Repairs and modifications

Prior to undertaking any repairs or modifications a risk assessment should be carried out and work planned to include the identified control measures. Systems and procedures should be introduced as necessary (see section 6) so that all people involved are aware of their duties and

responsibilities and can perform the work safely. Repairs and modifications, particularly those involving work on pipework and tanks that have contained petrol, may need to be agreed with the relevant enforcing authority prior to commencing work, except in emergencies where notification may be sufficient.

8.9.2 Tanks 8.9.2.1 General

Generally any corroded or defective tank or pipework should be replaced. Where a compartment of a multi-compartment tank is found to be leaking, the whole tank should be considered to be defective and all fuel should be uplifted from each compartment in the tank. No compartment of the tank should be used until a competent person has inspected the tank. A detailed inspection and assessment by a competent person may indicate that repair rather than replacement is feasible.

A comprehensive inspection report should be prepared that includes details of:

− tank age;

− type of backfill;

− prevailing ground conditions;

− visual examination of the internal surface;

− location and extent of corrosion or defect;

− the cause (internal or external), and

− readings from extensive ultrasonic thickness testing of the whole tank.

An assessment should be provided of the anticipated continuation of the corrosion and the effects this might have on the likely future integrity of any repair. A risk assessment may indicate the need to take steps to abate the continued corrosion by, for example, a suitable system of cathodic protection (CP).

8.9.2.2 Single-skin tanks

Only competent contractors who specialise in this type of work should carry out repairs. The SMS for the work should provide well documented procedures covering safety and all factors involved with the repair together with the standards to be achieved at each stage of the work and how these will be assessed.

8.9.2.3 Double-skin tanks

It will be necessary to determine whether the leak is in the outer or inner skin and what caused the fault before deciding on an appropriate course of action. A leak in the inner skin, providing its position can be determined, can be repaired by patching or alternatively by lining the tank. A leak in the outer skin will necessitate replacing the tank or lining it with a double-skin system where the interstitial space can be monitored.

For a recommended procedure if the interstitial monitoring alarm activates see section 11.7.

8.9.3 Pipework 8.9.3.1 General

Any defects in pipework found during either testing or inspection should be brought to the attention of the site operator together with recommendations for remedial action. This could include a recommendation to take the pipework out of use. Before pipework is modified or extended it should be tested for integrity and where possible inspected. If such pipework

shows signs of corrosion, deterioration, damage or adverse falls it should be replaced (but see 8.8.3). After the modification or extension has been carried out the pipework system should be tested before being brought back into use.

8.9.3.2 Steel pipework

Where steel pipework is repaired or extended this should be by means of a permanent joint (i.e. socket or welded joint). If this is not practicable then a long thread and back nut (i.e. removable) may be used provided the joint is located in an inspection chamber for accessibility and inspection.

Generally welding is not undertaken on filling stations that have been operational because of the risk of flammable atmospheres being present. If, however, welding is considered necessary it is essential to ensure that all necessary precautions are taken to provide gas free conditions and that a PTW is issued by a competent person before work starts. Reference should be made to HSE Guidance note Cleaning and gas freeing of tanks containing flammable residues, CS15, and section 6. Practical advice on identifying hazards and implementing appropriate control measures and systems of work during maintenance and other non-routine activities, together with advice on hot work and on PTW systems on identified high risk activities can be found in the HSE Approved code of practice and guidance, L137.

When working on any existing steel pipework (including the flexible pipe connecting the dispenser to the suction line), an earthing bridge should be fitted across any joint or section of pipework before it is disconnected or cut. The purpose of the bridge is to maintain earthing continuity to avoid the risk of incendive sparks should stray currents be flowing in the pipework. To ensure continuity the bridge connection should be attached to clean uncoated metal. This will necessitate the reinstatement of any pipework coating and protection when the work is completed to reduce the risk of corrosion to the steel at that point.

8.9.3.3 Non-metallic pipework

Where repairs or modifications to non-metallic pipework are required they should be carried out according to manufacturer's recommendations and the advice contained in 8.5.5.3.

8.9.3.4 Dropped suction lines

The term 'dropped suction line' is used to describe a short riser pipe that interrupts the continuous fall of suction pipework from the pump to a tank. Dropped lines should not be incorporated into suction pipework on new installations but may be used in certain exceptional circumstances as a method of overcoming inadequate fall back from pump to tank or insufficient cover on the pipework on existing sites. Where a dropped suction line is installed the following provisions should be incorporated:

− A permanent notice bearing the words 'beware dropped line' should be fastened to the termination points on the relevant suction pipework (i.e. the angle check valve housing or line test T-piece fitting in the access chamber and the flexible connector in the pump housing).

− The vertical section of dropped line should be located in either a dropped line dedicated liquid-tight access chamber or liquid-tight tank access chamber.

− The vertical section of the dropped pipework should be provided with a removable plug at its base to facilitate draining. There should be sufficient space underneath the drain plug to enable collection of liquid.

− The forecourt surface and reinforcement should be reinstated to provide the required standard and necessary load-bearing protection for the pipework.

− The site plans should be annotated accordingly.