Block Valve?? On/Off Valve?? Terminology from standard or codeor hand book please. 3

[fshnvce]

I am just out of university.

My background is Chemical Engineering, right now i am dealing with the specifications (related to valves).

Last month I spent close to 40 hours ( 5 working days, 8 hours a day, full time) studying API (6A, 6D, 6DSS, 598, 600, 602, 607, 6FA, 609) & ANSI B 16.34 to understand the basics and took down the notes and i visited our project stores and have seen various types of valves

My boss pulled few strings and i was taken on a tour of a couple of reputed valve manufacturers and i was there in their assembly & test shop for 2 days and witness various tests (seat test, back seat test, shell test and ome of the exotic tests including cryoginic testing, understand that this is not a common valve testing requirement and was lucky to witness vacuum test (though i did not understand a couple of aspects of it). I was reasonably confident till i stubbled this situation.

My boss has endowed me with the following task
I am supposed to write a purchase specification (not more than 3 pages long) but i am supposed to take care of all project requirements (which is not many) and i am supposed to be objective and not miss important requirements.

There are very few Project specific requirements

1) all Block valves are required to be subjected to additional high pressure gas test
2) All On/Off valves are required to be fugitive emission tested.


Since i have to write the purchase specificaiton for Gate valve, are all gate valves Block Valve, are Gate valves considered as On/Off valves

A) In which valve standard can i find what exactly are classified as block valves
B) How to deermine whether a valve is On/Off valve, from which code or standard can i determine whether Gate valve is On/Off or block or both.

Thank you in advance.

I request response with respect to standards and codes and not from any specific other clients (my boss's strict instructions is not to copy any other project specificaiton), the details is required to come from Handbook or from standard or codes or from our contract.Our contract does not specify the criteria on which valve is a on/Off valve and which are considered Block valve.

Thanks experts in advance.

 

[pennpiper]

The following may be of help:

http://www.traeger.com/technical/valve_terminology_glossary.pdf

http://www.prismflow.com/glossary.html

ASME B16.10 - Face to Face and End-to-End Dimensions of Valves
ASME B16.34 - Valves - Flanged, Threaded, and Welding End

prognosis: Lead or Lag

 

[DRWeig]

You have kind-of the right ideas, and pennpiper's links are good ones. My attachment is a great valve handbook from Emerson (formerly Fisher) that should give you some info too.

One note: Block Valve and On/Off Valve are not classifications of types of valves. Block and On/Off are purposes for which a valve may be used. A block valve is an on/off valve that meets your safety requirements for use in a double block and bleed or block and bleed arrangement. It can be any of several valve types, as long as it provides suitable sealing against the process pressure and is appropriate for the fluid in question.

An On/Off valve can be virtually any type, and it is a more general description of the application. Again, your spec needs to make sure that it is appropriate for the fluid, pressure, flow, and other characteristics of the application.

A globe valve, for example, can be installed for On/Off service, Block and Bleed service, or modulating service. Same with a ball valve, etc...

Give the Emerson/Fisher handbook a read. It's what a lot of us controls types were given right off the bat in our first jobs.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[zdas04]

I grew up in Nuclear Power and have always applied a bit different spin to valve nomenclature. In my designs, I never rely on a valve which is used in throttling to be a block valve. I always assume that globe valves will be throttled some time. The terminology I use in design is:
[ul]
[li]A "block valve" is a valve designed and designated for on/off service[/li]
[li]A "throttle valve" is a valve designated to be left in an intermediate position [/li]
[/ul]

Block valves are things like ball valves, gate valves, even butterfly valves and plug valves. These valves have very non-linear flow percent vs. valve open percent curves. "On/Off" refers to a valve that is only in an intermediate position during a change of state.

Throttle valves are things like globe valves, needle valves, variable chokes and exotics like Fisher's V-Ball. These valves tend to have reasonably linear flow percent vs. valve open percent curves. When (other) Engineers designate a really non-linear valve for throttling, the procedures I write disqualify those valves from being included in isolation schedules.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[EnergyMix]

I also am in the nuclear world. I too use zdas04's definitions -- 'on-off' means it won't be used for throttling. I would just about choke if I saw a globe valve in an on-off application. Vice-versa, I would be very surprised if I saw a gate or ball valve in a throttling application. Butterflies can be either, depending on how they are designed. Which isn't to say that the Emerson document isn't a good read.

