November 8, 2005 at 5:48 pm #4297
We are getting ready to work a project to automate a bunch of existing Coke Drum Valves. They are currently all Manually-operated. We are looking for User operating experience/feedback in the following areas:
1) Among sites with coker on/off valves that have either been initially fitted, or retrofitted, with electric actuators; is your site using a) Conventional electro-mechanical actuators or b) Smart solid-state electronic actuators?
2) If the answer to question 1 is (b);
– how has the solid-state electronic actuator behaved in the presence of high ambient radiated heat from the Process?
– Have you seen PC-board failures?
– How long have the smart actuators been in service?
3) Any type of Temperature Compensation used between Valve and Actuator?
4) What has maintenance experience been like with either Electro-mechanical, or Smart electronic actuators?
5) Any issues with Water Ingress into electrical compartment of Actuator?
6) Any issues with false Valve indication due to faulty limit switches?
7) Any Torque related issues with Actuator/Gear assembly due to Coke buildup?
8) What kind of Preventative Maintenance is performed, if any?
9) Any other comments….
From Mike Corbo of the Beaumont Coker Safety Project (by Mitch moloney)
December 17, 2005 at 1:39 pm #7691
Item 5: Remember the Non-Conductive Contact Lube at installation. Someone once wrote:
A properly formulated contact lubricant decreases the dynamic coefficient of friction, reduces adhesive wear, provides atmospheric corrosion protection, prevents fretting corrosion and does not migrate away from the point of contact.
A thin film of contact connector lubricant is applied on both the male and female parts where the connection will take place by either dipping, spraying, brushing or atomizing. This film of lubricant acts as a barrier between the metal parts and the atmosphere. It offers wear protection and lowers the insertion-withdrawal forces. The lubricant film also protects the connector from fretting corrosion as well as all other forms of corrosion such as galvanic, radiation, high temperature, chemical acid, biological, etc.
Connector lubricants, properly designed and formulated, will possess the following properties and characteristics.
High thermal and oxidation stability, so that the lubricant will last the life of the connector
High resistance to chemical, radiation, acids and other types of contaminants.
Compatibility with metals, elastomers and adhesives.
High surface tension so the lubricant will not migrate beyond the connector area.
Common industrial lubricants based on polyalphaolefins, esters, silicones and fluorinated hydrocarbons are migrating fluids as their surface tensions are in the range of 20-25 dynes/cm. This property, along with lack of long- term thermal stability, makes these lubricants less desirable for connector applications.
Item 6: Take the extra time (in fault-handling programming) to set up a little test routine at every signal from a limit switch. Even when they don’t matter to the current activity.
i.e. when Switch 1 is on, Switch 2 must be off. If not, then close (warning) relay.
(Wire N.C. to detect open circuits.)
Item 7: Include torque monitor in fault-handling routine. List to a file when operating, see trends develop, establish high-limit for signal to maint. (May need to signal only after high-limit is reached x no. of times – like a reverse de-bounce.
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