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Hytork® Fire Shield Fire Proof
Actuator |
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Excel "Fire Shield" Series
Valve Actuators |
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Modern process plants tend to be large, complex, highly automated
and controlled from a central control point. This normally creates a
smooth well-controlled sequence of events until an emergency arises.
A variety of emergency shut-down sequences may exist, but until all
the factors of the crisis are known, they cannot by evaluated and
this is where HYTORK®/FIRE SHIELD becomes an essential tool.
Most of the valve actuators have an unusual performance requirement.
For most of their life they are required to do nothing - but - when
the moment comes, they must operate.
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The
Fire Shield Solution |
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Hytork®/Fire Shield actuators offers the answer to the problem
because HYTORK®/FIRE SHIELD, by virtue of its common-sense approach,
ensures that the local as well as the remote control integrity of
the Actuator is guaranteed. This in association with advanced
monitoring of the Actuators control capabilities, provides the best
possible solution to the problem, by providing up to 30 minutes of
total valve control capability for valves located in the middle of a
hydrocarbon inferno, Hytork®/Fire Shield allows the correct sequence
to be chosen and actioned.
This may be by changing directional flow, isolating or dumping
product, or initiating flood or deluge systems.
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What Is The Hytork® Fire Shield? |
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The Hytork® Fire Shield actuators have a proprietary epoxy-based
intumescent material that is bonded to the external surfaces of
the actuator to be fire-proofed.
In its final moulded but unpainted form it is a hard durable
material visually similar to a smooth grey iron casting.
When finished and painted it presents a very smooth and attractive
finish. It is suitable for on-site application over small areas for
repair purposes. Patch-up kits are available.
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What is INTUMESCENT ?
The standard definition is to swell or enlarge. The
HYTORK®/FIRE SHIELD coating provides protection in a fire by swelling
4 to 5 times its original thickness, to form a lava-like char which
insulates from, and reflects back heat into the fire.
After the initial formation of char, the coating remains passive
until the heat penetration through the char reaches a temperature at
which the passive material is again activated. The process is
repeated until either the passive material is depleted or the fire
is extinguished.
The coating is effective in protection against fire through basic
thermodynamic principals. The initial layer of char that forms has
the following characteristics:
- A very low thermal conductivity coefficient.
- The surface temperature of the
char rises to within 38C of the fire.
The process to change the coating from "passive" to "active"
requires a substantial amount of heat energy. As this process begins
to take place, cooling vapours are released and heat is absorbed
away from the passive layer below. Heat rejection back to the fire
is through the following:
- Re-radiation - Heat rejection by an object through radiation
depends on the surface temperature of the object. Since the
surface temperature of the object is close to the fire
temperature, re-radiation will be high. The resulting heat
absorption through radiation is low.
- Convective Heat Transfer - The driving potential for
convective heat transfer to an object in a fire is the difference
between the temperature of the fire and the object. Again, since
the surface temperature of the char is close to the fire
temperature, the convective heat flux to the actuator will be
lower.
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The coating is done in association with THERMAL DESIGNS.
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This shows the thickness of the protective layer. |
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Back to Top |
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Tests & Approvals |
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Philosophy
Thermal Designs philosophy regarding testing, is illustrated by the
investment made in building its own in-house test furnace, which is
the only one in the U.S.A. that meets the proposed A.S.T.M.
(American Standard for Tests and Materials) fire tests standards of:
- 1100C (2000F) Minimum maintained temperature.
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622357KJ/m2/hour (55000 BTU/Sq.Ft./per hour) heat flux.
The second example is the gaining of FM (Factory & Mutual) approval
as the manufacturer of fire-proof equipment. This approval includes
mandatory annual quality audits.
Method
The test consists of subjecting the actuator to a simulated petro-chemical
fire with a minimum high temperature of 1100 C, maintained for at
least 30 minutes.
- At regular intervals within the 30 minutes, the actuator is operated
open and/or closed and its satisfactory operation observed and
recorded by watching the continuous and smooth operation of the
valve or by measuring actual liquid flow.
- The fire temperature and the internal temperature of the actuator
are displayed and recorded throughout the test.
- The effect of thermal shock, following the application of a
fire-hose at the end of the test is also noted.
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Benefits |
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The excellence of Hytork® Fire Shield protection as described earlier
is the major benefit and represents a significant step forward in
the degree of fire protection currently offered. Additionally,
it introduces "user-abuser" protection to the fire-proof enclosure
itself. There are other benefits that may not be quite so obvious at
first sight and we list these as follows:
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East of Use: The secret of the success of
HYTORK®/FIRE SHIELD is that the carefully controlled 13 mm
thickness of material, effectively leaves the actuator available
for every day use as a perfectly recognisable ordinary actuator.
When the actuated valve is sent to site it is virtually the same
as the standard actuator, but it happens to be fire-proof.
- Integrity: Permanent full integrity is assured on
site. It is not necessary to institute special
daily/weekly/monthly visual checks to see if doors or hatches have
been left open or off, or that the fire-bag lacing or pop-studs
are secure.
- Administrative and Design Cost Savings: Hytork®
Fire Shield is specified at actuated valve procurement stage.
Subsequent to this no further planning, ordering or other action
is necessary.
- User Ready: The complete, Hytork® Fire Shield fire-proof
actuator and valve is ready for use immediately following valve
installation and actuator cabling up.
- Cost Effective: All these very evident advantages
are available at a cost comparable to the additional fire-proof
box type enclosure, but without the extra costs involved in
installing boxes or bags on site, or providing the extra space
required for box enclosures when designing pipe runs.
- Re-Usability: If a flash fire occurs and assuming
that the bulk of the Hytork® Fire Shield remains intact, light
sandblasting and repainting results in an immediately available
fireproof actuated valve, that can be replaced at a more
convenient time, if so decided.
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The comparative size of a Fire Shield Actuator (above right) and a
standard actuator.
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- Fireproof Box Enclosures:
These have been around for a number of years, but they
do have inherent weakness. They are effective as a fire protection
device when properly installed, but annoying and suspect when
every day local operation of the actuated valve is necessary. When
low on-site integrity exists, hazards are created, for example:
- Doors are left open.
- Hatches are lost.
The temptation for artisans to use
the strong-looking box as both launching and landing-pad is
usually irresistible and sometimes damaging. Once enclosure
integrity is lost the box becomes a highly efficient oven that
cooks its contents rather than protects them. Extra and separate
procurement is necessary for the supply and installation of the
box. Extra space is necessary when designing piping layouts, if
bulky fire-boxes are required.
Many of the marketing points have been identified above, but one
striking benefit from Hytork® Fire Shield is that new Hytork® Fire
Shield fire-proofing actuator, can now be the subject of a single
order placed upon the valve or manufacturer.
This reduces the contractor/constructor workload appreciably at
purchasing stage and it is to be remembered that no additional
site installation work is necessary.
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