 

[bmoorthy]

In one of our projects, we were also confronted with almost same situation, in our project the client wanted us to conduct seat leak test after the valve are received (procured) and just prior to assembly in pipeline (They feared that handling and storage of the valves could have compromised on the leak tightness of the seat and they started asking us to test all block valves just prior to installation on the piping, there were over 10,000 valves in the project, Unfortunately in one of the paragraph in page number 23523 of our contract under the pre commissioning sub paragraph there was a statement that said that block valves are to be leak tested just prior to commissioning and this was used against us and we were forced by our client to perform the test.

At that time i searched the following standards and codes and could not get an objective definition for block valve, so the valves deemed as block valve (to be selected from the 10000 valves) were in the hands of process personnel (Our process, Project management Consultant personnel and client process personnel) all the 3 of them did not understand the significance of their decision. Although the process personnel were good in their area, when it came to selection of the valve in order to meet intent of contractual obligation they were confused and could not approach the issue objectively, that is they were not able to identify which valve is a deemed block valve and which are not. Since all Ball, SBB, DBB, Butterfly valve does the blocking function. Check valve blocks flow in one direction and globe is capable of blocking, needle is capable of blocking.


My search extended to API 6D, 6DSS (Not 6A), 11, 14, 20, 529,574, 576,594,595,597, 598,600,602,603,604,607,608,609, ANSI B 16.34,16.38,16.40,16.44, ANSI B 16.10, MSS SP-61, MSS SP-67,MSS SP-70, MSS SP-71, MSS SP-72,MSS SP-78,MSS SP-80,MSS SP-82,MSS SP-84,MSS SP-86, AWWA CodeC504,AWWA CodeC508,
BS EN 736-1 ,BS EN 736-2 ,BS 5351,BS 5352, BS 5353,BS 5417,BS 5418,BS BS 5793-4:BS 5793-6, ISO 17292, BSEN 12266.

Based on the above search i can assert that that no amount of study of code or standard will get you the answers you are looking for.

 

[bmoorthy]

Dear fshnvce
I do not want to sound condescending. It is my sincere view that if you include requirements in the specification without knowing the consequence, your company may spend more money than what is required. It is OK to be conservative and include all possible tests for all valves. But do we need those tests is the basic question here. Why would you want to perform high pressure gas test on valve in instrument air line or in N2 line or in drain or vent, unless of course you have compelling reason for do those tests.
I thought we were alone to face this kind of questions (We were in much worse situation explained in the previous post, the consequence had huge commercial and schedule issue).
I advise you to exercise caution and explain to your supervisor the consequence of including the requirement in the specification without understanding the consequence.
If you had seen the P & ID or the isometrics, you will notice, each vent and drain will have gate or ball valve. Most of the control valve may have a bypass valve, all these does blocking function.
It appears the specification writer for your client either did not understand the consequence of using non standard terminology or did not know what he put (he may have copied the requirement from somewhere or could have picked points discussion forums like this and put it in the specifications without realizing the consequence of what was put.
I do not know whether you have something call engineering query mechanism. That is you need to establish an understanding with the client on what constitutes On/Off Valve and which valves are considered block valve by your client.
I would send an engineering query to the client and attach a list of valve that in my view are deemed block valve and the list of valves that are considered on/off
Some say Double and block valve (This does not have standard) are the only block valves some say the valve that is just prior to PSV are block valves, some say all ball valves are block valves, there are so many ideas. On does not agree with the other. When people take positions the matter gets messy.
The terminology Block Valve has various definitions for various clients may even vary from person to person. Hence caution advised.
Kindly post your search outcome and kindly let us know what came off in your specification and the basis of the requirement.

 

[EnergyMix]

If you're in the petroleum field, I've heard many people refer to the NORSOK M630 standard. You can Google that. It's probably worth adding to your growing collection and reading.

I believe that some of the standards to which bmoorthy referred may not be active; however, you would need to check as I am not up on European standards. I'd suggest starting with the API ones. Though a lot depends on the country where you're working and the field that you're in. You have not specified either. It does make a difference. (Hint: ask around at work as to what's available; these standards cost money -- what does your company have on hand?)

Unlike bmoorthy, I have heard of the term "double block and bleed," especially in the petroleum field. It's used when you really want to be sure to have good isolation.

