MTZ Technology – Revolutionary sealing technology from
Tamar Technological Development Ltd.
What is a good seal?
Fact: Any conventional seal around a rotating shaft is prone to leakage!
In a domestic environment this is a minor problem easily fixed by a local technician. In a chemical
manufacturing process it can lead to leakage of toxic gases, dangerous chemicals, harmful powders or
slurries that require immediate process shutdown, expensive cleanup and costly production downtime. In
a steam-driven power generating plant, downtime from a leaky boiler feed or condensate pump can be a
costly nightmare.
This article discusses a variety of conventional sealing measures and introduces a revolutionary sealing
technology solution for a wide range of sealing problems.
1. The Problem:
Leakage is when a gas, liquid, powder, or slurry leaks or evaporates from a process or a mechanical
device such as a pump. Leakage in rotary equipment such as a pump is a well known occurrence and
since 1870, the technology used to reduce the leakage known as Compression Packing is continuously
being developed.
Leakage through a seal around a rotating shaft is caused by the rotational moment of the shaft
causing the shaft to bend and vibrate. Over time, this movement creates gaps in the seal allowing
material to escape into the environment.
(Fig 1) Diagram of a shaft rotating in a sealed environment:
Amount of leakage corresponds to the size of the gap, the process pressure, gap geometry and
the physical characteristics of the production process. Leakage can cause harm to humans,
animals, the environment and damage to the machine itself.
Gap
Shaft
Braided Packing
2. What is a good seal and why is it vitally important?
Although the answer seems to be simple “it should seal” there are a variety of important aspects that
should be addressed when defining what a good seal is. A better question should be – “what is the
TARGET performance of the seal?” Obviously, the target is to maintain uninterrupted production
with a minimum of interference to the process and to the environment.
Aspects of determining a good seal:
• Seal-ability – Very few sealing methods guarantee zero leakage. In many cases the
application itself does not require a 100% seal or the plant operator may not need such
ability.
Generally – A good seal provides the smallest leakage possible. (Less leakage -> Better seal)
• Operational Flexibility – The ability to maintain partial production even if the seal damaged
or the working environment goes outside of the limits of the designed seal capabilities. Such
a seal will enable the operator to complete the production quota.
• Independent – Ability to work reliably without impacting the process.
• Predictability – Ability to provide early warning when maintenance is required thus
preventing costly downtime due to seal failure.
• Cost - Minimum total cost of:
• Failure Cost– The most important parameter. What are the direct and more importantly
the indirect costs when a seal in the production process fails?
If downtime is critical to the success of a production plant an optimum sealing solution
should be urgently employed.
• Purchasing Cost – The price of the seal and its accessories.
• Installation Cost - Direct cost and installation downtime cost.
• Operation Cost – Waste of human resources, energy, production downtime and liquids
required to flush the seal, plus the cost of extracting the flushing liquid from the
process.
In general in order to flush mechanical seal minimum of 20 liter/min is required, the
amount per day is 28,800 liters, per year is about 10,500,000 liters.
The cost per year to flush mechanical seal can reach to 10,500 Euro and the cost to
extract this amount of water can cost around 21,000 Euro.
Total flushing cost for one mechanical seal can reach to 31500 Euro/year!
• Maintenance Cost – Direct cost to maintain the seal to prevent future downtime cost.
• Replacement Cost – Direct and indirect cost of removing the seal.
• Stock Cost – How many seals should be held in stock in order to maintain continuous
operation of the plant?
The above five aspects (S.O.I.P.C) define the cost-effectiveness of a sealing solution.
3. Solutions in the market
There are several technologies
Mechanical sealing, Injectable packing and for powder
a. Braided packing
The oldest solution
Graphite, Kevlar, etc
sealing area called
shaft. (See Fig 2) by a
0
10
20
30
40
50
60
70
80
90
100
0
Efficiency
Flange
Solutions in the market
technologies that can be employed to deal with leakage problems: Braided
Mechanical sealing, Injectable packing and for powder – air chamber.
Braided packing
The oldest solution, unchanged since 1870, is based on a braided material like Teflon,
, etc., (or combination of these materials) that surround
sealing area called a stuffing box. The braided material called Packing is p
Fig 2) by a bolted flange.
Cost - Effectiv (Empiric)
0 10 20 30 40 50 60 70 80 90
Slurry (% Solids in liquid)
Packing
Mechanical Seal
MTZ
Shaft
Packing
Stuffing Box
Cost effective (empiric)
deal with leakage problems: Braided packing,
based on a braided material like Teflon,
round the shaft in a
stuffing box. The braided material called Packing is pressed against the
90 100
Box
(Fig 2) Packing structure
generates heat that can
shaft. (See Fig 3)
(Fig 3) Erosion caused by Packing
To control the heat, a flushing ring i
fed to cool the seal. This often leads
Generally, Packing
� Basic Problem:
(Fig 4) FEM of Vibrating shaft sealed by compression packing
The leakage is unavoidable
) Packing structure: Friction from the pressure of the packing against the rotating shaft
that can damage the shaft and the packing and cause and erosion
. (See Fig 3)
rosion caused by Packing
o control the heat, a flushing ring is often added so that water or other material
seal. This often leads to leakages and contamination of the process.
