With increasing levels of sealing technology, industrial pump seal is being used by the traditional packing seal development in the machine. Mechanical seal technology with its reliable performance, less leakage, long life, low power consumption, without regular maintenance, used in metallurgy, petroleum, chemical industry industrial pump. Through years of experience, summed up in the industrial pump mechanical seal repair and maintenance of some experience, we had some effect control leakage.

First, the pump mechanical seal structure

Mechanical seal is by a pair or several pairs of vertical axis relative to the end face of the slide stretch (or magnetic) fluid pressure and compensation mechanism under the effect of keeping engage with the auxiliary sealing means to achieve the seal leakage resistance. Industrial pump mechanical seal used anti-rotation pin fixed to the lid to prevent rotation of the stationary ring. Rotating ring and stationary ring also according to whether they have the ability to compensate axial and ring called compensation or compensation ring.

Mechanical seals may leak fluid pathways have four kinds, namely, the stationary ring and the gland, the gland seal between housing, both belong to the static seal. B channel is a rotating seal ring and shaft. But face wear, it can only move with the compensation ring axially as trace, in fact, still a relatively static seal. Therefore, these leak paths are relatively easy to block. The most common static sealing rubber O-rings or PTFE V-ring, or as a rotating ring stationary ring secondary seal the compensation ring, sometimes using both functions rubber elastic element, PTFE and metal bellows structural tube. Rotating ring and the stationary ring bonded to each other relative to the sliding section of the dynamic seal. Thus, the machining of the seal faces demanding (flatness of 0.0009mm, surface roughness: hard ring Ra≤0.1μm, soft ring Ra≤0.2μm). In order to maintain the necessary seal faces between the lubricant film must be strictly controlled end face of the pressing force per unit area. Excessive pressure on the end face of the unit, difficult to form a stable lubricating film, will accelerate the wear section. Unit pressure on the section is too small, increase the amount of leakage. So, to get a good sealing performance with a long life, the installation of mechanical seals, we must maintain the pressure in the end face of the unit within the appropriate range.

Second, Leakage Cause Analysis and Maintenance

1. The installation of static leakage test. After installation of mechanical seals, generally the static test, observe leakage. As a large amount of leakage, it indicates dynamic and static ring seal problem. In preliminary observation leakage, leak site is determined on the basis of manually jigger observe, if leakage can be determined that no significant changes in style move, Deputy exist stationary ring friction problem; as media leaks along the jet axis, the ring seal Problems mostly media leaks to the surrounding water spray or leak from the cooling hole, but generally there are differences between primary and secondary, as long as careful observation, familiar with the structure, we will be able to judge correctly.

2. Leakage occurs when commissioning. Pump mechanical seal after the static test, the centrifugal force during operation of high-speed rotation, it will inhibit the media leaks. Therefore, the exclusion of commissioning mechanical seals leakage between the shaft seal failure after extreme cover, basically due to the dynamic and static ring friction caused by sabotage. The main cause of friction seal failure are:

(1) Operation, because evacuation, gas cloud, hold pressure and abnormal, causing large axial force, so dynamic and static ring contact surface separation;

(2) The installation of the mechanical seal compression is too large, leading to serious friction section wear, abrasion;

(3) Tight ring seals, spring can not adjust the axial float ring of the amount;

(4) Stationary ring seal is too loose, when the axial float ring, stationary ring from the stationary ring seat;

(5) Working medium is particulate matter, running into the friction, abrasions dynamic and static ring seal faces;

(6) The design selection is incorrect, the sealing face pressure is low or the sealing of large and other materials expand and contract. The above phenomenon often appear in commissioning, and sometimes can be adjusted to eliminate the stationary ring seat, etc., but most need to re-disassembly, replace the seal.

3. The normal operation of a sudden leak. Centrifugal pumps in operation suddenly leaking a few are due to normal wear and tear or end of life, but mostly due to large changes or operating conditions, caused by improper maintenance.

(1) Evacuated gas cloud or longer hold back pressure, resulting in seal damage;

(2) The actual output of the pump is too small, a lot of media in the pump cycle, heat build-up, causing the media gasification, resulting in seal failure;

(3) The return flow is too large, resulting in a suction pipe side container (tank, pond) at the bottom of the dregs, damage to the seal;

(4) The longer the outage, there is no manual disk drive when you restart, Mossadeq deputy due to adhesions and tearing the sealing surface;

(5) Medium corrosive, polymerizing, gumming substances increased;

(6) Environmental drastic changes in temperature;

(7) The condition frequently changes or adjustments;

(8) A sudden power failure or downtime and so on. Centrifugal sudden leak in normal operation, if not in time, tend to lead to more accidents or loss shall be seriously and take priority measures.

Third, the pump mechanical seal maintenance, overhaul should pay attention to several issues

1. Lubricating

Mechanical seal faces should be properly lubricated, which can reduce wear and extend the life of friction heat is taken away by the lubricant. General lubricants borne by the media itself, thus sealing face (ring, stationary ring) see spring pressure should not be too large.

2. Llush cooling

Pump mechanical seal work so that the end face of the heat generated should be promptly passed out, otherwise it will vaporize the liquid film is formed between the end faces of dry friction, flush cooling measures must be considered. Usually flushing coolant uses an internal sealing medium, it may also have an external water supply cooling water. In the mechanical seal use should absolutely ensure flushing coolant supply and flushing coolant flow, if necessary cleaned regularly.

3. The old and new seals update

In contrast with the new mechanical seal better than the old, but the new mechanical seal of quality or choice of material is not the time, with the larger size of the error will affect the sealing effect; in the polymerization of permeable medium, stationary ring, without excessive wear and tear, or not replaced at all. Because static ring in the stationary ring seat for a long time at rest, the polymer and impurities deposited as a whole, played a good seal.

4. Sealing overhaul

Once the mechanical seals leakage will appear eager to overhaul, in fact, sometimes sealed and not damaged, just adjust the working conditions or the appropriate adjustments to seal leaks can be eliminated. In this way, you can avoid wasting verify your fault judgment, maintenance experience accumulated improve maintenance quality.

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