 

[zdas04]

"Double block and bleed" is introduced in the U.S. OSHA regulations under "positive energy isolation". Simply put, DBB is two independent seating surfaces separated by an evacuated space. We argue a lot about what an "independent" seating surface is (i.e., does it have to have its own operating mechanism separate from the other surface, or does it just have to be energized independently?) Different companies and different regulators have a range of answers to that. When I was defining the answers for my company I said that the springs loading the seats in a trunnion ball valve constituted adequate independence. Within a year after I retired my replacement reversed that decision and the thousands of trunnion ball valves that were installed under my interpretation suddenly became single isolation points and not adequate for DBB.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[bmoorthy]

Jst to clarify, i said
"Double and block valve (This does not have standard) are the only block valves"

I did not say that i have not heard of the term Double block and bleed valve.
We specify. procure, inspect and install 1000s of these in a year for different projects in Oil and Gas projects.

Based on the search of Active and inactive standards, including regulations of OSHA, EPA, CFR, PED (Pressure Equipment Directive of Europe), i can assert that there is no standard of code for Double block and bleed valve.

It is just a hybrid of 2 ball (Now one European vendor has come out with Butterfly) valves and in between them there is a bleed (Needle valve)

We procure from Europe our sources are from France and Italy.


We use them for positive isolation, in locations where a particular instrument or on line item needs to be removed for mainteance or repair without taking the line on shutdown.

Most of the pressure instruments (including gauges) are now a days isolated by DBB.

In tubing lines, we include Mono(flange) Valve.

If large lines (when the client needs ball valve) where one needs double block function for positive isolation, (as suggested by "zdas04" ) we install valve with double piston effect, and in those valves, springs push the seats towards the ball instead ball puching to the farther seat, for leak tightness. The space between the seats are provided with a drain valve. So this big valve comes with a small baby valve.

 

[bmoorthy]

Norsok M630 does not define Block Valve or On/Off valve.

 

[BigInch]

Try reading some codes.
Block valve separates long sections of a pipeline from each other.

B31.4 434.15.2
(a) Mainline block valves shall be installed on the upstream side of major river crossings and public water supply reservoirs.
(b) A mainline block valve shall be installed at mainline pump stations, and a block or check valve shall be installed at other locations appropriate for the terrain features.
(c) A remotely operated mainline block valve shall be provided at remotely controlled pipelien facilities to isolate segments of the pipeline.
(d) On piping systems transporting LPG or liquid anhydrous ammonia, check valves shall be installed where applicable with each block valve to provide automatic blockage of reverse flow in the piping system.
(e) In order to facilitate operational control,, limit the duration of anoutage, and expedite repairs, mainline block valves shall be installed at 7.5 mile maximum spacing on piping systems transporting LPG or liquid anhydrous ammonia in industrial, commercial and residential areas.

B31.8 ss 803.2 - pipeline section
ss 843.3.4 (b) Pressure Relief "between the gas compressor and the first discharge block valve"

So as you can see, Block Valves typically separate major specific facilities from one another, as in separate a pipeline from a compressor/pump stations, platform topsides from pipeline. They might at times perform an ESD, or otehr positive isolation function. Block valves separate pipelines from meter stations, pressure regulation stations from meter stations, meters from inlet and outlet, pump area from their suction and discharge manifolds, pipelines and pumps from tank farm areas.

An on/off valve is a valve that turns the water on or off, opens to drain, or vent, engine oil tank to feed line, valve on pump recycle to suction, etc., generally contained within a battery, or sub-battery, or unit limit. Block valves are typically found between battery limits, etc.

B31.3 takes a more plant oriented perspective. Note that there are only two references to block valves in B31.3. Block valves are referred more as being between functional components, as going to relief lines. M322.3 (b) an accessible block valve shall be provided to isolate the (instrument) tubing from the pipeline.

It would appear that a block valve can be almost any valve you'd like it to be when you are not working in pipelines. In pipeline work they have a much more specific connotation.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[bmoorthy]

Here is the definition from Chemical Engineering Hand Book for On/Off valve:: Section 8-77

Valves for On/Off Applications Valves are often required for service that is primarily nonthrottling in nature. Valves in this category, depending on the service requirements, may be of the same design as the types used for throttling control or, as in the case of gate valves, different in design. Valves in this category usually have tight shutoff when they are closed and low pressure drops when they are wide open. The on/off valve can be operated manually, such as by handwheel or lever; or automatically, with pneumatic or electric actuators