Packing can be considered more as a leakage control tool than a seal.
asic Problem: Not a Zero Leakage solution.
FEM of Vibrating shaft sealed by compression packing –
The leakage is unavoidable
: Friction from the pressure of the packing against the rotating shaft
and erosion of the
r or other material can be
ontamination of the process.
leakage control tool than a seal.
Gap
Shaft
Braided Packing
b. Mechanical seal
The most common sealing solution, mainly
Company about 70 years ago and cont
The basic concept is based on two
another to form a seal. One face is
stationary face. (See Fig
The distance between the two faces
is theoretically prevented
increase to the point
is maintained bet
lubricating film is lost for whatever
rupture.
Since the two faces
from one another,
materials are brittle
To keep the faces
structure of this mechanical seal
wide run-outs (see Fig
Fig 5 – Mechanical seal basic concept (Wikipedia)
Rotating Face
Mechanical seal
The most common sealing solution, mainly for pumps, was introduced by
Company about 70 years ago and continues to be improved.
The basic concept is based on two hard and well-polished materials pressing against one
another to form a seal. One face is stationary and the other face rotates against the
. (See Fig 5)
The distance between the two faces stationary and rotating, is very small and thus leakage
prevented. However, due to the friction between the two faces, heat
point where the seal becomes damaged. To prevent this
is maintained between the two faces to reduce the friction and transfer heat away
is lost for whatever reason the seal may instantly become
he two faces must always remain polished to reduce friction and
from one another, they are generally made from Silicon Carbide or Tungsten Carbide.
are brittle, and limit the seal from working with wide shaft run
To keep the faces constantly pressed against one another, a spring is added
mechanical seal reasonably complicated and inefficient for s
(see Fig 6).
Mechanical seal basic concept (Wikipedia)
Stationary FaceRotating Face
by the John Crane
pressing against one
es against the
is very small and thus leakage
the two faces, heat may
this, a small film of fluid
to reduce the friction and transfer heat away. If the
instantly become damaged and
to reduce friction and transfer heat away
Silicon Carbide or Tungsten Carbide. These
run-out applications.
added making the
inefficient for slurries and
Stationary Face
There are many types of Mechanical seals; one of the most popular for gas applications is a
seal with a cooling liquid system between the two internal faces. This structure is
completely independent from the seal and does not impact upon the process it is designed
to cool.
� Basic Problem: Fragile, Sensitive to slurry and run-outs
c. Air Chamber – Lip seal
This method works mainly in dry powder applications. It is based on an area surrounded by
Teflon or Graphite V-rings and into this area (Chamber) air is constantly circulated. The
pressure in the chamber expands the V-rings and presses them against the shaft to limit the
entry of the powder.
Actually, this solution is very limited and in some cases can even be dangerous. The rings
wear down quickly and in some cases where the rings are made of rubber, they can actually
wear down the rotating shaft.
The moment the air pressure is stopped, the chamber fills with the powder. As soon as the
air pressure is restored, all the powder remaining in the chamber vents to the atmosphere
around the process. Powder in the air can be extremely dangerous in a working
environment.
� Basic Problem: Short time and Limited solution
d. Injectable packing
This method started about 20 year ago. The basic concept is to inject a material (Sealant)
made of Teflon fibers, Graphite and other combinations, into the stuffing box using a hand-
operated or electrical injector.
Since the injected material is flexible, it can track the shaft vibrations more closely and
minimize the openings that were normally created in a regular packing solution.
The main problem in this approach is the inability to control the actual pressure in the
stuffing box, as described in Fig 13.
Fig 13 - Pressure over Time graph in a regular inject able system
• Point A – The operator detects a leak and starts to inject a sealant.
• Point B – The pressure inside the stuffing box enters the Optimal Zone where there is
no leakage and no extra heat. The operator continues to inject the material in order
“to make sure” that no leak will develops.
• Point C – The pressure enters the Over Heated Zone, where the over-pressure
creates heat that the system cannot extract. In many cases, the heat burns and
destroys the sealant. In some cases it can overheat the shaft and destroy the
bearings. Such damage is not easy to repair.
• Point D – End of sealant injection. A regular stuffing box cannot hold the pressure
and the pressure immediately drops.
• Point E – The pressure drops to Optimal Zone again. If the sealant and the system are
not damaged, it starts to seal in the working operation.
• Point F – The fail point, the pressure drops to the leakage area and the operator has
to re-inject. If the sealant was damaged due to over-compression, the operator will
have to replace all the sealant.
