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Optimizing Your Steaming Operation: A Steam-In-Place Primer

by Pietro Perrone

Steaming is an important operation in a facility that handles biological products. When applied properly it provides reassurance for microbiological control and safety. The main function of steam in a process is to expose the equipment to a sufficiently high temperature for a specified time to achieve destruction or reduction of the unwelcome organisms. Selecting an appropriate steaming arrangement is important as it can have a significant effect on the cost and operation of the plant since a typical production facility can include many steam points. This article identifies the main Steam-In-Place (SIP) components and the various ways they can be arranged at the steam/condensate collection points. The article also provides guidance on how component selection can shift costs between capital and operating budgets while helping to determine if an automated steaming operation can provide a satisfactory return on your investment.

Steaming operations

Fundamental Steam-In-Place (SIP) processes consist of three main steps/activities:

  1. Apply steam.
  2. Remove condensate.
  3. Monitor temperature and time.

Engineers have developed a variety of innovative ways to implement these steps into the specific constraints of a process. The different ways are often a balance between the components used at the steam points and the amount of labor needed to monitor and validate the effectiveness of the steaming operation. A satisfactory steaming operation is one that yields an acceptable level of confidence in the steaming operation and one that:

  • confirms that a microbiologically effective temperature and exposure time is achieved, and
  • removes steam condensate effectively.

There is an array of components that can be applied to achieve an effective SIP operation. Several representative SIP arrangements are presented in Figure 1. Although each arrangement varies in the level of complexity, they all can provide effective steaming.

Figure 1 . Typical steaming arrangements at steam/condensate collection points. Three are for manual operation and two for automatic operation. Alternate permutations of these are possible with equivalent SIP capability.

Manual diaphragm valve (Fig. 1A) - manual operation.

This arrangement is the simplest method to steam. The primary function of the diaphragm valve is to isolates process lines from the steam manifold which typically is also the pipe specification breakpoint. This valve can be used for steaming if the valve is opened slightly to allow passage of steam or condensate. This option is the least expensive from a component perspective. It is, however, costly in terms of steam loss and it can be environmentally unfriendly. Additionally, this simple arrangement requires the most attention to record and validate that sufficient steaming is occurring. The combination of labor cost and the wasted steam cost make this an operationally expensive option.

Orifice plate (Fig. 1B) - manual operation.

Using an orifice plate that allows steam to escape continuously provides for another simple operation. It is easy to implement and is relatively reliable since there are no moving parts. The orifice provides more consistency than just opening a diaphragm valve. Similar to the diaphragm valve arrangement (Fig. 1A), the cost for components is low. The amount of labor to monitor and validate operations is significant. Correspondingly, the labor cost and wasted steam cost make this process operationally expensive.

Ball valve with orifice (not shown)

Replacing the orifice plate with a ball valve that has a small orifice provides for an improvement in operation. This setup is relatively simple as well. It has the same cost advantages and disadvantages as the orifice plate. Since a valve is replacing the orifice plate, it can be used for flushing the process pipe at process flow rates. The valve “closed” position allows the steam to pass through the orifice. The other, “open” position of the ball valve is for the full flow of flush liquid. This allows for flushing of the diaphragm valves and the corresponding process and steam lines.

The steam trap - an effective component for energy utilization.

Steam traps are typically applied in steaming operations. They are effective in extracting the most energy from steam. Although the complexity of the operation increases when a stream trap is added to the operation, the additional material cost is offset by the energy savings that result from minimizing steam loss. Steaming operations need to be analyzed from an engineering perspective to optimize heat transfer. Piping arrangement and effective removal of air from the piping is important for effective heat transfer. A detailed tutorial (1) on the thermodynamics can be found at the Spirax Sarco website ( www.spiraxsarco.com/learn ). The steam trap is a critical component in the process. Its function is to maintain a closed system for the steam while allowing condensate to exit.

Three types of steam traps are available. They are classified by the method each uses to separate steam from condensate as described in Table 1. You can find a detailed description on the features of each unit in Millipore's Technical bulletin, Lit. No. TB011EN00 (2) . The thermostatic type is the one most appropriate in biotech/biopharmaceutical applications. The steam trap maximizes energy utilization but increases the complexity of the operation. This complexity includes additional piping that needs to be cleaned. Since the steam condensate flow is relatively low, the standard steam trap hinders a full flow flush of the process line that is often needed for Cleaning-In-Place (CIP) protocols. Both of these issues are addressed in the steaming arrangements and components shown in Fig. 1C-E and described in the upcoming sections.

