Project Context
This walkthrough uses a representative refinery turnaround (TAR): a planned shutdown of a process unit for inspection, repairs and piping replacement, with a 21-day window for the piping scope on the Gulf Coast.
Turnarounds are estimated differently from new construction. The unit is offline for the whole window, so the schedule is fixed, work runs around the clock, and the owner’s lost production is far larger than the contractor’s price. The estimate has to reflect real turnaround productivity, not standard daytime rates.
What the Estimate Needs to Answer
- What piping, fittings, valves and supports are in the scope, by line and specification?
- How many welds are there, of which type and size, and how many need nondestructive examination (NDE)?
- What does testing cost when it is priced from weld counts rather than as an allowance?
- How many labor hours does the work really take on shift work in an operating plant?
Typical Challenges
1. Quantities from P&IDs and Isometrics
Process piping is quantified from piping and instrumentation diagrams (P&IDs), the line list and piping isometrics, not from architectural plans. A typical package includes dozens of P&IDs and several hundred isometrics. For each line, the estimator:
- Reads the piping class from the line list (for example a carbon steel, Class 300 specification designed to ASME B31.3)
- Measures pipe length from the isometric, by size and schedule
- Counts fittings (ASME B16.9 butt-weld, B16.11 socket-weld or threaded), flanges, valves, gaskets and bolt sets
- Counts and classifies every weld by type (butt weld, socket weld, branch connection), size and schedule, and marks which ones need NDE under the piping class and the owner’s specification
2. Material Classes and Alloy Labor
Turnaround scope often mixes carbon steel replacement with stainless or alloy piping. The takeoff keeps each class separate, because labor differs as much as material:
| Material | Labor considerations |
|---|---|
| Carbon steel (e.g. ASTM A106 Gr. B) | Baseline welding labor; preheat or PWHT only where the class requires it |
| Stainless steel (e.g. 316L) | Back purging, tighter heat-input control, dedicated grinding and handling tools to avoid contamination |
| Chrome-moly alloys | Preheat and post-weld heat treatment, hardness testing, qualified alloy welders |
Labor units for stainless and alloy work are higher than carbon steel for the same diameter-inch of weld. The multiplier should come from your own crew history or the labor unit system you use, not a single rule of thumb.
3. Pricing Radiographic Testing from Weld Counts
Radiographic testing (RT) is often carried as a lump-sum allowance. Pricing it from the weld list is more reliable:
- Number of welds requiring RT, by size, from the weld classification (the examination percentage comes from the piping class and owner specification)
- Cost per shot or per shift from the NDE subcontractor, including mobilization, radiation-safety requirements that can stop other work nearby, and reporting
- Repair allowance: some welds will fail and need repair and re-examination; carry a stated repair rate based on your own history
4. Turnaround Productivity Factors
Round-the-clock work in an operating refinery does not achieve standard production rates. The estimate applies factors for each condition that applies. The values below are an example only; calibrate them with your own records or a published loss-of-productivity study:
| Condition | Example efficiency factor |
|---|---|
| Night shift | 0.85 |
| Extended overtime (sustained 60+ hour weeks) | 0.85 |
| Confined space entry | 0.70 |
| Permit and gas-test waits for hot work | 0.90 |
Factors that apply to the same hours compound. For example, night-shift hot work with permit delays and sustained overtime: 0.85 x 0.85 x 0.90 = 0.65. That means about 1 / 0.65 = 1.54 times the labor hours of the same work on a standard day shift.
Applicable Codes and Standards
- ASME B31.3 – Process Piping
- ASME Section IX – welding procedure and welder qualification
- ASME Section V – nondestructive examination methods
- ASNT SNT-TC-1A – NDE personnel qualification
- OSHA 29 CFR 1910.119 – process safety management
- OSHA 29 CFR 1910.146 – permit-required confined spaces
Software Workflow
| Software | Purpose |
|---|---|
| PlanSwift | Pipe lengths and counts from isometrics |
| Bluebeam Revu | P&ID and isometric markups, weld mapping |
| Excel piping matrix | Line list by class, weld counts, labor factors |
Common Estimating Risks
| Risk area | Why it matters | Mitigation |
|---|---|---|
| RT carried as an allowance | Allowance rarely matches the real weld count | Price from weld counts and NDE quotes |
| Standard productivity on shift work | Labor hours understated | Apply documented factors per condition |
| Safety and permit costs left out | Fire watch, hole watch, orientation and gas testing are real labor | Price as line items |
| Alloy labor treated as carbon steel | Welding labor understated | Separate labor units by material class |
Takeaways
- Count welds, then price testing. RT follows the weld list, not a percentage of the job.
- Productivity factors compound. Price the conditions the crew will actually work under.
- Safety is scope. Watches, permits and orientation belong in the estimate.
How We Apply This on Real Bids
For industrial piping, we build the estimate from the line list and isometrics, keep each piping class separate, and price testing from weld counts. See our industrial estimating services or pricing.