Overview - Pipefreezing
Pipefreezing is an essential tool in the maintenance of all
types of liquid storage, process and transfer plant. The
range of applications in which pipefreezing can provide
cost effective solutions is both extensive and diverse,
from a small domestic water pipe to a huge oil pipeline,
from a hospital heating system to a brewery bulk storage
system, the freeze can be applied quickly and the results
are reliable.
 If
you need to isolate plant or equipment, or simply wish to
replace a leaking valve, the most practical solution to
the problem in terms of time and cost is pipe freezing.
 MCL
technicians can quickly apply freezing jackets to the pipe
upstream and downstream from the offending piece of equipment.
Diameters of pipe up to 48 inches can be frozen using our
standard range of equipment, and for larger or unusual applications
special custom equipment can be produced economically.
The
majority of liquids can be frozen and quickly form an ice
plug which provides a positive seal against fluid flow.
MCL
technicians can monitor the temperature and maintain the
condition of the ice plugs while your personnel carry out
the necessary rectification work.
The
ice plugs can be maintained over a period of days or even
weeks where necessary.
For a professional, reliable pipe freezing service
OUR REPUTATION IS YOUR GUARANTEE
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Advantages
Before
draining your system consider the advantages of pipe freezing:
-
Reduces down-time
- Eliminates
the need for costly liquid transfer and storage
- No
drain-down time or re-venting
- Provides
isolation for high pressure testing
- Provides
isolation for leak detection
- Avoids
contact and handling of toxic or corrosive liquids
- May
enable associated plant sharing the same system to continue
operating
In
general terms, the method of pipe freezing used by MCL is
carried out by clamping a specially designed insulated "jacket"
around the pipework at the point to be isolated, providing
an annular space between the pipewall and the inner skin
of the jacket. A cryogenic refrigerant, namely liquid nitrogen,
is then introduced into the annular space, creating a bath
around the pipe at cryogenic temperatures.
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Ice
Plug Formation
As
heat is exchanged between the pipe contents and the freeze
system, the temperature of the contents is reduced and an
ice plug gradually forms from the outer wall inwards towards
the centre of the pipe.
Meanwhile,
liquid nitrogen evaporates, is vented off, and is replenished
from a storage vessel. Once the ice plug is formed, suitably
checked and pressure tested, the pipe can be broken into
and work carried out. The ice plug can be maintained for
an indefinite period (dependant on liquid nitrogen supply)
until the work is completed and the pipework made safe.
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Purging
The
term purging means the replacement of an atmosphere of undesired
composition in an enclosure by another atmosphere of required
composition.
Purging
may be carried out for a variety of reasons, which fall
under two main headings:
-
To prevent fire or explosion where flammable or explosive
materials are present
- To
avoid unwanted reactions between materials being handled
and the atmosphere
In
the majority of cases, the requirement is to replace an
active atmosphere by an inert one, in MCL's case, almost
exclusively using Nitrogen.
Nitrogen
(N2) is used because it is fast, easy, cheap and in some
cases, the only practical way of achieving the objective.
Nitrogen, which constitutes almost 4/5 of air, is odourless,
tasteless, non-toxic and practically inert. The purity at
which Nitrogen is supplied, is chemically un-reactive and
inert towards a very wide range of materials. It is virtually
insoluble in most liquids and other materials commonly used
in the industry.
It
is necessary to consider the three distinct methods of purging
with Nitrogen, i.e.:
- Displacement
purging
- Dilution
purging
- Vacuum
cycle purging
Perlite
Injection
Vessels
which store low temperature liquid gases such as LNG, Nitrogen,
Oxygen, Propane, Butane are invariably insulated with Perlite.
After
some years in service settlement of the Perlite creates
cold spots on the outer sections of the tank showing its
failure. This failure of the insulation has the undesirable
affect of increased boil off resulting in wastage of product.
The
service we offer for the topping up of the Perlite is undertaken
whilst the tanks are in service and does not affect the
production process. We are also able to undertake removal
of old and ineffective Perlite and replace with new.
Our
specialist team are fully trained and their expertise makes
them totally aware of the hazards, examples of which are
as follows:
-
Gas flammability / explosion risk
- Gas
toxicity
- Gas
pressure
- Static
electricity
- Personnel
accident risk due to high working on tank perimeters
A
full inspection service is available to access the level
of the tank needs.
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Purging
& Helium / Nitrogen Leak Testing Package
The
leak detection package has been designed to best meet the
clients needs for location of leakages on pipelines / tanks
/ vessels, both offshore and onshore.
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Leak
detection on a cross country pipeline using several
pipe freezes. Each section of pipe between freezes
can be pressure tested independently to determine
the position of the leak
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Within
our equipment package we have the following portable equipment
ready to move to site for effective working:
- 2
x 90K nitrogen converters (90,000 s.c.f/hour)
- 2
x leak testing cabins complete with masspectrometer
and standard accessories
- 6
x 14,200m3 nitrogen tanks (standard 20ft I.S.O.)
- 1
x water bath vapouriser with output capacity of 13,000
s.c.f/min @ 350 P.S.I.
Each
of our leak testing team consists of six men, all fully
trained within their own specialised field.
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