From Cairo to Guangzhou: One Hardware Question, Two Grid Environments
8 October, 2026
TEL: +86-158-5877-7327
A shear head that breaks off is not, by itself, proof of a correct termination. The lug may still contain a partly inserted conductor, the wrong centering insert, damaged strands, trapped metal filings, or an unsupported cable construction. A controlled shear bolt lug installation therefore starts with model and cable verification and ends with a traceable inspection record.
This guide is for trained cable jointers and supervisors working on de-energized, isolated, grounded, and proven-dead LV or MV systems under an approved method statement. The exact lug instructions and the cable accessory kit instructions take priority over every generic step below.
Do not release the work from the permit stage until the team can match the lug, cable, terminal, and insulation system. Select the exact model from an approved mechanical lugs and connectors range, not only from a family headline such as 25–630 mm².
| Item to verify | Required evidence | Stop-work condition |
|---|---|---|
| Conductor | Material, cross-section, actual construction, class, round or sector shape, and diameter | Cable type is absent from the model selection table |
| Lug | Manufacturer, exact model, range, palm hole, bolt count, and batch marking | Marking differs from the approved bill of materials |
| Insert or sleeve | Part, color, position, and conductor range from the manufacturer’s table | Required insert is missing, damaged, or unidentified |
| Accessory system | Termination or joint kit, voltage class, cutback dimensions, sealing method, and compatibility approval | Lug dimensions or surface are not approved for the kit |
| Tools | Specified socket or hex key, holding tool, cable preparation tools, cleaning materials, and file if required | Correct bit, support tool, or work instruction is unavailable |
For MV work, verify the lug body diameter and finished bolt surface against the termination or separable connector envelope. An electrically suitable lug can still prevent the stress-control or insulation component from seating correctly.
Set the insulation cutback from the exact lug or accessory instruction. Do not estimate it from the visible barrel length. The prepared conductor must reach the internal stop while leaving the insulation edge in the position required by the sealing or stress-control system.
For aluminum conductors, many manufacturer instructions require the oxide layer to be removed with an approved brush immediately before insertion. Use jointing compound only when the lug is prefilled or the instruction identifies an approved compound. Do not add, remove, or mix compounds based on site habit. Copper conductors should receive only the preparation specified for the selected product.
A range-taking lug may use an insert, centering ring, or sleeve to position smaller conductors. Its purpose is not simply to fill empty space: it controls conductor location and the way bolt force reaches the strands.
Use the exact selection table supplied with the lug. Confirm the insert part or color against the conductor material, cross-section, construction, and diameter. “Use the tightest ring that fits” is valid only when the product instruction says so. Never cut, stack, reverse, or omit an insert to make the conductor enter.
Back out the shear bolts only far enough to clear the bore. Several manufacturers specifically instruct installers not to remove the bolts because removal can introduce dirt, damage threads, or lead to incorrect reassembly.
Push the conductor fully to the barrel stop without losing strands at the entry. For a sector conductor, follow the orientation shown in the model drawing. Do not rotate or pre-round the conductor unless the instructions require it.
Some prefilled designs require the lug to be rotated after insertion to distribute inhibitor. That action is product-specific. Once the conductor is seated, align the palm with the equipment terminal or accessory interface without applying bending stress to the cable. Hand-tighten every bolt until it contacts the conductor; this stabilizes the assembly before final tightening.
A CONWELL BLMT shear-bolt mechanical lug. Model markings, conductor range, palm hole, bolt arrangement, and instructions must agree with the installation package.
There is no safe universal sequence for every shear-bolt lug. Depending on the design, instructions may require sequential tightening from the cable-entry side toward the palm, alternate one-turn tightening across all bolts, or a separate pattern for three-bolt bodies. Copy the manufacturer’s diagram into the method statement and number the bolts on the inspection sheet.
The following controls apply regardless of the sequence:
Do not apply a generic torque value found in another catalogue. The shear feature is designed around a specific bolt and lug body. Tool limits, initial tightening stages, and final shear behavior must come from the exact model instruction.
