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.