or vice-versa, an interlocked road barrier will ensure spillage
cannot occur as a result of vehicle drive away.
Regardless of whether the product is hazardous or not, if it is spilt, there
may be expensive consequences.
With an interlock system in place a driver who has forgotten to
disconnect product transfer lines cannot vacate the loading point until the
road barrier is raised. However, the barrier is locked down and the
operating key is trapped in either the transfer valve lock or hose storage
container.
Only when these have been closed, or locked away can the key be
retrieved to unlock and raise the barrier, permitting drive away.
The range of process applications to
which SFC interlocks can be applied is
unlimited. As clients begin to understand
the immense operational capabilities of
SFC interlock systems, they often request
unique solutions to specific problems.
In this section we present some
examples of ‘specials’ we have developed
to meet clients’ specific operating safety
requirements.
SFC are always pleased to receive a
challenge to provide unique solutions to
clients’ individual or special problems.
Tony Griggs - ProjectEngineer has been with
SFC since 1995 and isresponsible for SFC
business with associateGroup companies andagents/distributors in
Australia and USA.
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Specials
PRODUCTS
Modular Control Panel
Customer Problem:
To provide complete visual positional status of motor operated valves
(MOV's) during each stage of a pigging procedure from a single location.
SFC Solution:
Complex pig launcher and receiver systems comprising Motor Operated
Valves (MOV's) sometimes require full 'visual aware/control' status.
This modular, locally mounted control panel comprises full graphical mimic
board with status beacons on critical valves. Below the graphic board,
interlocked hazardous area control switches, providing power isolation to the
MOV's are situated for easy operation.
The entire panel is protected with a stainless steel canopy.
Flare System Protection
Customer Problem:
To ensure high-pressure gas compressors are shut
down prior to isolating flare system Pressure Safety
Valves (PSV's).
SFC Solution:
An electro-mechanical interlocked soleniod control
switch which releases the PSV interlock system permit
key ONLY after the compressors are shut down and
isolated. The compressor can be either single or double
ended - whichever is the case, all sides have to be
isolated PRIOR to key release.
Electro-mechanical unit incorporates indication of
compressor power isolation for key release - this
indication also includes a signal to the Control Room that
the key has been removed. These functions can be
designed to meet customers' specific requirements - the
unit illustrated is for 3 compressors (one double-ended
and two single units).
Ian Binney - Project Engineer and agraduate in Chemical Engineering has
been involved in safety engineering forover 17 years and is responsible forSFC business with major clients in
Japan, the Middle East, South Africaand Latin America.
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Specials
PRODUCTS
Customer Problem:
To provide a visual signal from the remote
pig launcher door to the central control
room that the end closure is open.
SFC Solution:
Our DL3 interlock is used to secure all
types of vessel closure. In this illustration,
the interlock was fitted to a Pig Receiver to
ensure complete isolation, venting and
Customer Problem:
Restrictions of space require that a
modular style double block and bleed
valve is used in place of a conventional
3 valve piped arrangement. It is
required that the modular valve is
interlocked with other valves in the
system.
SFC Solution:
Modular valves of this type pose greater
problems for interlocking by virtue of their
Customer Problem:
To convert remote valve operation
(motorised valves) to local operation, and
still retain the integrity and safety of the
operating sequence.
SFC Solution:
For this problem, our solution was to
design and manufacture a solenoid key
release device. As a consequence of the
working environment, a hazardous area
enclosure to Eexd IIb T6 was also required.
size and space limitations.
SFC designed a bespoke
cam type interlock
espec ia l l y fo r th i s
host valve.
Used on the Brent Delta
platform, this interlock
provided the perfect solution to
our customer’s problem.
draining procedures were correctly
executed before the door was opened.
A proximity sensor was bolted to the
interlock casing and the sensor positioned
to detect the key being inserted into the
lock.
Positional indication can be provided
on our complete range of interlock
products.
The basic 'QL' lock body was fitted to the
operating lever (knob) of the switch.
BASEEFA certification for this adaptation
was approved.
A remote signal from the control room
activates the local solenoid which releases
the key. The key is used to operate other
valve control equipment in the system.
A proximity sensor fitted to the switch lock
provides evidence back to the control
room that operational activity is underway.
DL3 Interlock C/W Proximity Sensor
Modular Double Block & Bleed Valves
Solenoid Key Release Device
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Simple Valve Lock
Customer Problem:
To prevent tampering of valves on utility supplies, e.g. water, gas etc.