An acceptable result normally requires every specified head to shear cleanly at the position defined by the manufacturer, with no loose bolt, cracked body, damaged thread, or conductor movement. A head that breaks unusually early, remains high enough to obstruct the insulation system, or fails to shear is a nonconformance until the manufacturer or project engineer provides a disposition.
The shear-head condition controls the conductor-side connection. The palm-to-equipment fastener is a separate joint and must be tightened to the equipment manufacturer’s specified torque using the approved washer and locking arrangement.
Perform the conductor-side inspection before installing heat-shrink, cold-shrink, separable connector components, boots, or covers. Verify that the finished lug dimensions, palm direction, and cable position match the accessory instruction. Photograph the completed lug before it becomes concealed.
CONWELL lists its BLMT family for low- and medium-voltage terminations up to 35 kV, with a 25–630 mm² family range divided into individual model bands. The product page identifies a high-strength aluminum-alloy body, aluminum-alloy bolts, and a tin-plated surface. The BLMT mechanical lug information does not publish one universal strip length, insert schedule, or tightening sequence for every listed model, so those items should be requested before site work.
Installers and distributors can also review the broader cable lug portfolio and the intended mechanical cable connection application, but approval must remain tied to the exact product documents supplied for the order.
| Record field | What the inspector should capture |
|---|---|
| Asset identity | Project, circuit, cable ID, phase, location, equipment, and termination or joint kit |
| Cable | Manufacturer, cable designation, conductor material, shape, construction, cross-section, and diameter where required |
| Lug | Manufacturer, exact model, palm hole, bolt count, batch or traceability code |
| Preparation | Specified and measured strip length, square cut, undamaged strands, cleaning method, and compound status |
| Insert | Required or not required; part, size, color, and fitted orientation |
| Bolt installation | Numbered sequence, holding method, tool and bit, permitted power-tool setting, and installer |
| Final condition | All heads sheared, head count recovered, remnant condition, filings removed, caps fitted, and conductor fully seated |
| Equipment joint | Palm fastener size, specified torque, achieved torque, calibrated-tool ID, washer and locking arrangement |
| Evidence | Before-and-after photographs, inspection status, nonconformance reference, names, signatures, and date |
Stop and remove the lug only if the manufacturer’s procedure permits correction. Check the cutback, insert, conductor shape, strand condition, compound distribution, and bolt clearance. Do not shorten strands or force the conductor with impact.
Quarantine the termination. Record the bolt position, tool, setting, insert, conductor data, and photographs. Premature shearing can indicate an incorrect sequence, side loading, wrong insert, damaged thread, or an incompatible conductor.
Compare it with the acceptance image or dimensional limit in the instruction. Do not file deeply, re-torque the remnant, or proceed with an MV insulation component until the disposition is approved.
Do not close the accessory. Search the work area and all insulation components. A metal fragment trapped inside an MV termination or joint is an avoidable defect.
It indicates that the specific bolt reached its designed shear condition, but it does not verify conductor preparation, full insertion, insert selection, sequence, or accessory compatibility.
Many instructions require brushing immediately before insertion, but the exact brush, method, and compound treatment must follow the lug and cable accessory instructions.
No. Use the diagram for the exact lug. Similar-looking products may use different sequential or alternating patterns.
Only when the manufacturer permits it and states the required bit, tool condition, setting, and tightening method. The lug body must remain supported and the tool aligned with the bolt.
For a shear bolt lug installation quotation, submit the cable data sheet, conductor construction and diameter, voltage class, termination or joint kit, terminal drawing, quantity, delivery schedule, and required test and inspection documents through CONWELL’s contact page. Ask the supplier to return the exact model, conductor selection table, strip length, insert schedule, numbered bolt sequence, permitted tools, shear-head acceptance criteria, and traceability documents before installation begins.
TEL: +86-158-5877-7327
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