Types of Hydraulic and Pneumatic Seal
Other important part that is worth
mentioning, inside this system, in both Cylinder hydraulic and Cylinder
pneumatic there is a sealkit that placed inside the cylinder. As in other parts, the
cylinder Seal Kit also consists of several smaller parts, these parts are: Piston
Seal, Rod Seal, Dust Seal
or Wiper
and O-ring, which is the link between the cylinder parts.
Seal hydraulic comes in
many forms that suits different functions and made from various materials. The
materials used vary from standard material to heat resistant material that can
stand temperature above 100 C
Seal hydraulic comes in many shape and forms, and usually, each
manufacture uses a different type from the other. There also various materials
used depend on the type of load of the hydraulic and application of
temperature. For standard usages, materials that are commonly used are: poly
Urethane (PU), Nitrile Rubber (NBR), Hydrogenated Rubber (NHBR), Ethylene
Propylene Rubber (EPDM), Fluorine Rubber (FR) and many more special or
hydraulic This is important to know as to know how to choose a seal hydraulic.
For hydraulic seals applications
that operate at high temperatures (in hot areas such as around foundries and
furnaces), hydraulic seals come in various materials. The materials used are
usually made with; HNBR materials that can stand high temperature up to 135
degrees Celsius or hydraulic seal using EPDM materials, that can hold up to 150
degrees Celsius, can also be used, then there is FKM materials that are capable
to operate at high temperature up to 200 degrees Celsius, and PTFE
(Polytetrafluoroethylene) material which can stand extreme temperatures and
capable to operate at temperatures up to 260 degrees Celsius.
The following are the forms and
types of seal hydraulic adapted from the Sakagami
seal catalog. However, for applications with higher pressure, V-Packing
types are used for both rod seal and piston seal
depending on the needs. The stacked V Packing made the seal to be
more durable, but it is more expensive than other types. Aside from that seal
type, there is another cylinder equipped with O-ring which
functions as a static seal to prevent leakage of fluid (air or oil) from the
parts connected to the cylinder such as the cylinder tube with
end cup, cylinder tube with head cylinder or piston with rod.
In the other hand, for cylinder with
longer stroke, it usually equipped with wear ring which serves to
maintain the stability of the movement which functions as a sliding bearing. In
its practical applications, the original Cylinder hydraulic is often
modified to reduce the maintenance costs. This happens, because seal kit is
hard to obtain and/or the original cylinder hydraulic used does not
compatible to its application and resulted in cylinder underperforming most of
the time. In this case, it is better to replace the original seal (standard
seal in the cylinder) with seals in Indonesian market. The seal replacement can
also reduce the maintenance cost and in some cases can increase the cylinder
performance, because the standard seal is usually adjusted to where the
cylinder is made.
Many cylinders, which are made in
Europe or USA, used a seal with their respective country's standard which made
finding replacement for cylinder seal quite difficult. European or American
brand seals are hard to find in Indonesia except those manufactured by Hallite,
and even so certain types, market usually have no stock and be indent for up to
3 months. The brand parker which already established itself in
Indonesian market for quite long, the seals manufactured by parker are still
difficult to acquire because of the same reason, no stock and have to indent.
Because of the high cost and long
delivery time, a number of costum modification part is made and suited with
stock in Indonesian market as replacement for the brand and type that are hard
to acquire. Modification must be done with first observing some aspects, such
as: the seal material, seal mode, seal type, etc. If done properly, the
modification can maintain the performance, e.g. the amount of pressure and
resistance of the seal. Modifications should be made with little to no changes
on the dimensions of the seal holder both on the piston mount and head
cylinder.
In reality, when many changes are
done to the size of rod piston, it could cause a deformation or defect.
The rod piston or cylinder tube is usually repaired through
grinding and through re-hard chrome or by honing the cylinder tube.
Even, repair to rod piston or cylinder tube is done to reduce
cylinder maintenance cost, fatal error could occur when changes to diameter
dimension to the rod or cylinder tube is made too excessive. Because,
even after hard chrome has been done, the rod or tube would not reach the
default size. Then, changing the size (dimension) of seal hydraulic diameter
is inevitable.