SFC Solution:
A 'fully fledged' valve interlock might normally be prohibitively
priced so a purpose designed interlock has been developed
specifically for these applications.
This simple device can lock the valve in the open or closed
position with a single key.
Customer Problem:
To interlock a single acting, pneumatic
actuator on a ball valve.
SFC Solution:
Where single acting, spring return
pneumatically actuated valves have to be
incorporated into an interlock sequence,
an interlocked 3-way isolating valve is a
simple and effective solution.
The isolating valve is located upstream of
the actuator control panel. When operating
Customer Problem:
To ensure two ports on an instrument
manifold can never be simultaneously
opened.
SFC Solution:
Needle valves of all types can be fitted
with SFC interlocks. Regardless of body
design, number of operating handles or
method of operation, SFC can supply a
solution to your problem.
In this illustration a 4-port instrument
manifold is equipped with SFC's NVL
Specials
PRODUCTS
Pneumatic Control Valves
Customer Problem:
To interlock a double acting, pneumatic actuator on a ball valve.
SFC Solution:
For this requirement SFC adapted their QLA interlock to incorporate
a sliding control lever with forward and backwards motion.
This linear motion interfaced with the pneumatic valve operating
lever to provide double acting operation.
the isolating valve, air pressure to the
actuator is vented to atmosphere, thus
completely disabling the valve.
Single or double key arrangements
can be used to isolate the valve in
any position.
In the illustration the interlock
incorporates a chassis plate for local wall
mounting, and a proximity sensor for status
indication back to a control room.
This arrangement is a cost effective add-
on control feature to all types of pneumatic,
hydraulic or gas actuators.
interlock. The locking device ensures
that pairs of operating handles can
only be operated one at a time.
Upon opening the first port,
the key becomes trapped.
The second port cannot be
opened until such time that the first
port has been closed, thus releasing
the operating key.
The opposite pair of ports are
controlled in the same way with a differently
coded key.
3-way isolating Valve C/W Proximity Sensor
Needle Valve Locks
Explosion Proof Interlocked Switch
18
Specials
PRODUCTS
Customer Problem:
To ensure that a dangerous rotating
hazard was secured against access which
could result in serious injury.
Further, power isolation alone was not
enough because the rotating hazard had a
run down period in excess of 3 minutes.
Customer Problem:
To mechanically interlock an electrically
operated device, within a hazardous
environment.
SFC Solution:
Where mechanical (interlocked) control
of powered equipment is required in a
hazardous area, the SFC switch lock
provides the perfect solution.
Customer Problem:
To permit complex variations in
operating sequences on pig
launcher/receiver systems.
SFC Solution:
The simplest interlock systems will
normally feature a 'linear sequence'. This is
where the outward 'journey' (operating
steps) are mirrored by the return journey.
However, from time to time non-linear
sequences are necessary. A typical
SFC Solution:
An SFC timer controlled interlock is
interfaced with a closure door interlock
providing access to the hazard. Upon
pressing the isolating switch, the timer
commences (varying run-down times can
be programmed). Only when the
programmed period of time has elapsed
can the key be removed, which in turn, is
used to unlock and open the access door.
In this illustration our 'QL' quarter turn
interlock is fitted to the actuator lever of an
Eexd IIb T6 hazardous area control
switch.
A single or dual key configuration can be
supplied to lock in the ‘ON’, ‘OFF’ or both
positions.
Switches of all zone protection
specifications can be provided.
example of a non-linear sequence is a pig
receiving procedure where double block
and bleed valves control complex nitrogen
purging, pressure equalisation, venting
and draining.
The sequence control unit is a
mechanical key issuing device. It is
normally placed locally to the valve
system. It differs from a key exchange unit
in that, upon inserting a permit key, a
selector knob is rotated to a fixed position
before the next key is issued.
Timer Controlled Interlock
Sequence Control Unit
19
Where security lock-off devices are required to provide mechanical locking of manual operators, SFC offer a fullcomplement of security and commissioning tools.
If sequential control is unnecessary but a secure lock is required, the SFC range of security products canprovide the solution you need.
ChainlokThe Chainlok is a unique device which
combines the features of padlocks and
interlocks.
A durable body and chain made from
316 Stainless Steel makes it suitable for
use in the most hostile environments.
Chainlok comes with 0.5m chain as
Security Products
PRODUCTS
ISO-LOKA multi-clasp, when used in conjunction
with SFC padlocks enable individual
personnel to isolate equipment while they
carry out their work, safe in the knowledge
standard (longer lengths available on
request).
Flag style ‘colour aware key’ enables
incorporation into interlock (key exchange)
systems.
