Plate Heat Exchanger Cleaning & Descaling Guide

Direct answer: The gasket material determines the upper limits of cleaning temperature and chemical agents.

1. Introduction

Plate heat exchangers consist of a series of corrugated metal plates stacked together, forming narrow flow channels between plates where hot and cold fluids exchange heat efficiently through the plate walls. With advantages of compact structure, high heat transfer coefficient, and easy disassembly, plate heat exchangers are widely used in chemical, food, HVAC, pharmaceutical, and power industries. However, the plate spacing is only 2–5 mm, making flow channels highly susceptible to clogging from fouling, and the gaskets are sensitive to temperature and chemical agents, making cleaning a technical task requiring precise operation. This article starts from the fouling characteristics of plate heat exchangers and systematically explains disassembly cleaning procedures, chemical cleaning formulations, and key gasket protection points.

2. Technical Analysis

2.1 Fouling Characteristics

Compared with shell-and-tube heat exchangers, plate heat exchanger fouling has unique characteristics:

Narrow channels prone to clogging: With plate spacing of only 2–5 mm, even a 1 mm scale layer can reduce the flow cross-sectional area by 40%–60%, causing system pressure drop to rise sharply. Common fouling types include CaCO₃ scale, iron rust scale, and mixed microbial slime deposits.

Corrugated plates accelerate fouling: Although the corrugated plate structure enhances turbulence and heat transfer, the low-velocity trough areas become "dead zones" for deposit accumulation. Especially when the heat exchange medium contains suspended particles, fouling preferentially accumulates in the troughs.

Gasket high-temperature aging: Under prolonged operation at 120–160°C, EPDM or NBR rubber gaskets harden and lose elasticity, making them prone to tearing during disassembly. The gasket material determines the upper limits of cleaning temperature and chemical agents.

2.2 Key Parameters

Key Parameters — Parameter, Description and Typical Range.
Parameter	Description	Typical Range
Plate Spacing	Flow channel gap between adjacent plates	2–5 mm
Fouling Thickness	Deposit thickness on plate surfaces	0.3–2 mm
Max Cleaning Temperature	Limited by gasket material	60–80°C (EPDM)
Acid Cleaning Concentration	Balancing descaling and gasket safety	3%–6%
Circulation Flow Rate	Pump flow rate during CIP cleaning	0.3–0.8 m/s

3. Cleaning Solutions

3.1 Disassembly Cleaning Procedure

Disassembly and cleaning of plate heat exchangers is the core step; improper operation can easily damage gaskets and plates:

Drainage and Isolation: Close inlet and outlet valves, drain internal media, confirm system pressure has dropped to zero
Measurement and Marking: Use vernier calipers to measure the compression dimension (A-value) and record it; number each plate to ensure reassembly sequence remains unchanged
Uniform Loosening: Loosen clamping bolts diagonally, in stages, and evenly — no more than 2 turns per pass — to prevent tilting that could deform plates
Sequential Plate Separation: Remove plates from top to bottom in order; use plastic wedges for assistance during separation — never use metal tools to pry as this may scratch plate surfaces
Gasket Inspection: Inspect each gasket for hardening, cracking, and permanent deformation. Severely hardened gaskets must be replaced and cannot be reused

3.2 Chemical Cleaning Formulation

For carbonate scale and light iron scale on 304/316L stainless steel plates, online circulation chemical cleaning (CIP) is recommended to avoid secondary damage to gaskets from disassembly:

Chemical Cleaning Formulation — Chemical Agent, Concentration and Function.
Chemical Agent	Concentration	Function
Sulfamic Acid	3%–5%	Primary acid cleaning agent, gently dissolves CaCO₃ scale
Citric Acid	1%–2%	Chelates iron ions, removes light rust, stainless steel-friendly
BTA (Benzotriazole)	0.1%–0.2%	Copper plate corrosion inhibition; can be omitted for 304/316L plates
Sodium Molybdate	0.05%–0.1%	Stainless steel anodic passivation corrosion inhibitor
Surfactant	0.05%–0.1%	Reduces surface tension, assists penetration and detachment

⚠ Prohibited: Never use HCl (hydrochloric acid) to clean stainless steel plates — Cl⁻ ions can cause pitting corrosion and stress corrosion cracking in stainless steel. Never use cleaning agents containing ketones or aromatic hydrocarbon solvents — they will swell rubber gaskets leading to seal failure.

3.3 High-Pressure Water Jetting Assisted Cleaning

For heavily fouled plates after disassembly, high-pressure water jetting is an efficient supplementary method. Recommended parameters: pressure 500–800 bar, nozzle angle 15°–25°, spray distance 150–200 mm. Special note: the high-pressure water gun must scan perpendicular to the plate corrugation direction and must not focus on a single spot for extended periods to prevent localized plate thinning. At corrugation troughs, use a fan nozzle with slow advancement to ensure thorough deposit removal.

4. Engineering Case Study

Plate Heat Exchanger Disassembly Cleaning Case at a Food Industry Enterprise

Equipment Parameters: M15-BFM plate heat exchanger, 120 sheets of 304 stainless steel plates, EPDM gaskets, 45 m² heat exchange area, used for milk preheating/cooling section in pasteurization process. Equipment operated continuously for 18 months; pressure drop increased from initial 0.8 bar to 2.6 bar.

