Tuesday, 23 July 2013

Mechanical Seals: Creation Problems and Preservation

A List of Possible Design Problems of Mechanical Seals

When working with mechanical seals, you want to maintain their usefulness and good performance so that you'll receive great results. One way to make sure mechanical seals stay in good shape is by checking design problems. Even a small defect in your sealing equipment can cost production and operation dearly.

Here's a quick guide on mechanical seal design and maintenance problems.

Issues with Faces of Mechanical Seals

Selecting the wrong hard face or carbon seals can have negative effects. The material may turn out to be incompatible with the chemical or liquid you're trying to seal. The solvent, cleaner or flush system may also not work.

Problems with Face Flatness

If the face cross portion is way too narrow, the seal will experience pressure or temperature distortion problems. To prevent this distortion, the clamping forces should be "equal yet opposite."

Weak Heat Conductivity

Compared to seals made of other materials, such as hard face seals, carbon is a relatively poor heat conductor. Plenty of other ceramic items are weak heat conductors. If you're going to use carbon, the material should be dense enough as to prevent the expansion of air pockets and the formation of pits within the carbon face. Additionally, the best option would be unfilled carbon that has four impregnates.

Springs and Bellows

Springs found in the liquid can easily clog, especially when small springs are used. There's also the problem of chloride stress corrosion in stainless steel bellows and springs.

Small cross sections of springs and thin bellow plates are considerably probe to abrasive wear, and you also want to be careful when winding a single spring because winding it in the wrong direction can cause damage.

Also, be careful with rubber bellows because when the bellows rupture, a disastrous failure is sure to follow.

Metal bellows and springs are more exposed to high stress, and stressed metals experience corrosion and fatigue faster.

Severe Operating Conditions

It shouldn't be a surprise that extreme temperatures hasten damage in industrial equipment. Although industrial materials are continually being developed to resist severe temperature ranges, elastomers and several other seal faces are quite prone to damage from excessive heat.

Too much pressure can also deform the seal faces and case extrusion to the elastomer.

Although mechanical seals tend to be exposed to high speed because of rotating seal designs, a great deal of heat can lead to the seal faces overheating. A lot of movement can also cause the shaft to break apart.

Other Design Setbacks

Among other problems, the majority of seal faces tend to be weak in tension.

To preserve the effectiveness of seals, they should be packaged very securely because storage and shipment can be very hard on these devices.

If the application calls for high speed and lots of movement, consider using mechanical seals with a stationary design.

No matter how strong the material used to make sealing equipment, mechanical seal is bound to deteriorate at some point. However, there is something you can do about delaying their deterioration. With this guide, you'll be able to target the weakness point of mechanical seals, and take better care of them.

Article Source: http://EzineArticles.com/6646416

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How to Clean Your Mechanical Seals?

With Mechanical Seals, Cleanliness is Next to Productiveness

It's a must for the seals to withstand extreme conditions-in extremely cold surroundings, under the scorching sun, settings with abrupt temperature changes, locations with toxic chemicals, and so on. To cope with these demanding applications, sealing technology is constantly changing. New and improved seals are produced so that sealing products can last longer.

On the other hand, aside from the quality of the seals, another thing companies need to pay attention to is cleanliness. Since seals prevent liquid and gas leaks, they are constantly exposed to gas bubbles, suspended solids, hazardous chemicals, and other substances that are detrimental to the life span of mechanical seals.

Now, there are a lot of devices and cleaning liquid flush systems that keep seals clean and efficient. The problem with these solutions is that operating costs can go sky-high. Large volumes of liquid flush products alone don't come cheap.

New Concepts for the Maintenance of Mechanical Seals

Using Computational Fluid Dynamics (CFD)-a system used to evaluate the effectiveness and circulation of coolants in dual seals-new innovations for controlling sealing environments have been developed. Dramatic improvements in sealing maintenance have resulted from these breakthrough innovations. As sealing environments became more controllable, many seals started to operate in cleaner fluid environments without having to use pricey flush systems.

One such new technology involves the use of two contacting seal rings used to process liquid. One of the rings rotates along with the shaft, while the second ring is mounted to the seal's non-rotating components. There's an Environ Seal Spiracle spiral groove bushing at the seal chamber's impeller end. Along with a Chesterton seal's rotating sleeve, this spiral groove bushing gets rid of the solid particles inside the chamber. Thus, while the seal is at work, it eliminates unnecessary solid specks at the same time.

During the experimental phase of this new system, flush fluid was used to see the effectiveness of the cleaning contraption. When flush fluid is being used, the liquid enters the machine via nine circumferential spaced inlets. The fluid then circulates throughout the flow domain, and then is expelled via the system's annular outlet. Both the flush fluid and solid particles are then expelled through the annular outlet and into the flow located behind the impeller.

Controlling Fluid Leakage with Mechanical Seals

The key to controlling fluid leaks in industrial machines, such as mixers and centrifugal pumps, is isolating the rotating shaft as well as its housing with a seal. Although mechanical seals are simple in design, they play a huge role in industrial applications. They even pose engineering challenges to designers.

