P-UK
PERENCO-UK LIMITED Page
INTEGRITY 1 of 7
GROUP
LOKRING FITTING GUIDE
Piping Guide
Lokring Fitting
Guide
Issue Written By Date Approved By Date
1 N Brown 12/05/2010 D Miller 12/05/2010
P-UK
PERENCO-UK LIMITED Page
INTEGRITY 2 of 7
GROUP
LOKRING FITTING GUIDE
Contents
Purpose and Scope
Associated Documents
Abbreviations
Further Reading
1.0 Materials
1.1 Carbon Steel
1.2 Stainless Steel
1.3 Other Materials
2.0 Limitations
2.1 Pipe Geometry
2.2 Pipe Size
2.3 Wall Thickness / Schedule
2.4 Pressure Limits
2.5 Temperature Limits
2.6 Applications
2.7 Considerations for Crevice Corrosion and Cleanliness
2.8 Considerations Regarding Cracking and PWHT
2.9 Fluids
2.10 Minimum Installation Requirements
2.11 Hydrotesting
3.0 Services Acceptable for Lokrings
P-UK
PERENCO-UK LIMITED Page
INTEGRITY 3 of 7
GROUP
LOKRING FITTING GUIDE
Purpose and Scope
This guide is for use when considering the use of Lokring fittings to provide a joint in process
piping. The guide should be used when assessing the suitability and requirements necessary
to ensure an acceptable joint can be made. If, after reviewing this guide, there are still
questions on the applicability of Lokrings for an application, then consult with the Pressure
Systems Competent Person or contact Lokring for technical support.
The use of Lokring components may be considered when there is a need to make small
piping connections. The use of Lokrings requires approval by the Pressure Systems
Competent Person. The use of Lokring fittings for services other than those listed requires
written approval by the Pressure Systems Competent Person.
Lokrings use elastic/plastic preload technology to join small diameter piping up to 3” NPS and
smaller without threading or welding. The pipe is compressed first elastically, then plastically,
by the swaging action of the fittings. The fittings are installed with simple hydraulic tooling
and when properly installed by trained personnel, form a gas-tight, metal-to-metal seal without
O-rings or other elastomeric seals.
NOTE: The use of Lokring fittings in accordance with this guide exempts them from
being classified as Temporary Repairs.
Associated Documents
Lokring Installation Procedure LP-105
Abbreviations
NPS – Nominal Pipe Size
LTCS – Low Temperature Carbon Steel
SCC – Stress Corrosion Cracking
PWHT – Post Weld Heat Treatment
Further Reading
www.lokring.com
P-UK
PERENCO-UK LIMITED Page
INTEGRITY 4 of 7
GROUP
LOKRING FITTING GUIDE
1.0 Materials
1.1 Carbon Steel
Lokring carbon steel components may be used with uncoated pipe per ASTM A106 GrB.
ASTM A333 Gr6, API A53GrB and API 5L GrB.
Lokring components should receive the same surface preparation and coating system as the
piping system after installation. Carbon steel Lokrings are coated initially only to protect
against corrosion during its shelf life.
1.2 Stainless Steel
Lokring stainless steel components may be used with ASTM A312 pipe of the following
grades: TP304/304L, TP304, TP304L, TP316/316L, TP316, and TP316L.
1.3 Other Materials
Do not install Lokrings on pipe of dissimilar materials.
Do not install Lokrings on coated pipe.
P-UK
PERENCO-UK LIMITED Page
INTEGRITY 5 of 7
GROUP
LOKRING FITTING GUIDE
2.0 Limitations
2.1 Pipe Geometry
Before using a Lokring fitting the pipe external geometry and surface profile should be
checked using go/no-go Lokring gauges. For no-go gauge results Lokrings shall not be used.
Pitting to the external surface can affect the sealing ability of Lokrings. When a surface is
pitted use of a Lokring requires written approval from the Pressure Systems Competent
Person. Additional conditions may be attached to the approval.
2.2 Pipe Size
Lokrings can be used on piping up to 3” NPS.
Before using Lokrings on piping with a greater NPS size contact the Pressure Systems
Competent Person or Lokring.
2.3 Wall Thickness / Schedule
0.5” NPS 0.75” NPS 1” NPS 1.5” NPS 2” NPS 3” NPS
Carbon Steel 40 - 160 40 - 160 40 - 160 40 - 80 40 - 80 40 - 80
Stainless Steel 10s – 80s 10s – 80s 10s – 80s 10s – 80s 10s – 80s 10s – 80s
Before using Lokrings on piping with a wall thickness less than or greater than that above
contact the Pressure Systems Competent Person or Lokring.
2.4 Pressure Limits
Lokrings are limited to the ASME B16.5 pressures limits specified in the applicable material
class. For fittings used on systems rated above #300 written approval from the Pressure
Systems Competent Person. Additional conditions may be attached to the approval.
2.5 Temperature Limits
Lokrings can be used within the normal temperature range of the applicable piping material
with a temperature limit of 343°C for carbon steel and 427°C for stainless steel materials.
For low temperature limitations contact the Pressure Systems Competent Person or Lokring.
2.6 Applications
Lokrings should not be used on the following applications:
For internal piping on heaters
For internal piping on a jacketed system design
For services likely to give rise to severe cyclic stress
For the first connection from a pressure vessel
For the first connection from a Pipeline
2.7 Considerations for Crevice Corrosion and Cleanliness
Lokring design results in the production of crevices. The use of Lokrings in systems where
crevice corrosion is considered a problem should be avoided.
The existence of crevices is also a consideration where system cleanliness is required.
2.8 Considerations Regarding Cracking and PWHT
Lokrings should not be used in systems where there is a possibility of SCC.
Lokrings should not be used in systems where PWHT is required.
2.9 Fluids
Lokrings should not be used on the following services:
Chloride-contaminated Water (applies to stainless steel components only)
Hydrogen Sulphide
LPG
Acetic Acid
Sour Water
2.10 Minimum Installation Requirements
P-UK
PERENCO-UK LIMITED Page
INTEGRITY 6 of 7
GROUP
LOKRING FITTING GUIDE
Lokrings will only be installed in accordance with Lokring Installation Procedure LP-105, by
individuals who have been trained to the procedure and their competency verified by the work
supervisor.
NOTE: Tooling requirements for fitting LTCS are different from standard tooling
2.11 Hydrotesting
Hydrotesting may be required in some instances. Generally it should be planned to carry out
pressure testing to any Lokring fitted to an externally pitted surface, to full flange rating for
piping #300 or less, and to full line design pressure for all other ratings.
If Lokrings are used on piping systems rated greater than #300 then a pressure test to the full
line design pressure is likely to be required.
P-UK
PERENCO-UK LIMITED Page
INTEGRITY 7 of 7
GROUP
LOKRING FITTING GUIDE
3.0 Services Acceptable for Lokrings
3.1 The services acceptable for the use of Lokrings, subject to meeting the requirements
listed above in section 2, are:
Flare Systems
Foam Systems
Hydraulic Fluids
Hydrocarbon Solvents
Instrument Piping
Lubricating Oils/Seal
Gas
Hydrocarbons
Utilities (Air, Nitrogen and Water)
Vent Systems
Analyzer Systems
Drain Systems
Glycol
Diesel Fuel
Methanol
Propane
