Tube Sheet Drilling for Large Heat Exchangers

Customer Background

The customer is a heat exchanger manufacturer producing shell-and-tube units for power plants and industrial process plants. Each exchanger’s tube sheet — the circular plate that holds the tubes — carries a dense pattern of holes that must be positioned to the tube pitch and drilled cleanly through the full plate thickness. Hole position and bore quality decide whether tubes slide in, seal, and hold pressure for the exchanger’s service life.

The Challenge

Tube sheet drilling is a precision and productivity problem on a large scale:

Hundreds of holes per sheet. A large tube sheet carries up to 300 tube holes in a strict pitch pattern. Every hole must land at its grid coordinate — a missed position at the edge of the sheet still fails the tube fit, so accuracy has to hold across the whole 3-meter plate, not just at the center.

Thick sections demand deep-hole technique. Tube sheets range from 200mm to 800mm thick. Drilling Ø20–40mm holes through these sections requires gun drilling or BTA — chip evacuation and straightness — rather than conventional twist drilling, which wanders and clogs at depth.

Mixed tube sizes on one sheet. Exchangers commonly combine small tubes (Ø15–20mm) and large tubes (Ø25–40mm). One machine must cover both without tool-system changeovers between sizes.

Paired-hole pitch. Many tube layouts use a fixed pitch that repeats across the sheet. Drilling these holes as pairs at a matched center distance is faster and holds spacing better than positioning every hole individually.

Leak-tightness depends on the bore. A torn or stepped tube hole can become a leak path between shell side and tube side. The bore must be clean, round, and concentric so the tube-to-sheet joint seals under hydrostatic test and holds pressure for the exchanger’s life.

Long drilling programs. With hundreds of holes per sheet and multiple sheets per order, chip evacuation and coolant delivery have to stay reliable through the whole program — a clog mid-run costs more than the hole it stalls.

The Solution

RuidCNC supplied a Deep Hole Drilling Machine for Steel Plate (RD3020-06S) configured for tube sheet production:

• Dual spindles at 170–220mm adjustable centerline spacing — matched to the tube pitch, each tube-hole pair drilled in one pass across the pattern
• Gun + BTA drilling in one machine — Ø10–20mm gun drilling for small tubes and Ø20–40mm BTA drilling for large tubes, no tool-system changeover between sizes
• 800mm hole depth — continuous passes through the thickest tube sheets
• 3000 × 2000mm worktable, 20-ton capacity — full circular sheets held in a single setup, keeping the tube-pitch grid registered across the whole plate
• 2–10 MPa high-pressure coolant with 2000L tank — sustained chip evacuation over long, dense tube-hole programs
• Reinforced 50-ton machine structure — rigid under 20-ton sheets for stable hole position edge to edge

Key Machine Specifications

Parameter	Specification
Gun drilling range	Ø10 – Ø20 mm
BTA drilling range	Ø20 – Ø40 mm
Max hole depth	800 mm
Spindles	2 (centerline 170–220 mm, adjustable)
Max workpiece diameter	Ø3,000 mm
Worktable	3000 × 2000 mm
Max load capacity	20 tons
Coolant pressure	2 – 10 MPa

Results

Metric	Single-Spindle Tube Sheet Drilling	RD3020-06S	Improvement
Holes per shift (Ø25mm BTA × 600mm)	380	700	84% increase
Tube-hole pitch error	±0.08 mm	±0.03 mm	63% better
Tube-bore roundness	0.030 mm	0.012 mm	60% better
Hydrostatic first-pass yield	92%	99.4%	Leak-tight
Cycle time per sheet (240 holes)	8.5 hours	4.6 hours	46% reduction
Setups per tube sheet	2	1	Eliminated

Process Validation

The process was validated through:

• Tube hole position and pitch measurement on a CMM across the full sheet
• Bore roundness and surface finish inspection on sample holes
• Tube insertion trial and hydrostatic test of a representative exchanger
• First-article dimensional inspection against the drawing

Conclusion

The RD3020-06S converts tube sheet drilling from a slow, single-hole operation into a two-hole-per-pass process. With dual spindles matched to the tube pitch, mixed gun and BTA capability, and a table that holds the full sheet in one setup, the customer increased holes per shift by 84% while improving tube-hole pitch accuracy and reaching a 99.4% hydrostatic first-pass yield. For heat exchanger manufacturers whose tube sheets carry hundreds of pitch-accurate holes that must seal, the RD3020-06S is a direct path to shorter lead times and leak-tight tube fits.

Figures are representative of typical applications.