Double mechanical al seal
Savino Barbera horizontal pumps can also be equipped with double mechanical seal:
- Unpressurized dual seal in “tandem” arrangement.
- Primary seal: Savino Barbera mechanical seal (product side).
- Secondary seal: conventional commercial mechanical seal
General technical features
Our conventional horizontal pumps are designed to be easily equipped with double mechanical seal without
modifications, by simply adding a secondary seal and the relevant flushing connections. In this case, the
advantages of an “atmospheric side” seal is added to the common features of the single mechanical seal.
Two seals mounted in the same direction. The primary seal accomplishes the sealing function for the liquid being pumped (product side) whereas the secondary seal carries the pressure of the auxiliary fluid (atmospheric side).
Circuit independent from the liquid being pumped: the circulation of the auxiliary fluid occurs by means of the
differential pressure to the atmosphere. It can be made with open circuit (from external source) or with close
circuit (circulation from a reservoir).
Auxiliary fluid function
The auxiliary fluid has the function of separating, washing, cooling, condensation vapors. It usually circulates at a pressure not much greater than the atmosphere (0,3÷0,4 bar) and anyhow lower than the pumped liquid.
Auxiliary fluid features
The unpressurized auxiliary fluid, coming from a separate circuit, can have room-temperature. It must be clean, with good thermal conductivity and high boiling point. It must not be toxic, inflammable, explosive, or viscous. It must not contain vapor or impurity.
Compatibility between auxiliary fluid and pumped liquid
Clean water is usually ideal for this duty. The compatibility between pumped and auxiliary fluid must be verified to
exclude unwanted dilutions, exotermic chemical reactions, contaminations, explosions. The only possible exchange
is from the liquid being pumped to the auxiliary fluid.
Primary seal materials
|Stationary ring||Rotating ring||Gasket||Spring||Bellow|
|EPDM – FPM
Savino Barbera mechanical seal is available in different materials in perfect compliance with industrial pumping
needs. The possible combinations of seal faces material are innumerable: they are selected based on the specific
duty or the chemical nature of corrosive liquids. Obviously, our experience is always of great support for selecting
the best configuration to apply for the specific case.
The rings are manufactured with Sintered Ceramic or Silicon Carbide. They are also available in filled PTFE, but only for specific cases.
The mechanical seal bellow is made of PTFE: chemically inert material with great characteristics of self-lubricating and minimum friction coefficient.
The metal spring has a protective coating made of PFA, a chemically inert fluoropolymer, resisting all chemical agents and with low permeability.
Static element gaskets
The static ring gaskets are made of ethylene propylene rubber (EPDM) or fluorinated rubber (FPM). Alternative material for special applications: PTFE.
Secondary seal materials
The secondary mechanical seal (atmospheric side) is a conventional mechanical seal that is made-up of a spring and a rotating ring made of 316 stainless steel, a Carbon Graphite stationary ring and EPDM gaskets.
Mechanical seal for special applications
Our double seal pumps are the ideal solution when facing specific phenomena of the liquid (vaporizations or crystallizations), when operating conditions require extra safety features (tanker trucks, rail cars and tankers offloading) or in the event of a pump being accidentally dry run (pumps operating without liquid: not an uncommon occurrence at start-up!). In fact, this solution can solve the problems that a single mechanical seal may encounter: vaporization of the lubricating film, risk of seal faces sticking, crystallization of the pumped medium. In all of these cases the benefits of a secondary seal are directly reflected on the main mechanical seal, internally mounted, which may run and survive the event.
The horizontal pumps provided with a double mechanical seal are especially appropriate for services with very high risk of dry-running, as during loading and unloading of tanker trucks: the auxiliary cooling circuit allows a good service of the seal without any drawback, even when the liquid is no longer flowing inside the pump. This is, therefore, a useful environmental protection against possible leakage of liquid or vapor.
- Generic protection in case the pump may accidentally run dry.
- Less risk of sticking of the primary seal faces.
- No more liquid and vapor leakage, also when the mechanical seal is working properly.
- Correction of seal rings instability: in some cases (rotation speed, frictional overheating, boiling point of the liquid…) the liquid film between the faces may vaporize or may not develop correctly.
- Compensation of the pumped liquid when some factors (viscosity, thermal conductivity, boiling point, abrasive particles…) alter the lubrication and the cooling of the sliding parts.
- Barrier against air passing through the seal rings: the pressure of the hydraulic circuit can, in fact, be lower than the atmospheric pressure.
- Safe truck and tanker loading and unloading (permitting the dry-running of the pump).
- Pumping concentrated hydrochloric acid (avoiding damages caused by acidic vapors).
- Safe operations at very low temperatures (assuring the use of horizontal pumps with icy conditions).
- Chemical baths such as nickel or copper plating baths (contrasting possible solidifications).
- Safe start-up of empty pumps even in case of long standing in storage (occasional use of horizontal pumps).
- Pumping of aggressive fluids with crystals, oxides or suspensions (eliminating liquid to atmosphere contact).
Savino Barbera mechanical seal catalogues & manuals
Download here technical sheets of our pumps with mechanical seal:
|Savino Barbera single mechanical seal|
|Savino Barbera double mechanical seal|
Mechanical seal pump or mag-drive pump?
When choosing between mechanical seal pumps and magnetically driven pumps, incorrect installation habits may
be misleading. For example, we are sometimes asked to provide magnetic drive pumps for services not compatible with hermetically closed pumping: those who prefer magnet assembly can in fact presume that magnet coupling is the safest system compared to mechanical seal. However, while it is true that the mechanical seal is more easily subjected to leakages, on the other hand the supposed leak-proof design of mag-drive pumps can become a problem due to the nature of some liquids. To make an attentive technical choice, we invite you to read this section:
|Mechanical seal design VS sealless magnetic design|
Horizontal mag-drive pump (BM Series).
Horizontal mechanical seal pump (OMA Series).