Table 1 – The types of steam traps

 

Mechanical

Thermodynamic

Thermostatic

Method of Operation

Detects density difference between steam and condensate

Detects velocity difference between steam and condensate

Detects temperature difference between steam and condensate

Steam trap with check valve (Fig. 1C) - manual operation.

This is one of the simplest arrangements for the use of a steam trap. The diaphragm valve upstream of the trap segregates the process piping from the steam piping. This valve is manually opened during SIP and the steam trap will do the rest in separating steam from condensate. The check valve downstream of the steam trap prevents backflow. The steam piping is typically very small (½-¾ inch) which creates a section of low flow in the process piping. High flow steam traps have been applied to allow full CIP/flush flows. Since this arrangement is based on a manual operation, the operator monitors/records the temperature and confirms the temperature is maintained for the pre-defined time. The cost of the additional components in this arrangement is offset by the energy savings realized by maximizing the use of the steam. The manual operation still results in a significant labor cost.

Steam trap with parallel flush line (Fig. 1D) - automatic operation.

Automated operations provide a significant benefit in SIP processes. This arrangement will automatically activate steaming for a predetermined time. The 3-way ball valve allows for flushing to drain during the CIP process. The operator can use the sample port to insert a temperature probe and confirm appropriate temperature is reached. This temperature mapping procedure is typically done at all steaming points during validation. It can be done periodically during normal operations to confirm consistency in performance. This layout balances and minimizes component and labor costs.

Steam trap with parallel flush line and check valves (not shown) - automatic operation.

This arrangement is similar to Fig. 1D with the addition of check valves in each drain line. These are not typically critical in the operation, but have been seen in numerous processes where automatic operations are applied. It primarily provides a higher level of safety with minimal additional cost.

Steam trap with flush line and temperature monitoring (Fig. 1E) - automatic operation.

This full automatic operation proves its value in the labor savings that are realized while providing full monitoring and documentation of operation. There is a higher cost at the outset for the components and for the software. This arrangement yields the least risk in the operation as temperature and time are recordable and all CIP/flush sequences are automatic. This layout minimizes labor costs and minimizes risk for improper CIP/SIP as all process sequences are automatically controlled.

Table 2 summarizes the operational features for the five arrangements and provides guidance on the expected costs for components and labor. The more automated options (D-E) carry a relatively higher cost for the components while minimizing the amount of labor. These options are also more repeatable and reliable due to the automatic execution of operating sequences and the automatic recording of operating data.

Table 2. Material and labor cost for steaming operations

Arrangement →

A

B

C

D

E

 

 

 

 

 

 

Time tracking

Operator

Operator

Operator

Electronic

Electronic

 

Temperature

Temp sticks

Temp sticks

Temp sticks

Thermometer

Transmitter

 

Steam flow/loss

Yes

Yes

Minimal

Minimal

Minimal

 

Condensate flow

Minimal

Minimal

Yes

Yes

Yes

 

Estimated relative component cost

 

1X

1.2X

2X

5X

7X

Expected labor cost

High

High

High

Medium

Minimal

SIP operations can vary widely. The components and methods highlighted in this article cover a range of these operations. The automated and instrumented SIP arrangements typically result in a higher initial cost but provide for reduced long-term labor cost. The manual arrangements minimize initial costs, but result in higher operating/labor costs and potentially a higher risk for improper operating conditions. The optimized steaming operation is often a unique balance between the cost of the components and the labor required for the operation. Steaming arrangement can be developed to meet specific budget constraints while maintaining SIP effectiveness.


  1. Steam Engineering Principles and Heat Transfer, Spirax Sarco website. www.spiraxsarco.com/learn .
  2. Principles of Steam-In-Place, Millipore Technical bulletin, Lit. No. TB011EN00 Rev. B, May 2003. www.millipore.com .
  3. Designing a Shorter Vertical Leg for Sanitary Steam Traps, BioPharm International, September 2006. www.biopharminternational.com .

Pietro Perrone is a Proposals/Projects Manager at Millipore Corporation. He has a degree in chemical engineering from Tufts University with 20+ years purification/separation technology experience in process development/optimization, equipment scale-up, and project management.

Page last updated: 5 March 2009