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seal selection training


Seal Selection Internal Training
EBCN, 2009

Inhalt

Parameters for mechanical seals
Stuffing box pressure

bar
Rotation speed

U-1
Rotation direction Operating temperature Product / Medium / Viscosity °C

Shaft size / Size / Build shape
These parameters are the minimum requirement.

Pump pressures
Suction pressure [1]
Stuffing box pressure [2] Delivery pressure [3] Design pressure Vapour pressure Barrier pressure 1

3
2

Operating Data – Sealing Pressure pA, also named p1
At one-current, single-stage centrifugal pumps with back vanes in the impeller: pS < pA < pE. For water and media similar to Formula for approximate values: water with ?=1
N=1500 min-1: pA ? pS + 2/3 H*? N=3000 min-1: pA ? pS + 1/3 H*? pA ? pS + 2/3 (pE-pS)
H PE

pA ? pS + 1/3 (pE-pS)

PS

PA=?

Only the machine manufacturer is able to specify the actual sealing pressure.

Source: Burgmann Lexikon

Influence of shaft size

Vg =

Dm* n *? 60.000

Vg = Linear face speed [m/s] Dm = Mean face diameter [mm] n = Speed [r.p.m.]

Influence of rotational direction
Springs ? Cw or ccw springs ? Spring independent of rotation direction Pumping screws ? Cw or ccw rotation

? Rotating/stationary, counter rotating

Influence of temperature
? boiling point (depending on pressure)

?
? ? ?

Viscosity
Polymerisation Metal deformation Deformation due to Pressure, Temperature etc. Aggressiveness of product (Corrosion)

Influence of medium
? Specific gravity
? Concentration, crystallisation, solid particles Lubrication ability, build design, seal operation Material choice

? pH

Material choice Vapour pressure in seal gap

? Vapour pressure
? Melting point

Seal rotation direction
? Pour point

Influence of measurements (Specification)
? Diameter of shaft and shaft shape ? Diameter of shaft sleeve

and shaft shape
? Diameter of stuffing box ? Length of stuffing box

? PCD (pitch circle dia.)
? Number of bolts ? Maximum installation length

? Positioning of connections
? Reference dimension from housing to shaft sleeve Reference dimension

Additional influences
? Hydraulic loading ? Surface finish ? Face material paring ? Cooling and lubricating properties of medium ? Oscillations ? Shock

? Lack of lubrication
? Process cycles ? Poor heat transfer

Influence of measurements (Specification)
Pump standard API610 eg: OH2, BB3 pump ISO5199/ASME B73.1 Seal standard

API682
H75, MFL, HR, SH…

Cartridge: Cartex, Mtex, Unitex
Component: H7, M7, HJ, MG1, MFL…(seal gland provided by pump vendor)

eg: Goulds: 3196, IC Moret: MFR FS: Mark 3 KSB: CPK

Cartex Operating Limits

p1 [bar] Sliding materials

d1 = 25 - 100 mm (1"...4") t = -40 ...+200°C (-40°F...428°F)

25

Carbon graphite/SIC

12

SIC/SIC

8

Please observe operating limits of O-rings p1 = product pressure

10

16

vg [m/s]

API682 Classification of Sealing Systems
… … …

...

API682 Seal Selection

1): 2): 3):

A specific application may require another seal arrangement. Please contact Burgmann for further information. A specific application may require additional or different flush plans. Please contact Burgmann for further information. The Burgmann seal type and the required flush plans are depending on the specific service conditions.

Annex I TTV O-rings
Coefficient of thermal expansion for PTFE

TTV O-ring

Design related arrangement (main assembly direction)

Annex II/1 hydraulic of the mechanical seal (reverse pressure)

Annex II/2 hydraulic of the mechanical seal (reverse pressure))

Annex II/3 hydraulic of the mechanical seal (reverse pressure)

P3

Annex II/4 hydraulic of the mechanical seal (reverse pressure))

P3 > P1 P1

Annex II/5 hydraulic of the mechanical seal (reverse pressure)

P3 > P1
P1

Ah

D d

dh

Annex II/6 hydraulic of the mechanical seal (reverse pressure)

P3 < P1 P1
Ah

D d

dh

Annex II/7 hydraulic of the mechanical seal (reverse pressure)

Ah

dh d D

Annex III Vapour curve
P Delta temperature to vapour curve Liquid Vapour pressure Gas phase

Temperature

T

Annex IV Leakage assumption
1.000.000,000 100.000,000 2 drops/sec. 10.000,000 1.000,000 100,000 Liter Gush ? 1,6 mm 10,000 1,000 0,100 0,010 0,001 1 Minute 1 Hour 1 Day 1 Week Time 1 Month Gush ? 6,4 mm Gush ? 3,2 mm Steady drops 1 drop/sec.

Gush ? 4,8 mm

Annex V Function of a pumping screw
Circulation for: ? ? Media Barrierfluid media

Annex VI Sense of direction
Coolant OUT Coolant OUT

Type ?B“

Type ?A“

Drive side

Coolant IN

Pumping direction ?from drive“

Pumping direction ?towards drive“

Coolant IN

Direction of shaft rotation: cw (looking from the drive)

Annex VII Types of a pumping screws

Pumping screw rotating

Pumping screw stationar

Pumping screw contra-rotating

Annex VIII Secondary seals , temperature-limits
0C/32F - 30C/-20F - 40C/-40F - 20C/-4F Nitril Butadien Rubber + 100C/212F Perbunan* Ethylen Propylen Dien Rubber + 150C/302F (never use with any oil Static + 140C/284F (water) O-rings EPDM Fluor Carbon Rubber Viton* Nitril Butadien Rubber, Perbunan* + 75C/167F Ethylen Propylen Dien Rubber, EPDM Fluor Carbon Rubber, Viton* (never use with any oil) + 140C/284F (water) + 150C/302F (oil) + 75C/167F (water) Temperature Dynamic O-rings + 200C/392F + 75C/167F (water)

Temperature
- 20C/-4F - 20C/-4F - 5C/23F

Annex IX Thermal Conductivity of Face Materials
Carbon Carbon CrMo Al.Oxide Tungsten Silicon

(resin)

(antimony)

Carbide

Carbide

140 120 100 80 60 40 20 0 B-carbon A-carbon S-Bume5 V-Al-Oxide U2-WC 99,5% Q1-SiC

[ W/mK ]

Annex X Chemical Resistance of Face Materials
Carbon Carbon CrMo Al.Oxide Tungsten Silicon

(resin)

(antimony)

Carbide

Carbide

14 12 10 8 6 4 2 0 B-carbon A-carbon S-Bume5 V-Al-Oxide U2-WC 99,5% Q1-SiC

[pH-Value]

Annex XI Hardness of Face Materials
Carbon Carbon CrMo Al.Oxide Tungsten Silicon

3500 3000 2500 2000 1500 1000 500 0

(resin)

(antimony)

Carbide

Carbide

[ HB ]; [ HV ]

B-carbon A-carbon S-Bume5 V-Al-Oxide U2-WC [HB] [HB] [HB] 99,5% [HV] [HV]

Q1-SiC [HB]


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