MAWP adalah kondisi maksimum operasi yang diperbolehkan. Design pressure selalu lebih besar dari MAWP. Ini untuk mengakomodasi ketidak sempurnaan pengerjaan atau cacat material.. biasanya setting PSV akan berada di bawah nilai MAWP. Ini sebagai proteksi juga. FYI, dalam disain ada parameter lain yaitu corrosion allowance.

Tanya – iwan febrianto

Mohon pencerahan :

Sesuai rumus ketebalan pipa :

t =tc + th + Pi Do /(2(SE+Pi Y)

dimana Pi adalah design pressure

1. Jika kita ada data kondisi operasi maka kondisi design pressurenya berapa?

2. MAWP pipa dari table API RP 14 E apa bedanya dengan design pressure? bagaimana hubungannya dengan thickness hasil rumus diatas.

Terimakasih

Tanggapan 1 – Teguh Santoso

MAWP adalah kondisi maksimum operasi yang diperbolehkan. Design pressure selalu lebih besar dari MAWP. Ini untuk mengakomodasi ketidak sempurnaan pengerjaan atau cacat material.. biasanya setting PSV akan berada di bawah nilai MAWP. Ini sebagai proteksi juga. FYI, dalam disain ada parameter lain yaitu corrosion allowance..CMIIW.

Tanggapan 2 – Rifai, Boorham (Jakarta)

Maaf Mas Teguh, AFAIK, design pressure adalah tekanan maksimum yg mungkin akan dicapai selama pengoperasian equipment (vessel/piping?) dan digunakan sebagai basis utk perancangan equipment (vessel/piping?). Ketebalan vessel (/piping?) dihitung dgn menggunakan design pressure, dan hasil perhitungannya dicocokkan dgn standar ketebalan dan jenis material vessel (/piping?). Utk tiap2 jenis material dan ketebalannya, memiliki rentang operasi pressure – temperature maksimum yg berbeda2. Maksimum pressure ini yg dinamakan MAWP. Karena itu, design pressure < MAWP. PSV setahu saya biasanya di set di design pressure, bukan di MAWP. CMIIW supaya saya tidak makin tersesat (maklum, masih graduate).

Tanggapan 3 – Anto

Mas Iwan,

Referensi rumus pipe thk darimana ya ???? trus specific aplikasinya untuk apa ??? klo sy hubungkan dengan pertanyaan dibawah sepertinya untuk Design & Installation Offshore Prod. PF piping System, dan klo bener dengan ini, berarti untuk designnya typical dengan ASME B31.3, t= Pi Do /(2(SE+Pi Y) for internal press. Untuk Design press. sebenarnya bisa ditentukan dari kondisi operasi yang diketahui ‘Design press of each component shall be not less than the pressure at the most severe condition of coincident in/ex press and temp’, kesimpulannya design press tidak boleh kurang dari operating press yang ekstrim/tinggi.

Tanggapan 4 – muhammad rifai

cukup sering saya membaca diskusi soal hubungan design pressure dan MAWP, dan seringnya MAWP jadi bulan bulanan… yang menurut saya sering salah paham….

saya rasa kalimat ‘Design pressure selalu lebih besar dari MAWP’ adalah tidak benar.

Tanggapan 5 – Allan

Dari formula ditunjukan, bahwa design pressure sebagai dasar untuk menentukan minimum wall thickness yang diperlukan.

Biasanya, MAWP sedikit lebih besar dari design pressure, (design pressure tidak akan lebih besar dari MAWP) atau jikalau actual metal thickness tidak tersedia (new design) bisa di asumsikan MAWP = design pressure.

Sebagi general referensi :

Max Opreting Pressure (MOP) Design Pressure (DP) (barg) (barg)

>0<10 MOP + 1 bar (not less than 3.05)

>10 110% MOP

Tanggapan 6 – asoulisa

MAWP bisa lebih besar daripada design P?

Mungkin maksudnya MAP.

Tanggapan 7 – Allan

Ya, coba baca Di buku ‘Pressure Safety Design Practices for Refinery and Chemical Operations’ cukup detail di jelaskan.

Berikut kutipan nya

‘……The design pressure is never greater than maximum allowable working pressure.
In the case where the actual metal thickness available for strenght is not known, the design pressure is assumed to be equal to the maximum allowable working pressure……’.

Tanggapan 8 – Bakti Kumoro

quote : (design pressure tidak akan lebih besar dari MAWP)’

beneran nih mas Allan ??

bisa jebol semua tuh mas kalau design pressure < MAWP.......

