Line-Stopping Service RFQs: Pipe Data, Isolation Scope and Handover

A line-stopping enquiry is more than a request for a machine and a nominal pipe diameter. The buyer is asking whether a specialist can assess a particular line, propose a suitable temporary isolation arrangement, coordinate with the operator and document the condition in which the line is handed back. Two prices cannot be compared if one includes engineering, fittings, verification and reinstatement while the other covers only a field crew and equipment. An RFQ should make those boundaries visible before anyone quotes a method.

This guide is for procurement and scope review. It gives no procedure for working on a pressurized line and cannot establish that an intervention is feasible or safe. The owner or operator and competent specialists must assess the actual system, choose and approve the isolation philosophy, control work permits and authorize execution. The existing hot-tapping and line-stopping guide explains the terminology and equipment. Here the distinct question is what evidence and responsibilities an enquiry must specify so that proposals are reviewable.

Identify the line and its design basis

Start with the line number, site and controlled drawing revisions, including the relevant isometric, arrangement and pipeline records. Provide pipe outside diameter, nominal and measured wall thickness where available, material specification, seam or joint information, coating, supports and the location of nearby welds, branches or known damage. Label unknown or unverified data as such. A line schedule copied from an old drawing is useful background but is not proof of current wall condition at a proposed intervention point.

State the governing piping or pipeline code and project requirements selected by the responsible engineer. ASME describes B31.3 as covering materials, design, fabrication, examination, inspection and testing for process piping within its scope. That public description does not approve a particular line stop or replace the operator's design review. Ask bidders to identify the standards and edition assumed in their proposal and to flag any missing survey, inspection or engineering input before fixing the scope.

State the operating envelope, not a single normal value

Provide the medium and known hazards, normal and credible limiting pressure and temperature conditions, flow direction and operational constraints, including transients the operator considers relevant. State whether the line must remain in service, whether a bypass is part of the objective, and what shutdown or process changes are possible. An enquiry that gives only normal pressure may conceal a different design or isolation case. Do not infer feasibility from a provider's advertised size or pressure range; published capability is not evidence that the particular pipe, fluid and site are suitable.

The UK Health and Safety Executive's isolation guidance is directed at duty holders developing isolation standards and addresses work control and documentation across onshore and offshore oil and gas operations. Its specialist-technique discussion notes both the potential use of hot tapping and stopping and important limitations. A quotation should therefore record assumptions and any explicit no-go condition for engineering review, rather than imply that every live line can be stopped without a shutdown.

Describe the required outcome and interfaces

Tell bidders what work the temporary isolation must enable: a tie-in, replacement, repair or another defined modification. Show the intended section and the upstream and downstream boundaries on a controlled drawing. Identify whether the contractor is to provide the fitting, isolation equipment, bypass design or components, inspection, temporary works, reinstatement and final records. If another contractor performs the repair, state who coordinates interfaces and who accepts the handover between packages. The buyer should compare complete outcomes, not assume that the word “line stop” includes every adjoining activity.

Set out the approval chain without prescribing the technique. The operator retains the responsibility to define the isolation standard, assess the work and approve permits and release. The specialist may supply an engineered proposal and execution package within an agreed scope. An independent inspector may witness specified points but does not automatically become the design authority. Our hold-versus-witness explanation shows why attendance, review and authorization must be named separately. Record which decision is required before mobilization, before intrusive work and before the system returns to service.

Ask for reviewable engineering and quality submittals

Request a proposal that identifies the assessed pipe condition, selected equipment and fitting interfaces, pressure-boundary basis, limitations, survey needs and the documents the specialist will submit for approval. Where welding or examination is in scope, request the applicable qualifications, inspection plan and acceptance records required by the project. Ask for traceability from each permanent component to its specified material and inspection documents. An equipment brochure, a generic certificate or a photograph of a prior job cannot establish item-specific conformity for this installation.

The API publication catalogue describes RP 2201 as information to assist safe hot-tapping practice and explicitly notes that a document cannot address every situation. Cite the relevant project requirement and current applicable edition as determined by the responsible authority; do not treat the catalogue description as a design approval. A provider's technical exceptions should name the missing input and its effect on engineering, price or schedule so the operator can decide whether to obtain further evidence or alter the plan.

Make quotations comparable

Ask each bidder to separate engineering review, site survey, permanent fittings, temporary equipment, mobilization, field execution, inspection, tests, bypass scope if applicable, demobilization and reinstatement. State the work location, access and lifting constraints, intended work window and documents to be supplied by the operator. Ask who owns delays caused by missing line data, changed operating conditions or a rejected feasibility assessment. These are commercial scope questions, not reasons to promise a fixed price before technical review.

For supplied fittings or other permanent products, request the item-specific manufacturing origin, condition, material and conformity evidence, availability and quoted delivery terms. Country of manufacture is not the same as the dispatch country. Record whether a proposal is budgetary, conditional or technically reviewed; a low conditional number should not be presented as a fully compliant awardable offer. Oillinko receives enquiries for manual review and routing, and does not assert that a directory listing or equipment category proves an appointed provider, stock, qualification or approved method.

Define handover before award

Specify the closeout package expected from the selected provider: approved drawings and revisions, material identities for permanent components, inspection and test results, deviations and dispositions, completion records and the status of any permanent fitting left on the line. Name the party who reviews each record and the operator's release authority. If an item remains open, the handover should state its owner and required action rather than silently treating it as accepted. Define a secure route for controlled site documents and identify what the bidder must return after review.

For a useful first enquiry, send a controlled line-data pack, the intended isolation outcome, the required responsibility split, site constraints and a list of known gaps. Then ask for a scoped feasibility response with assumptions and exceptions before comparing final offers. The hot-tapping and line-stopping service page provides the relevant Oillinko enquiry route; the Oillinko home page explains how broader technical requests are coordinated. A clear RFQ makes a serious specialist easier to assess while leaving the engineering and authorization decisions with the people accountable for the actual line.