#1 -Engineering Question

“Hi Asad, what is CDTP in relief valve?

It is mandated by the client that CDTP must be included in Tag Plate of Relief valve.

But What is this?

Is there any standard that specifies it?

Your thoughts on this. “

Answer:

What is CDTP in Relief Valve?

CDTP stands for Cold differential test pressure (CDTP).

The conditions at which PRV is set to operate on a test stand could be different from the actual service conditions under which a PRV is required to open in the plant.

We need to *compensate* for this effect.

Thus, CDTP is specified for adjusting the set pressure of the relief valve on the test stand.

👉 Definition as per API 520 4.2.3.1

The CDTP in relief valve is the correction for actual service conditions of backpressure and/or temperature.

An example to understand CDTP

In control valve we have come across the concept of Inherent valve characteristics and installed valve characteristics.

Inherent valve characteristics (Ideal valve characteristics) get slightly deviated when a valve is installed in service

We call this as installed valve characteristics.

Similar, concept is that of CDTP in relief valves.

The Relief valve when tested on test stand will have different response as compared to valve that is installed in process conditions.

Few parameters that change are Temperature & Back pressure conditions.

Thus, we compensate for this by CDPT (Cold differential test pressure)

This is very important and hence the "Client" is asking you to include in Relief Valve Tag Plate.

If interested here is the procedure to calculate CDTP in Relief Valve.

#2- Engineering Standard

👉 Relief Valve API Standards

API 2000 Standard:

The basics segregation of relief valves in API standards is done as per how much pressure the relief valve needs to handle.

If the equipment is having a MAWP (maximum allowable working pressure) less than 15 Psig then API 2000 standard is applicable.

It has a little less stringent requirements as compared to other API Relief valves standards mentioned below.

API 521 Standard:

In simple words this standard caters towards selection of pressure relief device (Relief valves, Rupture disk, their combinations etc) based on various process scenarios.

It guides on the most appropriate device for the risks and circumstances involved in various installations.

API 520 Standard Part 1:

This standard deals with the Relief device itself.

In simple words we could say this standard deal with the operational characteristics and sizing procedures.

API 520 Standard Part 2:

This aspect is sometimes taken lightly but can lead to fatal consequences.

And that is “Installation details”.

A lot of times and incorrect installation has been the root cause of a fatal incident.

Thus, as per my humble opinion extreme consideration should be given to API 520 Part 2.

API Standard 526:

This standard deals with the purchase aspect of Pressure Relief devices.

API Standard 527:

One peculiar consideration for valves and especially relief valves is leakage consideration.

Thus API 527 comes handy and is one of the most frequently cited standards for relief valves

#3 -Career Tip

Happiness Trap

The reason you are reading this newsletter is because you want to grow.

You have ambitious goals, you want to improve.

else why would spend time reading this?

You could be watching all the Celebrity Gossip and News that is freely available!

But I want to share a trap that I keep falling over the years and I keep reminding myself.

We all know how important it is to set ambitious goals.

Like becoming the best in our field or leading groundbreaking projects.

But here's the thing: while it's great to aim high, we shouldn't tie our happiness solely to achieving those goals.

It's easy to fall into the trap of thinking, "I'll be happy when I achieve XYZ."

But the truth is, the journey itself can be incredibly fulfilling.

Celebrate the small wins, enjoy the process of learning and growing.

Find joy in the day-to-day challenges and successes.

Until next week,

Happy Learning

Asad Shaikh

Your Well Wisher and Instrumentation Buddy!! 😊

See you next week!

PS: If you have missed to read the FREE e-book on Control Valve Mastery. Here is the link to download it again.

Insider Secret: Soon Another edition to the E-book is coming.

Stay Tunned (💖)

If you have any engineering query, then you can reply to this email ID and let us try to answer in coming weeks.