One the other hand, to ensure mechanical seals stay fully operational, their critical components have to be protected from heat, friction, and other outside elements that can hasten deterioration. Seals' susceptibility to damage is aggravated by thermophile surroundings in which they operate.

Based on experience, industry experts have found that cooler environments allow mechanical seals to deliver more stable performance. Plus, wear and tear is reduced. However, the thing is mechanical seals absolutely have to be subjected to demanding, extreme conditions. A combination of top-quality materials and highly effective cleaning systems should allow mechanical seals to perform at their optimal level.

Article Source: http://EzineArticles.com/6620927

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Mechanical Seals at a Glance

The mechanical seal was invented by George Cook and was originally called a "Cook Seal". It was first used in refrigeration compressors. In a short time, it was becoming popular in the industrial proceeding. The demands for the mechanical seals had achieved the value about 1billion dollars.

A mechanical seal is simplified for an end face mechanical seal or a mechanical face seal. It is generally settled in rotating equipment, such as pumps and compressors. The mechanical seal is expected to prevent the liquid leak out of the pump between the rotating shaft and the stationary pump casting. In fact, with the competitive specifications, a mechanical seal does greater help than the mechanical packing which is widely used in the early times.

Generally speaking, a mechanical seal consist of four functional components: primary sealing surface, secondary sealing surfaces, a means of actuation and a means of drive. And the core part of the device is the primary sealing surface which combines two rings in a hard material like silicon carbide and a softer material like carbon respectively. The proper materials should chosen basing on liquid's chemical properties, pressure, and temperature. These two rings machined using a machining process called lapping in order to obtain the necessary degree of flatness, as one rotating with the shaft and the other being stationary. Then, there would be a number of secondary sealing surfaces require a fluid barrier but are not rotating relative to one another. And the actuation is provided to keep two primary sealing surfaces in intimate contact.

Since the mechanical seal is one of the particular seals in the industry, there exists more than one type of this term according to varied functional elements. Some common types are introduced in the following, It is generally classified into two main categories depending on whether the secondary seal to the shaft the dynamic or stationary. The dynamic one called pusher and the stationary one called non-pusher. Furthermore, there exists a common style called cartridge seal which is originally designed for installation in equipment where a component type seal was difficult due to the design of the equipment. For example, it is seen to design this type to fit pumps with varying stuffing box bore sizes and gland bolt patterns. What else, the gap seal is another type which is generally employed in bearings and other constructions highly susceptible to wear such as an O-ring.

Article Source: http://EzineArticles.com/4656883

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Monday, 15 July 2013

Mechanical Seals



There are two popular kinds of industrial seal: braided packing seals and Mechanical Seal. Braided packing seals have been all around for several thousands of years; however mechanical seals are a modern technology from the days of the invention of the automobile. Mechanical seals have rapidly found a wide range of purposes outside of the car industry, including paper and pulp industry, petrochemicals and utility sectors and many other industrial purposes where chemical processing is taken out in some type or other.

Mechanical seals are utilized when a braided packing seal is not capable to meet up with the design specification requirements. The design specifications may require a mechanical seal on cost or overall performance grounds, and even both. Mechanical seals are more costly than braided packing seals, however they have the capability to be more affordable because they are more powerful in terms of decreasing leakage or giving you higher performance in comparison to packing seals. Designers need to finely balance the use of either seal towards the need for environmental, performance and price aspects of the entire pumping system's operational performance.

The price aspect is important when deciding upon a mechanical seal: generally they can increase up to $1,400 per diameter inch, and there is also the installation and routine maintenance costs to be considered also. Mechanical seals commonly involve more customized procedure and maintenance staff to manage them in both the installation and operational stages of a pump deployment, while braided packing seal solutions do not.
Mechanical seals perform using two sealing surfaces; an inner surface performs within the pump shaft and moves around the inner shaft wall because it is fixed straight to the shaft. The second surface is attached to the shaft wall and is fixed, normally on the gland plate. The rotating, inner seal creates contact with the shaft wall towards the fixed counter seal delivering continuous seal strength and contact using hydraulic axial force or mechanical force. In inclusion, springs and elastomeric addendum's are used to manage and balance the seal connection.

The products which are utilized in the structure of the two main seals will include consideration of the operational environment first. If there is require functioning within particular temperature, pressure and other functional aspects, then the material must be capable to withstand them. When the pump is working, can the elements used hold up against the forces included, and there is also the matter of connections with the fluid itself. Cross contamination of the fluid may not be accepted, and the relative inertness of the material will play an aspect in both contamination and the effect on the reliability of the seal itself.

Cooling of the seal is necessary, as friction generates heat due to the spinning parts and constant contact. A mechanical seal will use less water than a braided packing seal for cooling purposes; on the other hand a mechanical seal will normally require water treatment to deal with the release.


Globe Star Engineers (India) Pvt. Ltd. is Professional Manufacturer of Mechanical Seals, Mechanical Seal Manufacturer, Pump Mechanical Seal, Mechanical Seal and Mechanical Seal for Pump in India.


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