PSG: Pure steam generator is widely used equipment in the Pharma industries. This equipment generates pure steam which is used to sterilize the biotech equipment, vessels, or machine parts that are used to manufacture the sterile products. In this article we are briefly dissed about the working principle, what is pure steam, pure steam specifications as per usp, PSG specifications and pure steam validations.
Pure steam generator working principle:
PSG Description and it’s working: PSG Description and its working: Pure Steam Generator is the type of boiler used for generating pure sterile steam as per Pharmacopeia Grade.
Purified water is preheated in Pre Heaters before going to the main column where it gets converted into Pure Pyrogen Free Sterile Steam by taking heat from boiler steam at 6 Kg/Cm² pressure.
Pure Pyrogen Free Sterile Steam is used for sterilization in autoclaves, pipelines, and vessels and also for humidification of the sterile area.
Controlling different Utilities as per requirement controlled through a fully automatic control panel with PLC.
Interconnecting Piping in PSG is Electro polished ≤ 0.5 Ra all contact parts, Passivation for all the Columns, Coolers, and pipelines.
Construction instructions: Minimum sharp corners, minimum crevices & ground finished welds joints and the C. Nozzles, Sanitary fittings, Dead leg ≤ 1.5 D, Slope – 1 in 100, and Double tube sheet for Evaporator and 1st Pre Heater.
Pure Steam Specification as per usp:
| Sr. No. | Tests | Acceptance Criteria |
| 1 | Description | A clear, colorless, odourless liquid. |
| 2 | pH | Between 5.0 to 7.0 |
| 3 | Total organic carbon | Not more than 500 ppb |
| 4 | Conductivity at 25°C | Not more than 1.3 µS/cm |
| 5 | Acidity and Alkalinity | Solution should not be red & blue Color |
| 6 | Nitrate | Not more than 0.2 ppm |
| 7 | Bacterial Endotoxin test | Not more than 0.250 EU/mL |
| 8 | Total viable aerobic counts | Not more than 10 CFU/100 mL |
Design Parameters of PSG system :
| Parameter | SHELL SIDE | TUBE SIDE |
| Operating Pressure | 6 (Kg/Cm2) | 6 (Kg/Cm2) |
| Operating Temp. | 165 0C | 165 0C |
| Design Pressure | 8 (Kg/Cm2) | 8 (Kg/Cm2) |
| Design Temp. | 185 0C | 185 0C |
| Hydro test Pressure | 12(Kg/Cm2) | 12(Kg/Cm2) |
PSG Major components and their utilization :
- Rota Meter: Feed Pump Discharge.
- Non-Return Valve: Feed Water Pump Discharge Line.
- Steam Trap: Evaporator Condensate removal.
- Safety Valve: Plant Steam In and Pure Steam Out.
- Pressure Gauge: Feed Water Pump Discharge, Pure Steam Out, and Plant Steam into Evaporator Column
- Level Switch: Evaporator Column.
- Pneumatic Angle Piston Valve: Plant Steam into Evaporator Column and Evaporator Drain.
- Manual Diaphragm valve. Pure Steam Into Sampling Port, Feed Pump Discharge, Pure Steam Out. and Pure Steam Sampling.
- Manual Ball valve: Evaporator Condensate Drain and in Evaporator Steam Trap Bypass.
- Pneumatic Actuated Diaphragm Valve: Feed Pump Discharge.
- Conductivity Sensor: Pure Steam Out.
- Conductivity Transmitter: Pure Steam Out.
- Temperature Sensor with Transmitter: Plant Steam In and Pure Steam Out.
- Pressure Switch: Plant Steam In, Feed Pump Inlet, and Compressed Air In.
- Pressure Transmitter: Pure Steam Out.
- Manifold with Solenoid Valve For All Pneumatic Valves.
- FRL: For Compressed Air.
| Critical Test Parameters to be tested. | |
| A | Chemical Test Parameter |
| 1. | Total Dissolved Solid |
| 2. | pH |
| 3. | Conductivity |
| 4. | TOC/ Oxidizable Substances |
| 5. | Other chemical tests as per in-house specifications (if any) |
| B | Microbial Test Parameter |
| 1. | Total aerobic microbial count |
| 2. | Bacterial Endotoxin test |
Material of construction and components details:
| SR.NO. | PARTICULARS | DETAILS |
MOC |
| 1 | Evaporator Colum 1 No. | Outer Column and Inner column. | SS 316L |
| 2 | Seamless Tubes | for Column | SS 316L |
| 3 | Pre Heater – 2 Nos. | Column | SS 316L |
| 4 | Mounting | (Tubular) Sq. Pipe) | SS 304 |
| 5 | Separator | Electro-polished 1.0 mm. | SS 316L |
| 6 | Sampling Port | SS 316L | |
| 7 | Insulation | 50 mm Thickness | RB Glass Wool |
| 8 | Cladding | Screwed, Mirror (Mechanical)1.0 mm. | SS 304 |
| 9 | Control Panel | Automatic Control Panel with the display. | SS 304 |
| 10 | Interconnecting | Plant Steam Piping, Pure Steam Line | SS 316L |
| 12 | MOC | In Contact | SS 316L |
| 13 | MOC | Non Contect parts | SS 304 |
| 14 | Gaskets | Food Grade, Temperature – 200º C | PTFE & Silicon |
| 15 | Fasteners | For still | SS 304 |
Utility Details:
| Sr. No. | UTILITY | SUPPLY | QUALITY |
| 1 | Plant Steam | At Min 6 kg/cm2 pressure and 165 °C temps. At PRV inlet. | Dry and saturated |
| 2 | Purified water | At 2 Kg/cm2 Pressure & Ambient Temperature | Cond.<2µs/cm @ambient. temp |
| 3 | Compressed Air | @ 5 to 6 Kg /Cm2 for SLV’s, Pneumatic Valve | Oil Free, Moisture Free, Lubricated |
| 4 | Electric Supply | 3 Ph / 440 VAC / 50 Hz, for equipment | 1 Ph / 230 VAC / 50 Hz for Panel |
Testing Methods and Acceptance Criteria of Pure Steam in PSG:
- Non-Condensable Gas Test: To check this test follow the following steps
- Take the volume of water displaced from the non-condensable gas collection tube, in ml for example its
- The volume of water collected in the water collection tube in ml say V2
- Percentage (%) of Non condensable gases = V1/V2 * 100 %
Acceptance criteria: The % Non-condensable gases should not be more than 3.5%.
