730 m³ Pharmaceutical Cold Storage Engineering Solution for Modern Pharmaceuticals

Design Solution

Temperature & Airflow Design

The warehouse temperature control range is set at 2°C–8°C with a design precision of ±0.5°C. Equipped with humidity adjustment functions, it maintains relative humidity between 45%–75% RH to meet pharmaceutical storage humidity standards.

A dual-side ceiling air supply layout is adopted for air distribution. Four air coolers are symmetrically arranged along the warehouse length, with air outlets facing aisles to prevent cold air from blowing directly onto stacked pharmaceutical goods. Return air outlets are installed at the lower part of the enclosure to form an upper-supply and lower-return circulating airflow, eliminating temperature dead zones in warehouse corners and the bottom of racks and guaranteeing uniform temperature across the entire space.

Refrigeration System Design

A parallel alternating operation structure with twin piston compressors is deployed. The two compressors feature identical models and cooling capacities; they automatically alternate startup and shutdown during normal operation to balance equipment wear and extend service life.

When one compressor malfunctions, the control system automatically detects the fault and starts the standby unit to run at full load, providing 100% redundant cooling capacity and preventing excessive temperature deviations inside the warehouse.

The two refrigeration systems are each equipped with independent air-cooled condensers, thermostatic expansion valves and refrigerant circuits with isolated pipelines, ensuring a single-point fault cannot crash the whole system.

Backup System Design

A three-tier power protection architecture is implemented: dual municipal power circuits + diesel generator set + UPS uninterruptible power supply.

Dual municipal power supplies are sourced from different plant substations, with an automatic switch realizing millisecond-level power transfer.

A matching 30 kW diesel generator automatically starts within 15 seconds upon complete mains failure to sustain continuous refrigeration.

A 2 kVA online UPS independently powers the control and temperature-humidity monitoring systems to avoid data loss at power cut moments and guarantee normal alarm triggering.

Equipment Configuration Table

Construction Process

Installation of Insulated Cold Storage Panels

Construction shall strictly follow the working sequence: ceiling first, then wall panels, and finally the floor.

100 mm-thick Class B2 flame-retardant double-sided color coated polyurethane panels are adopted with a core density of 38 kg/m³. The gap between spliced panels shall be controlled within 1.5 mm. Neutral silicone sealant is evenly coated on joint surfaces, which are fastened by special eccentric hook connectors at a horizontal spacing of 600 mm.

A spirit level is used for calibration throughout wall installation, with verticality deviation controlled within ≤2 mm/m. Galvanized steel reinforcing frames are installed around door openings to disperse stress from frequent door opening and closing and prevent permanent deformation over long-term use.

For floor construction: a polyethylene polypropylene vapor barrier is laid first with an overlapping width of 10 cm, followed by staggered floor insulation boards. A 100 mm-thick C20 concrete slab is poured on top, with an evenly distributed load capacity of ≥15 kN/㎡ to meet forklift operation demands. All wall-penetrating pipes and wiring holes are filled with polyurethane foam and sealed with sealant to completely eliminate cold bridges.

Installation of Refrigeration Equipment and Piping

Compressors are installed on dedicated outdoor equipment platforms with rubber vibration-damping bases underneath; the horizontal deviation of each unit is limited to ≤0.1 mm/m. Condensers are mounted with a minimum clearance of 1.5 m between ventilation surfaces and walls to avoid hot air recirculation and reduced heat dissipation efficiency.

Indoor air coolers are suspended by galvanized hangers, with thermal insulation gaskets fitted at joints between hangers and ceiling panels to block cold bridges. Air outlets are tilted downward by 15° to avoid direct cold airflow blowing onto pharmaceutical stacks.

TP2 copper tubes are used for refrigeration pipelines connected by brazing. The spacing of pipe supports and hangers complies with relevant standards, and sleeves are installed for protection where pipes penetrate walls.

After piping installation, nitrogen purging and air tightness tests are conducted: the system is charged with nitrogen at 1.6 MPa and held for 24 hours; a pressure drop of ≤0.02 MPa is deemed qualified. The system is then vacuumed down to -0.098 MPa, and refrigerant charging can only proceed if the vacuum degree remains stable without rebound within 24 hours.

All pipelines are wrapped externally with 20 mm-thick rubber-plastic thermal insulation cotton and wound with aluminum foil to prevent condensation.

Installation of Electrical and Monitoring Systems

Power cables and control cables are laid separately and protected by galvanized conduits. All indoor wiring is treated with moisture-proof sealing. Explosion-proof and moisture-resistant LED lamps equipped with emergency lighting modules are installed inside the warehouse, which can provide continuous illumination for more than 30 minutes after power failure.

Dual municipal power supplies are connected to an automatic transfer cabinet interlocked with the diesel generator set, programmed to automatically start the generator upon mains power loss and shut it down when mains power is restored.

Temperature and humidity sensors are arranged in compliance with GSP requirements: one sensor at each of the four warehouse corners, one at rack mid-height in the center, and one near the doorway. The sensor height aligns with the middle layer of pharmaceutical stacks to ensure collected data accurately reflects the actual storage environment.

The monitoring system is powered by an independent UPS. Data is stored locally and simultaneously uploaded to the plant management terminal, with a data retention period of over 5 years to satisfy traceability requirements.

Commissioning and Acceptance

No-load and Load Temperature Testing

No-load commissioning is carried out first: warehouse doors are closed, and the refrigeration system runs continuously for 72 hours. The temperature and humidity system records readings from all measuring points every 30 minutes to verify temperature stability and uniformity.

Test results show temperatures at all measuring points remain steadily within 2°C–8°C, with a maximum fluctuation of ≤±0.4°C, an overall indoor temperature difference of ≤0.8°C, and no obvious temperature dead zones.

An 80% load test is implemented subsequently: simulated cargo boxes are stacked to 80% of the designed storage capacity to replicate real storage conditions, with continuous operation for 48 hours to verify refrigeration performance and defrost logic under partial load. It is confirmed that temperature rise during defrost cycles does not exceed 1°C, complying with regulatory standards.

System Function Testing

Redundancy backup functions are tested item by item:

When power supply to one compressor is manually cut off, the control system identifies the fault within 25 seconds and activates the standby unit. Warehouse temperature fluctuation during switchover is ≤0.6°C, staying within the allowable range.

When mains power failure is simulated, the UPS instantly supplies power to the control and monitoring systems, and the diesel generator starts within 12 seconds to output stable voltage, with zero interruption to temperature control throughout the whole process.

Alarm function tests cover four scenarios respectively: over-temperature, under-temperature, power failure and equipment fault. Local audible and visual alarms trigger immediately in all cases, while SMS alerts are sent to the mobile phones of 3 pre-designated managers with a push delay of ≤10 seconds, meeting GSP alarm specifications.

Acceptance Procedure

The construction contractor completes self-inspection and submits a full set of construction documents, including air tightness test reports, electrical insulation test reports and equipment commissioning records.

The client’s warehousing and quality departments conduct preliminary acceptance to cross-check consistency between equipment models, operating parameters and design drawings.

A qualified third-party pharmaceutical cold chain verification institute is commissioned to complete temperature mapping validation in accordance with GSP specifications and issue an official validation report. Final acceptance is granted only after all cold storage indicators fully comply with the Good Supply Practice for Pharmaceutical Products (GSP).

← →