Flip caps prevent ingress of foreign
matter when key is removed.
that the equipment cannot be re-energised
until all padlocks have been removed from
the clasp.
Two body and cable sizes are
available, along with varying
lengths of cable. Cable breaking
strains are available to 1750kg.
Car SealFor ‘one time only’ securing of manual
operators, including valves, switches,
enclosures. A simple ‘break-away’ screw
secures the seal in place. Removal can only
be achieved by cutting the seal cable.
20
Pressure Protection
Whether onshore or offshore, maintenance procedures to Safety Relief Systems on live
plant cause concern in ensuring that an open path to relief is maintained at all times
during the work exercise.
Most modern piping arrangements include spare relief capacity enabling continuous
production while such maintenance
procedures are conducted on live plant -
eliminating the requirement to isolate and shut
down the process.
Twin or multiple safety relief valve systems
are usually fitted with isolation block valves
upstream and downstream of each safety relief
valve - it is essential to ensure that the block valves isolating the spare relief valve are
opened BEFORE the block valves of the workpiece relief valve are closed. This issue is a
more acute problem if the respective relief valves and isolating block valves are distant or
out of sight of each other.
Various API and ASME codes recognise this hazard and recommend the use of
interlocks to eliminate this possibility. API RP 520 (Pressure Relieving Systems for
Refinery Services - Part II : Section 4 - Isolation Valve
Requirements) and API RP 14E (Design and
Installation of Offshore Production Platform Piping
Systems - Para.5.8.b [2] - Relief Device Piping)
specifically recommend interlocks in this situation to
ensure that (over)pressure protection of the vessel is not
compromised. These recommendations are also in
accordance with the requirements of ASME - Section
VIII - Appendix M.
Fitting a valve interlock to the upstream and
downstream isolating valves on each safety relief valve
(PSV) will ensure these recommendations are
implemented.
An initiating key, issued from a secure location (Control
Room) commences the PSV changeover. Follow the Step
By Step procedures in the diagram.
....... ‘apart from the possibility of death or injury topersonnel, or pollution of the locality, what otherpossible impact could an over-pressure explosion orrupture of one of your main process vessels have onyour business’?
APPLICATIONS
Clive Lyme - Project Engineerhas been with SFC since1992 and is responsible forSFC business with associateGroup companies andagents/distrbutors in Europe.
Dave Selsby - Senior SiteEngineer has been with the
company since 1985 andheads a crew of 4 site
engineers responsible forinstallation and
commissioning of SFCsystems at client locations
worldwide.
21
• ILLUSTRATION STATUS:
PSV1 on line: PSV2 isolated
Block Valves V1, V2 & V4* are Locked Open (L.O.)
Block Valve V3 is Locked Closed (L.C.)
*Spare outlet (downstream) block valve normally L.O. especially if
lower pressure rated than corresponding inlet (upstream) block valve.
• REQUIREMENT:
There is always an open path to relief.
(Inlet block valves V2 & V3 must never be closed at the same time.)
• MAINTENANCE TASK:
To commission PSV2 into service.
To isolate and permit removal of PSV1 for testing/servicing.
• WORK SEQUENCE:
1. Key ‘D’ is issued from the Control Room to initiate the Permit to Work.
2. Key ‘D’ unlocks and enables the opening of spare inlet block valve V3.
Typical ‘4 Block Valve / 5 KeyInterlock System’
APPLICATIONS
3. V3 is operated to open and is L.O. by removing Key ‘C’.
PSV2 is now on line.
4. Key ‘C’ is transferred to unlock and close inlet block valve V2.
5. V2 is L.C. by removing Key ‘B’.
6. Key ‘B’ is transferred to unlock and close outlet block valve V1.
7. V1 is L.C. by removing Key ‘A’.
The return of Key ‘A’ to the Control Room closes-out the work
permit and enables the issue of instructions for removal of PSV1
for testing and servicing.
Twin PSV Changeover Sequence
It should be noted this interlock arrangement further ensures
that the higher pressure rated inlet block valve V2 is closed
before its corresponding lower pressure rated outlet block valve
(V1). Conversely, this key interlock arrangement would also
ensure opening of low pressure outlet block valves before
opening of high pressure inlet block valves.
KEYSA & BV1
KEYSE & DV4
KEYSB & CV2
KEYSD & CV3
PSV1
PSV2
22
Tankers
Transfer operations of cargo to or from
tankers involving bulk powder, liquid or
gaseous product (possibly flammable or
toxic) are prone to spillage unless some
positive safety arrangement is in place to
ensure the carrier unit cannot move away
before all transfer (loading) hoses are
disconnected.
