Field Service Inspection on Constant Spring Supports after 30 Years of Service on an Offshore Platform

March 12, 2018

Constant Spring Support after 30 Years of Service Constant Spring Support after 30 Years of Service

The use of zinc and galvanizing has a long history. The early patents for hot dip galvanizing were issued in France and England in 1836 and 1837. This technology was quickly adopted and was widely used in the late-1800s.

In the United States we have bridges more than 100 years old which have galvanized structures. In addition, we have transmission towers and substation structures that are over 70 years old. A pipe rack at a petrochemical plant near Houston was studied after 28 years of service. Measurements of the zinc thickness remaining provided a forecast of another 60 years of service.

Any coating which provides a barrier to the moisture and oxygen in the air will help protect carbon steel from corrosion. A properly painted surface will provide a barrier, but it is subject to scratching from contact with hard objects.

Constant Spring Support Inspection:

Visually inspect each Constant hanger:

Search for signs of visual cracks, fractures, and corrosion of the spring casing and the following:
(1) beam attachment
(2) pin
(3) constant hanger attachment
(4) pipe clamp attachment
(5) weldless eye nut
(6) threaded rod
(9) spring coil
(10) Check if travel stops are removed

Check (7) turnbuckle (if present), lock nuts (8) and other threaded items to ensure they are secured and fastened

Compare the position of the (10) coil with the hot/cold load indicator and operating range of the spring

Check the mobility of the (11) load column


Replacement Criteria:

– Signs of excessive corrosion or fatigue

– Rust damage of entire unit

– Modifications to operating conditions

– Consider condition of components (cam mechanisms, bearings, etc.)

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