Mechanical Seals With Fl Ushing; Mechanical Seals Balancing - OMAC B Series Operation And Maintenance Manual

5.6.3 Mechanical seals with fl ushing
• Flushed mechanical seals, as simple mechanical seals, do not require any maintenance;
• When one replaces the mechanical seal, also replace the rotating ring (pos. 224) and the lip ring (pos. 223) of the auxiliary seal.
• With fl ushing connected adequately, the pump can operate even in absence of the product to be pumped, because the seals do not risk
over-heating;
• Check that fl ushing is always effi cient, when the pump is operating, in order not to damage the auxiliary seals (connection diagram section
3.5.2);
• To disassemble the fl ushed mechanical seals, follow the instructions of the simple mechanical seals, described in this chapter;
• To remove the fi xed part of the mechanical seal, disassemble the chamber (pos. 22) from the pumping body;
• When assembling, before inserting the rotating part of the mechanical seal on the shaft, position the rotating ring properly (pos. 224) and fi t
the auxiliary sealing ring adequately (pos. 223) in its housing on the chamber (pos. 220), as per the section drawings in chapter 7, in the sections relative
to the sealing parts.
The purpose of fl ushing mechanical seals is generally to cool down and lubricate the sliding faces of the mechanical seal, via forced circulation of a
fl ushing liquid.
The fl ushing liquid and its distribution circuit must be provided by the Customer. The Customer must also check, through his Technical
Offi ce, the compatibility between the fl ushing liquid and the process fl uid, as well as the compatibility between the
fl ushing liquid and the components of the "B series lobe displacement Pump Unit" in close contact (pumping cham-
ber material, seals material, working temperature, etc.)
Once this requirement has been checked and validated, the Technical Offi ce of the Customer will see to expressly authorise the operator responsible for
the installation of the LDPU to fi t the fl ushing circuit on the seals fl ushing chamber and commission it, before starting the LDPU for the fi rst time.
ATTENTION
The operator responsible for fi tting the fl ushing circuit must be expressly authorised by the Technical Offi ce of the Customer to connect the same fl ushing
circuit to a system that uses "fl ushing liquid" compatible with the process fl uid.
O.M.A.C. s.r.l. is not responsible for improper use of the fl ushing liquid nor for damages deriving from contamination of the process fl uid.
DANGER
Improper use of the fl ushing system can cause breakage of the mechanical seals with consequent damage of the LDPU and contamination of the process
fl uid.
O.M.A.C. s.r.l. is not responsible for improper use of the fl ushing system.
The operator designated by the Customer must connect the fl ushing circuit joints to the input and output holes of the seals fl ushing chambers and adjust
the temperature and pressure according to the type of seal fi tted on the displacement pump, as described below:
• in case of single mechanical seals the fl ushing pressure must be about 1.5 - 2 bar with 0.5 - 1 lt of fl ow-rate;
• in the case of double mechanical seals the fl ushing pressure must be equal to the working pressure or higher by 1 bar, to ensure that the
fi lm created between the sliding faces of the seals is made up of the fl ushing liquid and not by the process fl uid, which according to its chemical compo-
sition may crystallise and solidify after machine down time and generate, upon restarting the unit, a "sticking" phenomenon of the faces, causing their
breakage.
The fl ushing temperature must be established according to the type of processed fl uid and to the fl ushing utility: generally using liquid at room tempera-
ture - about 15° - 20° - is necessary to disperse the heat generated by friction of the seals faces, or vice-versa, using liquid at higher temperatures, for
example 80° - 90°, can be useful for melting, removing, cleaning and lubricating the seals faces.
The dimensions of the inlet and outlet holes joints of the fl ushing circuit are listed in the table in section 1.3.9 in chapter 1.

5.6.4 Mechanical seals balancing

All mechanical seals fi tted on the B series lobe displacement pumps are equipped with a balancing ring of the fi xed parts, to cope with severe operating
conditions such as:
• pressure peaks due to the fi rst break-away or start-ups under load;
• particularly viscous or sticky product;
• frequent start-ups.
IMPORTANT
: the balancing ring must not strain on the fi xed part of the seal; check that there is slight play (about 0.05/0.3 mm).
5.6.5 Packing seals
• The tightening of packing seals is carried out when the pump is tested;
• After a few hours of operation there is an adjustment of the packing, consequently one must adjust it further, being careful to leave slight
dripping that enables lubrication of the sealing rings.
• When the dripping leakages are excessive and one cannot tighten any further, replace the packing and shaft protection sleeve.
6
Chap.5 - pag.
Via Giovanni Falcone, 8 42048 Rubiera (RE) - Italy
E-mail:info@omacpompe.com SitoWeb:www.omacpompe.com
O.M.A.C. s.r.l.
Tel.0522/629371 - 629923 Fax 0522/628980
Rev.4 del 01/2011 O.M.A.C. s.r.l.