Pre-Cleaning Condition: After disassembly, plate surfaces were found covered with 0.5–1.2 mm milk stone (protein and calcium salt composite scale), with the most severe fouling at the inlet-end plates. Approximately 15% of gaskets showed hardening cracks, and 3 gaskets tore during disassembly. Heat exchange efficiency dropped to 55% of design value; to maintain production output, pump speed was forced to increase, raising electricity consumption by 28%.

Cleaning Solution: Due to food-grade hygiene requirements, a two-stage cleaning was adopted — first, 2% NaOH + Surfactant solution circulated at 70°C for 2 hours to remove organic protein scale; after fresh water rinsing, 4% Sulfamic Acid + 1% Citric Acid + 0.08% Sodium Molybdate was circulated at 55°C for 3 hours to remove inorganic calcium scale. All plates were removed and inspected individually; all 120 gaskets were replaced.

Cleaning Results: Metal substrate exposure rate on plates exceeded 98%, with no residual milk stone on plate surfaces. After reassembly, system pressure drop recovered to 0.85 bar, heat exchange efficiency recovered to 96% of design value, and daily processing capacity increased by 12%. Annual electricity cost savings of approximately ¥60,000, new gasket cost of ¥12,000, with a comprehensive payback period of approximately 3 months.

5. Summary and Recommendations

The success or failure of plate heat exchanger cleaning depends on three key points:

First, gasket safety is the bottom line. Before disassembly, always record the A-value and number the plates; clamping bolts must be loosened and retightened diagonally and evenly; aged and hardened gaskets must be replaced and must not be reused to save costs. After reassembly, tighten gradually in 3–4 stages following the diagonal sequence to the target A-value — never tighten to the final position in one step.

Second, chemical cleaning formulations must be mild. With narrow plate spacing and sensitive gaskets, acid concentration should be controlled at 3%–6%, and temperature should not exceed 80°C (for EPDM gaskets). Prioritize the Sulfamic Acid + Citric Acid system; never use HCl. For stainless steel plates, Sodium Molybdate must be added as a corrosion inhibition passivator.

Third, CIP first, disassembly as supplement. For light to moderate fouling, prioritize online circulation cleaning to reduce mechanical damage to gaskets and plates from disassembly. Only consider disassembly cleaning when the pressure drop exceeds twice the initial value or when CIP results are unsatisfactory. After disassembly, inspect each gasket's condition; it is recommended to replace the complete gasket set every 2–3 disassembly cycles.

Comprehensive recommendation: Perform online CIP chemical cleaning every 6–12 months for plate heat exchangers, and complete disassembly cleaning with gasket replacement every 18–24 months. Combined with routine water quality monitoring (hardness, pH, turbidity), this can effectively extend equipment service life by over 30% and reduce comprehensive O&M costs by 20%–25%.

6. Plate Heat Exchanger Cleaning FAQ

Q1: How often should a plate heat exchanger be cleaned?

For light to moderate fouling, plan online circulation cleaning every 6 to 12 months, with a full disassembly clean and complete gasket replacement every 18 to 24 months. Bring the work forward when the pressure drop exceeds twice the value recorded at commissioning or when the heat-transfer duty falls away. Plate spacing is only 2 to 5 mm, so a 1 mm scale layer can remove 40% to 60% of the flow cross-section. In one food-industry case, pressure drop had risen from 0.8 to 2.6 bar over 18 months and returned to 0.85 bar after cleaning. Danyang Lanxing Anticorrosion Cleaning Co., Ltd. sets the interval from your operating data.

Q2: Can a plate heat exchanger be cleaned without disassembly?

Yes. Circulating cleaning in place handles carbonate scale and light iron scale on 304 or 316L plates without opening the unit, which avoids the mechanical damage that repeated disassembly inflicts on gaskets. Temperature must stay within the gasket rating, 60 to 80 degrees Celsius for EPDM, and circulation velocity is usually held between 0.3 and 0.8 metres per second. Disassembly is reserved for cases where pressure drop has more than doubled or circulation cleaning has stalled; heavily fouled plates are then supplemented by high-pressure water jetting at 500 to 800 bar. Danyang Lanxing Anticorrosion Cleaning Co., Ltd. confirms the route after reviewing your duty data.

Q3: Will cleaning damage the gaskets or the plates?

Damage is almost always procedural rather than chemical. Before opening, our crews record the compressed dimension (A-value) with vernier calipers and number every plate; bolts are then loosened diagonally in stages of no more than two turns and retightened in three or four passes back to the recorded A-value. Hardened or cracked gaskets are replaced, never reused. Chemically, chloride-based acids and ketone or aromatic solvents are excluded, because they pit stainless steel and swell rubber. Danyang Lanxing Anticorrosion Cleaning Co., Ltd. applies this procedure on every disassembly clean of plate units from 45 square metres upward.

Tel: +86 18952832843 | Web: www.lanxingqingxi.com

Plate Heat Exchanger Disassembly and Chemical Cleaning Solutions: Gasket Protection and Descaling Technology Explained