- Dryness Value Test (D):
D = [(T2-T1) (CPW (MS-ME)+A)]/ [L(MF-MS)] – [(T3-T2) CPW]/ [L]
- L = Latent heat of the dry saturated steam.
- ME = Mass of the flask in Kg.
- MS = Mass of (flask + water charge) in Kg.
- MF = Mass of (flask + water + condensate) in Kg.
- T1 = Initial Temperature of water in the flask, in °C
- T2 = Final temperature of water and condensate in the flask, in °C.
- T3 = Temperature of dry saturated steam in °C.
- CPW = Specific heat capacity of water (4.18 KJ/kg. K).
- A = Effective heat capacity of apparatus (0.24 kj/K).
Acceptance criteria: The dryness value should not be less than 0.95
- Superheat Test :
- The temperature of expanded steam in °C, i.e. a
- The boiling point of water in local atmospheric pressure in °C i.e. b
- Superheat temperature in °C = (a) – (b)
Acceptance criteria: The superheat measured in free steam at atmospheric pressure shall not exceed 25°C.
Performance Qualification of the Pure steam in PSG.
Steam Quality Testing in PSG:
The purpose of this test is to demonstrate that the steam being produced is of requisite physical quality such that the sterilization conditions are achieved and maintained during the sterilization purposes.
The same will be established by performing the following tests:
- Non-Condensable Gas Test
- Superheat Test
- Dryness Test
Steam Quality Testing Shall be Performed as per the above details and Record the observations.
Phase-I Validation Study :
After the successful completion of Installation and Operation qualification, the initial phase of Pure Steam generation & distribution system validation shall be undertaken.
In this phase, Pure steam sampling shall be done from all sampling points i.e. all sampling points in the generation unit, all sampling points in the distribution system and all user points daily for a period of 14 days.
In this period worst-case simulation conditions should be created before the sampling, which normally occurs during routine manufacturing conditions.
During the Phase-I study, Pure steam shall be sampled for analysis as per the sampling point and user points.
Phase-II Validation Study:
This study is to demonstrate that the system shall consistently produce the desired quality of pure steam when operated in conformance with the SOPs.
The sampling shall be followed similarly to the Phase-I validation study daily for a period of 14 days. In this phase, worst-case conditions need not be simulated.
During Phase II Pure steam shall be sampled for analysis as per the sampling point and user points. After
completion of Phase-I and Phase-II a provisional Alert Limit and Action limit shall be established for the
microbial count, which shall be based on the results of Phase-I and Phase II.
Phase-III Validation Study :
The third phase of validation is designed to demonstrate that when the pure steam generation & distribution system is operated in accordance with the SOPs over a long period of time 1 year with all seasonal variations, it shall consistently produce pure steam of desired quality attributes.
During this period sampling shall be done as per the routine sampling plan, which shall be based on established procedures proven during Phase-I/II and shall include one sampling point from, the generation & distribution system being sampled & tested at least once a week.
The Pure Steam generator shall be operated for at least 1 hour every day. After the successful completion of Phase III, the Alert Limit and action limit for microbial count shall be revised based on the complete data obtained during Phase-I, Phase II, and Phase III.
DOCUMENTS of PSG system:
- DQ
- Hydro test certificate
- Trial Reports
- Certificates for Bought out components
- Calibration certificates for critical instruments
- As built G.A., P& I Diagram
- Factory Acceptance Test Protocol
- Other drawings
- IQ, OQ Protocols, and operation instruction manual.
FAQ:
What is pure steam generation?
Answer: Purified Water that has been evaporate into steam by evaporator is used in the clean manufacturing process and is referred to as Pure Steam or Clean Steam. pure steam used for Equipment sterilisation, component sterilisation, and clean room humidification. Purified feedwater is typically pumped through a shell and tube evaporator, where it evaporates when heated by plant steam and moves to a centrifugal separator to produce pure steam. The centrifugal separator works to remove any remaining moisture from the steam, creating a dry, highly purified stream of Pure Steam. It contains a controlled amount of condensed, concentrated water.
What is steam generation process?
Answer: Pure steam or clean steam generated through the PSG in which the system take pharmacopial grade purified water and converted this water into the steam with the help of external raw steam heat.
How do you make pure steam?
Answer: Pure steam made from the purified water by PSG.
What is the difference between plant steam and pure steam?
Answer: Plant steam is also called as raw steam which in generated in the boiler by converting soft water into the steam or raw steam/plant steam. But pure steam generated by PSG from the pharma gared purified water.
What is pure steam generator?
Answer: Pure steam generator i.e. PSG used for the generation of pure steam which is utilized for the sterilization.
What is called steam generation?
Answer: The conversion of the soft water or purified water into the steam by the equipment called PSG or boiler.
What is the main difference between clean steam and pure steam?
Answer: These both clean steam & pure steam are same grade steam which are generated from the purified water.
What are the two main types of steam generators?
Answer: Mainly there are 2 types of pure steam generators, one is that which generate pure steam with the help of raw steam/plant steam. In second type pure steam generated from electrical heater i.e. external source of heat.
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