The period of time that the seal will remain in the optimal zone pressure is unknown due to
the fact that the regular stuffing box is not designed to hold the sealant pressure in a
steady state.
� Basic Problem: Inability to control the actual pressure
4. MTZ Technology
MTZ technology combines all of the benefits of the previous methods to create a synergetic solution
that contains eight layers of protection against leakage. The result is Zero leakage even under
extreme conditions of slurry and run-outs.
MTZ Technology presents new characteristics - Eight protection layers, Sealant Stock and
Cooling Jacket:
a. Eight layers of protection:
• Layer 1: Face-to-Face sealing – The front sealing rings are pressed against the sleeve
shoulder to become a Face-to-Face sealing solution similar to a mechanical seal.
• Layer 2: Radial sealing – The sealing ring is attached to the radial sleeve similar to a
packing seal.
Air Pressure
entrance (5)
Booster (4)
Cooling Jacket (2)
Crenellated Sleeve (1)
Sealant stock (3)
Sealant (9)
Process
Sealant meters (6)
Sealing Rings (7) Sleeve Shoulder (8)
Stuffing box (10)
Sealing Rings
Sleeve Shoulder
Sealing Rings Sleeve
• Layer 3: Sealant pressure –The Booster holds the sealant at a constant, positive, Optimal
Pressure against the process. The sealant is injected into the assembly and the cartridge
seal is plug-and-play.
The seal is maintained at the Optimal Pressure zone where zero-leakage is maintained
without heating the system.
• Layers 4, 5, 6, 7: Crenellated sleeve with 4 contact areas - The special and patented
sleeve designed to maintain contact with the sealant, even under extreme run-outs.
• Layers 8 : Back sealing rings
b. Sealant stock - MTZ technology adds a sealant stock to the injectable sealant. This new
approach brings two main improvements:
• The maintenance is done automatically by the booster. When the operator needs to add
more sealant, it is added to the stock while the machine is running. This translates into
absolute minimum downtime for maintenance, it is nonstop system.
Constant Air Pressure Sealant
Booster
Contact area 1
Contact area 2
Contact area 3
Contact area 4
Shaft Openings due
to rapid run out
Sealing Rings Sleeve
• Sealant meters provide the operator with an early warning of how much sealant stock
remains. It enables them to forecast when to refill the sealant before the booster gets to
its empty position thus preventing any pressure drop and potential leakage.
c. Cooling Jacket
The Cooling Jacket enables the seal to work efficiently without affecting the process. The
cooling jacket acts like a dual-mechanical seal. The cooling water is separated from the
process by an O-ring inserted at both ends.
� The MTZ Technology does not include any fragile materials such as Silicon or ceramic, thus
it is almost unbreakable. It is nonstop system that ensures zero leakage even in tough
situations of large run outs and heavy slurry.
Sealant meters
Cooling Jacket
Sealant stock
5. MTZ seal in the S.O.I.P.C test
a. Sealability – The MTZ seal with eight protection layers provides zero leakage even under extreme
run-out and slurry environments.
b. Operational Flexibility – The MTZ seal does not include any ceramic or silicon materials and it is
an almost infallible solution. Even when the environment goes way beyond the limits of the seal,
the seal will continue to work even if in a partial manner to prevent toxic emissions and costly
downtime.
c. Independent – The MTZ seal is a dry-running seal and uses a separate cooling jacket for cooling.
It operates without impacting the process it is designed to protect.
d. Predictability – The MTZ seal has a built-in mechanism that provides operators with an early
warning of around 3 – 4 weeks before a sealant refill is required. As long there is some sealant in
the stock, a positive pressure is maintained preventing pressure drops and leakage.
Adding sealant is done on line and does not require production shut down.
e. Cost – The cost of the MTZ seal is within the range of a mechanical seal. However, the huge
advantage of the MTZ seal is its ability to minimize production down-time, adding only a very
small maintenance cost. This combined with dry-running operation; minimal on-site maintenance
means an excellent cost-effective sealing solution.
Packing Seal Injectable packing Mechanical seal MTZ Seal
Sealability Low Medium High High
Operational flexibility High Medium Low High
Independent Low Low Medium High
Predictability Low Low Low High
Cost Purchasing Low Low High High
Cost installation Low Low High Medium
Cost Operation High Low Medium Low
Cost Maintenance High Medium Low Low
Cost Replacement Low Medium High Low
Cost Stock Low Low High Low
Cost Failure Low Low High Low
Total Cost-effectiveness Low Low Medium High
6. About Tamar Technologies ( www.tamar-tech.com)
Tamar Technologies specializes in the research, design and production of sealing technology for
rotating machinery. The company can also provide engineering and technical assistance, upon
request, as part of our customer service.
Knowledge accumulated over a period of years in the realm of seals for rotating machinery enables
the company to offer the best and most reliable solutions for most kinds of machinery.
The MTZ technology is patented in US, Europe, China, India and Australia and South Africa.