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Jacking of flat bottomed storage tanks

Health and Safety Executive - General Safety Notice
Department Name: Hazardous Installations Directorate
Bulletin No: HID 2-2011
Issue Date: 9 February 2011
Target Audience: Chemical processing and production, Chemicals and downstream oil industries, Construction, Engineering, Warehousing and storage, United Kingdom Petroleum Industry Association (UKPIA), Tank Storage Association (TSA), Engineering Equipment and Materials Users Association (EEMUA), Chemical Industries Association (CIA). Those involved in flat bottomed storage tank design, construction, repair and use.
Key Issues: This Notice deals with safety issues associated with the jacking of large flat bottomed cylindrical storage tanks. In a recent incident such a tank fell from its jacks. No-one was injured but subsequent investigation identified a lack of clear guidance aimed at such an operation and issues that could affect long term integrity of tank floors, as well as risks to people.

Introduction:

An incident where a 54m storage tank slipped sideways on its jacks causing one side of the tank to land demonstrated the importance of proper planning and execution of tank jacking. This safety notice is aimed at operators and is intended to raise awareness of some of the issues to be considered when engaging contractors to undertake tank jacking operations. This will enable operators to demonstrate that reasonable care has been taken to ensure the competence of any third party undertaking such work. The UK Petroleum Industry Association, Tank Storage Association and EEMUA have contributed to this Safety Notice.

Background:

Tank and ground stability when jacked

It is important that the loads imposed on the jacks and the ground during any lifting operation are fully considered in planning the operation and designing the jacking arrangement. The following key issues should be included within the assessment and jacking calculations where appropriate:-

Jacking with floor attached to shell

Jacking a tank with its floor and annular ring attached may subject the shell/annular ring and floor welds to excessive stress if the weight of the floor is not supported in some way. Where a tank is jacked with its floor and annular ring attached then it should be demonstrated that either:-

Even where design codes allow lifting of the shell with the floor and annular plate intact, then the lift should be assessed for the potential for additional loads to be imposed, over and above the floor weight (e.g. ground suction). This can lead to a need for further bracing in some cases, from an adequately assessed roof, shell or temporary structures.

Working under the tank floor

Work under the raised floor of a jacked tank requires exceptional scrutiny. Where temporary support structures are used to give protection in the case of catastrophic jack failure they should be properly designed and thoroughly assessed. Supports should be on firm ground, which is not liable to weakening e.g. by subsidence. Suitability of the ground support should be reviewed as necessary during the period the tank is raised, especially if it becomes necessary to excavate around support pads.

Action required:

When planning to carry out tank jacking operations, operators should use the information above in the demonstration that reasonable care has been taken to ensure the competence of tank jacking contractors.

Relevant legal documents:

Other relevant references:

Further information:

Mr. G Hughes
HM Specialist Inspector
Health and Safety Executive
Hazardous Installations Directorate
Chemical Industries (CI 1G)
Government Buildings,
Phase 1,
Ty Glas,
Llanishen,
Cardiff CF14 5SH

General note:

Please pass this information to a colleague who may have this Product/ Equipment or operate this type of system/process.

2011-10-17