This is the final article in a three-part NESTEC newsletter series:
- March: The Best RTO/RCO Actuator-Valve Available
- April: RTO and RCO Actuator and Valve Safety Factors
- May: Selecting the Correct Actuator and Valve for your RTO or RCO
Introduction
As indicated in the March 2022 issue “The Best RTO/RCO Actuator-Valve Available” and April 2022 issue “RTO and RCO Actuator and Valve Safety Factors,” it is essential to select the correct actuator and valve with the unique features necessary for the specific process to ensure maximum performance, reliability, and safety, especially with RTOs and RCOs.
A careful analysis of the following factors will assist in optimizing the valve selection for the specific RTO or RCO application:
- Operation
- Safety
- Service
- Construction
Operation
Factors listed in Table 1 are applicable to all values. However, the use of an automatic control valve requires
that the valve is integrated into the control loop. Special consideration of its fundamental metallurgic and operating conditions is essential.
Table 1
| Function | Speed | Flow | Line/valve position | Performance |
| Open-close | Fast | Full flow | Line | Bubble-tight (zero leakage) |
| Isolation | Slow | Reduced port | Vertical | Some leakage permissible |
| Flow check valve | Non-slamming | Straight flow | Horizontal | |
| Flow regulation | Deacceleration | Y-Flow | Sloped | |
| Pressure regulation | Seat exposure | Normally closed | ||
| Pressure relief |
|
|
||
| Special function |
|
|
Manual and automatic
Factors listed in Table 2 typically include visual indicators and/or provisions for locking in position. These provisions are listed in Table 3.
Table 2
| Manual | Automatic |
| Hand-operated | Electric |
| Hand wheel | Pneumatic |
| Chain wheel | Hydraulic |
| Lever | Motor |
| Ratchet | Diaphragm |
| Enclosed worm gear | Cylinder |
| Enclosed bevel gear | Unidirectional |
| Reversible | |
| Power-assisted | Manual override |
| Electric | Double acting |
| Pneumatic | Single acting |
| Hydraulic | Spring return |
| Motor | External stops |
| Diaphragm | Fail close |
| Cylinder | Fail open |
Table 3
| Manual indicators | Provisions for Locking |
| Post indicators | Lock and key shield |
| Rising stem | Locking plate |
| Revolving stem | Special |
| Revolving bushing | |
| Indexing plates |
Safety
OSHA, ASME code, and ANSI standards all provide safety margins for power, chemical and other processes. Beyond these regulations, specific company, plant, and process needs should be incorporated based on Haz-op reviews, etc. Table 4 provides a general list which should be expanded to cover all the specific needs.
See NECTEC’s ”THE IMPORTANCE OF OXIDIZER SAFETY”
The Importance of Oxidizer Safety | Nestec, Inc. (nestecinc.com)
Table 4
| Personnel life/health | Environmental | Special features |
| Toxic | Toxic | Fire safe seats |
| Hazardous | Hazardous | Leak proof |
| Carcinogenic | Carcinogenic | UL listing |
| Flammable | Flammable | Vacuum relief |
| Explosive | Explosive | Blow out resistance |
| Irritating | Radioactive | Nonreactive lubricants |
| Suffocating | Nonreactive packing | |
| Damaging | ||
| Hot | ||
| High Pressure |
Service Factors
Both external and internal service factors should also be reviewed to ensure the long-term reliability and performance of the valve and actuator. Table 5 provides a fairly comprehensive list of factors to consider.
Table 5
| Type of fluid | Transport properties |
| Service pressure | Erosive or abrasive properties |
| Service temperature | Solids or particulate content |
| Compressibility | Consistency |
| Density | External corrosion factors |
| Specific gravity | Corrosion rate |
| Specific heat | Coating of foiling |
| Specific volume | Cathode protection |
| Vapor pressure | Grounding |
| Viscosity | Chemical reactions |
| Solubility | PH |
| Concentration | Moisture content |
| Purity | Thermal expansion |
Construction
Standardized designs should comply with ANSI, MSS, or established guidelines. However, experienced manufacturers can optimize the design, as indicated in the RTO or RCO application above, to provide the best solution for the application. NESTEC offers in-depth experience with specific industries such as wood, pulp, paper, and can manufacturing, plus many others:
Conclusion
Selecting the correct actuator and valve should include all the above factors as well as any specific needs or requirements for the application. Some manufacturers offer design as well as service, repair, rebuild, and maintenance for their valves, which adds another factor in the evaluation process.
If you have an application or existing RTO or RCO for air emission control and/or energy conservation and want a system that will:
- Provide alternate solutions to minimize your capital expenditure
- Reduce your energy bill
- Reduce stack testing costs to a single stack
- Shrink your carbon footprint
- Include easy-to-maintain equipment
- Provide simple and long-term reliability components (see: https://nestecllc.com/news/innovation)
- Include 24/7 service and engineering support
- Offer access to NESTEC’s warehouse of replacement components
Contact NESTEC for a free process analysis and proposal
Office: 610.323.7670
Jim Nester, C.E.O.: jnester@nestecllc.com
Rick Reimlinger, Vice President: rick.reimlinger@nestecllc.com