Cargo transfer operations on road and
rail tankers employ the same basic
principles and commonly feature
barrier/gantry structures, hose couplings,
supply valve(s) and hose storage
facilities. For these applications SFC
provide a positive mechanical safety
system that interlocks the loading bay
barrier with the gantry unit. The barrier
cannot be raised (permitting drive-away)
until the gantry has also been raised - and
this cannot occur until the loading
arms/hoses have been
retracted/disconnected. The SFC safety
interlock system can also include the
vehicle ignition system to ensure total
disablement of the tractor unit until alI
hoses are disconnected and gantry and
barrier positions are cleared to permit
safe moving away. Indeed the US Federal
Pipeline Safety Regulations make specific
reference to this situation for LNG
facilities.
APPLICATIONS
.......‘imagine the mess if a road tanker loading milk drove awaywith the transfer hoses still connected.....imagine the bigger‘mess’ if the cargo was LPG or LNG!’.......
Loading / Discharging operations - Road, Rail or Sea
Simon Read - SalesManager Europehaving over 20 yearsinternationalexperience in designand installation ofmajor projects.
Once the loading arms are correctly
positioned a secondary trapped key is
released from the control panel which
enables energising of the actuated supply
valve which can be opened enabling
product transfer. The tanker cannot be
moved while the loading arm is in position
and the loading arm cannot be retracted
until the supply valve has been closed.The SFC safety system
ensures that only when the valve is closed can the trapped
(energising) key be released from the interlocked supply valve
control switch. This key is returned and inserted into the loading
arm control panel to enable retraction of the Ioading arm(s). When
alI related procedures are completed, the entire system is
disabled by removing the original initiating/permit key.
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These positive mechanical and electro-
mechanical arrangements ensure total safety
by eliminating the possibility of error or
violation - every operation executed by
h u m a n i n t e r v e n t i o n i s mechanically
regulated. Software-based electronic
management systems are also commonly
applied to regulate these procedures but are
vulnerable to the extent they are n o t
s c r u t a b l e a n d m a y b e p r o n e t o
s o f t w a r e contamination/corruption or
system failure.
APPLICATIONS
Sea tanker cargo transfer operations usually involve a push-
button station in the jetty control room regulating the operation of
automated loading arms and the (actuated) supply line valve(s).
When the tanker is berthed and ready for cargo transfer, the
automated loading arms are energised and located into position
on the tanker by insertion of an initiating/permit key into the
loading arm control panel.
Tim Hughes - SalesManager UK has been
with SFC for over 10years having
progressed to hispresent position fromdesign draughtsman
and with extensive siteexperience.
24
Pig trap accidents involving operator
intervention can be prevented by SFC
coded-card key interlock systems.
DNV TN B 302 Technical Notes for
Fixed Offshore Installations describes
pig traps as 'primary grades sources of
hazard'. ASME and API codes equally
recognise pig trap hazards - especially in relation to the risk of
opening closures while the vessel remains under pressure. The
Pipelines Safety Regulations 1996 enacted into UK law in April
1996 requires operators of pipelines to provide safety systems
that ensure persons are protected from risk to their health and
safety - again describing the hazard of opening pig trap vessels
under pressure.
SFC interlocks can be specified to ensure the minimum safety
arrangement of interlocking the vessel vent valve with the pig trap
closure. This arrangement ensures (to the exclusion of all other
methods) the vessel VENT valve is OPEN before any attempt can
be made to open the closure.
.....“Imagine the consequences of opening a pig trap closurewith product in the barrel”
.....“Imagine the effect of attempting to pass a pig through apartially open outlet valve”
.....“Imagine getting a sniff of H2S ”
.....these things can happen - have happened!
Pig Traps
With interlocks fitted to both the vent
valve and pig trap closure, a key is
released when the vent valve is opened
- removing the key from the vent valve
locks the valve in the open position. This
key is coded in common with the closure
lock - only by opening and locking the
vent valve can the operator secure the correct key to proceed to
unlock and open the closure.
APPLICATIONS
(Bleed devices fitted into closure opening
mechanisms are alone an unreliable safety
arrangement to detect the presence of
residual product - they are prone to wax or
hydrates formations which can obstruct the
bleed channel inside the vessel thereby
misleading the operator to believe it is safe to
open the closure).
Ian McDonnell - BusinessDevelopment Manager hasre-joined SFC after a twoyear interval in valve sales.Ian was originally involvedat SFC in project sales andre-joined the company inJanuary 2000 to developnew markets.
