MECHANICAL SEALS • PUMP SEALS • GLAND PACKINGS

Mechanical Seals Can Save You Money

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Lowara VS Pump Seal

ITT Lowara VS Pump Mechanical Shaft Seal
Silicon vs Silicon Carbide

IN MECHANICAL seals main friction happens in the axial direction, between faces (seal rings) lapped to a high precision. Wear is compensated in axial direction by springs or bellows.

Many mechanical seals do not wear shaft at all. Contact pressure and thus the friction force is kept to a minimum by a balanced design.

A balanced seal consumes much less power and it does not require product leakage to cool the seal faces. Actually when a mechanical seal leaks (visually seen leakage) usually it means that the seal needs to be repaired. Sometimes a perfectly normal mechanical seal leak. This is true if the sealed pressure is high. Good seals do not have visual leakage up to 50 bar and above.

Mechanical seals are generally classified into two main categories: “Pusher” or “Non-Pusher”. These distinctions refer to whether or not the secondary seal to the shaft/sleeve is dynamic or stationary. Pusher seals will employ a dynamic secondary seal (typically an o-ring) which moves axially with the primary seal face. Non-pusher seals will employ a static secondary seal (either an o-ring, high temperature graphite packing, or elastomeric bellows). In this case, the face tracking is independent of the secondary seal which is always static against the shaft/sleeve.

Several kinds of mechanical seals are available for you to use depending on the project that you are working on. They also come in a variety of shapes and sizes which makes choosing the right ones for a project’s needs a hassle-free affair. You should have all the specific seal requirements of your project listed down for reference when buying which ones to use.

The technology of mechanical seals is by no means new. It has been accepted in industry for decades. In most cases it has proven to be effective and reliable. The range of designs and materials extends from home heating circulating pumps to 380C hot hydrocarbons pumps at oil refineries or to 100 bar crude oil transfer pumps, costing from 10 dollars to 20,000 dollars and even more, depending on the industry and country.

Most double mechanical seals have a cavity defined by the sealing faces, the gland housing and the rotatable shaft through which a barrier fluid is circulated to support the correct running of both sets of faces by cooling the seal. The barrier fluid is stored in a header tank and circulated to the seal by means of inlet and outlet pipes. At present, there are two main systems for circulating the barrier fluid. The first makes use of a thermosyphon and the second a separate circulating pump.

All mechanical seals must contain the four elements described above but the way those functional elements are arranged may be quite varied. The standards of modern mechanical seals are widely defined by API Standard 682 – Shaft Sealing Systems for Centrifugal and Rotary Pumps.

A sealant is commonly described as a viscous material that has the capacity to change its state to a solidified form. This is used in order to prevent air, dust, gas, smoke and liquid penetration. The most common applications for seals include concrete and dry walls. Sealants are insoluble, corrosion resistant and have the best adhesive traits. Construction, aerospace and automotive industries benefit much from the use of these mechanical seals. Its main distinction from the adhesive is seen on the fact that sealants are not as strong as the other.

There are competent companies that provide mechanical seals for process pumps with high dependability and good value for money. Some mechanical seal manufacturers are strong in providing seals in huge quantities for automotive industry or home heating at very low cost, others are best in pulp and paper industry, third ones are very strong in making mechanical seals for the oil and gas industry.

Mechanical seals are especially needed by those machines that are in constant pressure and strain during use. Seals connect a machine’s shaft and pumps. It also sees to it that the machines last longer as it moves the seal’s point away from the shaft and into specially designed seal faces, presenting a more durable alternative than, say, lip seals (which connect directly to the shaft). This design makes the joint more resilient and less prone to unexpected breakdowns.