Thursday, February 26, 2015

High Performance Butterfly Valve Seating Principles - Metal Seats

high performance butterfly valve
High Performance Butterfly Valve
(courtesy of Flowseal)



PRINCIPLE OF METAL SEATING



Metal-to-metal sealing is accomplished by the “line contact” between a spherical surface and conical surface. Figure 1 illustrates a typical globe control valve seat and plug. The plug seating surface is the segment of a sphere; when engaged against the seat ring, a line contact seal is achieved.

In a metal seat design, it is necessary to apply enough force per linear inch to maintain a tight metal-to-metal contact between the seal- ing members; however, high linear thrust can cause a collapse of the seating members (“bearing failure”).




DISC CLOSED, Self-Energized Seal

In Figure 2, the Flowseal disc and seat are engaged, and the process fluid is under low pressure. The spherical edge of the disc, with a larger diameter than the conical seat tongue, imparts a thrust of approximately 600 pounds per linear inch against the seat. The mechanical properties and shape of the Inconel® seat allow it to both flex and maintain a constant thrust against the disc.

This controlled loading prevents the occurrence of bearing failure and reduces the leakage and wear between the components.

Wednesday, February 25, 2015

High Performance Butterfly Valve Seating Principles - Soft Seats

high performance butterfly valve
High Performance Butterfly Valve
(courtesy of Flowseal)

High performance butterfly valves (HPBV) are a standard in many industries including heating, ventilating and air conditioning, power generation, hydrocarbon processing, water and waste water treatment, and marine and commercial shipbuilding.

They are also installed in applications as diverse as food and beverage processing, snowmaking and pulp and paper production. Configurations are available for harsh conditions as well as applications requiring nominal pressure and temperature ratings.

The following describes the soft seating design principles for high performance butterfly valves:

soft seated HPBV valve
DISC OPEN 

In Figure 1, the disc and seat are not engaged. In this position, the shoulders of the seat are forced against the cavity shoulders by the compression of the o-ring.

The seat is recessed inside the seat cavity and acts as a gasket in the anchoring groove area.The seat cavity is sealed from exposure from the process fluid and protects the seat from abrasion and wear. The o-ring, which is completely encapsulated by the seat, is also isolated from exposure to the process fluid.

Tuesday, February 24, 2015

Applying Cooling Towers

Delta Cooling Tower
Delta Cooling Tower
Here is a presentation that explains how to apply cooling towers, including the basic cooling tower principles, design considerations, and construction issues.

The original presentation given in 2009 by Steve Lowe, PE to the Hampton Roads, VA Chapter of ASHRAE.






For more information on any cooling tower issue in Colorado, New Mexico, Wyoming, Montana, Utah, Nevada, Idaho, or the western Dakotas, contact:

Mountain States Engineering and Controls
1520 Iris Street
Lakewood, CO 80215
303.232.4100 Phone
303.232.4900 Fax
Email: info@mnteng.com
www.mnteng.com

Monday, February 16, 2015

Description of a Process Control Enclosure in a Hazardous, or Explosion Proof Location

This is a short video that explains what an explosion-proof enclosure looks like, how it works, and why it is safe to use in explosive or combustible atmospheres.

The definition of "explosion-proof" doesn't mean the enclosure can withstand the forces of an external explosion, but rather that it will cool any escaping hot gases (caused by an internal spark or arcing contacts) sufficiently enough as to not to allow the ignition of combustible gases or dusts in the surrounding area.

For more detailed information on electrical equipment enclosures in hazardous areas, visit this page.


Tuesday, January 27, 2015

Control Valve Application Checklist

Specifying of applying an industrial control valve? Here is a comprehensive checklist to help:

PROCESS CONSIDERATIONS:
Warren Control Valve
Control Valve
  1. What is the medium to be controlled. Is it a liquid, gas, or slurry?
  2. Is it corrosive, abrasive, explosive or clean single-phase medium?
  3. What is the upstream or inlet pressure. Don’t guess – use a gauge.
  4. What is the downstream pressure when valve is closed, and when flowing?
  5. Are the Vapor pressure, viscosity or specific gravity and critical properties known?
  6. What are the inlet and outlet pipe size(s) [ May be different ] and schedule?
  7. Normal, Minimal, and Startup conditions for flow, pressures and temperatures?
  8. What impact will even a small seat leakage create when shut off?
  9. What Class is required?
  10. Is the installation in an occupied area. Noise or other hazardous considerations?
  11. What is the “fail safe” orientation? In place, closed or open?
  12. If in a fail safe orientation, is a manual readjustment to be expected?
  13. What is the ANSI Pressure Class of the pipe flanges and valves in the loop?
  14. What has been the operational history in an existing application?
  15. What material is the existing piping made of. Is it considered compatible?
  16. Is there an existing valve in place and a face-to-face dimension to match?
  17. Where will the valve be located – elevation – within a piping nightmare?
  18. What maintenance – routine or preventative is normal and expected?
  19. What are preferences for Control Valve Actuation – pneumatic or electric? WHY?
  20. Is the customer going to actuate it himself and buy a “bare stem” valve?
  21. Is the stem boss compatible with his actuator stem. Double “D” or square?
  22. Is the calculated flow velocity below limits of 100 – 125 fps for saturated steam?
  23. Is the calculated flow velocity below limits of 5 fps for liquids?
  24. Is the calculated flow velocity below limits of 250 – 400 fps for gases?
"REAL WORLD" APPLICATIONS CONSIDERATIONS:
  1. Could moving vehicles damage the valve, in a specific installed location.
  2. Might seismic forces or fires present a danger to workers.
  3. What codes may be in effect? Body pressure Code, Leakage Criteria
  4. Might workers use the valve as a stepladder when conditions dictate?
  5. Is the application a “continuously modulating” or an on / off practice?
  6. Might the process be shutdown for nights or weekends?
  7. What might result when started back up after an extended shutdown?
  8. Use your imagination, anticipate the worst, and ask more questions – more, in this case, is always better.
  9. What range air set is available for actuator or positioner?
  10. Could it allow a higher than safe pressure?
  11. Where will the user store documentation for IO&M purposes?
  12. Is routine maintenance allowed or is an annual shutdown more typical?
  13. Could moving vehicles damage the valve, in a specific installed location?
  14. Might seismic forces or fires present a danger to workers?
  15. What codes may be in effect? Body pressure Code, Leakage Criteria?
  16. Might workers use the valve as a stepladder when conditions dictate?
  17. Is the application a “continuously modulating” or an on / off practice?
  18. Might the process be shutdown for nights or weekends?
  19. What might result when started back up after an extended shutdown?
  20. Use your imagination, anticipate the worst, and ask more questions – more, in this case, is always better.
  21. What range air set is available for actuator or positioner?
  22. Could it allow a higher than safe pressure?
  23. Where will the user store documentation for IO&M purposes?
  24. Is routine maintenance allowed or is an annual shutdown more typical?
PHYSICAL AND CONFIGURATION CONSIDERATIONS:
  1. Flowing media to be controlled. Steam, Liquid or Gas?
  2. Pressures upstream and downstream, therefore the differential.
  3. Two way – modulating, or on/off. Three way diverting or mixing?
  4. Is the material abrasive, explosive, or clean?
  5. Hot or Cold water chemically treated?
  6. What are inlet and outlet pipe sizes and schedules?
  7. Maximum, Normal and Startup conditions?
  8. Leakage allowed?
  9. Valve in occupied area?
  10. Previous usage history?
  11. Pipe material of construction?
  12. Actuation Pneumatic or Electric
  13. Maintenance allowed or anticipated?
  14. IO&M storage and accessibility?
  15. Control signal – PID compatibility?
  16. Mounting restrictions?
  17. How was valve “sized?”
Checklist courtesy of Warren Controls

Please consult with a application expert before selecting or installing a control valve.

Wednesday, January 21, 2015

Safety Relief Valve Basics

safety relief valve
Safety Relief Valve (Kunkle)
The safety relief valve is used to control or limit the buildup of pressure in a piping system, tank or vessel. Uncontrolled pressure can occur because of valve malfunction, process system upset, instrument failure, or fire.

In generally accepted practices, pressure build-up is relieved by allowing the fluid to flow from an alternate path in the piping system. A safety relief valve is engineered so that it opens at a predetermined pressure setpoint to protect vessel, piping or ancillary equipment equipment from being subjected to pressures that exceed their design limits.

When process pressure is exceeded, a safety relief valve becomes the “weak link”, and the valve opens to divert a portion of the fluid to another path. The diverted liquid, gas or liquid–gas mix is usually routed through a piping system to a process where it is safely contained or burned off via a flaring system. Once the liquid or gas is diverted, the pressure inside the vessel drops below the safety relief valves' re-seating pressure, and the valve closes.

Tuesday, January 20, 2015

Non-Hazardous Industrial Pressure and Temperature Switches

A quick reference to Custom Control Sensors (CCS) DualSnap non-hazardous pressure and temperature switches for industrial process control application.

Used in petrochemical, chemical, water treatment, pulp & paper, military, aerospace, commercial food processing, power generation, pipelines, bulk storage facilities and mining.