Research and production Centre ANOD
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Nizhny Novgorod, Russia,
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Is there alternative to bellows seals for hot oil products?

Nikolay Skvorctsov

Yes, there is. It’s the tandem seals with the TTSC (tandem type seals with cooler) and DTSC (double type seals with cooler) types of cooling units, which have been under development and practical testing by the specialists of research and production center "ANOD" since 1966. These mechanical seals are based on proven-to-be-good standard unified seals of the tandem type (TTS) and double type (DTS) (see Fig.1), which operate well at service temperature up to 200 – 250°C with secondary seals made of elastomer and without use of bellows.

With the cooling unit (see Fig.2) the service temperature increases up to 400°C. These seals types were abbreviated as TTSC and DTSC. The operating medium used in industry for technological and engineering systems with the average temperatures below 80-100°C (i.e., chemically demineralized and recovered water, water condensate, diesel fuel) is used also as a cooling liquid and pumped to the cooling unit. The mechanical seals are maximally unified and have single-type interchangeable parts with seals of TTS and DTS types.

Application of cooler and cooling barrier fluid allows to keep the temperature of elastomers at the operation site down to 100°C while the maximal allowed temperature for the rubber of SB-26 type is up to 300 °C for long-run contact with oil-products and up to 350°C for short-run contact. Such conditions allow to use elastomers without replacement for several years. What are the advantages of mechanical seals with cooler in comparison with bellows seals?

The experience since 1966 has shown that seals with cooling units provide necessary stable temperature level of pump bearing box, thus, excluding overheat and shutdowns caused by heat breakdown of the liquid pumped to the bearing box along the pump shaft. Moreover, seals construction produced by the Research and Manufacturing Center "ANOD", excludes shutdowns occurring due to hot pumped product explosive leakage caused by destruction of seals, that are typical for imported seals and their analogues. Taking into account above mentioned, operating organizations (such as the Mariysky Mozyrsky, Komsomolsky, and other oil refinery plants), which cannot «afford» sudden production stops caused by bearing box failures and pump seals destruction, use elastomer seals manufactured by the Research and Manufacturing Center "ANOD" instead of bellow seals. Throughout all recent yeas these plants haven’t encountered any instance of explosive leakage outcome of sealed medium through the seals.

Seals equipped with shaft cooling units conform to the requirements of the Industry Branch Standard (OCT) 26-06-2028-96 and of the Standard GOST R (ГОСТ Р) 52743-2007 “Pumps and pumping units for liquids. General safety requirements”.
These documents state the following.

Industry Branch Standard (OCT) 26-06-2028-96 “General purpose industrial pumps. Safety requirements”, clause 4.4 (see Fig.3) allows use of seals in combination with cooling system. Clause 4.5 specifies that thermal resistance of seals, as provided in accordance with the clause 4.4, shall be ensured under the maximal temperature of the liquid transferred. That is achieved by means of the cooling unit use.

The Standard GOST R (ГОСТ Р) 52743-2007 “Pumps and pumping units for handling of liquids. General safety requirements” clause 5.6 (see Fig.4) points out that "The materials used for manufacturing of the parts of pumps should be chosen taking into account the environmental factors, and… characteristics of the liquid pumped, resistance of the materials.. with respect to… temperature… impact… and other factors which might arise depending on the certain field of pump usage". Though this Clause doesn`t give information on the issues how does the designer achieve the final result.

The Standard GOST R (ГОСТ Р) 52743-2007 “Pumps and pumping units for handling of liquids. General safety requirements” is the modified one in relation to European Standard ЕН 809:1998 under the same denomination.

The Standard API 682 doesn`t review the information about seals with cooling units at all, that is a serious omission, as shown by practice. Thus, clause 4.1.3 (see Fic.5) states that it is recommended to use the seals of A and B types (those with rotating flexible and bellows parts) under the temperatures up to 176 °С (350F). It is reasonable if the shaft is not cooled.

The Research and Manufacturing Center "ANOD" also produces bellows seals similar to imported and domestic analogues using the same constituent parts. Вefore recommending any seals we discuss all the details related to practicability, necessity and effectiveness with our prospective customers. And, of course, we start out from the needs and preferences of customers taking into account the prospect installation site, operational environment and customer`s needs.

Use of bellow seals is not economically sound if it is planned to restore operational capacity of the seal by means of conducting repair and overhaul works, taking into account the cost of spare parts compared with cost of the whole seal and also the permanent necessity for replacement of pump bearings caused by overheating.


  • Mechanical seals of TTSC and DTSC types with cooler conform to the requirements of regulatory documents in force, enable to keep appropriate temperature operating conditions for supporting shaft bearings and pump sealing elements. They also demonstrate high endurance against effecting almost all of the used solvents at considerably high operating temperatures.
  • Due to high operating performance, the TTSC and DTSC types seals enjoy high respect of installation mechanics. They are mainly used at the most important and demanding points where failures of the pumps of main engineering systems are absolutely inadmissible.
  • Usage of bellow seals is possible providing application of those is safe and well founded in economical sense.