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Mechanical selas according to standards

Acc. to API 610/ API 682
(API = American Petroleum Institute)
  
  
  API standards are referred to world-wide and mainly in the area of refineries.
API 610 and API 682 are relevant specifically for mechanical seals.
      
  API 610
(8th edition) prescribes specific design features and materials for mechanical seals.

Materials
Metal parts (except multiple springs): AISI 316 or equivalent
Multiple springs: Hastelloy C
Metal bellows: corrosion-proof material (max. corrosion wear 51µm p.a.)
Seal faces/ stationary seats: solid; no sprayed coating

For design specifications and materials see sealing and material code acc. to API 610 (8th edition):
     
 
1st letter B = balanced
U = unbalanced
2nd letter S = single-acting
T = double-acting (tandem/ unpressurized)
D = double-acting (pressurized with barrier pressure)
3rd letter type of cover
P = plain, without throttle bush
T = throttle bush with quench, leakage and / or drainage connection
A = additional/ auxiliary seal (has to be stated)
4th letter secondary seal materials (sep. chart on request)
5th letter face materials (sep. chart on request)
     
  Example for sealing and material code:
BSTFO = balanced, single-acting mechanical seal with throttle bush, with dynamic and static secondary seals (O-rings) made of FKM and seal faces/ secondary seats made of tungsten carbide against silicon carbide
     
  API plans for various circulation systems
The most widely used API plans (610/682):
     
  API plan 01:
Inherent product circulation from pump pressure connection to mechanical seal
     
  API plan 11:
Inherent product circulation from pressure connection via orifice to mechanical seal
     
  API plan 32:
Auxiliary flushing/ auxiliary injection with pure liquid to mechanical seal
     
  API plan 52:
pressureless, circulating quench - external vessel (thermosiphon and/or forced circulation); tandem mechanical seal
     
  API plan 53:
pressure superimposed, circulating quench - external vessel (thermosiphon and/ or forced circulation), back-to-back arrangement
     
  API plan 62:
external quench (steam, gas, water)
     
   
Typ
207A
  • single-acting
  • preassembled cartridge mechanical seal ready for operation
  • balanced
  • independent of direction of rotation
  • multiple springs (protected)
  • stationary design
 
Dimensions: 20-100 mm
(also in inches)
pmax: 50 bar
t: -20°C...+220°C
(acc. to secondary seal)
vmax: 35 m/s
 

Single seal for almost all applications in the area of refineries and petrochemical industry up to a max. of 220°C

Mechanical seal complete with throttle bush, circulation and quench connections

Universal high-quality material design with exchange components

Specifically suitable for standardization measures = shortening of repair time = increased availability factor of plant

Upgrade of MTBF/ MTBR value

     
   
Typ
851T
  • double-acting
  • preassembled cartridge mechanical seal ready for operation
  • balanced
  • independent of direction of rotation
  • multiple springs
Dimensions: 20-200 mm
(also in inches)
pmax: 50 bar
t: -120°C...+315°C
(acc. to secondary seal)
vmax: 25 m/s
 
  Operation: API plan 52

Safety tandem mechanical seal, specifically suited for sealing of easy inflammable or spontaneously inflammable media, light hydrocarbons, LPG/ liquid gas, solvents and similar media in connection with flare; also for low temperature applications.

Special seal face geometry as well as use of excl. solid seal face/ stationary seats combine to form mechanical seal with lowest level of seal face distortion when exposed to compressive load and thermic pressure - leading to higher safety of operation and improved service life.

Mechanical seal complies with TA-Luft-requirements as well as with TÜV-LPG regulation TRB 1801.

As double-acting mechanical seal in back-to-back arrangement available: style 851B
 Operation: API plan 53 (higher barrier fluid pressure) with adequate auxiliary equipment (supervision of measured values recommended) specifically suited for:
sealing of toxic and explosive media, e.g. aromatics like benzene, toluene, xylol and others.
     
      
Typ
875
  • double-acting
  • preassembled cartridge mechanical seal ready for operation
  • balanced
  • independent of direction of rotation
  • metal bellows
 
Dimensions: 30-150 mm
(also in inches)
pmax: 28 bar
t: -40°C...+400°C
vmax: 25 m/s
  Operation: API plan 52

Guided and optimized circulation guiding for better cooling in the area of seal faces

The refinery seal for "hot" pumps, for sealing of hot-oils, for hot cracking products with catalyzer, in FCC plants and others (acc. to use of adequate auxiliary equipment)
     
     
  API 682
API 682 "Sealing systems for centrifugal pumps" refers to pumps used in refineries/ petrochemical industry (hydrocarbon-processing industries).

API 682 specifies cartridge (cartridge preassembled) mechanical seals, as well as dynamic test runs for all types of mechanical seals and arrangements with defined conditions.

API 682 requires continuous operation of at least 3 years, increased safety of operation and simplified maintenance.
     
 
Arrangement and types of seals:
Arrangement 1: single seal
Arrangement 2: double seal without pressurization
Arrangement 3: double seal with pressurization
Type A: O-ring seal/group springbacking
Type B: seal with metal bellows, with O-ring secondary seals
Type C: seal with metal bellows, with graphite secondary seals
Type SD: special sealing design
     
Dimensions from 30-120 mm (also in inches)
API 682 CHETRA mech. seal Application
A1 207A
pmax:
t:
vmax:
50 bar
-40°C...+220°C
25 m/s 		universal for applications non-hydrocarbons, volatile and non-volatile hydrocarbons, alkaline solutions, amines, acids, crude oil
B1 700A
pmax:
t:
vmax:
25 bar
-40°C...+260°C
25 m/s 		hydrocarbon condensatefuel oil (heavy)hydrocarbons (general)
C1 700SA
pmax:
t:
vmax:
25 bar
-80°C...+400°C
25 m/s 		heavy gas oil; high temp. up to 350°Cheat transfer oils
A2 851T-A
pmax:
t:
vmax:
50 bar
-120°C...+260°C
25 m/s 		easy and self-inflammable media,light hydrocarbons,LPG, solvents a.o. (in connection with flare)
A3 851B-A
pmax:
t:
vmax:
50 bar
-120°C...+260°C
25 m/s 		toxic, highly explosive media, e.g. aromatics like benzene, toluene, xylol
C2 875A
pmax:
t:
vmax:
28 bar
-40°C...+400°C
25 m/s 		high temperature applications- hot-oils- hot cracking products with catalyzer (auxiliary equipment required, dep. on application)
SD 2 und 3 881D-A
pmax:
t:
vmax:
50 bar
-120°C...+280°C
35 m/s 		specifically difficult environment, such as: solid material, frequent changing of operating conditions; mechanical seal with double pressure balance
       
Materials:
Metal components 316SS
Springs: Hastelloy C (ZM.Cabot)
Secondary seals: fluorine elastomer/ graphite
Seal face/ stat. seats: hard carbon, reaction bounded silicon carbide
Throttle bush: carbon
Metal bellows: Inconel 718 / Hastelloy C
Further information on request: chetra@chetra.de
  
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