Caution
Omega
20
8.2.2
Mechanical Seal -- ”Type M74N ”
(Shaft unit d
w
= 90 mm)
This mechanical seal type is a single--acting, bi--rotational,
non--balanced mechanical seal with multiple spring arran-
gement.
It is imperative to avoid dry running of the
mechanical seal!
Special instructions for mechanical seal installation
·
Application limits
Pressure to be sealed off, p max.
25 bar
Product temperature, t
--40...220
°
C
Sliding velocity, vg
20 m/s
·
Safety
Any
work on the mechanical seal
shall only be performed af-
ter the
pump has stopped
and pump pressure has been relea-
sed.
In addition to the safety instructions contained in this manual,
the general
health and accident prevention regulations
shall be observed.
Preparations for installation
Check pump components for:
·
chamfered edge
s (sliding cones 2 mm/ 30
_
or to DIN
24960).
·
radiused transitions
·
locating surfaces
, surfaces for O--rings: fine finished Rz
10 (DIN 4768)
·
Shaft surface
in the area of the dynamically loaded joint
ring: roughness depth
R
max
5
m
m.
The shaft must be provided with the requisite recesses for
the housing screws of the mechanical seal.
Check pump for:
·
damage at the mating surfaces with the mechanical seal
·
connecting dimensions, rectangularity and concentricity to
the shaft axis
Installation
For the installation of the total seal assembly (mechanical seal,
seal housing) see operating instructions for the pump.
The shaft protection sleeves and also the surfaces of the casing
are subjected to accurate finishing processes with regard to the
O--ring seats, in order to achieve a complete and reliable seal.
Care must be taken during installation to keep these parts ab-
solutely clean, to avoid the surfaces from being damaged and
prevent entry of foreign particles.
The seat ring (8) together with the relevant O--ring (9), is fitted
into the seal cover (see general drawing). The O--ring can be
lubricated for easy sliding movement. Special attention must
be given to ensure that pressure is applied evenly. The contact
surfaces are generally fitted dry.
In mechanical seals of the
M 74 N
design, the rotating assembly
is supplied as one unit, consisting of a housing and pin ( 1 + 5),
fitted spring loaded ring (6), O--ring (2), spring (3), thrust plate
(4) and grub screws (7). The grub screws (7) must be loosened
so far as to prevent them from protruding from the housing (1)
at the inner diameter. The O--ring (2) can be slightly lubricated
to facilitate assembly.
The complete rotating assembly is pushed onto the shaft pro-
tection sleeve in compliance with the installation dimensions
which are given in the mech. seal drawing, or until it reaches the
stop on the shaft protection sleeve. Finally the grub screws are
tightened and secured with LOCTITE.
Degrease the grub
screws and insert
with a thread sealant
(e.g. Loctite). Use
new grub screws
whenever the me-
chanical seal has
been dismantled!
Item
Description
Material
No. of
items
1
Housing
Cr-Ni-Mo-steel
1
2
O--ring
Compat. elastomers
1
3
Spring
Cr-Ni-Mo-steel
1
4
Thrust plate
Cr-Ni-Mo-steel
1
5
Pin
Cr-Ni-Mo-steel
2
6
Rotating ring
Buka, Buke, Bume
1
7
Grub screw
Cr-Ni-Mo-steel
2
8
Seat ring
Buke, Buko, Buka
1
9
O--ring
Compat. elastomers
1
·
Apply a thin coat of grease to the shaft in the mechanical
seal area.
Sealing elements made of
EP rubber must never come
into contact with mineral oil base lubricants
(swelling,
possibly decomposition).
·
Unwrap the mechanical seal and inspect for damage to the
spring--loaded ring and the seat ring, the O--rings and the
mating surfaces.
Never put the spring--loaded ring and the seat ring face
down on the contact faces without the protective wrapping.
·
Thoroughly clean all components with alcohol and cellulose
tissue.
