Maintenance and Inspection of Tank Vent Devices 1

[don1980]

Low pressure API tanks seldom have installed spare vent devices (PVRV, ERV, VRV, etc). How does your company handle maintenance and inspections of these devices when there isn't an installed spare? Do you do all of this testing/inspection in-situ, without removing the device to the shop? Do you remove the device and install a temporary shelter over the open tank nozzle while the device is in the shop? Does your company have a standard maintenance procedure for safely protecting the tank while these devices are removed for inspection?

Thanks

 

[gocougs1]

I believe the tank would typically be placed out of service to perform work on the vent valve. Usually there is a way to temporarily divert flow to another tank while maintenance is being performed.

 

[EmmanuelTop]

Putting a tank out of service (in terms of diverting the inflow to another location) does not necessarily mean that all possible scenarios for overpressure or vacuum are mitigated successfully - there's always the ambient effect, failure of blanketing system, failure of vent controls, etc. One would need to perform a detailed review (what-if or FMEA, for example) and see if just isolating the tank is a sufficient barrier. Sometimes it is, sometimes it is not. Based on the outcome of such an assessment, one would be able to make the right decision, i.e. if process isolation is sufficient or a complete de-inventory is required.

Dejan IVANOVIC
Process Engineer, MSChE

 

[don1980]

I'm interested to learn what people are actually doing. Few API tanks are equipped with installed spare vent devices, so almost every operating company is managing this in some way. Hopefully those who work in an operating company will share how their company does this.

Are you installing a temporary goose-neck on the nozzle while the vent device is in the shop? Do you keep a shelf-spare, and install it when the tank device is removed? Do you just leave the nozzle open until the vent device is ready to be re-installed?

Thanks.

 

[EmmanuelTop]

I think all of those apply - depending on the fluid/service, risk assessment, and inspection requirements. I can think of at least one example when each of the methods you mentioned could apply. But not a single method for all cases and all tanks.

Dejan IVANOVIC
Process Engineer, MSChE