TROUBLE SHOOTING FOR VALVES
The process flow control Industry at large has Valves at its epicenter.
The Valves have a few Chronic Problems which can be easily solved if proper care is taken during (1) Selection of Valves for Specific Application; (2) Valves Installations and Storage are done as per the International Specifications like MSS-SP 92 (3) Testing at the manufacturing stage is done properly (4) Preventative maintenance is well.
If these things are done properly issue like un-planned plant stoppage can be easily avoided and the optimal utilization of the process plant would be much better.
We at M/s. Venus Engineering Works; now have experience of 50+ years of catering to the needs of we have identified 6 common and major problems which can be solved easily if some care is taken.
The problems are
- PASSING OF VALVES/ VALVE LEAKAGE
The major reason for metal seated Valves for Valve passing is that at the time of manufacturing the Valves are not provided with zero leakage (which may not be needed as per standard Specifications especially for large sizes metal seated Valves).
In metal seated Valves the coated and machined materials should have the needed chemical and physical properties then and only then properties of (i) Edge Retention (ii) Work Hardening (iii) superior corrosion and erosion resistance can be achieved. We at M/s. Venus Engineering Works check each and every metal overlayed components for their chemical properties; physical properties and internal defects using non-destructive methods thus ensuring a long life our Valves.
Allowance for Wear Travel is another major factor that ultimately defines the life of the Valves especially for metal seated multi-turn Valves needs to have enough wear travel so as even after years of usage when the Disc/Wedge sinks the Valves is able to have positive shut off.
There is a need to make sure that proper Valves are selected for application if at all there are Valves with suspended particles (due to the fluid or due to the lack of cleaning of line and external materials like Welding slag coming in the line) the Valves seats tend to damage and thus Valves start passing.
Disc Should Ride High To Factor Wear Travel
Positive Material Identification (PMI) Testing In Progress
Cobalt Channel PMI Gun Readings
2. GEARBOX FAILURE IN VALVES
Gear Box actually is a fail-safe mechanism so as if at all over torque is applied then the Gear Box fails it is possible to change the gears or the gearbox itself and operate the Valves but if the Gear does not fail then the spindle will get bent and then it would be very difficult to troubleshoot the Valves while the plant is operational and an emergency shut down would be needed.
As per the common practice the total load on the rim of the handwheel should not be more than 30 kgs and it at all the load is more then there is a need for a gearbox or if the Valve is designed well then the internal moving parts have somewhere jammed which needs to be cleared instead of doing something with the gearbox.
If over torque is required to operate the Valve instead of using F-fork and Pipe just try to de-jam the Valve by taking help of an expert Valve operator.
Pneumatic and Electric Impact Wrenches are available so a controlled level of torque can be applied to operate the Valves.
We at M/s. Venus Engineering Works have started offering Helical Gear Boxes along with a system so as Our Manual Valves can be operated by hand as well as by Impact Wrenches making our Valves very versatile and easy to operate.
Gear & Pinion Damage in Bevel Gear Box For Valves
3. SPINDLE BREAKAGE OF VALVES
This is a very common problem in Instrumentation Valves and Quarter Term Valves mostly because of the over-torque.
There is a need to check the physical (including Tensile Properties and Hardness) and chemical properties of bar stock from which the spindles are made and they are as per the Standard Specifications.
There are internal defects that are parallel to the centerline of the bar stocks and there is a need to do Ultrasonic testing for such defects which can be devastating for the Spindle.
Enough thickness of the spindle needs to be kept based on the fluid that is being controlled. While working with Slurries; Fibres and high viscosity fluids the stem diameter as mentioned in the Standard Specifications thus expert manufacturers with a deep understanding of fuilds to be controlled and have strong Design Capabilities should be considered. we at M/s. Venus Engineering Works have strong tie-ups with Research centers and have an in-house R&D center that does such analysis regularly for its customers.
Spindle/Stem Breakage In Globe Valves
Pile of Eroded Spindles
4. LEAKAGE FROM GLAND AREA
This is another chronic problem across the Valve categories and plants and leads to a lot of plant efficiency loss in Steam applications; for slurry lines, the Valves get jammed and they become in-operatable; for obnoxious gases and dangerous fluids, it is a big life-threatening hazard.
The reason why gland leakage happens is that this is a dynamic joint and due to the changes in the internal pressure of the Valves (while opening and closing of the Valves) and due to the external attachments including vibrations in the line etc the Gland Bolts gets loosened and this gland leakage starts.
Moreover, there is a need to regularly lubricate the Gland area and for the same again the Valves need to be loosened and if the same does not get tighten again then Gland leakage will start.
With our experience of making Valves for extreme services like Hydrogen gas services; toluene services; and Chlorine; Bromine and other Halogen services we have been able to find few best practices which can be used in conventional Valves that would be cost-effective and also practically eliminate the problem.
To resolve this issue, we provide Valves with "LIVE LOAD STUFFING BOX" which would totally eliminate the issue of gland leakage while giving long life of Metal seated Valves. We have already given Helium Leak Test for large-sized Gate Valves; Globe Valves and Even Swing Check Valves using this technology.
Gland Leakage In Slurry Services Valves
Valves with Live Load Stuffing Box
Greasing Duct For Valves
Helium Leak Test in progress
5. Plant Corrosion
Just like termites eat away wood Corrosion eats away plants drastically reducing the plant life. Just like termites corrosion gets in from the seemly innocent source and reduces the plant life.
In plants that are near the sea coast or are handling very corrosive fluids the problem of plant corrosion is the major point of concern.
With the advent of paint technologies, there is a lot that can be done to avoid plant corrosion but the need of the hour is to follow the latest processes and procedures.
Current International Specifications of Valves do not enforce a proper painting regime where we can follow the protocols of paint inspections and the codes of ASTM D series of specifications. We at M/s. Venus Engineering Works have an in-house Paint Shop with approved procedures and testing facilities to cater to all the unique specific requirements of our customers.
For internal corrosion inside the Valves while dealing with pressurized applications there is a need to go for metallic Valves aided by a variety of internal lining/coating/painting.
All these Rubber or PTFE coating/linings need to be checked for using High Voltage Spark Tests which is regularly done at M/s. Venus Engineering Works
There are latest Paints like Glass Flake Coating; Nickel Coating/Lining that is being offered for specifications
Internal Corrosion In Valves
Paint Inspection Using DFT Test
High Voltage Spark Test For Lining & Coating
Glass Flake Coating