Tanggapan 9 – MahadiCapa

Betul mass, beberapa code/rules hampir sama tentang MAWP : 1.1 DP untuk pneumatic test dan 1.3 DP untuk hydrostatic test.

Tanggapan 10 – muhammad rifai

yang ini hubungannya bagaimana ya?… kok nyambungnya MAWP : 1.1 DP dan 1.3 DP…

Tanggapan 11 – Bakti Kumoro

maaf, saya yang salah…….

thanks atas koreksinya mas……

Tanggapan 12 – Harry Satriadi

Jelasnya bisa dilihat di API 520 P1 Figure. 1

Tanggapan 13 – Rifai, Boorham (Jakarta)

Mas Bakti, sepertinya Mas Allan bener deh.

Beberapa temuan yg menarik tentang design pressure vs MAWP dari Mas Google. Semoga berguna…

Max allowable working pressure is always equal to or higher than the design pressure.The design pressure is normally the PRV set pressure of a vessel.This pressure is used to determine the minimum wall thickness. Say a calculated thickness is 9.2 mm based on a des press. However, a standard material may have athickness of 10 mm. If the press is now back calculated based on this thickness this will be the MAWP.

http://www.eng-tips.com/faqs.cfm?fid=133

MAWP and Design Pressure

In paragraph 1.2.3.2 (b), API 520 defines maximum allowable working pressure (MAWP) as

‘… the maximum gauge pressure permissible at the top of a completed vessel in its normal operating position at the designated coincident temperature specified for that pressure.’

The operative word here is ‘completed’. The vessel is completed when a fabricator, according to the code laid down by ASME, has designed it. The vessel’s fabricator, not the Process Engineer, determines MAWP. (Some may try to stretch my definition of ‘completed’ to mean that the vessel is also erected in place. Not quite because the certified vessel drawings, which are delivered way before the vessel is, contains this information).

In the same paragraph, API 520 says that the MAWP is normally greater than design pressure. The Process Engineer usually sets the design pressure at the time the vessel specification is being written. The design pressure is the value obtained after adding a margin to the most severe pressure expected during normal operation at a coincident temperature. Depending upon the company the engineer works for, this margin is typically the maximum of 25 psig or 10%. The vessel specification sheet contains the design pressure, along with the design temperature, size, normal operating conditions and material of construction among others. It is this document that will eventually end up in a fabricator’s lap and from which the mechanical design is made.

http://www.cheresources.com/asiseeit1.shtml

The ‘Design’ pressure is that pressure that the engineer decides is the value of the pressure at which the vessel will normally operate (or which it must withstand under operating conditions). This value must include any normal excess pressure that can occur during the vessel’s operation. This is a discretionary value that depends on the background and experience of the design engineer. Sometimes the design value can be 10% over the pressure calculated (as in a simulation) or as much as 25% more. Good engineering judgment is employed in arriving at this design figure.

Once the Specification Sheet is received by the vessel fabricator, mechanical fabrication design takes place in which alloys, fabrication techniques, available materials, and other factors are taken into consideration to generate a fabrication drawing. Although the design pressure given is employed to generate the required vessel physical characteristics, some practical factors – such as available materials, fabrication efficiency factors, and alloys employed – will result in a vessel that not only meets the required design pressure, but often EXCEEDS it. This is a fortunate and conservative procedure because it ensures that the vessel will meet pressure safety expectations. The Maximum Allowable Working Pressure (MAWP) is a result of back-calculating the ultimate resulting fabricated vessel and is the prime factor in setting the pressure at which the corresponding vessel Safety Relief Devices will be activated. I consider the MAWP the most important pressure value attached to a vessel and one that should be clearly understood and stamped on the vessel for all to clearly read. The MAWP will change with time (as will the related design value) due to wear, corrosion, and vessel fatigue. This is why it is so important to religiously keep and maintain current and accurate data sheets and calculations on all pressure vessels as they are inspected and repaired through the years of service.

http://www.cheresources.com/invision/lofiversion/index.php/t2544.html

Tanggapan 14 – muhammad rifai

lebih bagus lagi kalau merefernya ke prasasti yang asli, misalnya ASME VIII… kalau nggak salah, PRV dihubungkan dengan MAWP… soal MAWP bisa sama dengan PRV (atau disamakan), itu masalah lain.. ini juga pernah dibahas panjang lebar…

jadi, kalimat ‘The design pressure is normally the PRV set pressure of a vessel’ jangan ditelan mentah mentah…

gimana kabare mas Rifai? WP jakarta aman?