By doing modifications, through
these steps, instead of reducing maintenance cost, the cost could end up to be
more expensive. Because, every time the seal kit is replaced overtime,
the replacement will be a custom made/special order because the size of
cylinder tube or rod piston already changed. For consideration, the
cost of a nonstandard seal or custom made/special order seal will be expensive
and to manufacture the seal is very time consuming. In addition, aside from the
high price of special order seals, another matter to take into consideration
is, the dimension of special seal is usually done through machining
process and not through molding process. This resulted in the dimension of
the seal being less accurate, because of miscalculation on the machine or
human (human error and machining precision). Also, as a user, we will never
know the quality of the material, because the quality of the material used is
only known by the manufacturer. That is why, when problem is found in the rod
cylinder or cylinder tube, which when repaired could caused extreme
change to dimension, it is recommended to replace the rod cylinder or tube
cylinder because it is safer and cheaper on overall maintenance cost.
Types of Hydraulic Seal (Seal Kit)
In this section we will discuss the types,
variation, and shapes of seals, and also functions of the seals that manufactured
by Sakagami (Japan) dan Hallite (Europe)
- Piston Seal
- Rod seal
- Dust seal
- O Ring and wear ring
Dimension of the Piston seal
is identical with the size of the cylinder (bore size), where dimensions diameter
of seal that need to be considered are outside seal diameter because this
refers to the size of the diameter of cylinder tube,. Then followed by
inside diameter and height of the seal refer to piston dimension as its
mounting. Products made by Sakagami the piston seal models vary
in:
1. GPY Seal
This model has dimension with
diameter ranging from 32mm to 250mm. GPY Seal model or commonly referred as GPY
Packing, has standard material (RN919) made from Nitrile Rubber (NBR) with 85
Hs hardness and tensile strength 175 kgf/cm2, also with working temperature
ranging from -30 to 100 C and most suitable for mining or excavating oil
mineral
2. RGY Seal
Seal hydraulic Model ini mempunyai ukuran dimensi dengan diameter
mulai 40 mm hingga diameter 250. GPY seal model or often referred to as GPY
Packing, is using standard material (RN923) made from Nitrile Rubber (NBR) with
hardness of 85 Hs and tensile strength of 140 kgf/cm2, and working temperature
of -30 s/d 100 C. It is very suitable for operation that uses mineral oil fluid.
More information about size and types of sakagami seal both seal hydraulic and seal pneumatic, click on seal sakagami on type of seals section and the bottom of this article.
More information about size and types of sakagami seal both seal hydraulic and seal pneumatic, click on seal sakagami on type of seals section and the bottom of this article.
Seal Installment
Seal installment of head cylinder and piston cylinder, also
O-ring, seems easy, yet many maintenance operators do not understand this
properly. This causes reduced resistance on the seal. Even, when not properly installed, leakage
will happen and it will not perform as expected in its first use.
This happen due to the direction of
the profile seal might be reversed or defect/deformation on the profile seal.
Do not rush and take your time. Because installment of some specific seals
could break your machine because the material is not elastic and placement
position is difficult (narrow gap).
Aside from seal hydraulic, leakage
also often caused by careless installment of the O-ring. This cause the O-ring shifted and
stuck, and worse, it could cause the O-ring to snap. Keep in mind, not every
seal installment is difficult and need to use equipment, like rope (rope with
plastic material is recommended) and clamp, especially when sliding a piston
inside a cylinder to avoid damage to the profile seal.
One simple thing that neglected most of the time, but can affect the life time of seal, piston rod and cylinder
tube is sanitation problem. Because of this, make sure the component parts
of seal hydraulic, cylinder tube and rod piston are clean
from dust, dirt, scrap, etc. before installing. If there is any dust, dirt, or scraps enter the cylinder or stuck in the
seal lips, it can cause leak for a long period of time.
Below are some types of seal:
1. Sakagami Seal
2. Hallite Seal
3. Seal Parker
4. NOK Seal
5. Meiwa Seal
6. National seal
7. Etc.
1. Sakagami Seal
2. Hallite Seal
3. Seal Parker
4. NOK Seal
5. Meiwa Seal
6. National seal
7. Etc.
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