Construction Management, Contracts and Quantity Surveying for Mechanical Works
This domain tests measurement, payment and contract administration for mechanical installations: how quantities are taken off, how the price list is applied, and how progress payments, adjustments and claims are handled.
Measurement rules
Mechanical quantities are measured under the applicable price list for mechanical installations, by discipline chapter (water, drainage, gas, heating, ventilation, fire). Pipe is measured in metres by nominal size along the centreline, fittings and valves by number, insulation by area or length, supports and steel by kilogram, and equipment by unit with its accessories. Use the outside diameter and wall thickness for weights - for steel pipe, kg/m = (OD − t) × t × 0.02466. Waste allowances apply only where the price list permits them; fittings, supports and testing are often already included in the pipe item, so do not add them twice.
Contract administration
Progress statements (صورت وضعیت) are prepared from measured work, checked by the supervisor, and paid against the contract; retention, advance-payment recovery, performance guarantees and price adjustment are applied as the contract and its general conditions require. Delays are analysed against the programme, and only excusable delay relieves the contractor of delay damages. Variation orders need prior written instruction; claims raised late are usually time-barred.
Worked example
DN 100 Schedule 40 pipe has OD 114.3 mm and wall 6.02 mm. Weight = (114.3 − 6.02) × 6.02 × 0.02466 = 16.07 kg/m. For 250 m: 250 × 16.07 = 4,018 kg. If the price-list rate is R per kg, the item value is 4,018 × R, before any permitted waste or adjustment factor.
Traps
Using nominal diameter instead of outside diameter; counting fittings and hangers already included in the pipe item; ignoring the contract's waste rule; and certifying a progress statement before measurement and test records are complete.