Further procedure sequences can be regulated by interlocks to
include drain valves, nitrogen purge and water flush valves,
corrosion inhibitor and isotope functions, and indeed main
inlet/outlet and kicker valve functions - every system is designed
to meet clients' unique operating conditions/requirements.
Key interlocks can be integrated into pig trap control systems
even where the main inlet/outlet valves and kicker valve are
actuated (MOV's). In this situation, launching or receiving pigs is
a semi-automatic process with operator intervention limited to
push-button action either through a local control panel or effected
from a remote control station. Indeed, these valves may even be
programmed with ESD functions.
However, when it comes to loading or unloading of pigs, an
abnormal condition arises where software or electronic
interlocking arrangements between these valves are suspended
through the necessity to isolate these valves both from 'Remote'
and 'Local' settings to the 'Off' position. An SFC coded-card key
interlock system can be fitted to these valves to mechanically
prove their 'closed and isolated' status - releasing a key which
then enables operation of manually-operated valves related to
vent, drain, N2 purge and water flush procedures before enabling
any attempt to unlock and open the pig trap closure.
Only an SFC coded-card key interlock system can achieve the
condition of creating a positive link that makes the
operation/status of MOV's and manually-operated valves
completely interdependent and absolutely reliably ensures total
isolation, venting and draining of the vessel BEFORE any attempt
can be made to open the vessel closure!
APPLICATIONS
25
26
Fire Deluge Systems
APPLICATIONS
.......‘what's colourless, odourless, is all around us and can kill aperson in less than 2 minutes’ ?.......
International concern over the environmental effect of widespread use of CFC gases
has led to the phasing out of HALON (Halon 1301) as a fire extinguishing medium and its
substitution with Carbon Dioxide (CO2) or other inert gases.
CO2 is a very effective extinguishing agent and works by reducing oxygen levels to a
point where combustion cannot be sustained. It is a naturally occuring substance and
has no corrupting or polluting effect when released into the atmosphere - unlike HALON
which is a CFC compound.
Automatic CO2 fire extinguishing systems when activated are
designed to deluge an area within seconds. Typical installations
include turbine/generator enclosures, plenum chambers, computer
rooms, archives or any other enclosed area designated as being
not normally occupied. Such areas are occupied only on an
occasional basis usually for the purposes of inspection,
maintenance or repair.
CO2 is potentially fatal - anyone who may become
trapped in an enclosed space flooded with CO2
would very quickly suffocate.
Cliff Roberts - ProductionManager has been with thecompany since 1986 and isresponsible formanufacturing output timelyto clients’ delivery daterequirements.
27
APPLICATIONS
For the period in which work is being carried out
inside the enclosed space, the CO2 Supply is isolated
and the worker(s) cannot be locked in. However, to
ensure total worker safety each interlocked access
door within the system is fitted with a failsafe
emergency override escape mechanism which
permits a worker to strike a panic button or crash rail
that mechanically overrides the door latch mechanism.
Safe practice requires an arrangement which prevents casual or
unauthorised access into a (CO2) protected space and also
enables emergency exit at all times from the protected area. The
safety arrangements should also ensure that all doors and access
hatches remain locked during periods of normal operations and
that access to the protected area is controlled and authorised
only by the appointed authority.
SFC interlock systems can be applied for maximum effect to
permit access only under the strictest conditions. Access for
inspection or maintenance purposes is only possible by the issue
of an initiating 'permit key' by the appointed authority. This key
may be used to activate visual or audible alarms which denote
'work in progress' and / or the release of secondary key(s) which
enable isolation of the CO2 supply. Based on a key exchange
principle, further keys are released which enable unlocking of the
access door(s) and permit the entry of the worker(s) to undertake
the task at hand.
This safety solution from SFC fulfills the safety
requirements of NFPA12 * and BS 5306. #
* National Fire Protection Association (USA) - Carbon Dioxide
Extinguishing Systems - 1993 Edition.
# British Standard - Part 4 1986 - Specification for Carbon
Dioxide Systems.
Bryan Hughes - QualityManager has been with SFCsince 1992 and isresponsible for maintainingSFC’s accreditation to ISO9001.
Smith Flow Control Limited6 Waterside Business ParkEastways Industrial Estate
Witham, Essex CM8 3YQ, United KingdomTel. +44 (0)1376 517901 Fax. +44 (0)1376 518720
E-mail: [email protected]: HTTP://www.smithflowcontrol.com