6 replies to this topic

[gvdlans]

Okki,

Did you check API RP 520, Part II, Section 4?

According to this section, valves shall be full bore. This means that no additional pressure drop is to be expected due to the valve.

Someone told you that a hammer blind valve is not safe. Did you ask that someone why he/she told you so?

[avsp]

Okki,

First of all, a HAMER blind is a proprietary design for a somewhat "mechanised" spectacle blind and it's USP is that it is so designed that a single person could do the job of swinging the spectacle blind from an "open" position to a "closed" position (especially for a huge line) in a matter of minutes, as compared to a conventional spectacle blind, which may take several minutes to change positions and may involve several persons to do the job, if it is a big line.

Regarding your concern about a Hamer Blind , I think you should have enquired further as to why it is not safe. However you should note that blinds, whether they be spectacle, Hamer or pure blanks, may many times be left in the closed position inadvertantly in the plant particularly after resumption of plant operations after any shutdown / maintenance schedule and this may create a unsafe situation for the running plant. Especially so with a Hamer Blind due to the ease of it's operation. (Some operating companies maintain a list of critical valves / Blinds in the plant and this is used by them as a checklist to check the valves / blinds operating position at the time of a strart-up / shut down).

Also, a Hamer Blind's constructional features are such that I do not think that pressure drop is an issue.

Cheers,

[gvdlans]

Funny, I get more hits with Google for "hammer blind" than for "hamer blind"... See for example http://www.shreepad....lind_valves.htm

I don't see why it would be an improvement to install a gate valve instead of a ham(m)er blind. Without proper management procedures, it is equally easy to leave a gate valve in the closed position. The requirement for such procedures is described in API 520, part II, section 4.5.

[avsp]

Dear all,

Please look up the following link

http://www.rmenergy....erlinevalve.pdf

The above article/product literature is a part of the website of the company by the name of R&M Energy Systems Inc., USA and the name HAMER and the blind valve design is supposedly a registered trademark of this company. This company apparently has been in existence for quite some time now.

I am aware of this company and it appears that Shreepad Engg. have borrowed this design and got around any trade mark issues by naming their blind valves as "hammer" instead of "hamer". However, I am not sure.

Regarding the usage of gate valves, I agree with gvdlans that it is equally easy to leave a gate valve in the closed position. However, in several of my previous projects, I have ensured that if ever I introduce any isolation valve upstream and/or downstream of the relief valve, I ensure, after review and discussion with the client, that

i) the isolation valves are full bore
ii) the isolation valves shall be kept "locked open"

Cheers

[bri-ion]

Hamer blind is somewhat unsafe because pipefitter is exposed to line materials when he looses bolts to rotate blind to a different position. This exposes him to chemicals and or high pressure from a potential relief valve discharge.

A full ported gate valve's position would be easily identified and the line would not have to be out of service to change gate valve position.

Bri-ion